diff --git a/compiler/rustc_borrowck/src/constraint_generation.rs b/compiler/rustc_borrowck/src/constraint_generation.rs
index 743d117e00f2b..1f642099f0899 100644
--- a/compiler/rustc_borrowck/src/constraint_generation.rs
+++ b/compiler/rustc_borrowck/src/constraint_generation.rs
@@ -7,8 +7,8 @@ use rustc_middle::mir::{
     Body, Local, Location, Place, PlaceRef, ProjectionElem, Rvalue, SourceInfo, Statement,
     StatementKind, Terminator, TerminatorKind, UserTypeProjection,
 };
-use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::visit::TypeVisitable;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, RegionVid, Ty, TyCtxt};
 
 use crate::{
@@ -49,11 +49,11 @@ struct ConstraintGeneration<'cg, 'tcx> {
 }
 
 impl<'cg, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'tcx> {
-    /// We sometimes have `substs` within an rvalue, or within a
+    /// We sometimes have `args` within an rvalue, or within a
     /// call. Make them live at the location where they appear.
-    fn visit_substs(&mut self, substs: &SubstsRef<'tcx>, location: Location) {
-        self.add_regular_live_constraint(*substs, location);
-        self.super_substs(substs);
+    fn visit_args(&mut self, args: &GenericArgsRef<'tcx>, location: Location) {
+        self.add_regular_live_constraint(*args, location);
+        self.super_args(args);
     }
 
     /// We sometimes have `region` within an rvalue, or within a
diff --git a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
index 6e7b0c2e11f45..b08d2f90d2689 100644
--- a/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs
@@ -702,11 +702,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 .iter()
                 .copied()
                 .find_map(find_fn_kind_from_did),
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => tcx
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => tcx
                 .explicit_item_bounds(def_id)
-                .subst_iter_copied(tcx, substs)
+                .arg_iter_copied(tcx, args)
                 .find_map(|(clause, span)| find_fn_kind_from_did((clause, span))),
-            ty::Closure(_, substs) => match substs.as_closure().kind() {
+            ty::Closure(_, args) => match args.as_closure().kind() {
                 ty::ClosureKind::Fn => Some(hir::Mutability::Not),
                 ty::ClosureKind::FnMut => Some(hir::Mutability::Mut),
                 _ => None,
@@ -1448,11 +1448,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
         }
 
         // Get closure's arguments
-        let ty::Closure(_, substs) = typeck_results.expr_ty(closure_expr).kind() else {
+        let ty::Closure(_, args) = typeck_results.expr_ty(closure_expr).kind() else {
             /* hir::Closure can be a generator too */
             return;
         };
-        let sig = substs.as_closure().sig();
+        let sig = args.as_closure().sig();
         let tupled_params =
             tcx.erase_late_bound_regions(sig.inputs().iter().next().unwrap().map_bound(|&b| b));
         let ty::Tuple(params) = tupled_params.kind() else { return };
@@ -2676,7 +2676,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 kind: TerminatorKind::Call { call_source: CallSource::OverloadedOperator, .. },
                 ..
             }),
-            Some((method_did, method_substs)),
+            Some((method_did, method_args)),
         ) = (
             &self.body[loan.reserve_location.block].terminator,
             rustc_middle::util::find_self_call(
@@ -2689,7 +2689,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if tcx.is_diagnostic_item(sym::deref_method, method_did) {
                 let deref_target =
                     tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| {
-                        Instance::resolve(tcx, self.param_env, deref_target, method_substs)
+                        Instance::resolve(tcx, self.param_env, deref_target, method_args)
                             .transpose()
                     });
                 if let Some(Ok(instance)) = deref_target {
@@ -2856,11 +2856,11 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             if is_closure {
                 None
             } else {
-                let ty = self.infcx.tcx.type_of(self.mir_def_id()).subst_identity();
+                let ty = self.infcx.tcx.type_of(self.mir_def_id()).instantiate_identity();
                 match ty.kind() {
                     ty::FnDef(_, _) | ty::FnPtr(_) => self.annotate_fn_sig(
                         self.mir_def_id(),
-                        self.infcx.tcx.fn_sig(self.mir_def_id()).subst_identity(),
+                        self.infcx.tcx.fn_sig(self.mir_def_id()).instantiate_identity(),
                     ),
                     _ => None,
                 }
@@ -2902,7 +2902,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         );
                         // Check if our `target` was captured by a closure.
                         if let Rvalue::Aggregate(
-                            box AggregateKind::Closure(def_id, substs),
+                            box AggregateKind::Closure(def_id, args),
                             operands,
                         ) = rvalue
                         {
@@ -2933,7 +2933,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                                 // into a place then we should annotate the closure in
                                 // case it ends up being assigned into the return place.
                                 annotated_closure =
-                                    self.annotate_fn_sig(def_id, substs.as_closure().sig());
+                                    self.annotate_fn_sig(def_id, args.as_closure().sig());
                                 debug!(
                                     "annotate_argument_and_return_for_borrow: \
                                      annotated_closure={:?} assigned_from_local={:?} \
diff --git a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
index 225c38efb2cdc..c92f32071f4ba 100644
--- a/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs
@@ -168,17 +168,17 @@ impl<'tcx> BorrowExplanation<'tcx> {
                 let local_decl = &body.local_decls[dropped_local];
                 let mut ty = local_decl.ty;
                 if local_decl.source_info.span.desugaring_kind() == Some(DesugaringKind::ForLoop) {
-                    if let ty::Adt(adt, substs) = local_decl.ty.kind() {
+                    if let ty::Adt(adt, args) = local_decl.ty.kind() {
                         if tcx.is_diagnostic_item(sym::Option, adt.did()) {
                             // in for loop desugaring, only look at the `Some(..)` inner type
-                            ty = substs.type_at(0);
+                            ty = args.type_at(0);
                         }
                     }
                 }
                 let (dtor_desc, type_desc) = match ty.kind() {
                     // If type is an ADT that implements Drop, then
                     // simplify output by reporting just the ADT name.
-                    ty::Adt(adt, _substs) if adt.has_dtor(tcx) && !adt.is_box() => {
+                    ty::Adt(adt, _args) if adt.has_dtor(tcx) && !adt.is_box() => {
                         ("`Drop` code", format!("type `{}`", tcx.def_path_str(adt.did())))
                     }
 
diff --git a/compiler/rustc_borrowck/src/diagnostics/mod.rs b/compiler/rustc_borrowck/src/diagnostics/mod.rs
index e51da961add23..099e07e88414a 100644
--- a/compiler/rustc_borrowck/src/diagnostics/mod.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/mod.rs
@@ -732,18 +732,18 @@ impl<'tcx> BorrowedContentSource<'tcx> {
 
     fn from_call(func: Ty<'tcx>, tcx: TyCtxt<'tcx>) -> Option<Self> {
         match *func.kind() {
-            ty::FnDef(def_id, substs) => {
+            ty::FnDef(def_id, args) => {
                 let trait_id = tcx.trait_of_item(def_id)?;
 
                 let lang_items = tcx.lang_items();
                 if Some(trait_id) == lang_items.deref_trait()
                     || Some(trait_id) == lang_items.deref_mut_trait()
                 {
-                    Some(BorrowedContentSource::OverloadedDeref(substs.type_at(0)))
+                    Some(BorrowedContentSource::OverloadedDeref(args.type_at(0)))
                 } else if Some(trait_id) == lang_items.index_trait()
                     || Some(trait_id) == lang_items.index_mut_trait()
                 {
-                    Some(BorrowedContentSource::OverloadedIndex(substs.type_at(0)))
+                    Some(BorrowedContentSource::OverloadedIndex(args.type_at(0)))
                 } else {
                     None
                 }
@@ -847,7 +847,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
             kind: TerminatorKind::Call { fn_span, call_source, .. }, ..
         }) = &self.body[location.block].terminator
         {
-            let Some((method_did, method_substs)) = rustc_middle::util::find_self_call(
+            let Some((method_did, method_args)) = rustc_middle::util::find_self_call(
                 self.infcx.tcx,
                 &self.body,
                 target_temp,
@@ -860,7 +860,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                 self.infcx.tcx,
                 self.param_env,
                 method_did,
-                method_substs,
+                method_args,
                 *fn_span,
                 call_source.from_hir_call(),
                 Some(self.infcx.tcx.fn_arg_names(method_did)[0]),
@@ -1039,7 +1039,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         });
                     }
                 }
-                CallKind::Normal { self_arg, desugaring, method_did, method_substs } => {
+                CallKind::Normal { self_arg, desugaring, method_did, method_args } => {
                     let self_arg = self_arg.unwrap();
                     let tcx = self.infcx.tcx;
                     if let Some((CallDesugaringKind::ForLoopIntoIter, _)) = desugaring {
@@ -1106,13 +1106,13 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                         // Erase and shadow everything that could be passed to the new infcx.
                         let ty = moved_place.ty(self.body, tcx).ty;
 
-                        if let ty::Adt(def, substs) = ty.kind()
+                        if let ty::Adt(def, args) = ty.kind()
                             && Some(def.did()) == tcx.lang_items().pin_type()
-                            && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()
+                            && let ty::Ref(_, _, hir::Mutability::Mut) = args.type_at(0).kind()
                             && let self_ty = self.infcx.instantiate_binder_with_fresh_vars(
                                 fn_call_span,
                                 LateBoundRegionConversionTime::FnCall,
-                                tcx.fn_sig(method_did).subst(tcx, method_substs).input(0),
+                                tcx.fn_sig(method_did).instantiate(tcx, method_args).input(0),
                             )
                             && self.infcx.can_eq(self.param_env, ty, self_ty)
                         {
@@ -1161,7 +1161,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
                     let parent_self_ty =
                         matches!(tcx.def_kind(parent_did), rustc_hir::def::DefKind::Impl { .. })
                             .then_some(parent_did)
-                            .and_then(|did| match tcx.type_of(did).subst_identity().kind() {
+                            .and_then(|did| match tcx.type_of(did).instantiate_identity().kind() {
                                 ty::Adt(def, ..) => Some(def.did()),
                                 _ => None,
                             });
diff --git a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
index 3d4ca320ac368..e05c04e118808 100644
--- a/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/move_errors.rs
@@ -324,10 +324,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
             ty::Array(..) | ty::Slice(..) => {
                 self.cannot_move_out_of_interior_noncopy(span, ty, None)
             }
-            ty::Closure(def_id, closure_substs)
+            ty::Closure(def_id, closure_args)
                 if def_id.as_local() == Some(self.mir_def_id()) && upvar_field.is_some() =>
             {
-                let closure_kind_ty = closure_substs.as_closure().kind_ty();
+                let closure_kind_ty = closure_args.as_closure().kind_ty();
                 let closure_kind = match closure_kind_ty.to_opt_closure_kind() {
                     Some(kind @ (ty::ClosureKind::Fn | ty::ClosureKind::FnMut)) => kind,
                     Some(ty::ClosureKind::FnOnce) => {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
index 415ff5aea0345..2ea399789b9a3 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_errors.rs
@@ -22,7 +22,7 @@ use rustc_infer::infer::{
 };
 use rustc_middle::hir::place::PlaceBase;
 use rustc_middle::mir::{ConstraintCategory, ReturnConstraint};
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::TypeVisitor;
 use rustc_middle::ty::{self, RegionVid, Ty};
 use rustc_middle::ty::{Region, TyCtxt};
@@ -183,9 +183,9 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
     fn is_closure_fn_mut(&self, fr: RegionVid) -> bool {
         if let Some(ty::ReFree(free_region)) = self.to_error_region(fr).as_deref()
             && let ty::BoundRegionKind::BrEnv = free_region.bound_region
-            && let DefiningTy::Closure(_, substs) = self.regioncx.universal_regions().defining_ty
+            && let DefiningTy::Closure(_, args) = self.regioncx.universal_regions().defining_ty
         {
-            return substs.as_closure().kind() == ty::ClosureKind::FnMut;
+            return args.as_closure().kind() == ty::ClosureKind::FnMut;
         }
 
         false
@@ -502,12 +502,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                                 .to_string(),
                         )
                     }
-                    ty::Adt(adt, substs) => {
-                        let generic_arg = substs[param_index as usize];
-                        let identity_substs =
-                            InternalSubsts::identity_for_item(self.infcx.tcx, adt.did());
-                        let base_ty = Ty::new_adt(self.infcx.tcx, *adt, identity_substs);
-                        let base_generic_arg = identity_substs[param_index as usize];
+                    ty::Adt(adt, args) => {
+                        let generic_arg = args[param_index as usize];
+                        let identity_args =
+                            GenericArgs::identity_for_item(self.infcx.tcx, adt.did());
+                        let base_ty = Ty::new_adt(self.infcx.tcx, *adt, identity_args);
+                        let base_generic_arg = identity_args[param_index as usize];
                         let adt_desc = adt.descr();
 
                         let desc = format!(
@@ -520,12 +520,11 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     }
                     ty::FnDef(def_id, _) => {
                         let name = self.infcx.tcx.item_name(*def_id);
-                        let identity_substs =
-                            InternalSubsts::identity_for_item(self.infcx.tcx, *def_id);
+                        let identity_args = GenericArgs::identity_for_item(self.infcx.tcx, *def_id);
                         let desc = format!("a function pointer to `{name}`");
                         let note = format!(
                             "the function `{name}` is invariant over the parameter `{}`",
-                            identity_substs[param_index as usize]
+                            identity_args[param_index as usize]
                         );
                         (desc, note)
                     }
@@ -573,7 +572,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
 
         let mut output_ty = self.regioncx.universal_regions().unnormalized_output_ty;
         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *output_ty.kind() {
-            output_ty = self.infcx.tcx.type_of(def_id).subst_identity()
+            output_ty = self.infcx.tcx.type_of(def_id).instantiate_identity()
         };
 
         debug!("report_fnmut_error: output_ty={:?}", output_ty);
@@ -899,14 +898,14 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
         let tcx = self.infcx.tcx;
 
         let instance = if let ConstraintCategory::CallArgument(Some(func_ty)) = category {
-            let (fn_did, substs) = match func_ty.kind() {
-                ty::FnDef(fn_did, substs) => (fn_did, substs),
+            let (fn_did, args) = match func_ty.kind() {
+                ty::FnDef(fn_did, args) => (fn_did, args),
                 _ => return,
             };
-            debug!(?fn_did, ?substs);
+            debug!(?fn_did, ?args);
 
             // Only suggest this on function calls, not closures
-            let ty = tcx.type_of(fn_did).subst_identity();
+            let ty = tcx.type_of(fn_did).instantiate_identity();
             debug!("ty: {:?}, ty.kind: {:?}", ty, ty.kind());
             if let ty::Closure(_, _) = ty.kind() {
                 return;
@@ -916,7 +915,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                 tcx,
                 self.param_env,
                 *fn_did,
-                self.infcx.resolve_vars_if_possible(substs),
+                self.infcx.resolve_vars_if_possible(args),
             ) {
                 instance
             } else {
diff --git a/compiler/rustc_borrowck/src/diagnostics/region_name.rs b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
index 963adc01894c2..9cad8fa53186c 100644
--- a/compiler/rustc_borrowck/src/diagnostics/region_name.rs
+++ b/compiler/rustc_borrowck/src/diagnostics/region_name.rs
@@ -5,8 +5,8 @@ use rustc_errors::Diagnostic;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
 use rustc_middle::ty::print::RegionHighlightMode;
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::{self, RegionVid, Ty};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
@@ -321,7 +321,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 ty::BoundRegionKind::BrEnv => {
                     let def_ty = self.regioncx.universal_regions().defining_ty;
 
-                    let DefiningTy::Closure(_, substs) = def_ty else {
+                    let DefiningTy::Closure(_, args) = def_ty else {
                         // Can't have BrEnv in functions, constants or generators.
                         bug!("BrEnv outside of closure.");
                     };
@@ -332,7 +332,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                     };
                     let region_name = self.synthesize_region_name();
 
-                    let closure_kind_ty = substs.as_closure().kind_ty();
+                    let closure_kind_ty = args.as_closure().kind_ty();
                     let note = match closure_kind_ty.to_opt_closure_kind() {
                         Some(ty::ClosureKind::Fn) => {
                             "closure implements `Fn`, so references to captured variables \
@@ -510,10 +510,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                 }
 
                 // Match up something like `Foo<'1>`
-                (
-                    ty::Adt(_adt_def, substs),
-                    hir::TyKind::Path(hir::QPath::Resolved(None, path)),
-                ) => {
+                (ty::Adt(_adt_def, args), hir::TyKind::Path(hir::QPath::Resolved(None, path))) => {
                     match path.res {
                         // Type parameters of the type alias have no reason to
                         // be the same as those of the ADT.
@@ -523,7 +520,7 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
                         _ => {
                             if let Some(last_segment) = path.segments.last() {
                                 if let Some(highlight) = self.match_adt_and_segment(
-                                    substs,
+                                    args,
                                     needle_fr,
                                     last_segment,
                                     search_stack,
@@ -560,22 +557,22 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         None
     }
 
-    /// We've found an enum/struct/union type with the substitutions
-    /// `substs` and -- in the HIR -- a path type with the final
+    /// We've found an enum/struct/union type with the generic args
+    /// `args` and -- in the HIR -- a path type with the final
     /// segment `last_segment`. Try to find a `'_` to highlight in
     /// the generic args (or, if not, to produce new zipped pairs of
     /// types+hir to search through).
     fn match_adt_and_segment<'hir>(
         &self,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         needle_fr: RegionVid,
         last_segment: &'hir hir::PathSegment<'hir>,
         search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty<'hir>)>,
     ) -> Option<RegionNameHighlight> {
         // Did the user give explicit arguments? (e.g., `Foo<..>`)
-        let args = last_segment.args.as_ref()?;
+        let explicit_args = last_segment.args.as_ref()?;
         let lifetime =
-            self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?;
+            self.try_match_adt_and_generic_args(args, needle_fr, explicit_args, search_stack)?;
         if lifetime.is_anonymous() {
             None
         } else {
@@ -583,19 +580,19 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         }
     }
 
-    /// We've found an enum/struct/union type with the substitutions
-    /// `substs` and -- in the HIR -- a path with the generic
-    /// arguments `args`. If `needle_fr` appears in the args, return
+    /// We've found an enum/struct/union type with the generic args
+    /// `args` and -- in the HIR -- a path with the generic
+    /// arguments `hir_args`. If `needle_fr` appears in the args, return
     /// the `hir::Lifetime` that corresponds to it. If not, push onto
     /// `search_stack` the types+hir to search through.
     fn try_match_adt_and_generic_args<'hir>(
         &self,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         needle_fr: RegionVid,
-        args: &'hir hir::GenericArgs<'hir>,
+        hir_args: &'hir hir::GenericArgs<'hir>,
         search_stack: &mut Vec<(Ty<'tcx>, &'hir hir::Ty<'hir>)>,
     ) -> Option<&'hir hir::Lifetime> {
-        for (kind, hir_arg) in iter::zip(substs, args.args) {
+        for (kind, hir_arg) in iter::zip(args, hir_args.args) {
             match (kind.unpack(), hir_arg) {
                 (GenericArgKind::Lifetime(r), hir::GenericArg::Lifetime(lt)) => {
                     if r.as_var() == needle_fr {
@@ -849,9 +846,10 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
             return None;
         };
 
-        let found = tcx.any_free_region_meets(&tcx.type_of(region_parent).subst_identity(), |r| {
-            *r == ty::ReEarlyBound(region)
-        });
+        let found = tcx
+            .any_free_region_meets(&tcx.type_of(region_parent).instantiate_identity(), |r| {
+                *r == ty::ReEarlyBound(region)
+            });
 
         Some(RegionName {
             name: self.synthesize_region_name(),
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 97d15cb53dbb3..ea32506fc8980 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -301,7 +301,7 @@ fn do_mir_borrowck<'tcx>(
     let movable_generator =
         // The first argument is the generator type passed by value
         if let Some(local) = body.local_decls.raw.get(1)
-        // Get the interior types and substs which typeck computed
+        // Get the interior types and args which typeck computed
         && let ty::Generator(_, _, hir::Movability::Static) = local.ty.kind()
     {
         false
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs
index 9202d0b06fffc..fbbccc58ad666 100644
--- a/compiler/rustc_borrowck/src/region_infer/mod.rs
+++ b/compiler/rustc_borrowck/src/region_infer/mod.rs
@@ -1115,7 +1115,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) -> Option<ClosureOutlivesSubject<'tcx>> {
         let tcx = infcx.tcx;
 
-        // Opaque types' substs may include useless lifetimes.
+        // Opaque types' args may include useless lifetimes.
         // We will replace them with ReStatic.
         struct OpaqueFolder<'tcx> {
             tcx: TyCtxt<'tcx>,
@@ -1127,19 +1127,18 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
                 use ty::TypeSuperFoldable as _;
                 let tcx = self.tcx;
-                let &ty::Alias(ty::Opaque, ty::AliasTy { substs, def_id, .. }) = t.kind() else {
+                let &ty::Alias(ty::Opaque, ty::AliasTy { args, def_id, .. }) = t.kind() else {
                     return t.super_fold_with(self);
                 };
-                let substs =
-                    std::iter::zip(substs, tcx.variances_of(def_id)).map(|(arg, v)| {
-                        match (arg.unpack(), v) {
-                            (ty::GenericArgKind::Lifetime(_), ty::Bivariant) => {
-                                tcx.lifetimes.re_static.into()
-                            }
-                            _ => arg.fold_with(self),
+                let args = std::iter::zip(args, tcx.variances_of(def_id)).map(|(arg, v)| {
+                    match (arg.unpack(), v) {
+                        (ty::GenericArgKind::Lifetime(_), ty::Bivariant) => {
+                            tcx.lifetimes.re_static.into()
                         }
-                    });
-                Ty::new_opaque(tcx, def_id, tcx.mk_substs_from_iter(substs))
+                        _ => arg.fold_with(self),
+                    }
+                });
+                Ty::new_opaque(tcx, def_id, tcx.mk_args_from_iter(args))
             }
         }
 
diff --git a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
index 1a227f2d11039..d8e81827a3be1 100644
--- a/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
+++ b/compiler/rustc_borrowck/src/region_infer/opaque_types.rs
@@ -6,9 +6,9 @@ use rustc_infer::infer::InferCtxt;
 use rustc_infer::infer::TyCtxtInferExt as _;
 use rustc_infer::traits::{Obligation, ObligationCause};
 use rustc_middle::traits::DefiningAnchor;
-use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, OpaqueHiddenType, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_span::Span;
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt as _;
 use rustc_trait_selection::traits::ObligationCtxt;
@@ -38,15 +38,15 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// back to concrete lifetimes: `'static`, `ReEarlyBound` or `ReFree`.
     ///
     /// First we map all the lifetimes in the concrete type to an equal
-    /// universal region that occurs in the concrete type's substs, in this case
-    /// this would result in `&'1 i32`. We only consider regions in the substs
+    /// universal region that occurs in the concrete type's args, in this case
+    /// this would result in `&'1 i32`. We only consider regions in the args
     /// in case there is an equal region that does not. For example, this should
     /// be allowed:
     /// `fn f<'a: 'b, 'b: 'a>(x: *mut &'b i32) -> impl Sized + 'a { x }`
     ///
     /// Then we map the regions in both the type and the subst to their
     /// `external_name` giving `concrete_type = &'a i32`,
-    /// `substs = ['static, 'a]`. This will then allow
+    /// `args = ['static, 'a]`. This will then allow
     /// `infer_opaque_definition_from_instantiation` to determine that
     /// `_Return<'_a> = &'_a i32`.
     ///
@@ -73,8 +73,8 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         debug!(?member_constraints);
 
         for (opaque_type_key, concrete_type) in opaque_ty_decls {
-            let substs = opaque_type_key.substs;
-            debug!(?concrete_type, ?substs);
+            let args = opaque_type_key.args;
+            debug!(?concrete_type, ?args);
 
             let mut subst_regions = vec![self.universal_regions.fr_static];
 
@@ -95,7 +95,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                         ty::Region::new_error_with_message(
                             infcx.tcx,
                             concrete_type.span,
-                            "opaque type with non-universal region substs",
+                            "opaque type with non-universal region args",
                         )
                     }
                 }
@@ -110,17 +110,17 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
             debug!(?subst_regions);
 
-            // Next, insert universal regions from substs, so we can translate regions that appear
-            // in them but are not subject to member constraints, for instance closure substs.
-            let universal_substs = infcx.tcx.fold_regions(substs, |region, _| {
+            // Next, insert universal regions from args, so we can translate regions that appear
+            // in them but are not subject to member constraints, for instance closure args.
+            let universal_args = infcx.tcx.fold_regions(args, |region, _| {
                 if let ty::RePlaceholder(..) = region.kind() {
-                    // Higher kinded regions don't need remapping, they don't refer to anything outside of this the substs.
+                    // Higher kinded regions don't need remapping, they don't refer to anything outside of this the args.
                     return region;
                 }
                 let vid = self.to_region_vid(region);
                 to_universal_region(vid, &mut subst_regions)
             });
-            debug!(?universal_substs);
+            debug!(?universal_args);
             debug!(?subst_regions);
 
             // Deduplicate the set of regions while keeping the chosen order.
@@ -139,7 +139,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             debug!(?universal_concrete_type);
 
             let opaque_type_key =
-                OpaqueTypeKey { def_id: opaque_type_key.def_id, substs: universal_substs };
+                OpaqueTypeKey { def_id: opaque_type_key.def_id, args: universal_args };
             let ty = infcx.infer_opaque_definition_from_instantiation(
                 opaque_type_key,
                 universal_concrete_type,
@@ -175,7 +175,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
     /// Map the regions in the type to named regions. This is similar to what
     /// `infer_opaque_types` does, but can infer any universal region, not only
-    /// ones from the substs for the opaque type. It also doesn't double check
+    /// ones from the args for the opaque type. It also doesn't double check
     /// that the regions produced are in fact equal to the named region they are
     /// replaced with. This is fine because this function is only to improve the
     /// region names in error messages.
@@ -238,7 +238,7 @@ impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
     /// # Parameters
     ///
     /// - `def_id`, the `impl Trait` type
-    /// - `substs`, the substs used to instantiate this opaque type
+    /// - `args`, the args used to instantiate this opaque type
     /// - `instantiated_ty`, the inferred type C1 -- fully resolved, lifted version of
     ///   `opaque_defn.concrete_ty`
     #[instrument(level = "debug", skip(self))]
@@ -309,11 +309,11 @@ fn check_opaque_type_well_formed<'tcx>(
         })
         .build();
     let ocx = ObligationCtxt::new(&infcx);
-    let identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+    let identity_args = GenericArgs::identity_for_item(tcx, def_id);
 
     // Require that the hidden type actually fulfills all the bounds of the opaque type, even without
     // the bounds that the function supplies.
-    let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), identity_substs);
+    let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), identity_args);
     ocx.eq(&ObligationCause::misc(definition_span, def_id), param_env, opaque_ty, definition_ty)
         .map_err(|err| {
             infcx
@@ -384,7 +384,7 @@ fn check_opaque_type_parameter_valid(
     }
     let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
     let mut seen_params: FxIndexMap<_, Vec<_>> = FxIndexMap::default();
-    for (i, arg) in opaque_type_key.substs.iter().enumerate() {
+    for (i, arg) in opaque_type_key.args.iter().enumerate() {
         let arg_is_param = match arg.unpack() {
             GenericArgKind::Type(ty) => matches!(ty.kind(), ty::Param(_)),
             GenericArgKind::Lifetime(lt) => {
diff --git a/compiler/rustc_borrowck/src/renumber.rs b/compiler/rustc_borrowck/src/renumber.rs
index 4389d2b60bc55..4c69ea843c724 100644
--- a/compiler/rustc_borrowck/src/renumber.rs
+++ b/compiler/rustc_borrowck/src/renumber.rs
@@ -6,7 +6,7 @@ use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::mir::visit::{MutVisitor, TyContext};
 use rustc_middle::mir::Constant;
 use rustc_middle::mir::{Body, Location, Promoted};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc_span::{Span, Symbol};
 
@@ -94,10 +94,10 @@ impl<'a, 'tcx> MutVisitor<'tcx> for RegionRenumberer<'a, 'tcx> {
     }
 
     #[instrument(skip(self), level = "debug")]
-    fn visit_substs(&mut self, substs: &mut SubstsRef<'tcx>, location: Location) {
-        *substs = self.renumber_regions(*substs, || RegionCtxt::Location(location));
+    fn visit_args(&mut self, args: &mut GenericArgsRef<'tcx>, location: Location) {
+        *args = self.renumber_regions(*args, || RegionCtxt::Location(location));
 
-        debug!(?substs);
+        debug!(?args);
     }
 
     #[instrument(skip(self), level = "debug")]
diff --git a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
index 71eae7b27d1db..21d8026e17089 100644
--- a/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
+++ b/compiler/rustc_borrowck/src/type_check/constraint_conversion.rs
@@ -5,7 +5,7 @@ use rustc_infer::infer::outlives::obligations::{TypeOutlives, TypeOutlivesDelega
 use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound};
 use rustc_infer::infer::{self, InferCtxt, SubregionOrigin};
 use rustc_middle::mir::{ClosureOutlivesSubject, ClosureRegionRequirements, ConstraintCategory};
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_middle::ty::{TypeFoldable, TypeVisitableExt};
 use rustc_span::{Span, DUMMY_SP};
@@ -89,20 +89,20 @@ impl<'a, 'tcx> ConstraintConversion<'a, 'tcx> {
 
     /// Given an instance of the closure type, this method instantiates the "extra" requirements
     /// that we computed for the closure. This has the effect of adding new outlives obligations
-    /// to existing region variables in `closure_substs`.
+    /// to existing region variables in `closure_args`.
     #[instrument(skip(self), level = "debug")]
     pub fn apply_closure_requirements(
         &mut self,
         closure_requirements: &ClosureRegionRequirements<'tcx>,
         closure_def_id: DefId,
-        closure_substs: ty::SubstsRef<'tcx>,
+        closure_args: ty::GenericArgsRef<'tcx>,
     ) {
-        // Extract the values of the free regions in `closure_substs`
+        // Extract the values of the free regions in `closure_args`
         // into a vector. These are the regions that we will be
         // relating to one another.
         let closure_mapping = &UniversalRegions::closure_mapping(
             self.tcx,
-            closure_substs,
+            closure_args,
             closure_requirements.num_external_vids,
             closure_def_id.expect_local(),
         );
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs b/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
index 012075d711450..c621df37106b2 100644
--- a/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
+++ b/compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
@@ -2,7 +2,7 @@ use crate::def_use::{self, DefUse};
 use crate::location::{LocationIndex, LocationTable};
 use rustc_middle::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::{Body, Local, Location, Place};
-use rustc_middle::ty::subst::GenericArg;
+use rustc_middle::ty::GenericArg;
 use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
 
 use super::TypeChecker;
diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
index 638cede6aaaaa..78aa513033c92 100644
--- a/compiler/rustc_borrowck/src/type_check/mod.rs
+++ b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -30,12 +30,12 @@ use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::adjustment::PointerCoercion;
 use rustc_middle::ty::cast::CastTy;
-use rustc_middle::ty::subst::{SubstsRef, UserSubsts};
 use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{
     self, Binder, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations, Dynamic,
     OpaqueHiddenType, OpaqueTypeKey, RegionVid, Ty, TyCtxt, UserType, UserTypeAnnotationIndex,
 };
+use rustc_middle::ty::{GenericArgsRef, UserArgs};
 use rustc_span::def_id::CRATE_DEF_ID;
 use rustc_span::symbol::sym;
 use rustc_span::{Span, DUMMY_SP};
@@ -389,15 +389,12 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 } else {
                     self.cx.ascribe_user_type(
                         constant.literal.ty(),
-                        UserType::TypeOf(
-                            uv.def,
-                            UserSubsts { substs: uv.substs, user_self_ty: None },
-                        ),
+                        UserType::TypeOf(uv.def, UserArgs { args: uv.args, user_self_ty: None }),
                         locations.span(&self.cx.body),
                     );
                 }
             } else if let Some(static_def_id) = constant.check_static_ptr(tcx) {
-                let unnormalized_ty = tcx.type_of(static_def_id).subst_identity();
+                let unnormalized_ty = tcx.type_of(static_def_id).instantiate_identity();
                 let normalized_ty = self.cx.normalize(unnormalized_ty, locations);
                 let literal_ty = constant.literal.ty().builtin_deref(true).unwrap().ty;
 
@@ -411,11 +408,11 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                 }
             }
 
-            if let ty::FnDef(def_id, substs) = *constant.literal.ty().kind() {
+            if let ty::FnDef(def_id, args) = *constant.literal.ty().kind() {
                 // const_trait_impl: use a non-const param env when checking that a FnDef type is well formed.
                 // this is because the well-formedness of the function does not need to be proved to have `const`
                 // impls for trait bounds.
-                let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
+                let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, args);
                 let prev = self.cx.param_env;
                 self.cx.param_env = prev.without_const();
                 self.cx.normalize_and_prove_instantiated_predicates(
@@ -666,7 +663,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 })
             }
             ProjectionElem::Downcast(maybe_name, index) => match base_ty.kind() {
-                ty::Adt(adt_def, _substs) if adt_def.is_enum() => {
+                ty::Adt(adt_def, _args) if adt_def.is_enum() => {
                     if index.as_usize() >= adt_def.variants().len() {
                         PlaceTy::from_ty(span_mirbug_and_err!(
                             self,
@@ -776,16 +773,16 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
     ) -> Result<Ty<'tcx>, FieldAccessError> {
         let tcx = self.tcx();
 
-        let (variant, substs) = match base_ty {
+        let (variant, args) = match base_ty {
             PlaceTy { ty, variant_index: Some(variant_index) } => match *ty.kind() {
-                ty::Adt(adt_def, substs) => (adt_def.variant(variant_index), substs),
-                ty::Generator(def_id, substs, _) => {
-                    let mut variants = substs.as_generator().state_tys(def_id, tcx);
+                ty::Adt(adt_def, args) => (adt_def.variant(variant_index), args),
+                ty::Generator(def_id, args, _) => {
+                    let mut variants = args.as_generator().state_tys(def_id, tcx);
                     let Some(mut variant) = variants.nth(variant_index.into()) else {
                         bug!(
                             "variant_index of generator out of range: {:?}/{:?}",
                             variant_index,
-                            substs.as_generator().state_tys(def_id, tcx).count()
+                            args.as_generator().state_tys(def_id, tcx).count()
                         );
                     };
                     return match variant.nth(field.index()) {
@@ -796,11 +793,11 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                 _ => bug!("can't have downcast of non-adt non-generator type"),
             },
             PlaceTy { ty, variant_index: None } => match *ty.kind() {
-                ty::Adt(adt_def, substs) if !adt_def.is_enum() => {
-                    (adt_def.variant(FIRST_VARIANT), substs)
+                ty::Adt(adt_def, args) if !adt_def.is_enum() => {
+                    (adt_def.variant(FIRST_VARIANT), args)
                 }
-                ty::Closure(_, substs) => {
-                    return match substs
+                ty::Closure(_, args) => {
+                    return match args
                         .as_closure()
                         .tupled_upvars_ty()
                         .tuple_fields()
@@ -808,17 +805,17 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
                     {
                         Some(&ty) => Ok(ty),
                         None => Err(FieldAccessError::OutOfRange {
-                            field_count: substs.as_closure().upvar_tys().count(),
+                            field_count: args.as_closure().upvar_tys().count(),
                         }),
                     };
                 }
-                ty::Generator(_, substs, _) => {
+                ty::Generator(_, args, _) => {
                     // Only prefix fields (upvars and current state) are
                     // accessible without a variant index.
-                    return match substs.as_generator().prefix_tys().nth(field.index()) {
+                    return match args.as_generator().prefix_tys().nth(field.index()) {
                         Some(ty) => Ok(ty),
                         None => Err(FieldAccessError::OutOfRange {
-                            field_count: substs.as_generator().prefix_tys().count(),
+                            field_count: args.as_generator().prefix_tys().count(),
                         }),
                     };
                 }
@@ -840,7 +837,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         };
 
         if let Some(field) = variant.fields.get(field) {
-            Ok(self.cx.normalize(field.ty(tcx, substs), location))
+            Ok(self.cx.normalize(field.ty(tcx, args), location))
         } else {
             Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
         }
@@ -1065,7 +1062,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                         ocx.infcx.add_item_bounds_for_hidden_type(
                             opaque_type_key.def_id.to_def_id(),
-                            opaque_type_key.substs,
+                            opaque_type_key.args,
                             cause,
                             param_env,
                             hidden_ty.ty,
@@ -1770,32 +1767,32 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         let tcx = self.tcx();
 
         match *ak {
-            AggregateKind::Adt(adt_did, variant_index, substs, _, active_field_index) => {
+            AggregateKind::Adt(adt_did, variant_index, args, _, active_field_index) => {
                 let def = tcx.adt_def(adt_did);
                 let variant = &def.variant(variant_index);
                 let adj_field_index = active_field_index.unwrap_or(field_index);
                 if let Some(field) = variant.fields.get(adj_field_index) {
-                    Ok(self.normalize(field.ty(tcx, substs), location))
+                    Ok(self.normalize(field.ty(tcx, args), location))
                 } else {
                     Err(FieldAccessError::OutOfRange { field_count: variant.fields.len() })
                 }
             }
-            AggregateKind::Closure(_, substs) => {
-                match substs.as_closure().upvar_tys().nth(field_index.as_usize()) {
+            AggregateKind::Closure(_, args) => {
+                match args.as_closure().upvar_tys().nth(field_index.as_usize()) {
                     Some(ty) => Ok(ty),
                     None => Err(FieldAccessError::OutOfRange {
-                        field_count: substs.as_closure().upvar_tys().count(),
+                        field_count: args.as_closure().upvar_tys().count(),
                     }),
                 }
             }
-            AggregateKind::Generator(_, substs, _) => {
+            AggregateKind::Generator(_, args, _) => {
                 // It doesn't make sense to look at a field beyond the prefix;
                 // these require a variant index, and are not initialized in
                 // aggregate rvalues.
-                match substs.as_generator().prefix_tys().nth(field_index.as_usize()) {
+                match args.as_generator().prefix_tys().nth(field_index.as_usize()) {
                     Some(ty) => Ok(ty),
                     None => Err(FieldAccessError::OutOfRange {
-                        field_count: substs.as_generator().prefix_tys().count(),
+                        field_count: args.as_generator().prefix_tys().count(),
                     }),
                 }
             }
@@ -1821,8 +1818,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     let def_id = uv.def;
                     if tcx.def_kind(def_id) == DefKind::InlineConst {
                         let def_id = def_id.expect_local();
-                        let predicates =
-                            self.prove_closure_bounds(tcx, def_id, uv.substs, location);
+                        let predicates = self.prove_closure_bounds(tcx, def_id, uv.args, location);
                         self.normalize_and_prove_instantiated_predicates(
                             def_id.to_def_id(),
                             predicates,
@@ -1939,7 +1935,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
 
                     CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(unsafety)) => {
                         let sig = match op.ty(body, tcx).kind() {
-                            ty::Closure(_, substs) => substs.as_closure().sig(),
+                            ty::Closure(_, args) => args.as_closure().sig(),
                             _ => bug!(),
                         };
                         let ty_fn_ptr_from =
@@ -2591,8 +2587,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         );
 
         let (def_id, instantiated_predicates) = match *aggregate_kind {
-            AggregateKind::Adt(adt_did, _, substs, _, _) => {
-                (adt_did, tcx.predicates_of(adt_did).instantiate(tcx, substs))
+            AggregateKind::Adt(adt_did, _, args, _, _) => {
+                (adt_did, tcx.predicates_of(adt_did).instantiate(tcx, args))
             }
 
             // For closures, we have some **extra requirements** we
@@ -2614,9 +2610,8 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             // desugaring. A closure gets desugared to a struct, and
             // these extra requirements are basically like where
             // clauses on the struct.
-            AggregateKind::Closure(def_id, substs)
-            | AggregateKind::Generator(def_id, substs, _) => {
-                (def_id, self.prove_closure_bounds(tcx, def_id.expect_local(), substs, location))
+            AggregateKind::Closure(def_id, args) | AggregateKind::Generator(def_id, args, _) => {
+                (def_id, self.prove_closure_bounds(tcx, def_id.expect_local(), args, location))
             }
 
             AggregateKind::Array(_) | AggregateKind::Tuple => {
@@ -2635,7 +2630,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
         &mut self,
         tcx: TyCtxt<'tcx>,
         def_id: LocalDefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         location: Location,
     ) -> ty::InstantiatedPredicates<'tcx> {
         if let Some(closure_requirements) = &tcx.mir_borrowck(def_id).closure_requirements {
@@ -2653,26 +2648,26 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             .apply_closure_requirements(
                 &closure_requirements,
                 def_id.to_def_id(),
-                substs,
+                args,
             );
         }
 
-        // Now equate closure substs to regions inherited from `typeck_root_def_id`. Fixes #98589.
+        // Now equate closure args to regions inherited from `typeck_root_def_id`. Fixes #98589.
         let typeck_root_def_id = tcx.typeck_root_def_id(self.body.source.def_id());
-        let typeck_root_substs = ty::InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
+        let typeck_root_args = ty::GenericArgs::identity_for_item(tcx, typeck_root_def_id);
 
-        let parent_substs = match tcx.def_kind(def_id) {
-            DefKind::Closure => substs.as_closure().parent_substs(),
-            DefKind::Generator => substs.as_generator().parent_substs(),
-            DefKind::InlineConst => substs.as_inline_const().parent_substs(),
+        let parent_args = match tcx.def_kind(def_id) {
+            DefKind::Closure => args.as_closure().parent_args(),
+            DefKind::Generator => args.as_generator().parent_args(),
+            DefKind::InlineConst => args.as_inline_const().parent_args(),
             other => bug!("unexpected item {:?}", other),
         };
-        let parent_substs = tcx.mk_substs(parent_substs);
+        let parent_args = tcx.mk_args(parent_args);
 
-        assert_eq!(typeck_root_substs.len(), parent_substs.len());
-        if let Err(_) = self.eq_substs(
-            typeck_root_substs,
-            parent_substs,
+        assert_eq!(typeck_root_args.len(), parent_args.len());
+        if let Err(_) = self.eq_args(
+            typeck_root_args,
+            parent_args,
             location.to_locations(),
             ConstraintCategory::BoringNoLocation,
         ) {
@@ -2680,12 +2675,12 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self,
                 def_id,
                 "could not relate closure to parent {:?} != {:?}",
-                typeck_root_substs,
-                parent_substs
+                typeck_root_args,
+                parent_args
             );
         }
 
-        tcx.predicates_of(def_id).instantiate(tcx, substs)
+        tcx.predicates_of(def_id).instantiate(tcx, args)
     }
 
     #[instrument(skip(self, body), level = "debug")]
diff --git a/compiler/rustc_borrowck/src/type_check/relate_tys.rs b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
index 8c4bfb2c6e0d3..e0c6295627bbf 100644
--- a/compiler/rustc_borrowck/src/type_check/relate_tys.rs
+++ b/compiler/rustc_borrowck/src/type_check/relate_tys.rs
@@ -42,10 +42,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
     }
 
     /// Add sufficient constraints to ensure `a == b`. See also [Self::relate_types].
-    pub(super) fn eq_substs(
+    pub(super) fn eq_args(
         &mut self,
-        a: ty::SubstsRef<'tcx>,
-        b: ty::SubstsRef<'tcx>,
+        a: ty::GenericArgsRef<'tcx>,
+        b: ty::GenericArgsRef<'tcx>,
         locations: Locations,
         category: ConstraintCategory<'tcx>,
     ) -> Result<(), NoSolution> {
diff --git a/compiler/rustc_borrowck/src/universal_regions.rs b/compiler/rustc_borrowck/src/universal_regions.rs
index 4d9c4b178dc07..a751a9732f016 100644
--- a/compiler/rustc_borrowck/src/universal_regions.rs
+++ b/compiler/rustc_borrowck/src/universal_regions.rs
@@ -22,8 +22,8 @@ use rustc_hir::BodyOwnerKind;
 use rustc_index::IndexVec;
 use rustc_infer::infer::NllRegionVariableOrigin;
 use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::{self, InlineConstSubsts, InlineConstSubstsParts, RegionVid, Ty, TyCtxt};
-use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{self, InlineConstArgs, InlineConstArgsParts, RegionVid, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_span::symbol::{kw, sym};
 use rustc_span::Symbol;
 use std::iter;
@@ -88,26 +88,26 @@ pub struct UniversalRegions<'tcx> {
 #[derive(Copy, Clone, Debug)]
 pub enum DefiningTy<'tcx> {
     /// The MIR is a closure. The signature is found via
-    /// `ClosureSubsts::closure_sig_ty`.
-    Closure(DefId, SubstsRef<'tcx>),
+    /// `ClosureArgs::closure_sig_ty`.
+    Closure(DefId, GenericArgsRef<'tcx>),
 
     /// The MIR is a generator. The signature is that generators take
     /// no parameters and return the result of
-    /// `ClosureSubsts::generator_return_ty`.
-    Generator(DefId, SubstsRef<'tcx>, hir::Movability),
+    /// `ClosureArgs::generator_return_ty`.
+    Generator(DefId, GenericArgsRef<'tcx>, hir::Movability),
 
-    /// The MIR is a fn item with the given `DefId` and substs. The signature
+    /// The MIR is a fn item with the given `DefId` and args. The signature
     /// of the function can be bound then with the `fn_sig` query.
-    FnDef(DefId, SubstsRef<'tcx>),
+    FnDef(DefId, GenericArgsRef<'tcx>),
 
     /// The MIR represents some form of constant. The signature then
     /// is that it has no inputs and a single return value, which is
     /// the value of the constant.
-    Const(DefId, SubstsRef<'tcx>),
+    Const(DefId, GenericArgsRef<'tcx>),
 
     /// The MIR represents an inline const. The signature has no inputs and a
-    /// single return value found via `InlineConstSubsts::ty`.
-    InlineConst(DefId, SubstsRef<'tcx>),
+    /// single return value found via `InlineConstArgs::ty`.
+    InlineConst(DefId, GenericArgsRef<'tcx>),
 }
 
 impl<'tcx> DefiningTy<'tcx> {
@@ -117,9 +117,9 @@ impl<'tcx> DefiningTy<'tcx> {
     /// match up with the upvar order in the HIR, typesystem, and MIR.
     pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
         match self {
-            DefiningTy::Closure(_, substs) => Either::Left(substs.as_closure().upvar_tys()),
-            DefiningTy::Generator(_, substs, _) => {
-                Either::Right(Either::Left(substs.as_generator().upvar_tys()))
+            DefiningTy::Closure(_, args) => Either::Left(args.as_closure().upvar_tys()),
+            DefiningTy::Generator(_, args, _) => {
+                Either::Right(Either::Left(args.as_generator().upvar_tys()))
             }
             DefiningTy::FnDef(..) | DefiningTy::Const(..) | DefiningTy::InlineConst(..) => {
                 Either::Right(Either::Right(iter::empty()))
@@ -164,9 +164,9 @@ struct UniversalRegionIndices<'tcx> {
     /// used because trait matching and type-checking will feed us
     /// region constraints that reference those regions and we need to
     /// be able to map them to our internal `RegionVid`. This is
-    /// basically equivalent to an `InternalSubsts`, except that it also
+    /// basically equivalent to an `GenericArgs`, except that it also
     /// contains an entry for `ReStatic` -- it might be nice to just
-    /// use a substs, and then handle `ReStatic` another way.
+    /// use a args, and then handle `ReStatic` another way.
     indices: FxHashMap<ty::Region<'tcx>, RegionVid>,
 
     /// The vid assigned to `'static`. Used only for diagnostics.
@@ -243,13 +243,13 @@ impl<'tcx> UniversalRegions<'tcx> {
     /// `V[1]: V[2]`.
     pub fn closure_mapping(
         tcx: TyCtxt<'tcx>,
-        closure_substs: SubstsRef<'tcx>,
+        closure_args: GenericArgsRef<'tcx>,
         expected_num_vars: usize,
         closure_def_id: LocalDefId,
     ) -> IndexVec<RegionVid, ty::Region<'tcx>> {
         let mut region_mapping = IndexVec::with_capacity(expected_num_vars);
         region_mapping.push(tcx.lifetimes.re_static);
-        tcx.for_each_free_region(&closure_substs, |fr| {
+        tcx.for_each_free_region(&closure_args, |fr| {
             region_mapping.push(fr);
         });
 
@@ -334,11 +334,11 @@ impl<'tcx> UniversalRegions<'tcx> {
     /// state.
     pub(crate) fn annotate(&self, tcx: TyCtxt<'tcx>, err: &mut Diagnostic) {
         match self.defining_ty {
-            DefiningTy::Closure(def_id, substs) => {
+            DefiningTy::Closure(def_id, args) => {
                 err.note(format!(
-                    "defining type: {} with closure substs {:#?}",
-                    tcx.def_path_str_with_substs(def_id, substs),
-                    &substs[tcx.generics_of(def_id).parent_count..],
+                    "defining type: {} with closure args {:#?}",
+                    tcx.def_path_str_with_args(def_id, args),
+                    &args[tcx.generics_of(def_id).parent_count..],
                 ));
 
                 // FIXME: It'd be nice to print the late-bound regions
@@ -350,11 +350,11 @@ impl<'tcx> UniversalRegions<'tcx> {
                     err.note(format!("late-bound region is {:?}", self.to_region_vid(r)));
                 });
             }
-            DefiningTy::Generator(def_id, substs, _) => {
+            DefiningTy::Generator(def_id, args, _) => {
                 err.note(format!(
-                    "defining type: {} with generator substs {:#?}",
-                    tcx.def_path_str_with_substs(def_id, substs),
-                    &substs[tcx.generics_of(def_id).parent_count..],
+                    "defining type: {} with generator args {:#?}",
+                    tcx.def_path_str_with_args(def_id, args),
+                    &args[tcx.generics_of(def_id).parent_count..],
                 ));
 
                 // FIXME: As above, we'd like to print out the region
@@ -364,22 +364,19 @@ impl<'tcx> UniversalRegions<'tcx> {
                     err.note(format!("late-bound region is {:?}", self.to_region_vid(r)));
                 });
             }
-            DefiningTy::FnDef(def_id, substs) => {
-                err.note(format!(
-                    "defining type: {}",
-                    tcx.def_path_str_with_substs(def_id, substs),
-                ));
+            DefiningTy::FnDef(def_id, args) => {
+                err.note(format!("defining type: {}", tcx.def_path_str_with_args(def_id, args),));
             }
-            DefiningTy::Const(def_id, substs) => {
+            DefiningTy::Const(def_id, args) => {
                 err.note(format!(
                     "defining constant type: {}",
-                    tcx.def_path_str_with_substs(def_id, substs),
+                    tcx.def_path_str_with_args(def_id, args),
                 ));
             }
-            DefiningTy::InlineConst(def_id, substs) => {
+            DefiningTy::InlineConst(def_id, args) => {
                 err.note(format!(
                     "defining inline constant type: {}",
-                    tcx.def_path_str_with_substs(def_id, substs),
+                    tcx.def_path_str_with_args(def_id, args),
                 ));
             }
         }
@@ -501,8 +498,11 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     .as_var();
 
                 let region = ty::Region::new_var(self.infcx.tcx, reg_vid);
-                let va_list_ty =
-                    self.infcx.tcx.type_of(va_list_did).subst(self.infcx.tcx, &[region.into()]);
+                let va_list_ty = self
+                    .infcx
+                    .tcx
+                    .type_of(va_list_did)
+                    .instantiate(self.infcx.tcx, &[region.into()]);
 
                 unnormalized_input_tys = self.infcx.tcx.mk_type_list_from_iter(
                     unnormalized_input_tys.iter().copied().chain(iter::once(va_list_ty)),
@@ -522,7 +522,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         debug!("build: local regions  = {}..{}", first_local_index, num_universals);
 
         let yield_ty = match defining_ty {
-            DefiningTy::Generator(_, substs, _) => Some(substs.as_generator().yield_ty()),
+            DefiningTy::Generator(_, args, _) => Some(args.as_generator().yield_ty()),
             _ => None,
         };
 
@@ -548,7 +548,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
 
         match tcx.hir().body_owner_kind(self.mir_def) {
             BodyOwnerKind::Closure | BodyOwnerKind::Fn => {
-                let defining_ty = tcx.type_of(self.mir_def).subst_identity();
+                let defining_ty = tcx.type_of(self.mir_def).instantiate_identity();
 
                 debug!("defining_ty (pre-replacement): {:?}", defining_ty);
 
@@ -556,11 +556,11 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     self.infcx.replace_free_regions_with_nll_infer_vars(FR, defining_ty);
 
                 match *defining_ty.kind() {
-                    ty::Closure(def_id, substs) => DefiningTy::Closure(def_id, substs),
-                    ty::Generator(def_id, substs, movability) => {
-                        DefiningTy::Generator(def_id, substs, movability)
+                    ty::Closure(def_id, args) => DefiningTy::Closure(def_id, args),
+                    ty::Generator(def_id, args, movability) => {
+                        DefiningTy::Generator(def_id, args, movability)
                     }
-                    ty::FnDef(def_id, substs) => DefiningTy::FnDef(def_id, substs),
+                    ty::FnDef(def_id, args) => DefiningTy::FnDef(def_id, args),
                     _ => span_bug!(
                         tcx.def_span(self.mir_def),
                         "expected defining type for `{:?}`: `{:?}`",
@@ -571,11 +571,11 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
             }
 
             BodyOwnerKind::Const | BodyOwnerKind::Static(..) => {
-                let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
+                let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id);
                 if self.mir_def.to_def_id() == typeck_root_def_id {
-                    let substs =
-                        self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_substs);
-                    DefiningTy::Const(self.mir_def.to_def_id(), substs)
+                    let args =
+                        self.infcx.replace_free_regions_with_nll_infer_vars(FR, identity_args);
+                    DefiningTy::Const(self.mir_def.to_def_id(), args)
                 } else {
                     // FIXME this line creates a dependency between borrowck and typeck.
                     //
@@ -584,18 +584,18 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     // into borrowck, which is ICE #78174.
                     //
                     // As a workaround, inline consts have an additional generic param (`ty`
-                    // below), so that `type_of(inline_const_def_id).substs(substs)` uses the
+                    // below), so that `type_of(inline_const_def_id).args(args)` uses the
                     // proper type with NLL infer vars.
                     let ty = tcx
                         .typeck(self.mir_def)
                         .node_type(tcx.local_def_id_to_hir_id(self.mir_def));
-                    let substs = InlineConstSubsts::new(
+                    let args = InlineConstArgs::new(
                         tcx,
-                        InlineConstSubstsParts { parent_substs: identity_substs, ty },
+                        InlineConstArgsParts { parent_args: identity_args, ty },
                     )
-                    .substs;
-                    let substs = self.infcx.replace_free_regions_with_nll_infer_vars(FR, substs);
-                    DefiningTy::InlineConst(self.mir_def.to_def_id(), substs)
+                    .args;
+                    let args = self.infcx.replace_free_regions_with_nll_infer_vars(FR, args);
+                    DefiningTy::InlineConst(self.mir_def.to_def_id(), args)
                 }
             }
         }
@@ -612,29 +612,29 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
     ) -> UniversalRegionIndices<'tcx> {
         let tcx = self.infcx.tcx;
         let typeck_root_def_id = tcx.typeck_root_def_id(self.mir_def.to_def_id());
-        let identity_substs = InternalSubsts::identity_for_item(tcx, typeck_root_def_id);
-        let fr_substs = match defining_ty {
-            DefiningTy::Closure(_, substs)
-            | DefiningTy::Generator(_, substs, _)
-            | DefiningTy::InlineConst(_, substs) => {
+        let identity_args = GenericArgs::identity_for_item(tcx, typeck_root_def_id);
+        let fr_args = match defining_ty {
+            DefiningTy::Closure(_, args)
+            | DefiningTy::Generator(_, args, _)
+            | DefiningTy::InlineConst(_, args) => {
                 // In the case of closures, we rely on the fact that
-                // the first N elements in the ClosureSubsts are
+                // the first N elements in the ClosureArgs are
                 // inherited from the `typeck_root_def_id`.
                 // Therefore, when we zip together (below) with
-                // `identity_substs`, we will get only those regions
+                // `identity_args`, we will get only those regions
                 // that correspond to early-bound regions declared on
                 // the `typeck_root_def_id`.
-                assert!(substs.len() >= identity_substs.len());
-                assert_eq!(substs.regions().count(), identity_substs.regions().count());
-                substs
+                assert!(args.len() >= identity_args.len());
+                assert_eq!(args.regions().count(), identity_args.regions().count());
+                args
             }
 
-            DefiningTy::FnDef(_, substs) | DefiningTy::Const(_, substs) => substs,
+            DefiningTy::FnDef(_, args) | DefiningTy::Const(_, args) => args,
         };
 
         let global_mapping = iter::once((tcx.lifetimes.re_static, fr_static));
         let subst_mapping =
-            iter::zip(identity_substs.regions(), fr_substs.regions().map(|r| r.as_var()));
+            iter::zip(identity_args.regions(), fr_args.regions().map(|r| r.as_var()));
 
         UniversalRegionIndices { indices: global_mapping.chain(subst_mapping).collect(), fr_static }
     }
@@ -646,9 +646,9 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
     ) -> ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>> {
         let tcx = self.infcx.tcx;
         match defining_ty {
-            DefiningTy::Closure(def_id, substs) => {
+            DefiningTy::Closure(def_id, args) => {
                 assert_eq!(self.mir_def.to_def_id(), def_id);
-                let closure_sig = substs.as_closure().sig();
+                let closure_sig = args.as_closure().sig();
                 let inputs_and_output = closure_sig.inputs_and_output();
                 let bound_vars = tcx.mk_bound_variable_kinds_from_iter(
                     inputs_and_output
@@ -661,7 +661,7 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                     kind: ty::BrEnv,
                 };
                 let env_region = ty::Region::new_late_bound(tcx, ty::INNERMOST, br);
-                let closure_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
+                let closure_ty = tcx.closure_env_ty(def_id, args, env_region).unwrap();
 
                 // The "inputs" of the closure in the
                 // signature appear as a tuple. The MIR side
@@ -681,18 +681,18 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                 )
             }
 
-            DefiningTy::Generator(def_id, substs, movability) => {
+            DefiningTy::Generator(def_id, args, movability) => {
                 assert_eq!(self.mir_def.to_def_id(), def_id);
-                let resume_ty = substs.as_generator().resume_ty();
-                let output = substs.as_generator().return_ty();
-                let generator_ty = Ty::new_generator(tcx, def_id, substs, movability);
+                let resume_ty = args.as_generator().resume_ty();
+                let output = args.as_generator().return_ty();
+                let generator_ty = Ty::new_generator(tcx, def_id, args, movability);
                 let inputs_and_output =
                     self.infcx.tcx.mk_type_list(&[generator_ty, resume_ty, output]);
                 ty::Binder::dummy(inputs_and_output)
             }
 
             DefiningTy::FnDef(def_id, _) => {
-                let sig = tcx.fn_sig(def_id).subst_identity();
+                let sig = tcx.fn_sig(def_id).instantiate_identity();
                 let sig = indices.fold_to_region_vids(tcx, sig);
                 sig.inputs_and_output()
             }
@@ -701,14 +701,14 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
                 // For a constant body, there are no inputs, and one
                 // "output" (the type of the constant).
                 assert_eq!(self.mir_def.to_def_id(), def_id);
-                let ty = tcx.type_of(self.mir_def).subst_identity();
+                let ty = tcx.type_of(self.mir_def).instantiate_identity();
                 let ty = indices.fold_to_region_vids(tcx, ty);
                 ty::Binder::dummy(tcx.mk_type_list(&[ty]))
             }
 
-            DefiningTy::InlineConst(def_id, substs) => {
+            DefiningTy::InlineConst(def_id, args) => {
                 assert_eq!(self.mir_def.to_def_id(), def_id);
-                let ty = substs.as_inline_const().ty();
+                let ty = args.as_inline_const().ty();
                 ty::Binder::dummy(tcx.mk_type_list(&[ty]))
             }
         }
diff --git a/compiler/rustc_codegen_cranelift/src/abi/mod.rs b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
index 199fa6861cf58..eddb479073c31 100644
--- a/compiler/rustc_codegen_cranelift/src/abi/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/abi/mod.rs
@@ -70,7 +70,7 @@ pub(crate) fn get_function_sig<'tcx>(
     default_call_conv: CallConv,
     inst: Instance<'tcx>,
 ) -> Signature {
-    assert!(!inst.substs.has_infer());
+    assert!(!inst.args.has_infer());
     clif_sig_from_fn_abi(
         tcx,
         default_call_conv,
@@ -377,16 +377,16 @@ pub(crate) fn codegen_terminator_call<'tcx>(
     let ret_place = codegen_place(fx, destination);
 
     // Handle special calls like intrinsics and empty drop glue.
-    let instance = if let ty::FnDef(def_id, substs) = *func.layout().ty.kind() {
+    let instance = if let ty::FnDef(def_id, fn_args) = *func.layout().ty.kind() {
         let instance =
-            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, substs)
+            ty::Instance::expect_resolve(fx.tcx, ty::ParamEnv::reveal_all(), def_id, fn_args)
                 .polymorphize(fx.tcx);
 
         if fx.tcx.symbol_name(instance).name.starts_with("llvm.") {
             crate::intrinsics::codegen_llvm_intrinsic_call(
                 fx,
                 &fx.tcx.symbol_name(instance).name,
-                substs,
+                fn_args,
                 args,
                 ret_place,
                 target,
@@ -611,7 +611,7 @@ pub(crate) fn codegen_drop<'tcx>(
                 // `Instance::resolve_drop_in_place`?
                 let virtual_drop = Instance {
                     def: ty::InstanceDef::Virtual(drop_instance.def_id(), 0),
-                    substs: drop_instance.substs,
+                    args: drop_instance.args,
                 };
                 let fn_abi =
                     RevealAllLayoutCx(fx.tcx).fn_abi_of_instance(virtual_drop, ty::List::empty());
@@ -648,7 +648,7 @@ pub(crate) fn codegen_drop<'tcx>(
 
                 let virtual_drop = Instance {
                     def: ty::InstanceDef::Virtual(drop_instance.def_id(), 0),
-                    substs: drop_instance.substs,
+                    args: drop_instance.args,
                 };
                 let fn_abi =
                     RevealAllLayoutCx(fx.tcx).fn_abi_of_instance(virtual_drop, ty::List::empty());
diff --git a/compiler/rustc_codegen_cranelift/src/base.rs b/compiler/rustc_codegen_cranelift/src/base.rs
index 334b2780b499b..e05f2146f0c30 100644
--- a/compiler/rustc_codegen_cranelift/src/base.rs
+++ b/compiler/rustc_codegen_cranelift/src/base.rs
@@ -28,7 +28,7 @@ pub(crate) fn codegen_fn<'tcx>(
     module: &mut dyn Module,
     instance: Instance<'tcx>,
 ) -> CodegenedFunction {
-    debug_assert!(!instance.substs.has_infer());
+    debug_assert!(!instance.args.has_infer());
 
     let symbol_name = tcx.symbol_name(instance).name.to_string();
     let _timer = tcx.prof.generic_activity_with_arg("codegen fn", &*symbol_name);
@@ -578,13 +578,13 @@ fn codegen_stmt<'tcx>(
                     let from_ty = fx.monomorphize(operand.ty(&fx.mir.local_decls, fx.tcx));
                     let to_layout = fx.layout_of(fx.monomorphize(to_ty));
                     match *from_ty.kind() {
-                        ty::FnDef(def_id, substs) => {
+                        ty::FnDef(def_id, args) => {
                             let func_ref = fx.get_function_ref(
                                 Instance::resolve_for_fn_ptr(
                                     fx.tcx,
                                     ParamEnv::reveal_all(),
                                     def_id,
-                                    substs,
+                                    args,
                                 )
                                 .unwrap()
                                 .polymorphize(fx.tcx),
@@ -668,11 +668,11 @@ fn codegen_stmt<'tcx>(
                 ) => {
                     let operand = codegen_operand(fx, operand);
                     match *operand.layout().ty.kind() {
-                        ty::Closure(def_id, substs) => {
+                        ty::Closure(def_id, args) => {
                             let instance = Instance::resolve_closure(
                                 fx.tcx,
                                 def_id,
-                                substs,
+                                args,
                                 ty::ClosureKind::FnOnce,
                             )
                             .expect("failed to normalize and resolve closure during codegen")
diff --git a/compiler/rustc_codegen_cranelift/src/constant.rs b/compiler/rustc_codegen_cranelift/src/constant.rs
index 427340c333e5a..c31535742957c 100644
--- a/compiler/rustc_codegen_cranelift/src/constant.rs
+++ b/compiler/rustc_codegen_cranelift/src/constant.rs
@@ -57,7 +57,7 @@ pub(crate) fn codegen_tls_ref<'tcx>(
     let tls_ptr = if !def_id.is_local() && fx.tcx.needs_thread_local_shim(def_id) {
         let instance = ty::Instance {
             def: ty::InstanceDef::ThreadLocalShim(def_id),
-            substs: ty::InternalSubsts::empty(),
+            args: ty::GenericArgs::empty(),
         };
         let func_ref = fx.get_function_ref(instance);
         let call = fx.bcx.ins().call(func_ref, &[]);
diff --git a/compiler/rustc_codegen_cranelift/src/global_asm.rs b/compiler/rustc_codegen_cranelift/src/global_asm.rs
index 63a1f6959ddae..baadd7a9e812b 100644
--- a/compiler/rustc_codegen_cranelift/src/global_asm.rs
+++ b/compiler/rustc_codegen_cranelift/src/global_asm.rs
@@ -42,7 +42,7 @@ pub(crate) fn codegen_global_asm_item(tcx: TyCtxt<'_>, global_asm: &mut String,
                         InlineAsmOperand::SymFn { anon_const } => {
                             let ty = tcx.typeck_body(anon_const.body).node_type(anon_const.hir_id);
                             let instance = match ty.kind() {
-                                &ty::FnDef(def_id, substs) => Instance::new(def_id, substs),
+                                &ty::FnDef(def_id, args) => Instance::new(def_id, args),
                                 _ => span_bug!(op_sp, "asm sym is not a function"),
                             };
                             let symbol = tcx.symbol_name(instance);
diff --git a/compiler/rustc_codegen_cranelift/src/inline_asm.rs b/compiler/rustc_codegen_cranelift/src/inline_asm.rs
index 3ba530c040f7f..518e3da07a44d 100644
--- a/compiler/rustc_codegen_cranelift/src/inline_asm.rs
+++ b/compiler/rustc_codegen_cranelift/src/inline_asm.rs
@@ -254,12 +254,12 @@ pub(crate) fn codegen_inline_asm<'tcx>(
             }
             InlineAsmOperand::SymFn { ref value } => {
                 let literal = fx.monomorphize(value.literal);
-                if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
+                if let ty::FnDef(def_id, args) = *literal.ty().kind() {
                     let instance = ty::Instance::resolve_for_fn_ptr(
                         fx.tcx,
                         ty::ParamEnv::reveal_all(),
                         def_id,
-                        substs,
+                        args,
                     )
                     .unwrap();
                     let symbol = fx.tcx.symbol_name(instance);
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm.rs
index f67fdb592700f..63b5402f2b6d9 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm.rs
@@ -3,23 +3,35 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    substs: SubstsRef<'tcx>,
+    generic_args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
 ) {
     if intrinsic.starts_with("llvm.aarch64") {
         return llvm_aarch64::codegen_aarch64_llvm_intrinsic_call(
-            fx, intrinsic, substs, args, ret, target,
+            fx,
+            intrinsic,
+            generic_args,
+            args,
+            ret,
+            target,
         );
     }
     if intrinsic.starts_with("llvm.x86") {
-        return llvm_x86::codegen_x86_llvm_intrinsic_call(fx, intrinsic, substs, args, ret, target);
+        return llvm_x86::codegen_x86_llvm_intrinsic_call(
+            fx,
+            intrinsic,
+            generic_args,
+            args,
+            ret,
+            target,
+        );
     }
 
     match intrinsic {
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_aarch64.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_aarch64.rs
index 33b2f4702a7a3..c20a9915930eb 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_aarch64.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_aarch64.rs
@@ -3,12 +3,12 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
index 24ad0083a2233..18162fb5ab25b 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs
@@ -3,12 +3,12 @@
 use crate::intrinsics::*;
 use crate::prelude::*;
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 
 pub(crate) fn codegen_x86_llvm_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: &str,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: Option<BasicBlock>,
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
index 5862f18299e90..da8ab361331e7 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs
@@ -24,7 +24,7 @@ pub(crate) use llvm::codegen_llvm_intrinsic_call;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{HasParamEnv, ValidityRequirement};
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_span::symbol::{kw, sym, Symbol};
 
 use crate::prelude::*;
@@ -213,13 +213,13 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
     source_info: mir::SourceInfo,
 ) {
     let intrinsic = fx.tcx.item_name(instance.def_id());
-    let substs = instance.substs;
+    let instance_args = instance.args;
 
     if intrinsic.as_str().starts_with("simd_") {
         self::simd::codegen_simd_intrinsic_call(
             fx,
             intrinsic,
-            substs,
+            instance_args,
             args,
             destination,
             target.expect("target for simd intrinsic"),
@@ -233,7 +233,7 @@ pub(crate) fn codegen_intrinsic_call<'tcx>(
             fx,
             instance,
             intrinsic,
-            substs,
+            instance_args,
             args,
             destination,
             target,
@@ -365,7 +365,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     instance: Instance<'tcx>,
     intrinsic: Symbol,
-    substs: SubstsRef<'tcx>,
+    generic_args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     destination: Option<BasicBlock>,
@@ -394,7 +394,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let dst = dst.load_scalar(fx);
             let count = count.load_scalar(fx);
 
-            let elem_ty = substs.type_at(0);
+            let elem_ty = generic_args.type_at(0);
             let elem_size: u64 = fx.layout_of(elem_ty).size.bytes();
             assert_eq!(args.len(), 3);
             let byte_amount =
@@ -410,7 +410,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let src = src.load_scalar(fx);
             let count = count.load_scalar(fx);
 
-            let elem_ty = substs.type_at(0);
+            let elem_ty = generic_args.type_at(0);
             let elem_size: u64 = fx.layout_of(elem_ty).size.bytes();
             assert_eq!(args.len(), 3);
             let byte_amount =
@@ -428,7 +428,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::size_of_val => {
             intrinsic_args!(fx, args => (ptr); intrinsic);
 
-            let layout = fx.layout_of(substs.type_at(0));
+            let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
             let size = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
@@ -443,7 +443,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::min_align_of_val => {
             intrinsic_args!(fx, args => (ptr); intrinsic);
 
-            let layout = fx.layout_of(substs.type_at(0));
+            let layout = fx.layout_of(generic_args.type_at(0));
             // Note: Can't use is_unsized here as truly unsized types need to take the fixed size
             // branch
             let align = if let Abi::ScalarPair(_, _) = ptr.layout().abi {
@@ -602,7 +602,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
         sym::assert_inhabited | sym::assert_zero_valid | sym::assert_mem_uninitialized_valid => {
             intrinsic_args!(fx, args => (); intrinsic);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
 
             let requirement = ValidityRequirement::from_intrinsic(intrinsic);
 
@@ -674,7 +674,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr, base); intrinsic);
             let ptr = ptr.load_scalar(fx);
             let base = base.load_scalar(fx);
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
 
             let pointee_size: u64 = fx.layout_of(ty).size.bytes();
             let diff_bytes = fx.bcx.ins().isub(ptr, base);
@@ -720,7 +720,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
             match ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
                     // FIXME implement 128bit atomics
@@ -751,7 +751,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             intrinsic_args!(fx, args => (ptr, val); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
-            let ty = substs.type_at(0);
+            let ty = generic_args.type_at(0);
             match ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
                     // FIXME implement 128bit atomics
@@ -1128,7 +1128,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let lhs_ref = lhs_ref.load_scalar(fx);
             let rhs_ref = rhs_ref.load_scalar(fx);
 
-            let size = fx.layout_of(substs.type_at(0)).layout.size();
+            let size = fx.layout_of(generic_args.type_at(0)).layout.size();
             // FIXME add and use emit_small_memcmp
             let is_eq_value = if size == Size::ZERO {
                 // No bytes means they're trivially equal
diff --git a/compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs b/compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs
index 6741362e8b6c6..d1c29f24ab96d 100644
--- a/compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs
+++ b/compiler/rustc_codegen_cranelift/src/intrinsics/simd.rs
@@ -1,6 +1,6 @@
 //! Codegen `extern "platform-intrinsic"` intrinsics.
 
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_span::Symbol;
 use rustc_target::abi::Endian;
 
@@ -21,7 +21,7 @@ fn report_simd_type_validation_error(
 pub(super) fn codegen_simd_intrinsic_call<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     intrinsic: Symbol,
-    _substs: SubstsRef<'tcx>,
+    _args: GenericArgsRef<'tcx>,
     args: &[mir::Operand<'tcx>],
     ret: CPlace<'tcx>,
     target: BasicBlock,
diff --git a/compiler/rustc_codegen_cranelift/src/main_shim.rs b/compiler/rustc_codegen_cranelift/src/main_shim.rs
index 20ba73f38523a..b5efe44d8b3c8 100644
--- a/compiler/rustc_codegen_cranelift/src/main_shim.rs
+++ b/compiler/rustc_codegen_cranelift/src/main_shim.rs
@@ -1,6 +1,6 @@
 use rustc_hir::LangItem;
-use rustc_middle::ty::subst::GenericArg;
 use rustc_middle::ty::AssocKind;
+use rustc_middle::ty::GenericArg;
 use rustc_session::config::{sigpipe, EntryFnType};
 use rustc_span::symbol::Ident;
 
@@ -119,7 +119,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     tcx,
                     ParamEnv::reveal_all(),
                     report.def_id,
-                    tcx.mk_substs(&[GenericArg::from(main_ret_ty)]),
+                    tcx.mk_args(&[GenericArg::from(main_ret_ty)]),
                 )
                 .unwrap()
                 .unwrap()
@@ -146,7 +146,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                     tcx,
                     ParamEnv::reveal_all(),
                     start_def_id,
-                    tcx.mk_substs(&[main_ret_ty.into()]),
+                    tcx.mk_args(&[main_ret_ty.into()]),
                 )
                 .unwrap()
                 .unwrap()
diff --git a/compiler/rustc_codegen_cranelift/src/pretty_clif.rs b/compiler/rustc_codegen_cranelift/src/pretty_clif.rs
index 5a4f9e804453f..0ead50c34eac4 100644
--- a/compiler/rustc_codegen_cranelift/src/pretty_clif.rs
+++ b/compiler/rustc_codegen_cranelift/src/pretty_clif.rs
@@ -9,7 +9,7 @@
 //!
 //! function u0:22(i64) -> i8, i8 system_v {
 //! ; symbol _ZN97_$LT$example..IsNotEmpty$u20$as$u20$mini_core..FnOnce$LT$$LP$$RF$$RF$$u5b$u16$u5d$$C$$RP$$GT$$GT$9call_once17hd517c453d67c0915E
-//! ; instance Instance { def: Item(WithOptConstParam { did: DefId(0:42 ~ example[4e51]::{impl#0}::call_once), const_param_did: None }), substs: [ReErased, ReErased] }
+//! ; instance Instance { def: Item(WithOptConstParam { did: DefId(0:42 ~ example[4e51]::{impl#0}::call_once), const_param_did: None }), args: [ReErased, ReErased] }
 //! ; abi FnAbi { args: [ArgAbi { layout: TyAndLayout { ty: IsNotEmpty, layout: Layout { size: Size(0 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: Aggregate { sized: true }, fields: Arbitrary { offsets: [], memory_index: [] }, largest_niche: None, variants: Single { index: 0 } } }, mode: Ignore }, ArgAbi { layout: TyAndLayout { ty: &&[u16], layout: Layout { size: Size(8 bytes), align: AbiAndPrefAlign { abi: Align(8 bytes), pref: Align(8 bytes) }, abi: Scalar(Initialized { value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), fields: Primitive, largest_niche: Some(Niche { offset: Size(0 bytes), value: Pointer(AddressSpace(0)), valid_range: 1..=18446744073709551615 }), variants: Single { index: 0 } } }, mode: Direct(ArgAttributes { regular: NonNull | NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: Some(Align(8 bytes)) }) }], ret: ArgAbi { layout: TyAndLayout { ty: (u8, u8), layout: Layout { size: Size(2 bytes), align: AbiAndPrefAlign { abi: Align(1 bytes), pref: Align(8 bytes) }, abi: ScalarPair(Initialized { value: Int(I8, false), valid_range: 0..=255 }, Initialized { value: Int(I8, false), valid_range: 0..=255 }), fields: Arbitrary { offsets: [Size(0 bytes), Size(1 bytes)], memory_index: [0, 1] }, largest_niche: None, variants: Single { index: 0 } } }, mode: Pair(ArgAttributes { regular: NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: None }, ArgAttributes { regular: NoUndef, arg_ext: None, pointee_size: Size(0 bytes), pointee_align: None }) }, c_variadic: false, fixed_count: 1, conv: Rust, can_unwind: false }
 //!
 //! ; kind  loc.idx   param    pass mode                            ty
@@ -25,7 +25,7 @@
 //!
 //!     ss0 = explicit_slot 16
 //!     sig0 = (i64, i64) -> i8, i8 system_v
-//!     fn0 = colocated u0:23 sig0 ; Instance { def: Item(WithOptConstParam { did: DefId(0:46 ~ example[4e51]::{impl#1}::call_mut), const_param_did: None }), substs: [ReErased, ReErased] }
+//!     fn0 = colocated u0:23 sig0 ; Instance { def: Item(WithOptConstParam { did: DefId(0:46 ~ example[4e51]::{impl#1}::call_mut), const_param_did: None }), args: [ReErased, ReErased] }
 //!
 //! block0(v0: i64):
 //!     nop
@@ -261,7 +261,7 @@ pub(crate) fn write_clif_file(
 
 impl fmt::Debug for FunctionCx<'_, '_, '_> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        writeln!(f, "{:?}", self.instance.substs)?;
+        writeln!(f, "{:?}", self.instance.args)?;
         writeln!(f, "{:?}", self.local_map)?;
 
         let mut clif = String::new();
diff --git a/compiler/rustc_codegen_cranelift/src/value_and_place.rs b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
index 133c989b68643..ec0b61a7ce50b 100644
--- a/compiler/rustc_codegen_cranelift/src/value_and_place.rs
+++ b/compiler/rustc_codegen_cranelift/src/value_and_place.rs
@@ -850,11 +850,11 @@ pub(crate) fn assert_assignable<'tcx>(
                 }
             }
         }
-        (&ty::Adt(adt_def_a, substs_a), &ty::Adt(adt_def_b, substs_b))
+        (&ty::Adt(adt_def_a, args_a), &ty::Adt(adt_def_b, args_b))
             if adt_def_a.did() == adt_def_b.did() =>
         {
-            let mut types_a = substs_a.types();
-            let mut types_b = substs_b.types();
+            let mut types_a = args_a.types();
+            let mut types_b = args_b.types();
             loop {
                 match (types_a.next(), types_b.next()) {
                     (Some(a), Some(b)) => assert_assignable(fx, a, b, limit - 1),
@@ -864,11 +864,11 @@ pub(crate) fn assert_assignable<'tcx>(
             }
         }
         (ty::Array(a, _), ty::Array(b, _)) => assert_assignable(fx, *a, *b, limit - 1),
-        (&ty::Closure(def_id_a, substs_a), &ty::Closure(def_id_b, substs_b))
+        (&ty::Closure(def_id_a, args_a), &ty::Closure(def_id_b, args_b))
             if def_id_a == def_id_b =>
         {
-            let mut types_a = substs_a.types();
-            let mut types_b = substs_b.types();
+            let mut types_a = args_a.types();
+            let mut types_b = args_b.types();
             loop {
                 match (types_a.next(), types_b.next()) {
                     (Some(a), Some(b)) => assert_assignable(fx, a, b, limit - 1),
diff --git a/compiler/rustc_codegen_gcc/src/callee.rs b/compiler/rustc_codegen_gcc/src/callee.rs
index 433b2585f82a8..a96bd66ba79ef 100644
--- a/compiler/rustc_codegen_gcc/src/callee.rs
+++ b/compiler/rustc_codegen_gcc/src/callee.rs
@@ -17,8 +17,8 @@ use crate::context::CodegenCx;
 pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>) -> Function<'gcc> {
     let tcx = cx.tcx();
 
-    assert!(!instance.substs.has_infer());
-    assert!(!instance.substs.has_escaping_bound_vars());
+    assert!(!instance.args.has_infer());
+    assert!(!instance.args.has_escaping_bound_vars());
 
     let sym = tcx.symbol_name(instance).name;
 
@@ -100,7 +100,7 @@ pub fn get_fn<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, instance: Instance<'tcx>)
             // whether we are sharing generics or not. The important thing here is
             // that the visibility we apply to the declaration is the same one that
             // has been applied to the definition (wherever that definition may be).
-            let is_generic = instance.substs.non_erasable_generics().next().is_some();
+            let is_generic = instance.args.non_erasable_generics().next().is_some();
 
             if is_generic {
                 // This is a monomorphization. Its expected visibility depends
diff --git a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
index 0b208be4e6293..fe604be33b677 100644
--- a/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
+++ b/compiler/rustc_codegen_gcc/src/intrinsic/mod.rs
@@ -92,8 +92,8 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
         let tcx = self.tcx;
         let callee_ty = instance.ty(tcx, ty::ParamEnv::reveal_all());
 
-        let (def_id, substs) = match *callee_ty.kind() {
-            ty::FnDef(def_id, substs) => (def_id, substs),
+        let (def_id, fn_args) = match *callee_ty.kind() {
+            ty::FnDef(def_id, fn_args) => (def_id, fn_args),
             _ => bug!("expected fn item type, found {}", callee_ty),
         };
 
@@ -142,7 +142,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
                 }
 
                 sym::volatile_load | sym::unaligned_volatile_load => {
-                    let tp_ty = substs.type_at(0);
+                    let tp_ty = fn_args.type_at(0);
                     let mut ptr = args[0].immediate();
                     if let PassMode::Cast(ty, _) = &fn_abi.ret.mode {
                         ptr = self.pointercast(ptr, self.type_ptr_to(ty.gcc_type(self)));
@@ -264,7 +264,7 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'a, 'gcc, 'tcx> {
 
                 sym::raw_eq => {
                     use rustc_target::abi::Abi::*;
-                    let tp_ty = substs.type_at(0);
+                    let tp_ty = fn_args.type_at(0);
                     let layout = self.layout_of(tp_ty).layout;
                     let _use_integer_compare = match layout.abi() {
                         Scalar(_) | ScalarPair(_, _) => true,
diff --git a/compiler/rustc_codegen_gcc/src/mono_item.rs b/compiler/rustc_codegen_gcc/src/mono_item.rs
index 342b830cedb12..3322d56513bbe 100644
--- a/compiler/rustc_codegen_gcc/src/mono_item.rs
+++ b/compiler/rustc_codegen_gcc/src/mono_item.rs
@@ -31,7 +31,7 @@ impl<'gcc, 'tcx> PreDefineMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
 
     #[cfg_attr(not(feature="master"), allow(unused_variables))]
     fn predefine_fn(&self, instance: Instance<'tcx>, linkage: Linkage, visibility: Visibility, symbol_name: &str) {
-        assert!(!instance.substs.has_infer());
+        assert!(!instance.args.has_infer());
 
         let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
         self.linkage.set(base::linkage_to_gcc(linkage));
diff --git a/compiler/rustc_codegen_gcc/src/type_of.rs b/compiler/rustc_codegen_gcc/src/type_of.rs
index e0823888f6752..84d5783851273 100644
--- a/compiler/rustc_codegen_gcc/src/type_of.rs
+++ b/compiler/rustc_codegen_gcc/src/type_of.rs
@@ -101,7 +101,7 @@ fn uncached_gcc_type<'gcc, 'tcx>(cx: &CodegenCx<'gcc, 'tcx>, layout: TyAndLayout
             if let (&ty::Generator(_, _, _), &Variants::Single { index }) =
                 (layout.ty.kind(), &layout.variants)
             {
-                write!(&mut name, "::{}", ty::GeneratorSubsts::variant_name(index)).unwrap();
+                write!(&mut name, "::{}", ty::GeneratorArgs::variant_name(index)).unwrap();
             }
             Some(name)
         }
@@ -282,7 +282,7 @@ impl<'tcx> LayoutGccExt<'tcx> for TyAndLayout<'tcx> {
             }
             // only wide pointer boxes are handled as pointers
             // thin pointer boxes with scalar allocators are handled by the general logic below
-            ty::Adt(def, substs) if def.is_box() && cx.layout_of(substs.type_at(1)).is_zst() => {
+            ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
                 let ptr_ty = Ty::new_mut_ptr(cx.tcx,self.ty.boxed_ty());
                 return cx.layout_of(ptr_ty).scalar_pair_element_gcc_type(cx, index, immediate);
             }
diff --git a/compiler/rustc_codegen_llvm/src/callee.rs b/compiler/rustc_codegen_llvm/src/callee.rs
index 4b9ca2e7d19c3..5d3e245f45f08 100644
--- a/compiler/rustc_codegen_llvm/src/callee.rs
+++ b/compiler/rustc_codegen_llvm/src/callee.rs
@@ -27,8 +27,8 @@ pub fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) ->
 
     debug!("get_fn(instance={:?})", instance);
 
-    assert!(!instance.substs.has_infer());
-    assert!(!instance.substs.has_escaping_bound_vars());
+    assert!(!instance.args.has_infer());
+    assert!(!instance.args.has_escaping_bound_vars());
 
     if let Some(&llfn) = cx.instances.borrow().get(&instance) {
         return llfn;
@@ -129,7 +129,7 @@ pub fn get_fn<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, instance: Instance<'tcx>) ->
         unsafe {
             llvm::LLVMRustSetLinkage(llfn, llvm::Linkage::ExternalLinkage);
 
-            let is_generic = instance.substs.non_erasable_generics().next().is_some();
+            let is_generic = instance.args.non_erasable_generics().next().is_some();
 
             if is_generic {
                 // This is a monomorphization. Its expected visibility depends
diff --git a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
index 42fdbd786185e..56a5c9e9061af 100644
--- a/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/coverageinfo/mod.rs
@@ -22,7 +22,7 @@ use rustc_middle::mir::coverage::{
 use rustc_middle::mir::Coverage;
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt};
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::Ty;
 
@@ -250,7 +250,7 @@ fn declare_unused_fn<'tcx>(cx: &CodegenCx<'_, 'tcx>, def_id: DefId) -> Instance<
 
     let instance = Instance::new(
         def_id,
-        InternalSubsts::for_item(tcx, def_id, |param, _| {
+        GenericArgs::for_item(tcx, def_id, |param, _| {
             if let ty::GenericParamDefKind::Lifetime = param.kind {
                 tcx.lifetimes.re_erased.into()
             } else {
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
index 65cbd5edc5927..d174a3593b999 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/create_scope_map.rs
@@ -91,7 +91,7 @@ fn make_mir_scope<'ll, 'tcx>(
             // FIXME(eddyb) this would be `self.monomorphize(&callee)`
             // if this is moved to `rustc_codegen_ssa::mir::debuginfo`.
             let callee = cx.tcx.subst_and_normalize_erasing_regions(
-                instance.substs,
+                instance.args,
                 ty::ParamEnv::reveal_all(),
                 ty::EarlyBinder::bind(callee),
             );
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
index a56faf735f162..c6996f2e16acf 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata.rs
@@ -449,7 +449,7 @@ pub fn type_di_node<'ll, 'tcx>(cx: &CodegenCx<'ll, 'tcx>, t: Ty<'tcx>) -> &'ll D
         }
         // Box<T, A> may have a non-ZST allocator A. In that case, we
         // cannot treat Box<T, A> as just an owned alias of `*mut T`.
-        ty::Adt(def, substs) if def.is_box() && cx.layout_of(substs.type_at(1)).is_zst() => {
+        ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
             build_pointer_or_reference_di_node(cx, t, t.boxed_ty(), unique_type_id)
         }
         ty::FnDef(..) | ty::FnPtr(_) => build_subroutine_type_di_node(cx, unique_type_id),
@@ -1007,12 +1007,12 @@ fn build_upvar_field_di_nodes<'ll, 'tcx>(
     closure_or_generator_di_node: &'ll DIType,
 ) -> SmallVec<&'ll DIType> {
     let (&def_id, up_var_tys) = match closure_or_generator_ty.kind() {
-        ty::Generator(def_id, substs, _) => {
-            let upvar_tys: SmallVec<_> = substs.as_generator().prefix_tys().collect();
+        ty::Generator(def_id, args, _) => {
+            let upvar_tys: SmallVec<_> = args.as_generator().prefix_tys().collect();
             (def_id, upvar_tys)
         }
-        ty::Closure(def_id, substs) => {
-            let upvar_tys: SmallVec<_> = substs.as_closure().upvar_tys().collect();
+        ty::Closure(def_id, args) => {
+            let upvar_tys: SmallVec<_> = args.as_closure().upvar_tys().collect();
             (def_id, upvar_tys)
         }
         _ => {
@@ -1102,7 +1102,7 @@ fn build_closure_env_di_node<'ll, 'tcx>(
     unique_type_id: UniqueTypeId<'tcx>,
 ) -> DINodeCreationResult<'ll> {
     let closure_env_type = unique_type_id.expect_ty();
-    let &ty::Closure(def_id, _substs) = closure_env_type.kind() else {
+    let &ty::Closure(def_id, _args) = closure_env_type.kind() else {
         bug!("build_closure_env_di_node() called with non-closure-type: {:?}", closure_env_type)
     };
     let containing_scope = get_namespace_for_item(cx, def_id);
@@ -1180,11 +1180,11 @@ fn build_generic_type_param_di_nodes<'ll, 'tcx>(
     cx: &CodegenCx<'ll, 'tcx>,
     ty: Ty<'tcx>,
 ) -> SmallVec<&'ll DIType> {
-    if let ty::Adt(def, substs) = *ty.kind() {
-        if substs.types().next().is_some() {
+    if let ty::Adt(def, args) = *ty.kind() {
+        if args.types().next().is_some() {
             let generics = cx.tcx.generics_of(def.did());
             let names = get_parameter_names(cx, generics);
-            let template_params: SmallVec<_> = iter::zip(substs, names)
+            let template_params: SmallVec<_> = iter::zip(args, names)
                 .filter_map(|(kind, name)| {
                     kind.as_type().map(|ty| {
                         let actual_type =
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
index 45698407e83b3..88040557a9b33 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs
@@ -12,7 +12,7 @@ use rustc_middle::{
     ty::{
         self,
         layout::{LayoutOf, TyAndLayout},
-        AdtDef, GeneratorSubsts, Ty,
+        AdtDef, GeneratorArgs, Ty,
     },
 };
 use rustc_target::abi::{Align, Endian, Size, TagEncoding, VariantIdx, Variants};
@@ -673,15 +673,15 @@ fn build_union_fields_for_direct_tag_generator<'ll, 'tcx>(
         bug!("This function only supports layouts with directly encoded tags.")
     };
 
-    let (generator_def_id, generator_substs) = match generator_type_and_layout.ty.kind() {
-        &ty::Generator(def_id, substs, _) => (def_id, substs.as_generator()),
+    let (generator_def_id, generator_args) = match generator_type_and_layout.ty.kind() {
+        &ty::Generator(def_id, args, _) => (def_id, args.as_generator()),
         _ => unreachable!(),
     };
 
     let generator_layout = cx.tcx.optimized_mir(generator_def_id).generator_layout().unwrap();
 
     let common_upvar_names = cx.tcx.closure_saved_names_of_captured_variables(generator_def_id);
-    let variant_range = generator_substs.variant_range(generator_def_id, cx.tcx);
+    let variant_range = generator_args.variant_range(generator_def_id, cx.tcx);
     let variant_count = (variant_range.start.as_u32()..variant_range.end.as_u32()).len();
 
     let tag_base_type = tag_base_type(cx, generator_type_and_layout);
@@ -691,11 +691,11 @@ fn build_union_fields_for_direct_tag_generator<'ll, 'tcx>(
         generator_type_di_node,
         variant_range
             .clone()
-            .map(|variant_index| (variant_index, GeneratorSubsts::variant_name(variant_index))),
+            .map(|variant_index| (variant_index, GeneratorArgs::variant_name(variant_index))),
     );
 
     let discriminants: IndexVec<VariantIdx, DiscrResult> = {
-        let discriminants_iter = generator_substs.discriminants(generator_def_id, cx.tcx);
+        let discriminants_iter = generator_args.discriminants(generator_def_id, cx.tcx);
         let mut discriminants: IndexVec<VariantIdx, DiscrResult> =
             IndexVec::with_capacity(variant_count);
         for (variant_index, discr) in discriminants_iter {
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
index 008f21ae3f5fd..b4beb80ca8b5b 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/mod.rs
@@ -10,7 +10,7 @@ use rustc_middle::{
     ty::{
         self,
         layout::{IntegerExt, LayoutOf, PrimitiveExt, TyAndLayout},
-        AdtDef, GeneratorSubsts, Ty, VariantDef,
+        AdtDef, GeneratorArgs, Ty, VariantDef,
     },
 };
 use rustc_span::Symbol;
@@ -325,7 +325,7 @@ pub fn build_generator_variant_struct_type_di_node<'ll, 'tcx>(
     generator_layout: &GeneratorLayout<'tcx>,
     common_upvar_names: &IndexSlice<FieldIdx, Symbol>,
 ) -> &'ll DIType {
-    let variant_name = GeneratorSubsts::variant_name(variant_index);
+    let variant_name = GeneratorArgs::variant_name(variant_index);
     let unique_type_id = UniqueTypeId::for_enum_variant_struct_type(
         cx.tcx,
         generator_type_and_layout.ty,
@@ -334,8 +334,8 @@ pub fn build_generator_variant_struct_type_di_node<'ll, 'tcx>(
 
     let variant_layout = generator_type_and_layout.for_variant(cx, variant_index);
 
-    let generator_substs = match generator_type_and_layout.ty.kind() {
-        ty::Generator(_, substs, _) => substs.as_generator(),
+    let generator_args = match generator_type_and_layout.ty.kind() {
+        ty::Generator(_, args, _) => args.as_generator(),
         _ => unreachable!(),
     };
 
@@ -377,7 +377,7 @@ pub fn build_generator_variant_struct_type_di_node<'ll, 'tcx>(
                 .collect();
 
             // Fields that are common to all states
-            let common_fields: SmallVec<_> = generator_substs
+            let common_fields: SmallVec<_> = generator_args
                 .prefix_tys()
                 .zip(common_upvar_names)
                 .enumerate()
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
index 3799b69ee10ea..feac40d8c306c 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs
@@ -175,7 +175,7 @@ pub(super) fn build_generator_di_node<'ll, 'tcx>(
                 .indices()
                 .map(|variant_index| {
                     // FIXME: This is problematic because just a number is not a valid identifier.
-                    //        GeneratorSubsts::variant_name(variant_index), would be consistent
+                    //        GeneratorArgs::variant_name(variant_index), would be consistent
                     //        with enums?
                     let variant_name = format!("{}", variant_index.as_usize()).into();
 
diff --git a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
index b924c771af706..40714a0afe91c 100644
--- a/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
+++ b/compiler/rustc_codegen_llvm/src/debuginfo/mod.rs
@@ -27,7 +27,7 @@ use rustc_hir::def_id::{DefId, DefIdMap};
 use rustc_index::IndexVec;
 use rustc_middle::mir;
 use rustc_middle::ty::layout::LayoutOf;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Instance, ParamEnv, Ty, TypeVisitableExt};
 use rustc_session::config::{self, DebugInfo};
 use rustc_session::Session;
@@ -338,19 +338,19 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         // Find the enclosing function, in case this is a closure.
         let enclosing_fn_def_id = tcx.typeck_root_def_id(def_id);
 
-        // We look up the generics of the enclosing function and truncate the substs
+        // We look up the generics of the enclosing function and truncate the args
         // to their length in order to cut off extra stuff that might be in there for
         // closures or generators.
         let generics = tcx.generics_of(enclosing_fn_def_id);
-        let substs = instance.substs.truncate_to(tcx, generics);
+        let args = instance.args.truncate_to(tcx, generics);
 
         type_names::push_generic_params(
             tcx,
-            tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substs),
+            tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), args),
             &mut name,
         );
 
-        let template_parameters = get_template_parameters(self, generics, substs);
+        let template_parameters = get_template_parameters(self, generics, args);
 
         let linkage_name = &mangled_name_of_instance(self, instance).name;
         // Omit the linkage_name if it is the same as subprogram name.
@@ -471,16 +471,16 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         fn get_template_parameters<'ll, 'tcx>(
             cx: &CodegenCx<'ll, 'tcx>,
             generics: &ty::Generics,
-            substs: SubstsRef<'tcx>,
+            args: GenericArgsRef<'tcx>,
         ) -> &'ll DIArray {
-            if substs.types().next().is_none() {
+            if args.types().next().is_none() {
                 return create_DIArray(DIB(cx), &[]);
             }
 
             // Again, only create type information if full debuginfo is enabled
             let template_params: Vec<_> = if cx.sess().opts.debuginfo == DebugInfo::Full {
                 let names = get_parameter_names(cx, generics);
-                iter::zip(substs, names)
+                iter::zip(args, names)
                     .filter_map(|(kind, name)| {
                         kind.as_type().map(|ty| {
                             let actual_type =
@@ -527,7 +527,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                 // If the method does *not* belong to a trait, proceed
                 if cx.tcx.trait_id_of_impl(impl_def_id).is_none() {
                     let impl_self_ty = cx.tcx.subst_and_normalize_erasing_regions(
-                        instance.substs,
+                        instance.args,
                         ty::ParamEnv::reveal_all(),
                         cx.tcx.type_of(impl_def_id),
                     );
diff --git a/compiler/rustc_codegen_llvm/src/intrinsic.rs b/compiler/rustc_codegen_llvm/src/intrinsic.rs
index a254c86c291c6..6df1b708ccd45 100644
--- a/compiler/rustc_codegen_llvm/src/intrinsic.rs
+++ b/compiler/rustc_codegen_llvm/src/intrinsic.rs
@@ -90,7 +90,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         let tcx = self.tcx;
         let callee_ty = instance.ty(tcx, ty::ParamEnv::reveal_all());
 
-        let ty::FnDef(def_id, substs) = *callee_ty.kind() else {
+        let ty::FnDef(def_id, fn_args) = *callee_ty.kind() else {
             bug!("expected fn item type, found {}", callee_ty);
         };
 
@@ -163,7 +163,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             }
 
             sym::volatile_load | sym::unaligned_volatile_load => {
-                let tp_ty = substs.type_at(0);
+                let tp_ty = fn_args.type_at(0);
                 let ptr = args[0].immediate();
                 let load = if let PassMode::Cast(ty, _) = &fn_abi.ret.mode {
                     let llty = ty.llvm_type(self);
@@ -298,7 +298,7 @@ impl<'ll, 'tcx> IntrinsicCallMethods<'tcx> for Builder<'_, 'll, 'tcx> {
 
             sym::raw_eq => {
                 use abi::Abi::*;
-                let tp_ty = substs.type_at(0);
+                let tp_ty = fn_args.type_at(0);
                 let layout = self.layout_of(tp_ty).layout;
                 let use_integer_compare = match layout.abi() {
                     Scalar(_) | ScalarPair(_, _) => true,
diff --git a/compiler/rustc_codegen_llvm/src/mono_item.rs b/compiler/rustc_codegen_llvm/src/mono_item.rs
index c24854b27a02e..e8cda626f549b 100644
--- a/compiler/rustc_codegen_llvm/src/mono_item.rs
+++ b/compiler/rustc_codegen_llvm/src/mono_item.rs
@@ -48,7 +48,7 @@ impl<'tcx> PreDefineMethods<'tcx> for CodegenCx<'_, 'tcx> {
         visibility: Visibility,
         symbol_name: &str,
     ) {
-        assert!(!instance.substs.has_infer());
+        assert!(!instance.args.has_infer());
 
         let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty());
         let lldecl = self.declare_fn(symbol_name, fn_abi, Some(instance));
diff --git a/compiler/rustc_codegen_llvm/src/type_of.rs b/compiler/rustc_codegen_llvm/src/type_of.rs
index 58e97be34f280..2dbd467cc84c3 100644
--- a/compiler/rustc_codegen_llvm/src/type_of.rs
+++ b/compiler/rustc_codegen_llvm/src/type_of.rs
@@ -57,7 +57,7 @@ fn uncached_llvm_type<'a, 'tcx>(
             if let (&ty::Generator(_, _, _), &Variants::Single { index }) =
                 (layout.ty.kind(), &layout.variants)
             {
-                write!(&mut name, "::{}", ty::GeneratorSubsts::variant_name(index)).unwrap();
+                write!(&mut name, "::{}", ty::GeneratorArgs::variant_name(index)).unwrap();
             }
             Some(name)
         }
@@ -336,7 +336,7 @@ impl<'tcx> LayoutLlvmExt<'tcx> for TyAndLayout<'tcx> {
             }
             // only wide pointer boxes are handled as pointers
             // thin pointer boxes with scalar allocators are handled by the general logic below
-            ty::Adt(def, substs) if def.is_box() && cx.layout_of(substs.type_at(1)).is_zst() => {
+            ty::Adt(def, args) if def.is_box() && cx.layout_of(args.type_at(1)).is_zst() => {
                 let ptr_ty = Ty::new_mut_ptr(cx.tcx, self.ty.boxed_ty());
                 return cx.layout_of(ptr_ty).scalar_pair_element_llvm_type(cx, index, immediate);
             }
diff --git a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
index a8b6030ac85c3..406048bfe0598 100644
--- a/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
+++ b/compiler/rustc_codegen_ssa/src/back/symbol_export.rs
@@ -12,9 +12,9 @@ use rustc_middle::middle::exported_symbols::{
 };
 use rustc_middle::query::LocalCrate;
 use rustc_middle::query::{ExternProviders, Providers};
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::Instance;
 use rustc_middle::ty::{self, SymbolName, TyCtxt};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
 use rustc_session::config::{CrateType, OomStrategy};
 use rustc_target::spec::SanitizerSet;
 
@@ -342,9 +342,9 @@ fn exported_symbols_provider_local(
             }
 
             match *mono_item {
-                MonoItem::Fn(Instance { def: InstanceDef::Item(def), substs }) => {
-                    if substs.non_erasable_generics().next().is_some() {
-                        let symbol = ExportedSymbol::Generic(def, substs);
+                MonoItem::Fn(Instance { def: InstanceDef::Item(def), args }) => {
+                    if args.non_erasable_generics().next().is_some() {
+                        let symbol = ExportedSymbol::Generic(def, args);
                         symbols.push((
                             symbol,
                             SymbolExportInfo {
@@ -355,10 +355,10 @@ fn exported_symbols_provider_local(
                         ));
                     }
                 }
-                MonoItem::Fn(Instance { def: InstanceDef::DropGlue(_, Some(ty)), substs }) => {
+                MonoItem::Fn(Instance { def: InstanceDef::DropGlue(_, Some(ty)), args }) => {
                     // A little sanity-check
                     debug_assert_eq!(
-                        substs.non_erasable_generics().next(),
+                        args.non_erasable_generics().next(),
                         Some(GenericArgKind::Type(ty))
                     );
                     symbols.push((
@@ -386,7 +386,7 @@ fn exported_symbols_provider_local(
 fn upstream_monomorphizations_provider(
     tcx: TyCtxt<'_>,
     (): (),
-) -> DefIdMap<FxHashMap<SubstsRef<'_>, CrateNum>> {
+) -> DefIdMap<FxHashMap<GenericArgsRef<'_>, CrateNum>> {
     let cnums = tcx.crates(());
 
     let mut instances: DefIdMap<FxHashMap<_, _>> = Default::default();
@@ -395,11 +395,11 @@ fn upstream_monomorphizations_provider(
 
     for &cnum in cnums.iter() {
         for (exported_symbol, _) in tcx.exported_symbols(cnum).iter() {
-            let (def_id, substs) = match *exported_symbol {
-                ExportedSymbol::Generic(def_id, substs) => (def_id, substs),
+            let (def_id, args) = match *exported_symbol {
+                ExportedSymbol::Generic(def_id, args) => (def_id, args),
                 ExportedSymbol::DropGlue(ty) => {
                     if let Some(drop_in_place_fn_def_id) = drop_in_place_fn_def_id {
-                        (drop_in_place_fn_def_id, tcx.mk_substs(&[ty.into()]))
+                        (drop_in_place_fn_def_id, tcx.mk_args(&[ty.into()]))
                     } else {
                         // `drop_in_place` in place does not exist, don't try
                         // to use it.
@@ -414,9 +414,9 @@ fn upstream_monomorphizations_provider(
                 }
             };
 
-            let substs_map = instances.entry(def_id).or_default();
+            let args_map = instances.entry(def_id).or_default();
 
-            match substs_map.entry(substs) {
+            match args_map.entry(args) {
                 Occupied(mut e) => {
                     // If there are multiple monomorphizations available,
                     // we select one deterministically.
@@ -438,17 +438,17 @@ fn upstream_monomorphizations_provider(
 fn upstream_monomorphizations_for_provider(
     tcx: TyCtxt<'_>,
     def_id: DefId,
-) -> Option<&FxHashMap<SubstsRef<'_>, CrateNum>> {
+) -> Option<&FxHashMap<GenericArgsRef<'_>, CrateNum>> {
     debug_assert!(!def_id.is_local());
     tcx.upstream_monomorphizations(()).get(&def_id)
 }
 
 fn upstream_drop_glue_for_provider<'tcx>(
     tcx: TyCtxt<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
 ) -> Option<CrateNum> {
     if let Some(def_id) = tcx.lang_items().drop_in_place_fn() {
-        tcx.upstream_monomorphizations_for(def_id).and_then(|monos| monos.get(&substs).cloned())
+        tcx.upstream_monomorphizations_for(def_id).and_then(|monos| monos.get(&args).cloned())
     } else {
         None
     }
@@ -521,10 +521,10 @@ pub fn symbol_name_for_instance_in_crate<'tcx>(
                 instantiating_crate,
             )
         }
-        ExportedSymbol::Generic(def_id, substs) => {
+        ExportedSymbol::Generic(def_id, args) => {
             rustc_symbol_mangling::symbol_name_for_instance_in_crate(
                 tcx,
-                Instance::new(def_id, substs),
+                Instance::new(def_id, args),
                 instantiating_crate,
             )
         }
@@ -533,7 +533,7 @@ pub fn symbol_name_for_instance_in_crate<'tcx>(
                 tcx,
                 ty::Instance {
                     def: ty::InstanceDef::ThreadLocalShim(def_id),
-                    substs: ty::InternalSubsts::empty(),
+                    args: ty::GenericArgs::empty(),
                 },
                 instantiating_crate,
             )
@@ -580,7 +580,7 @@ pub fn linking_symbol_name_for_instance_in_crate<'tcx>(
             None
         }
         ExportedSymbol::NonGeneric(def_id) => Some(Instance::mono(tcx, def_id)),
-        ExportedSymbol::Generic(def_id, substs) => Some(Instance::new(def_id, substs)),
+        ExportedSymbol::Generic(def_id, args) => Some(Instance::new(def_id, args)),
         // DropGlue always use the Rust calling convention and thus follow the target's default
         // symbol decoration scheme.
         ExportedSymbol::DropGlue(..) => None,
diff --git a/compiler/rustc_codegen_ssa/src/base.rs b/compiler/rustc_codegen_ssa/src/base.rs
index 9133601ecd126..dc86280327492 100644
--- a/compiler/rustc_codegen_ssa/src/base.rs
+++ b/compiler/rustc_codegen_ssa/src/base.rs
@@ -499,7 +499,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
                     cx.tcx(),
                     ty::ParamEnv::reveal_all(),
                     start_def_id,
-                    cx.tcx().mk_substs(&[main_ret_ty.into()]),
+                    cx.tcx().mk_args(&[main_ret_ty.into()]),
                 )
                 .unwrap()
                 .unwrap(),
diff --git a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
index e91f7b86e5ed6..64f799bb1e68e 100644
--- a/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
+++ b/compiler/rustc_codegen_ssa/src/debuginfo/type_names.rs
@@ -17,8 +17,8 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::definitions::{DefPathData, DefPathDataName, DisambiguatedDefPathData};
 use rustc_hir::{AsyncGeneratorKind, GeneratorKind, Mutability};
 use rustc_middle::ty::layout::{IntegerExt, TyAndLayout};
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::{self, ExistentialProjection, ParamEnv, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
 use rustc_target::abi::Integer;
 use smallvec::SmallVec;
 
@@ -77,7 +77,7 @@ fn push_debuginfo_type_name<'tcx>(
         ty::Uint(uint_ty) => output.push_str(uint_ty.name_str()),
         ty::Float(float_ty) => output.push_str(float_ty.name_str()),
         ty::Foreign(def_id) => push_item_name(tcx, def_id, qualified, output),
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             // `layout_for_cpp_like_fallback` will be `Some` if we want to use the fallback encoding.
             let layout_for_cpp_like_fallback = if cpp_like_debuginfo && def.is_enum() {
                 match tcx.layout_of(ParamEnv::reveal_all().and(t)) {
@@ -106,14 +106,14 @@ fn push_debuginfo_type_name<'tcx>(
                     ty_and_layout,
                     &|output, visited| {
                         push_item_name(tcx, def.did(), true, output);
-                        push_generic_params_internal(tcx, substs, output, visited);
+                        push_generic_params_internal(tcx, args, output, visited);
                     },
                     output,
                     visited,
                 );
             } else {
                 push_item_name(tcx, def.did(), qualified, output);
-                push_generic_params_internal(tcx, substs, output, visited);
+                push_generic_params_internal(tcx, args, output, visited);
             }
         }
         ty::Tuple(component_types) => {
@@ -238,7 +238,7 @@ fn push_debuginfo_type_name<'tcx>(
                     tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), principal);
                 push_item_name(tcx, principal.def_id, qualified, output);
                 let principal_has_generic_params =
-                    push_generic_params_internal(tcx, principal.substs, output, visited);
+                    push_generic_params_internal(tcx, principal.args, output, visited);
 
                 let projection_bounds: SmallVec<[_; 4]> = trait_data
                     .projection_bounds()
@@ -393,7 +393,7 @@ fn push_debuginfo_type_name<'tcx>(
             // processing
             visited.remove(&t);
         }
-        ty::Closure(def_id, substs) | ty::Generator(def_id, substs, ..) => {
+        ty::Closure(def_id, args) | ty::Generator(def_id, args, ..) => {
             // Name will be "{closure_env#0}<T1, T2, ...>", "{generator_env#0}<T1, T2, ...>", or
             // "{async_fn_env#0}<T1, T2, ...>", etc.
             // In the case of cpp-like debuginfo, the name additionally gets wrapped inside of
@@ -403,13 +403,13 @@ fn push_debuginfo_type_name<'tcx>(
                 msvc_enum_fallback(
                     ty_and_layout,
                     &|output, visited| {
-                        push_closure_or_generator_name(tcx, def_id, substs, true, output, visited);
+                        push_closure_or_generator_name(tcx, def_id, args, true, output, visited);
                     },
                     output,
                     visited,
                 );
             } else {
-                push_closure_or_generator_name(tcx, def_id, substs, qualified, output, visited);
+                push_closure_or_generator_name(tcx, def_id, args, qualified, output, visited);
             }
         }
         // Type parameters from polymorphized functions.
@@ -516,7 +516,7 @@ pub fn compute_debuginfo_vtable_name<'tcx>(
             tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), trait_ref);
         push_item_name(tcx, trait_ref.def_id, true, &mut vtable_name);
         visited.clear();
-        push_generic_params_internal(tcx, trait_ref.substs, &mut vtable_name, &mut visited);
+        push_generic_params_internal(tcx, trait_ref.args, &mut vtable_name, &mut visited);
     } else {
         vtable_name.push('_');
     }
@@ -609,21 +609,21 @@ fn push_unqualified_item_name(
 
 fn push_generic_params_internal<'tcx>(
     tcx: TyCtxt<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     output: &mut String,
     visited: &mut FxHashSet<Ty<'tcx>>,
 ) -> bool {
-    if substs.non_erasable_generics().next().is_none() {
+    if args.non_erasable_generics().next().is_none() {
         return false;
     }
 
-    debug_assert_eq!(substs, tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), substs));
+    debug_assert_eq!(args, tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), args));
 
     let cpp_like_debuginfo = cpp_like_debuginfo(tcx);
 
     output.push('<');
 
-    for type_parameter in substs.non_erasable_generics() {
+    for type_parameter in args.non_erasable_generics() {
         match type_parameter {
             GenericArgKind::Type(type_parameter) => {
                 push_debuginfo_type_name(tcx, type_parameter, true, output, visited);
@@ -688,16 +688,20 @@ fn push_const_param<'tcx>(tcx: TyCtxt<'tcx>, ct: ty::Const<'tcx>, output: &mut S
     .unwrap();
 }
 
-pub fn push_generic_params<'tcx>(tcx: TyCtxt<'tcx>, substs: SubstsRef<'tcx>, output: &mut String) {
+pub fn push_generic_params<'tcx>(
+    tcx: TyCtxt<'tcx>,
+    args: GenericArgsRef<'tcx>,
+    output: &mut String,
+) {
     let _prof = tcx.prof.generic_activity("compute_debuginfo_type_name");
     let mut visited = FxHashSet::default();
-    push_generic_params_internal(tcx, substs, output, &mut visited);
+    push_generic_params_internal(tcx, args, output, &mut visited);
 }
 
 fn push_closure_or_generator_name<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: DefId,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     qualified: bool,
     output: &mut String,
     visited: &mut FxHashSet<Ty<'tcx>>,
@@ -731,10 +735,10 @@ fn push_closure_or_generator_name<'tcx>(
     let enclosing_fn_def_id = tcx.typeck_root_def_id(def_id);
     let generics = tcx.generics_of(enclosing_fn_def_id);
 
-    // Truncate the substs to the length of the above generics. This will cut off
+    // Truncate the args to the length of the above generics. This will cut off
     // anything closure- or generator-specific.
-    let substs = substs.truncate_to(tcx, generics);
-    push_generic_params_internal(tcx, substs, output, visited);
+    let args = args.truncate_to(tcx, generics);
+    push_generic_params_internal(tcx, args, output, visited);
 }
 
 fn push_close_angle_bracket(cpp_like_debuginfo: bool, output: &mut String) {
diff --git a/compiler/rustc_codegen_ssa/src/meth.rs b/compiler/rustc_codegen_ssa/src/meth.rs
index a8b935bd65ce1..9abe7b25d0e93 100644
--- a/compiler/rustc_codegen_ssa/src/meth.rs
+++ b/compiler/rustc_codegen_ssa/src/meth.rs
@@ -1,6 +1,6 @@
 use crate::traits::*;
 
-use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
+use rustc_middle::ty::{self, GenericArgKind, Ty};
 use rustc_session::config::Lto;
 use rustc_symbol_mangling::typeid_for_trait_ref;
 use rustc_target::abi::call::FnAbi;
diff --git a/compiler/rustc_codegen_ssa/src/mir/block.rs b/compiler/rustc_codegen_ssa/src/mir/block.rs
index 9d1b3ce82661a..269c12e7a68e0 100644
--- a/compiler/rustc_codegen_ssa/src/mir/block.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/block.rs
@@ -491,7 +491,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     //
                     let virtual_drop = Instance {
                         def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
-                        substs: drop_fn.substs,
+                        args: drop_fn.args,
                     };
                     debug!("ty = {:?}", ty);
                     debug!("drop_fn = {:?}", drop_fn);
@@ -531,7 +531,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     // SO THEN WE CAN USE THE ABOVE CODE.
                     let virtual_drop = Instance {
                         def: ty::InstanceDef::Virtual(drop_fn.def_id(), 0),
-                        substs: drop_fn.substs,
+                        args: drop_fn.args,
                     };
                     debug!("ty = {:?}", ty);
                     debug!("drop_fn = {:?}", drop_fn);
@@ -687,7 +687,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         // which mentions the offending type, even from a const context.
         let panic_intrinsic = intrinsic.and_then(|s| ValidityRequirement::from_intrinsic(s));
         if let Some(requirement) = panic_intrinsic {
-            let ty = instance.unwrap().substs.type_at(0);
+            let ty = instance.unwrap().args.type_at(0);
 
             let do_panic = !bx
                 .tcx()
@@ -760,13 +760,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let callee = self.codegen_operand(bx, func);
 
         let (instance, mut llfn) = match *callee.layout.ty.kind() {
-            ty::FnDef(def_id, substs) => (
+            ty::FnDef(def_id, args) => (
                 Some(
                     ty::Instance::expect_resolve(
                         bx.tcx(),
                         ty::ParamEnv::reveal_all(),
                         def_id,
-                        substs,
+                        args,
                     )
                     .polymorphize(bx.tcx()),
                 ),
@@ -1125,12 +1125,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
                 mir::InlineAsmOperand::SymFn { ref value } => {
                     let literal = self.monomorphize(value.literal);
-                    if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
+                    if let ty::FnDef(def_id, args) = *literal.ty().kind() {
                         let instance = ty::Instance::resolve_for_fn_ptr(
                             bx.tcx(),
                             ty::ParamEnv::reveal_all(),
                             def_id,
-                            substs,
+                            args,
                         )
                         .unwrap();
                         InlineAsmOperandRef::SymFn { instance }
diff --git a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
index 8a65dd593b8c1..18201abd63180 100644
--- a/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/intrinsic.rs
@@ -64,7 +64,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
     ) {
         let callee_ty = instance.ty(bx.tcx(), ty::ParamEnv::reveal_all());
 
-        let ty::FnDef(def_id, substs) = *callee_ty.kind() else {
+        let ty::FnDef(def_id, fn_args) = *callee_ty.kind() else {
             bug!("expected fn item type, found {}", callee_ty);
         };
 
@@ -87,7 +87,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             sym::va_start => bx.va_start(args[0].immediate()),
             sym::va_end => bx.va_end(args[0].immediate()),
             sym::size_of_val => {
-                let tp_ty = substs.type_at(0);
+                let tp_ty = fn_args.type_at(0);
                 if let OperandValue::Pair(_, meta) = args[0].val {
                     let (llsize, _) = glue::size_and_align_of_dst(bx, tp_ty, Some(meta));
                     llsize
@@ -96,7 +96,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
             }
             sym::min_align_of_val => {
-                let tp_ty = substs.type_at(0);
+                let tp_ty = fn_args.type_at(0);
                 if let OperandValue::Pair(_, meta) = args[0].val {
                     let (_, llalign) = glue::size_and_align_of_dst(bx, tp_ty, Some(meta));
                     llalign
@@ -136,7 +136,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 OperandRef::from_const(bx, value, ret_ty).immediate_or_packed_pair(bx)
             }
             sym::arith_offset => {
-                let ty = substs.type_at(0);
+                let ty = fn_args.type_at(0);
                 let layout = bx.layout_of(ty);
                 let ptr = args[0].immediate();
                 let offset = args[1].immediate();
@@ -147,7 +147,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     bx,
                     true,
                     false,
-                    substs.type_at(0),
+                    fn_args.type_at(0),
                     args[1].immediate(),
                     args[0].immediate(),
                     args[2].immediate(),
@@ -158,7 +158,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 memset_intrinsic(
                     bx,
                     false,
-                    substs.type_at(0),
+                    fn_args.type_at(0),
                     args[0].immediate(),
                     args[1].immediate(),
                     args[2].immediate(),
@@ -171,7 +171,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     bx,
                     false,
                     true,
-                    substs.type_at(0),
+                    fn_args.type_at(0),
                     args[0].immediate(),
                     args[1].immediate(),
                     args[2].immediate(),
@@ -183,7 +183,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     bx,
                     true,
                     true,
-                    substs.type_at(0),
+                    fn_args.type_at(0),
                     args[0].immediate(),
                     args[1].immediate(),
                     args[2].immediate(),
@@ -194,7 +194,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 memset_intrinsic(
                     bx,
                     true,
-                    substs.type_at(0),
+                    fn_args.type_at(0),
                     args[0].immediate(),
                     args[1].immediate(),
                     args[2].immediate(),
@@ -307,7 +307,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                         let Some((success, failure)) = ordering.split_once('_') else {
                             bx.sess().emit_fatal(errors::AtomicCompareExchange);
                         };
-                        let ty = substs.type_at(0);
+                        let ty = fn_args.type_at(0);
                         if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                             let weak = instruction == "cxchgweak";
                             let mut dst = args[0].immediate();
@@ -338,7 +338,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
 
                     "load" => {
-                        let ty = substs.type_at(0);
+                        let ty = fn_args.type_at(0);
                         if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                             let layout = bx.layout_of(ty);
                             let size = layout.size;
@@ -361,7 +361,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
 
                     "store" => {
-                        let ty = substs.type_at(0);
+                        let ty = fn_args.type_at(0);
                         if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                             let size = bx.layout_of(ty).size;
                             let mut val = args[1].immediate();
@@ -407,7 +407,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             _ => bx.sess().emit_fatal(errors::UnknownAtomicOperation),
                         };
 
-                        let ty = substs.type_at(0);
+                        let ty = fn_args.type_at(0);
                         if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_unsafe_ptr() {
                             let mut ptr = args[0].immediate();
                             let mut val = args[1].immediate();
@@ -439,7 +439,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
 
             sym::ptr_offset_from | sym::ptr_offset_from_unsigned => {
-                let ty = substs.type_at(0);
+                let ty = fn_args.type_at(0);
                 let pointee_size = bx.layout_of(ty).size;
 
                 let a = args[0].immediate();
diff --git a/compiler/rustc_codegen_ssa/src/mir/mod.rs b/compiler/rustc_codegen_ssa/src/mir/mod.rs
index 9ff6a2497481f..3464f910829da 100644
--- a/compiler/rustc_codegen_ssa/src/mir/mod.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/mod.rs
@@ -159,7 +159,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     cx: &'a Bx::CodegenCx,
     instance: Instance<'tcx>,
 ) {
-    assert!(!instance.substs.has_infer());
+    assert!(!instance.args.has_infer());
 
     let llfn = cx.get_fn(instance);
 
diff --git a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
index 956f03d257835..1f90a28eb8eef 100644
--- a/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
+++ b/compiler/rustc_codegen_ssa/src/mir/rvalue.rs
@@ -417,12 +417,12 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                     mir::CastKind::PointerCoercion(PointerCoercion::ReifyFnPointer) => {
                         match *operand.layout.ty.kind() {
-                            ty::FnDef(def_id, substs) => {
+                            ty::FnDef(def_id, args) => {
                                 let instance = ty::Instance::resolve_for_fn_ptr(
                                     bx.tcx(),
                                     ty::ParamEnv::reveal_all(),
                                     def_id,
-                                    substs,
+                                    args,
                                 )
                                 .unwrap()
                                 .polymorphize(bx.cx().tcx());
@@ -433,11 +433,11 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     }
                     mir::CastKind::PointerCoercion(PointerCoercion::ClosureFnPointer(_)) => {
                         match *operand.layout.ty.kind() {
-                            ty::Closure(def_id, substs) => {
+                            ty::Closure(def_id, args) => {
                                 let instance = Instance::resolve_closure(
                                     bx.cx().tcx(),
                                     def_id,
-                                    substs,
+                                    args,
                                     ty::ClosureKind::FnOnce,
                                 )
                                 .expect("failed to normalize and resolve closure during codegen")
@@ -711,7 +711,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 {
                     let instance = ty::Instance {
                         def: ty::InstanceDef::ThreadLocalShim(def_id),
-                        substs: ty::InternalSubsts::empty(),
+                        args: ty::GenericArgs::empty(),
                     };
                     let fn_ptr = bx.get_fn_addr(instance);
                     let fn_abi = bx.fn_abi_of_instance(instance, ty::List::empty());
diff --git a/compiler/rustc_codegen_ssa/src/mono_item.rs b/compiler/rustc_codegen_ssa/src/mono_item.rs
index 27da33581a1a9..b72a1a07866df 100644
--- a/compiler/rustc_codegen_ssa/src/mono_item.rs
+++ b/compiler/rustc_codegen_ssa/src/mono_item.rs
@@ -64,7 +64,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
                                     .typeck_body(anon_const.body)
                                     .node_type(anon_const.hir_id);
                                 let instance = match ty.kind() {
-                                    &ty::FnDef(def_id, substs) => Instance::new(def_id, substs),
+                                    &ty::FnDef(def_id, args) => Instance::new(def_id, args),
                                     _ => span_bug!(*op_sp, "asm sym is not a function"),
                                 };
 
@@ -138,7 +138,7 @@ impl<'a, 'tcx: 'a> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
     fn to_raw_string(&self) -> String {
         match *self {
             MonoItem::Fn(instance) => {
-                format!("Fn({:?}, {})", instance.def, instance.substs.as_ptr().addr())
+                format!("Fn({:?}, {})", instance.def, instance.args.as_ptr().addr())
             }
             MonoItem::Static(id) => format!("Static({:?})", id),
             MonoItem::GlobalAsm(id) => format!("GlobalAsm({:?})", id),
diff --git a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
index 417ab78fd5481..b21cb984de67f 100644
--- a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
@@ -45,7 +45,7 @@ fn eval_body_using_ecx<'mir, 'tcx>(
         "Unexpected DefKind: {:?}",
         ecx.tcx.def_kind(cid.instance.def_id())
     );
-    let layout = ecx.layout_of(body.bound_return_ty().subst(tcx, cid.instance.substs))?;
+    let layout = ecx.layout_of(body.bound_return_ty().instantiate(tcx, cid.instance.args))?;
     assert!(layout.is_sized());
     let ret = ecx.allocate(layout, MemoryKind::Stack)?;
 
@@ -245,10 +245,10 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
     // Catch such calls and evaluate them instead of trying to load a constant's MIR.
     if let ty::InstanceDef::Intrinsic(def_id) = key.value.instance.def {
         let ty = key.value.instance.ty(tcx, key.param_env);
-        let ty::FnDef(_, substs) = ty.kind() else {
+        let ty::FnDef(_, args) = ty.kind() else {
             bug!("intrinsic with type {:?}", ty);
         };
-        return eval_nullary_intrinsic(tcx, key.param_env, def_id, substs).map_err(|error| {
+        return eval_nullary_intrinsic(tcx, key.param_env, def_id, args).map_err(|error| {
             let span = tcx.def_span(def_id);
 
             super::report(
@@ -328,10 +328,10 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
                 ("static", String::new())
             } else {
                 // If the current item has generics, we'd like to enrich the message with the
-                // instance and its substs: to show the actual compile-time values, in addition to
+                // instance and its args: to show the actual compile-time values, in addition to
                 // the expression, leading to the const eval error.
                 let instance = &key.value.instance;
-                if !instance.substs.is_empty() {
+                if !instance.args.is_empty() {
                     let instance = with_no_trimmed_paths!(instance.to_string());
                     ("const_with_path", instance)
                 } else {
diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs
index a20f0276b3e52..267795a6cb4ab 100644
--- a/compiler/rustc_const_eval/src/const_eval/machine.rs
+++ b/compiler/rustc_const_eval/src/const_eval/machine.rs
@@ -230,7 +230,7 @@ impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
                 *self.tcx,
                 ty::ParamEnv::reveal_all(),
                 const_def_id,
-                instance.substs,
+                instance.args,
             )
             .unwrap()
             .unwrap();
diff --git a/compiler/rustc_const_eval/src/const_eval/mod.rs b/compiler/rustc_const_eval/src/const_eval/mod.rs
index a3064b53db1b0..0a3c3914ff971 100644
--- a/compiler/rustc_const_eval/src/const_eval/mod.rs
+++ b/compiler/rustc_const_eval/src/const_eval/mod.rs
@@ -105,7 +105,7 @@ pub(crate) fn try_destructure_mir_constant_for_diagnostics<'tcx>(
             let down = ecx.operand_downcast(&op, variant).ok()?;
             (def.variants()[variant].fields.len(), Some(variant), down)
         }
-        ty::Tuple(substs) => (substs.len(), None, op),
+        ty::Tuple(args) => (args.len(), None, op),
         _ => bug!("cannot destructure mir constant {:?}", val),
     };
 
diff --git a/compiler/rustc_const_eval/src/const_eval/valtrees.rs b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
index e574df27694f9..9531d973eb323 100644
--- a/compiler/rustc_const_eval/src/const_eval/valtrees.rs
+++ b/compiler/rustc_const_eval/src/const_eval/valtrees.rs
@@ -416,9 +416,9 @@ fn valtree_into_mplace<'tcx>(
                         debug!(?unsized_inner_ty);
 
                         let inner_ty = match ty.kind() {
-                            ty::Adt(def, substs) => {
+                            ty::Adt(def, args) => {
                                 let i = FieldIdx::from_usize(i);
-                                def.variant(FIRST_VARIANT).fields[i].ty(tcx, substs)
+                                def.variant(FIRST_VARIANT).fields[i].ty(tcx, args)
                             }
                             ty::Tuple(inner_tys) => inner_tys[i],
                             _ => bug!("unexpected unsized type {:?}", ty),
diff --git a/compiler/rustc_const_eval/src/interpret/cast.rs b/compiler/rustc_const_eval/src/interpret/cast.rs
index 83a072d6f8b62..dd7a1fcc16594 100644
--- a/compiler/rustc_const_eval/src/interpret/cast.rs
+++ b/compiler/rustc_const_eval/src/interpret/cast.rs
@@ -75,12 +75,12 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
                 // The src operand does not matter, just its type
                 match *src.layout.ty.kind() {
-                    ty::FnDef(def_id, substs) => {
+                    ty::FnDef(def_id, args) => {
                         let instance = ty::Instance::resolve_for_fn_ptr(
                             *self.tcx,
                             self.param_env,
                             def_id,
-                            substs,
+                            args,
                         )
                         .ok_or_else(|| err_inval!(TooGeneric))?;
 
@@ -108,11 +108,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
                 // The src operand does not matter, just its type
                 match *src.layout.ty.kind() {
-                    ty::Closure(def_id, substs) => {
+                    ty::Closure(def_id, args) => {
                         let instance = ty::Instance::resolve_closure(
                             *self.tcx,
                             def_id,
-                            substs,
+                            args,
                             ty::ClosureKind::FnOnce,
                         )
                         .ok_or_else(|| err_inval!(TooGeneric))?;
diff --git a/compiler/rustc_const_eval/src/interpret/discriminant.rs b/compiler/rustc_const_eval/src/interpret/discriminant.rs
index 015a9beab832d..f23a455c2ca30 100644
--- a/compiler/rustc_const_eval/src/interpret/discriminant.rs
+++ b/compiler/rustc_const_eval/src/interpret/discriminant.rs
@@ -164,11 +164,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     ty::Adt(adt, _) => {
                         adt.discriminants(*self.tcx).find(|(_, var)| var.val == discr_bits)
                     }
-                    ty::Generator(def_id, substs, _) => {
-                        let substs = substs.as_generator();
-                        substs
-                            .discriminants(def_id, *self.tcx)
-                            .find(|(_, var)| var.val == discr_bits)
+                    ty::Generator(def_id, args, _) => {
+                        let args = args.as_generator();
+                        args.discriminants(def_id, *self.tcx).find(|(_, var)| var.val == discr_bits)
                     }
                     _ => span_bug!(self.cur_span(), "tagged layout for non-adt non-generator"),
                 }
diff --git a/compiler/rustc_const_eval/src/interpret/eval_context.rs b/compiler/rustc_const_eval/src/interpret/eval_context.rs
index 568618908e3f9..04e046fbda352 100644
--- a/compiler/rustc_const_eval/src/interpret/eval_context.rs
+++ b/compiler/rustc_const_eval/src/interpret/eval_context.rs
@@ -13,7 +13,7 @@ use rustc_middle::ty::layout::{
     self, FnAbiError, FnAbiOfHelpers, FnAbiRequest, LayoutError, LayoutOf, LayoutOfHelpers,
     TyAndLayout,
 };
-use rustc_middle::ty::{self, subst::SubstsRef, ParamEnv, Ty, TyCtxt, TypeFoldable};
+use rustc_middle::ty::{self, GenericArgsRef, ParamEnv, Ty, TyCtxt, TypeFoldable};
 use rustc_mir_dataflow::storage::always_storage_live_locals;
 use rustc_session::Limit;
 use rustc_span::Span;
@@ -91,7 +91,7 @@ pub struct Frame<'mir, 'tcx, Prov: Provenance = AllocId, Extra = ()> {
     /// The MIR for the function called on this frame.
     pub body: &'mir mir::Body<'tcx>,
 
-    /// The def_id and substs of the current function.
+    /// The def_id and args of the current function.
     pub instance: ty::Instance<'tcx>,
 
     /// Extra data for the machine.
@@ -529,16 +529,16 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             .map_err(|_| err_inval!(TooGeneric))
     }
 
-    /// The `substs` are assumed to already be in our interpreter "universe" (param_env).
+    /// The `args` are assumed to already be in our interpreter "universe" (param_env).
     pub(super) fn resolve(
         &self,
         def: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> InterpResult<'tcx, ty::Instance<'tcx>> {
-        trace!("resolve: {:?}, {:#?}", def, substs);
+        trace!("resolve: {:?}, {:#?}", def, args);
         trace!("param_env: {:#?}", self.param_env);
-        trace!("substs: {:#?}", substs);
-        match ty::Instance::resolve(*self.tcx, self.param_env, def, substs) {
+        trace!("args: {:#?}", args);
+        match ty::Instance::resolve(*self.tcx, self.param_env, def, args) {
             Ok(Some(instance)) => Ok(instance),
             Ok(None) => throw_inval!(TooGeneric),
 
@@ -684,7 +684,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         return_to_block: StackPopCleanup,
     ) -> InterpResult<'tcx> {
         trace!("body: {:#?}", body);
-        // First push a stack frame so we have access to the local substs
+        // First push a stack frame so we have access to the local args
         let pre_frame = Frame {
             body,
             loc: Right(body.span), // Span used for errors caused during preamble.
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics.rs b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
index ed64a7655b587..04cae23f852a1 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics.rs
@@ -12,7 +12,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty;
 use rustc_middle::ty::layout::{LayoutOf as _, ValidityRequirement};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{Ty, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_target::abi::{Abi, Align, Primitive, Size};
@@ -56,9 +56,9 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     def_id: DefId,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
 ) -> InterpResult<'tcx, ConstValue<'tcx>> {
-    let tp_ty = substs.type_at(0);
+    let tp_ty = args.type_at(0);
     let name = tcx.item_name(def_id);
     Ok(match name {
         sym::type_name => {
@@ -123,7 +123,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         dest: &PlaceTy<'tcx, M::Provenance>,
         ret: Option<mir::BasicBlock>,
     ) -> InterpResult<'tcx, bool> {
-        let substs = instance.substs;
+        let instance_args = instance.args;
         let intrinsic_name = self.tcx.item_name(instance.def_id());
 
         // First handle intrinsics without return place.
@@ -187,7 +187,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             | sym::ctlz_nonzero
             | sym::bswap
             | sym::bitreverse => {
-                let ty = substs.type_at(0);
+                let ty = instance_args.type_at(0);
                 let layout_of = self.layout_of(ty)?;
                 let val = self.read_scalar(&args[0])?;
                 let bits = val.to_bits(layout_of.size)?;
@@ -237,7 +237,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             sym::rotate_left | sym::rotate_right => {
                 // rotate_left: (X << (S % BW)) | (X >> ((BW - S) % BW))
                 // rotate_right: (X << ((BW - S) % BW)) | (X >> (S % BW))
-                let layout = self.layout_of(substs.type_at(0))?;
+                let layout = self.layout_of(instance_args.type_at(0))?;
                 let val = self.read_scalar(&args[0])?;
                 let val_bits = val.to_bits(layout.size)?;
                 let raw_shift = self.read_scalar(&args[1])?;
@@ -263,7 +263,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             sym::arith_offset => {
                 let ptr = self.read_pointer(&args[0])?;
                 let offset_count = self.read_target_isize(&args[1])?;
-                let pointee_ty = substs.type_at(0);
+                let pointee_ty = instance_args.type_at(0);
 
                 let pointee_size = i64::try_from(self.layout_of(pointee_ty)?.size.bytes()).unwrap();
                 let offset_bytes = offset_count.wrapping_mul(pointee_size);
@@ -368,7 +368,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                     assert!(self.target_isize_min() <= dist && dist <= self.target_isize_max());
                     isize_layout
                 };
-                let pointee_layout = self.layout_of(substs.type_at(0))?;
+                let pointee_layout = self.layout_of(instance_args.type_at(0))?;
                 // If ret_layout is unsigned, we checked that so is the distance, so we are good.
                 let val = ImmTy::from_int(dist, ret_layout);
                 let size = ImmTy::from_int(pointee_layout.size.bytes(), ret_layout);
@@ -378,7 +378,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             sym::assert_inhabited
             | sym::assert_zero_valid
             | sym::assert_mem_uninitialized_valid => {
-                let ty = instance.substs.type_at(0);
+                let ty = instance.args.type_at(0);
                 let requirement = ValidityRequirement::from_intrinsic(intrinsic_name).unwrap();
 
                 let should_panic = !self
diff --git a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
index df5b581000b7d..c4fe293bfaccc 100644
--- a/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
+++ b/compiler/rustc_const_eval/src/interpret/intrinsics/caller_location.rs
@@ -96,7 +96,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let loc_ty = self
             .tcx
             .type_of(self.tcx.require_lang_item(LangItem::PanicLocation, None))
-            .subst(*self.tcx, self.tcx.mk_substs(&[self.tcx.lifetimes.re_erased.into()]));
+            .instantiate(*self.tcx, self.tcx.mk_args(&[self.tcx.lifetimes.re_erased.into()]));
         let loc_layout = self.layout_of(loc_ty).unwrap();
         let location = self.allocate(loc_layout, MemoryKind::CallerLocation).unwrap();
 
diff --git a/compiler/rustc_const_eval/src/interpret/operand.rs b/compiler/rustc_const_eval/src/interpret/operand.rs
index 6727937363ec3..da45fdca1a12c 100644
--- a/compiler/rustc_const_eval/src/interpret/operand.rs
+++ b/compiler/rustc_const_eval/src/interpret/operand.rs
@@ -590,7 +590,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 throw_inval!(AlreadyReported(reported.into()))
             }
             ty::ConstKind::Unevaluated(uv) => {
-                let instance = self.resolve(uv.def, uv.substs)?;
+                let instance = self.resolve(uv.def, uv.args)?;
                 let cid = GlobalId { instance, promoted: None };
                 self.ctfe_query(span, |tcx| {
                     tcx.eval_to_valtree(self.param_env.with_const().and(cid))
@@ -619,7 +619,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             }
             mir::ConstantKind::Val(val, ty) => self.const_val_to_op(val, ty, layout),
             mir::ConstantKind::Unevaluated(uv, _) => {
-                let instance = self.resolve(uv.def, uv.substs)?;
+                let instance = self.resolve(uv.def, uv.args)?;
                 Ok(self.eval_global(GlobalId { instance, promoted: uv.promoted }, span)?.into())
             }
         }
diff --git a/compiler/rustc_const_eval/src/interpret/terminator.rs b/compiler/rustc_const_eval/src/interpret/terminator.rs
index 9c500790ce6d6..c944782b487de 100644
--- a/compiler/rustc_const_eval/src/interpret/terminator.rs
+++ b/compiler/rustc_const_eval/src/interpret/terminator.rs
@@ -135,8 +135,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         let fn_val = self.get_ptr_fn(fn_ptr)?;
                         (fn_val, self.fn_abi_of_fn_ptr(fn_sig_binder, extra_args)?, false)
                     }
-                    ty::FnDef(def_id, substs) => {
-                        let instance = self.resolve(def_id, substs)?;
+                    ty::FnDef(def_id, args) => {
+                        let instance = self.resolve(def_id, args)?;
                         (
                             FnVal::Instance(instance),
                             self.fn_abi_of_instance(instance, extra_args)?,
@@ -748,7 +748,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
 
                     let trait_def_id = tcx.trait_of_item(def_id).unwrap();
                     let virtual_trait_ref =
-                        ty::TraitRef::from_method(tcx, trait_def_id, instance.substs);
+                        ty::TraitRef::from_method(tcx, trait_def_id, instance.args);
                     let existential_trait_ref =
                         ty::ExistentialTraitRef::erase_self_ty(tcx, virtual_trait_ref);
                     let concrete_trait_ref = existential_trait_ref.with_self_ty(tcx, dyn_ty);
@@ -757,7 +757,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                         tcx,
                         self.param_env,
                         def_id,
-                        instance.substs.rebase_onto(tcx, trait_def_id, concrete_trait_ref.substs),
+                        instance.args.rebase_onto(tcx, trait_def_id, concrete_trait_ref.args),
                     )
                     .unwrap();
                     assert_eq!(fn_inst, concrete_method);
diff --git a/compiler/rustc_const_eval/src/interpret/util.rs b/compiler/rustc_const_eval/src/interpret/util.rs
index 22bdd4d2c3fbc..b33194423887c 100644
--- a/compiler/rustc_const_eval/src/interpret/util.rs
+++ b/compiler/rustc_const_eval/src/interpret/util.rs
@@ -33,12 +33,12 @@ where
 
             match *ty.kind() {
                 ty::Param(_) => ControlFlow::Break(FoundParam),
-                ty::Closure(def_id, substs)
-                | ty::Generator(def_id, substs, ..)
-                | ty::FnDef(def_id, substs) => {
+                ty::Closure(def_id, args)
+                | ty::Generator(def_id, args, ..)
+                | ty::FnDef(def_id, args) => {
                     let instance = ty::InstanceDef::Item(def_id);
                     let unused_params = self.tcx.unused_generic_params(instance);
-                    for (index, subst) in substs.into_iter().enumerate() {
+                    for (index, subst) in args.into_iter().enumerate() {
                         let index = index
                             .try_into()
                             .expect("more generic parameters than can fit into a `u32`");
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/check.rs b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
index fa71606eeb22e..d8b8fa927c7ee 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/check.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/check.rs
@@ -8,8 +8,8 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
 use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
-use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::{self, adjustment::PointerCoercion, Instance, InstanceDef, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_middle::ty::{TraitRef, TypeVisitableExt};
 use rustc_mir_dataflow::{self, Analysis};
 use rustc_span::{sym, Span, Symbol};
@@ -701,8 +701,8 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                 let fn_ty = func.ty(body, tcx);
 
-                let (mut callee, mut substs) = match *fn_ty.kind() {
-                    ty::FnDef(def_id, substs) => (def_id, substs),
+                let (mut callee, mut fn_args) = match *fn_ty.kind() {
+                    ty::FnDef(def_id, fn_args) => (def_id, fn_args),
 
                     ty::FnPtr(_) => {
                         self.check_op(ops::FnCallIndirect);
@@ -721,7 +721,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                 let infcx = tcx.infer_ctxt().build();
                 let ocx = ObligationCtxt::new(&infcx);
 
-                let predicates = tcx.predicates_of(callee).instantiate(tcx, substs);
+                let predicates = tcx.predicates_of(callee).instantiate(tcx, fn_args);
                 let cause = ObligationCause::new(
                     terminator.source_info.span,
                     self.body.source.def_id().expect_local(),
@@ -746,7 +746,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         self.check_op(ops::FnCallNonConst {
                             caller,
                             callee,
-                            substs,
+                            args: fn_args,
                             span: *fn_span,
                             call_source: *call_source,
                             feature: Some(sym::const_trait_impl),
@@ -754,7 +754,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         return;
                     }
 
-                    let trait_ref = TraitRef::from_method(tcx, trait_id, substs);
+                    let trait_ref = TraitRef::from_method(tcx, trait_id, fn_args);
                     let trait_ref = trait_ref.with_constness(ty::BoundConstness::ConstIfConst);
                     let obligation =
                         Obligation::new(tcx, ObligationCause::dummy(), param_env, trait_ref);
@@ -778,7 +778,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                             if trait_ref.self_ty().is_closure()
                                 && tcx.fn_trait_kind_from_def_id(trait_id).is_some() =>
                         {
-                            let ty::Closure(closure_def_id, substs) = *trait_ref.self_ty().kind()
+                            let ty::Closure(closure_def_id, fn_args) = *trait_ref.self_ty().kind()
                             else {
                                 unreachable!()
                             };
@@ -786,7 +786,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 self.check_op(ops::FnCallNonConst {
                                     caller,
                                     callee,
-                                    substs,
+                                    args: fn_args,
                                     span: *fn_span,
                                     call_source: *call_source,
                                     feature: None,
@@ -802,9 +802,9 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 .iter()
                                 .find(|did| tcx.item_name(**did) == callee_name)
                             {
-                                // using internal substs is ok here, since this is only
+                                // using internal args is ok here, since this is only
                                 // used for the `resolve` call below
-                                substs = InternalSubsts::identity_for_item(tcx, did);
+                                fn_args = GenericArgs::identity_for_item(tcx, did);
                                 callee = did;
                             }
 
@@ -812,7 +812,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 self.check_op(ops::FnCallNonConst {
                                     caller,
                                     callee,
-                                    substs,
+                                    args: fn_args,
                                     span: *fn_span,
                                     call_source: *call_source,
                                     feature: None,
@@ -828,7 +828,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 && tcx.has_attr(callee_trait, sym::const_trait)
                                 && Some(callee_trait) == tcx.trait_of_item(caller.to_def_id())
                                 // Can only call methods when it's `<Self as TheTrait>::f`.
-                                && tcx.types.self_param == substs.type_at(0)
+                                && tcx.types.self_param == fn_args.type_at(0)
                             {
                                 nonconst_call_permission = true;
                             }
@@ -855,7 +855,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                                 self.check_op(ops::FnCallNonConst {
                                     caller,
                                     callee,
-                                    substs,
+                                    args: fn_args,
                                     span: *fn_span,
                                     call_source: *call_source,
                                     feature: None,
@@ -868,7 +868,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
                     // Resolve a trait method call to its concrete implementation, which may be in a
                     // `const` trait impl.
-                    let instance = Instance::resolve(tcx, param_env, callee, substs);
+                    let instance = Instance::resolve(tcx, param_env, callee, fn_args);
                     debug!("Resolving ({:?}) -> {:?}", callee, instance);
                     if let Ok(Some(func)) = instance {
                         if let InstanceDef::Item(def) = func.def {
@@ -915,7 +915,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
                         self.check_op(ops::FnCallNonConst {
                             caller,
                             callee,
-                            substs,
+                            args: fn_args,
                             span: *fn_span,
                             call_source: *call_source,
                             feature: None,
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/mod.rs b/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
index 8ebfee8878cbb..e77fb4ea2a2c7 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/mod.rs
@@ -68,11 +68,11 @@ impl<'mir, 'tcx> ConstCx<'mir, 'tcx> {
     pub fn fn_sig(&self) -> PolyFnSig<'tcx> {
         let did = self.def_id().to_def_id();
         if self.tcx.is_closure(did) {
-            let ty = self.tcx.type_of(did).subst_identity();
-            let ty::Closure(_, substs) = ty.kind() else { bug!("type_of closure not ty::Closure") };
-            substs.as_closure().sig()
+            let ty = self.tcx.type_of(did).instantiate_identity();
+            let ty::Closure(_, args) = ty.kind() else { bug!("type_of closure not ty::Closure") };
+            args.as_closure().sig()
         } else {
-            self.tcx.fn_sig(did).subst_identity()
+            self.tcx.fn_sig(did).instantiate_identity()
         }
     }
 }
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
index 4eb278252c191..81337079af232 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/ops.rs
@@ -9,9 +9,9 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::{ImplSource, Obligation, ObligationCause};
 use rustc_middle::mir::{self, CallSource};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::TraitRef;
 use rustc_middle::ty::{suggest_constraining_type_param, Adt, Closure, FnDef, FnPtr, Param, Ty};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
 use rustc_middle::util::{call_kind, CallDesugaringKind, CallKind};
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::sym;
@@ -98,7 +98,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallIndirect {
 pub struct FnCallNonConst<'tcx> {
     pub caller: LocalDefId,
     pub callee: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
     pub span: Span,
     pub call_source: CallSource,
     pub feature: Option<Symbol>,
@@ -110,11 +110,11 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
         ccx: &ConstCx<'_, 'tcx>,
         _: Span,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
-        let FnCallNonConst { caller, callee, substs, span, call_source, feature } = *self;
+        let FnCallNonConst { caller, callee, args, span, call_source, feature } = *self;
         let ConstCx { tcx, param_env, .. } = *ccx;
 
         let diag_trait = |err, self_ty: Ty<'_>, trait_id| {
-            let trait_ref = TraitRef::from_method(tcx, trait_id, substs);
+            let trait_ref = TraitRef::from_method(tcx, trait_id, args);
 
             match self_ty.kind() {
                 Param(param_ty) => {
@@ -154,7 +154,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
         };
 
         let call_kind =
-            call_kind(tcx, ccx.param_env, callee, substs, span, call_source.from_hir_call(), None);
+            call_kind(tcx, ccx.param_env, callee, args, span, call_source.from_hir_call(), None);
 
         debug!(?call_kind);
 
@@ -226,7 +226,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                     let mut sugg = None;
 
                     if Some(trait_id) == ccx.tcx.lang_items().eq_trait() {
-                        match (substs[0].unpack(), substs[1].unpack()) {
+                        match (args[0].unpack(), args[1].unpack()) {
                             (GenericArgKind::Type(self_ty), GenericArgKind::Type(rhs_ty))
                                 if self_ty == rhs_ty
                                     && self_ty.is_ref()
@@ -297,7 +297,7 @@ impl<'tcx> NonConstOp<'tcx> for FnCallNonConst<'tcx> {
                 .create_err(errors::NonConstFmtMacroCall { span, kind: ccx.const_kind() }),
             _ => ccx.tcx.sess.create_err(errors::NonConstFnCall {
                 span,
-                def_path_str: ccx.tcx.def_path_str_with_substs(callee, substs),
+                def_path_str: ccx.tcx.def_path_str_with_args(callee, args),
                 kind: ccx.const_kind(),
             }),
         };
diff --git a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
index 015a4aa94cd42..0ef7ace696532 100644
--- a/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
+++ b/compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs
@@ -7,7 +7,7 @@ use rustc_hir::LangItem;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::mir;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, subst::SubstsRef, AdtDef, Ty};
+use rustc_middle::ty::{self, AdtDef, GenericArgsRef, Ty};
 use rustc_trait_selection::traits::{
     self, ImplSource, Obligation, ObligationCause, ObligationCtxt, SelectionContext,
 };
@@ -72,7 +72,7 @@ pub trait Qualif {
     fn in_adt_inherently<'tcx>(
         cx: &ConstCx<'_, 'tcx>,
         adt: AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> bool;
 }
 
@@ -97,7 +97,7 @@ impl Qualif for HasMutInterior {
     fn in_adt_inherently<'tcx>(
         _cx: &ConstCx<'_, 'tcx>,
         adt: AdtDef<'tcx>,
-        _: SubstsRef<'tcx>,
+        _: GenericArgsRef<'tcx>,
     ) -> bool {
         // Exactly one type, `UnsafeCell`, has the `HasMutInterior` qualif inherently.
         // It arises structurally for all other types.
@@ -127,7 +127,7 @@ impl Qualif for NeedsDrop {
     fn in_adt_inherently<'tcx>(
         cx: &ConstCx<'_, 'tcx>,
         adt: AdtDef<'tcx>,
-        _: SubstsRef<'tcx>,
+        _: GenericArgsRef<'tcx>,
     ) -> bool {
         adt.has_dtor(cx.tcx)
     }
@@ -193,7 +193,7 @@ impl Qualif for NeedsNonConstDrop {
     fn in_adt_inherently<'tcx>(
         cx: &ConstCx<'_, 'tcx>,
         adt: AdtDef<'tcx>,
-        _: SubstsRef<'tcx>,
+        _: GenericArgsRef<'tcx>,
     ) -> bool {
         adt.has_non_const_dtor(cx.tcx)
     }
@@ -221,9 +221,9 @@ impl Qualif for CustomEq {
     fn in_adt_inherently<'tcx>(
         cx: &ConstCx<'_, 'tcx>,
         def: AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> bool {
-        let ty = Ty::new_adt(cx.tcx, def, substs);
+        let ty = Ty::new_adt(cx.tcx, def, args);
         !ty.is_structural_eq_shallow(cx.tcx)
     }
 }
@@ -276,9 +276,9 @@ where
         Rvalue::Aggregate(kind, operands) => {
             // Return early if we know that the struct or enum being constructed is always
             // qualified.
-            if let AggregateKind::Adt(adt_did, _, substs, ..) = **kind {
+            if let AggregateKind::Adt(adt_did, _, args, ..) = **kind {
                 let def = cx.tcx.adt_def(adt_did);
-                if Q::in_adt_inherently(cx, def, substs) {
+                if Q::in_adt_inherently(cx, def, args) {
                     return true;
                 }
                 if def.is_union() && Q::in_any_value_of_ty(cx, rvalue.ty(cx.body, cx.tcx)) {
@@ -360,7 +360,7 @@ where
         ConstantKind::Val(..) => None,
     };
 
-    if let Some(mir::UnevaluatedConst { def, substs: _, promoted }) = uneval {
+    if let Some(mir::UnevaluatedConst { def, args: _, promoted }) = uneval {
         // Use qualifs of the type for the promoted. Promoteds in MIR body should be possible
         // only for `NeedsNonConstDrop` with precise drop checking. This is the only const
         // check performed after the promotion. Verify that with an assertion.
diff --git a/compiler/rustc_const_eval/src/transform/promote_consts.rs b/compiler/rustc_const_eval/src/transform/promote_consts.rs
index 0df110f8fbeae..d79c65f1d1fee 100644
--- a/compiler/rustc_const_eval/src/transform/promote_consts.rs
+++ b/compiler/rustc_const_eval/src/transform/promote_consts.rs
@@ -16,7 +16,7 @@ use rustc_hir as hir;
 use rustc_middle::mir;
 use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, List, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::Span;
 
@@ -841,8 +841,8 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
             let mut promoted_operand = |ty, span| {
                 promoted.span = span;
                 promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span);
-                let substs = tcx.erase_regions(InternalSubsts::identity_for_item(tcx, def));
-                let uneval = mir::UnevaluatedConst { def, substs, promoted: Some(promoted_id) };
+                let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def));
+                let uneval = mir::UnevaluatedConst { def, args, promoted: Some(promoted_id) };
 
                 Operand::Constant(Box::new(Constant {
                     span,
diff --git a/compiler/rustc_const_eval/src/transform/validate.rs b/compiler/rustc_const_eval/src/transform/validate.rs
index e516145894b2b..ea0d90dbd514d 100644
--- a/compiler/rustc_const_eval/src/transform/validate.rs
+++ b/compiler/rustc_const_eval/src/transform/validate.rs
@@ -358,8 +358,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 };
 
                 let kind = match parent_ty.ty.kind() {
-                    &ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                        self.tcx.type_of(def_id).subst(self.tcx, substs).kind()
+                    &ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                        self.tcx.type_of(def_id).instantiate(self.tcx, args).kind()
                     }
                     kind => kind,
                 };
@@ -372,23 +372,23 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         };
                         check_equal(self, location, *f_ty);
                     }
-                    ty::Adt(adt_def, substs) => {
+                    ty::Adt(adt_def, args) => {
                         let var = parent_ty.variant_index.unwrap_or(FIRST_VARIANT);
                         let Some(field) = adt_def.variant(var).fields.get(f) else {
                             fail_out_of_bounds(self, location);
                             return;
                         };
-                        check_equal(self, location, field.ty(self.tcx, substs));
+                        check_equal(self, location, field.ty(self.tcx, args));
                     }
-                    ty::Closure(_, substs) => {
-                        let substs = substs.as_closure();
-                        let Some(f_ty) = substs.upvar_tys().nth(f.as_usize()) else {
+                    ty::Closure(_, args) => {
+                        let args = args.as_closure();
+                        let Some(f_ty) = args.upvar_tys().nth(f.as_usize()) else {
                             fail_out_of_bounds(self, location);
                             return;
                         };
                         check_equal(self, location, f_ty);
                     }
-                    &ty::Generator(def_id, substs, _) => {
+                    &ty::Generator(def_id, args, _) => {
                         let f_ty = if let Some(var) = parent_ty.variant_index {
                             let gen_body = if def_id == self.body.source.def_id() {
                                 self.body
@@ -419,8 +419,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
 
                             f_ty.ty
                         } else {
-                            let Some(f_ty) = substs.as_generator().prefix_tys().nth(f.index())
-                            else {
+                            let Some(f_ty) = args.as_generator().prefix_tys().nth(f.index()) else {
                                 fail_out_of_bounds(self, location);
                                 return;
                             };
@@ -735,7 +734,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
 
                             current_ty = self.tcx.normalize_erasing_regions(self.param_env, f_ty);
                         }
-                        ty::Adt(adt_def, substs) => {
+                        ty::Adt(adt_def, args) => {
                             if adt_def.is_enum() {
                                 self.fail(
                                     location,
@@ -749,7 +748,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                                 return;
                             };
 
-                            let f_ty = field.ty(self.tcx, substs);
+                            let f_ty = field.ty(self.tcx, args);
                             current_ty = self.tcx.normalize_erasing_regions(self.param_env, f_ty);
                         }
                         _ => {
diff --git a/compiler/rustc_const_eval/src/util/type_name.rs b/compiler/rustc_const_eval/src/util/type_name.rs
index 4f01e0a24a5d4..14a840ad1b1e8 100644
--- a/compiler/rustc_const_eval/src/util/type_name.rs
+++ b/compiler/rustc_const_eval/src/util/type_name.rs
@@ -4,8 +4,7 @@ use rustc_hir::definitions::DisambiguatedDefPathData;
 use rustc_middle::ty::{
     self,
     print::{PrettyPrinter, Print, Printer},
-    subst::{GenericArg, GenericArgKind},
-    Ty, TyCtxt,
+    GenericArg, GenericArgKind, Ty, TyCtxt,
 };
 use std::fmt::Write;
 
@@ -56,11 +55,11 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
             }
 
             // Types with identity (print the module path).
-            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
-            | ty::FnDef(def_id, substs)
-            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
-            | ty::Closure(def_id, substs)
-            | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
+            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
+            | ty::FnDef(def_id, args)
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
+            | ty::Closure(def_id, args)
+            | ty::Generator(def_id, args, _) => self.print_def_path(def_id, args),
             ty::Foreign(def_id) => self.print_def_path(def_id, &[]),
 
             ty::Alias(ty::Weak, _) => bug!("type_name: unexpected weak projection"),
diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs
index 36600004404ad..a70671dd9fb66 100644
--- a/compiler/rustc_feature/src/builtin_attrs.rs
+++ b/compiler/rustc_feature/src/builtin_attrs.rs
@@ -812,7 +812,7 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         TEST, rustc_error, Normal,
         template!(Word, List: "delay_span_bug_from_inside_query"), WarnFollowingWordOnly
     ),
-    rustc_attr!(TEST, rustc_dump_user_substs, Normal, template!(Word), WarnFollowing),
+    rustc_attr!(TEST, rustc_dump_user_args, Normal, template!(Word), WarnFollowing),
     rustc_attr!(TEST, rustc_evaluate_where_clauses, Normal, template!(Word), WarnFollowing),
     rustc_attr!(
         TEST, rustc_if_this_changed, Normal, template!(Word, List: "DepNode"), DuplicatesOk
diff --git a/compiler/rustc_hir_analysis/src/astconv/bounds.rs b/compiler/rustc_hir_analysis/src/astconv/bounds.rs
index b13de770137ef..30145b1a185ac 100644
--- a/compiler/rustc_hir_analysis/src/astconv/bounds.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/bounds.rs
@@ -341,8 +341,8 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             // If we have an method return type bound, then we need to substitute
             // the method's early bound params with suitable late-bound params.
             let mut num_bound_vars = candidate.bound_vars().len();
-            let substs =
-                candidate.skip_binder().substs.extend_to(tcx, assoc_item.def_id, |param, _| {
+            let args =
+                candidate.skip_binder().args.extend_to(tcx, assoc_item.def_id, |param, _| {
                     let subst = match param.kind {
                         ty::GenericParamDefKind::Lifetime => ty::Region::new_late_bound(
                             tcx,
@@ -422,7 +422,7 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
             // params (and trait ref's late bound params). This logic is very similar to
             // `Predicate::subst_supertrait`, and it's no coincidence why.
             let shifted_output = tcx.shift_bound_var_indices(num_bound_vars, output);
-            let subst_output = ty::EarlyBinder::bind(shifted_output).subst(tcx, substs);
+            let subst_output = ty::EarlyBinder::bind(shifted_output).instantiate(tcx, args);
 
             let bound_vars = tcx.late_bound_vars(binding.hir_id);
             ty::Binder::bind_with_vars(subst_output, bound_vars)
@@ -438,16 +438,16 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
                     infer_args: false,
                 };
 
-                let substs_trait_ref_and_assoc_item = self.create_substs_for_associated_item(
+                let args_trait_ref_and_assoc_item = self.create_args_for_associated_item(
                     path_span,
                     assoc_item.def_id,
                     &item_segment,
-                    trait_ref.substs,
+                    trait_ref.args,
                 );
 
-                debug!(?substs_trait_ref_and_assoc_item);
+                debug!(?args_trait_ref_and_assoc_item);
 
-                tcx.mk_alias_ty(assoc_item.def_id, substs_trait_ref_and_assoc_item)
+                tcx.mk_alias_ty(assoc_item.def_id, args_trait_ref_and_assoc_item)
             })
         };
 
@@ -533,7 +533,7 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
                                 tcx,
                                 reported,
                                 tcx.type_of(assoc_item_def_id)
-                                    .subst(tcx, projection_ty.skip_binder().substs),
+                                    .instantiate(tcx, projection_ty.skip_binder().args),
                             )
                             .into(),
                             _ => unreachable!(),
diff --git a/compiler/rustc_hir_analysis/src/astconv/errors.rs b/compiler/rustc_hir_analysis/src/astconv/errors.rs
index ddf99853b2e52..8aaa005a24d1d 100644
--- a/compiler/rustc_hir_analysis/src/astconv/errors.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/errors.rs
@@ -247,7 +247,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 "the candidate".into()
             };
 
-            let impl_ty = tcx.at(span).type_of(impl_).subst_identity();
+            let impl_ty = tcx.at(span).type_of(impl_).instantiate_identity();
             let note = format!("{title} is defined in an impl for the type `{impl_ty}`");
 
             if let Some(span) = note_span {
@@ -295,7 +295,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let type_candidates = candidates
                 .iter()
                 .take(limit)
-                .map(|&(impl_, _)| format!("- `{}`", tcx.at(span).type_of(impl_).subst_identity()))
+                .map(|&(impl_, _)| {
+                    format!("- `{}`", tcx.at(span).type_of(impl_).instantiate_identity())
+                })
                 .collect::<Vec<_>>()
                 .join("\n");
             let additional_types = if candidates.len() > limit {
@@ -356,13 +358,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     // `<Foo as Iterator>::Item = String`.
                     let projection_ty = pred.skip_binder().projection_ty;
 
-                    let substs_with_infer_self = tcx.mk_substs_from_iter(
+                    let args_with_infer_self = tcx.mk_args_from_iter(
                         std::iter::once(Ty::new_var(tcx, ty::TyVid::from_u32(0)).into())
-                            .chain(projection_ty.substs.iter().skip(1)),
+                            .chain(projection_ty.args.iter().skip(1)),
                     );
 
                     let quiet_projection_ty =
-                        tcx.mk_alias_ty(projection_ty.def_id, substs_with_infer_self);
+                        tcx.mk_alias_ty(projection_ty.def_id, args_with_infer_self);
 
                     let term = pred.skip_binder().term;
 
diff --git a/compiler/rustc_hir_analysis/src/astconv/generics.rs b/compiler/rustc_hir_analysis/src/astconv/generics.rs
index 39d1d1f2de52a..e81c61d80eddb 100644
--- a/compiler/rustc_hir_analysis/src/astconv/generics.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/generics.rs
@@ -11,7 +11,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::DefId;
 use rustc_hir::GenericArg;
 use rustc_middle::ty::{
-    self, subst, subst::SubstsRef, GenericParamDef, GenericParamDefKind, IsSuggestable, Ty, TyCtxt,
+    self, GenericArgsRef, GenericParamDef, GenericParamDefKind, IsSuggestable, Ty, TyCtxt,
 };
 use rustc_session::lint::builtin::LATE_BOUND_LIFETIME_ARGUMENTS;
 use rustc_span::{symbol::kw, Span};
@@ -76,7 +76,7 @@ fn generic_arg_mismatch_err(
             Res::Def(DefKind::TyParam, src_def_id) => {
                 if let Some(param_local_id) = param.def_id.as_local() {
                     let param_name = tcx.hir().ty_param_name(param_local_id);
-                    let param_type = tcx.type_of(param.def_id).subst_identity();
+                    let param_type = tcx.type_of(param.def_id).instantiate_identity();
                     if param_type.is_suggestable(tcx, false) {
                         err.span_suggestion(
                             tcx.def_span(src_def_id),
@@ -146,14 +146,14 @@ fn generic_arg_mismatch_err(
 ///
 /// To start, we are given the `def_id` of the thing we are
 /// creating the substitutions for, and a partial set of
-/// substitutions `parent_substs`. In general, the substitutions
+/// substitutions `parent_args`. In general, the substitutions
 /// for an item begin with substitutions for all the "parents" of
 /// that item -- e.g., for a method it might include the
 /// parameters from the impl.
 ///
 /// Therefore, the method begins by walking down these parents,
 /// starting with the outermost parent and proceed inwards until
-/// it reaches `def_id`. For each parent `P`, it will check `parent_substs`
+/// it reaches `def_id`. For each parent `P`, it will check `parent_args`
 /// first to see if the parent's substitutions are listed in there. If so,
 /// we can append those and move on. Otherwise, it invokes the
 /// three callback functions:
@@ -168,15 +168,15 @@ fn generic_arg_mismatch_err(
 ///   instantiate a `GenericArg`.
 /// - `inferred_kind`: if no parameter was provided, and inference is enabled, then
 ///   creates a suitable inference variable.
-pub fn create_substs_for_generic_args<'tcx, 'a>(
+pub fn create_args_for_parent_generic_args<'tcx, 'a>(
     tcx: TyCtxt<'tcx>,
     def_id: DefId,
-    parent_substs: &[subst::GenericArg<'tcx>],
+    parent_args: &[ty::GenericArg<'tcx>],
     has_self: bool,
     self_ty: Option<Ty<'tcx>>,
     arg_count: &GenericArgCountResult,
     ctx: &mut impl CreateSubstsForGenericArgsCtxt<'a, 'tcx>,
-) -> SubstsRef<'tcx> {
+) -> GenericArgsRef<'tcx> {
     // Collect the segments of the path; we need to substitute arguments
     // for parameters throughout the entire path (wherever there are
     // generic parameters).
@@ -191,27 +191,27 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
     // We manually build up the substitution, rather than using convenience
     // methods in `subst.rs`, so that we can iterate over the arguments and
     // parameters in lock-step linearly, instead of trying to match each pair.
-    let mut substs: SmallVec<[subst::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count);
+    let mut args: SmallVec<[ty::GenericArg<'tcx>; 8]> = SmallVec::with_capacity(count);
     // Iterate over each segment of the path.
     while let Some((def_id, defs)) = stack.pop() {
         let mut params = defs.params.iter().peekable();
 
         // If we have already computed substitutions for parents, we can use those directly.
         while let Some(&param) = params.peek() {
-            if let Some(&kind) = parent_substs.get(param.index as usize) {
-                substs.push(kind);
+            if let Some(&kind) = parent_args.get(param.index as usize) {
+                args.push(kind);
                 params.next();
             } else {
                 break;
             }
         }
 
-        // `Self` is handled first, unless it's been handled in `parent_substs`.
+        // `Self` is handled first, unless it's been handled in `parent_args`.
         if has_self {
             if let Some(&param) = params.peek() {
                 if param.index == 0 {
                     if let GenericParamDefKind::Type { .. } = param.kind {
-                        substs.push(
+                        args.push(
                             self_ty
                                 .map(|ty| ty.into())
                                 .unwrap_or_else(|| ctx.inferred_kind(None, param, true)),
@@ -226,7 +226,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
         let (generic_args, infer_args) = ctx.args_for_def_id(def_id);
 
         let args_iter = generic_args.iter().flat_map(|generic_args| generic_args.args.iter());
-        let mut args = args_iter.clone().peekable();
+        let mut args_iter = args_iter.clone().peekable();
 
         // If we encounter a type or const when we expect a lifetime, we infer the lifetimes.
         // If we later encounter a lifetime, we know that the arguments were provided in the
@@ -239,7 +239,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
             // provided, matching them with the generic parameters we expect.
             // Mismatches can occur as a result of elided lifetimes, or for malformed
             // input. We try to handle both sensibly.
-            match (args.peek(), params.peek()) {
+            match (args_iter.peek(), params.peek()) {
                 (Some(&arg), Some(&param)) => {
                     match (arg, &param.kind, arg_count.explicit_late_bound) {
                         (GenericArg::Lifetime(_), GenericParamDefKind::Lifetime, _)
@@ -253,8 +253,8 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
                             GenericParamDefKind::Const { .. },
                             _,
                         ) => {
-                            substs.push(ctx.provided_kind(param, arg));
-                            args.next();
+                            args.push(ctx.provided_kind(param, arg));
+                            args_iter.next();
                             params.next();
                         }
                         (
@@ -264,7 +264,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
                         ) => {
                             // We expected a lifetime argument, but got a type or const
                             // argument. That means we're inferring the lifetimes.
-                            substs.push(ctx.inferred_kind(None, param, infer_args));
+                            args.push(ctx.inferred_kind(None, param, infer_args));
                             force_infer_lt = Some((arg, param));
                             params.next();
                         }
@@ -273,7 +273,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
                             // the presence of explicit late bounds. This is most likely
                             // due to the presence of the explicit bound so we're just going to
                             // ignore it.
-                            args.next();
+                            args_iter.next();
                         }
                         (_, _, _) => {
                             // We expected one kind of parameter, but the user provided
@@ -327,7 +327,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
                             // errors. In this case, we're simply going to ignore the argument
                             // and any following arguments. The rest of the parameters will be
                             // inferred.
-                            while args.next().is_some() {}
+                            while args_iter.next().is_some() {}
                         }
                     }
                 }
@@ -360,7 +360,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
                 (None, Some(&param)) => {
                     // If there are fewer arguments than parameters, it means
                     // we're inferring the remaining arguments.
-                    substs.push(ctx.inferred_kind(Some(&substs), param, infer_args));
+                    args.push(ctx.inferred_kind(Some(&args), param, infer_args));
                     params.next();
                 }
 
@@ -369,7 +369,7 @@ pub fn create_substs_for_generic_args<'tcx, 'a>(
         }
     }
 
-    tcx.mk_substs(&substs)
+    tcx.mk_args(&args)
 }
 
 /// Checks that the correct number of generic arguments have been provided.
diff --git a/compiler/rustc_hir_analysis/src/astconv/mod.rs b/compiler/rustc_hir_analysis/src/astconv/mod.rs
index e9c9151ca2376..ecbbfd9253903 100644
--- a/compiler/rustc_hir_analysis/src/astconv/mod.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/mod.rs
@@ -9,7 +9,7 @@ mod lint;
 mod object_safety;
 
 use crate::astconv::errors::prohibit_assoc_ty_binding;
-use crate::astconv::generics::{check_generic_arg_count, create_substs_for_generic_args};
+use crate::astconv::generics::{check_generic_arg_count, create_args_for_parent_generic_args};
 use crate::bounds::Bounds;
 use crate::collect::HirPlaceholderCollector;
 use crate::errors::{AmbiguousLifetimeBound, TypeofReservedKeywordUsed};
@@ -29,9 +29,10 @@ use rustc_hir::{GenericArg, GenericArgs, OpaqueTyOrigin};
 use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
 use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability::AllowUnstable;
-use rustc_middle::ty::subst::{self, GenericArgKind, InternalSubsts, SubstsRef};
 use rustc_middle::ty::GenericParamDefKind;
-use rustc_middle::ty::{self, Const, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{
+    self, Const, GenericArgKind, GenericArgsRef, IsSuggestable, Ty, TyCtxt, TypeVisitableExt,
+};
 use rustc_session::lint::builtin::AMBIGUOUS_ASSOCIATED_ITEMS;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::symbol::{kw, Ident, Symbol};
@@ -220,14 +221,14 @@ pub trait CreateSubstsForGenericArgsCtxt<'a, 'tcx> {
         &mut self,
         param: &ty::GenericParamDef,
         arg: &GenericArg<'_>,
-    ) -> subst::GenericArg<'tcx>;
+    ) -> ty::GenericArg<'tcx>;
 
     fn inferred_kind(
         &mut self,
-        substs: Option<&[subst::GenericArg<'tcx>]>,
+        args: Option<&[ty::GenericArg<'tcx>]>,
         param: &ty::GenericParamDef,
         infer_args: bool,
-    ) -> subst::GenericArg<'tcx>;
+    ) -> ty::GenericArg<'tcx>;
 }
 
 impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
@@ -291,13 +292,13 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
     /// Given a path `path` that refers to an item `I` with the declared generics `decl_generics`,
     /// returns an appropriate set of substitutions for this particular reference to `I`.
-    pub fn ast_path_substs_for_ty(
+    pub fn ast_path_args_for_ty(
         &self,
         span: Span,
         def_id: DefId,
         item_segment: &hir::PathSegment<'_>,
-    ) -> SubstsRef<'tcx> {
-        let (substs, _) = self.create_substs_for_ast_path(
+    ) -> GenericArgsRef<'tcx> {
+        let (args, _) = self.create_args_for_ast_path(
             span,
             def_id,
             &[],
@@ -311,7 +312,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             prohibit_assoc_ty_binding(self.tcx(), b.span, Some((item_segment, span)));
         }
 
-        substs
+        args
     }
 
     /// Given the type/lifetime/const arguments provided to some path (along with
@@ -330,7 +331,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     /// 2. The path in question is the path to the trait `std::ops::Index`,
     ///    which will have been resolved to a `def_id`
     /// 3. The `generic_args` contains info on the `<...>` contents. The `usize` type
-    ///    parameters are returned in the `SubstsRef`, the associated type bindings like
+    ///    parameters are returned in the `GenericArgsRef`, the associated type bindings like
     ///    `Output = u32` are returned from `create_assoc_bindings_for_generic_args`.
     ///
     /// Note that the type listing given here is *exactly* what the user provided.
@@ -341,22 +342,22 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     /// <Vec<u8> as Iterable<u8>>::Iter::<'a>
     /// ```
     ///
-    /// We have the parent substs are the substs for the parent trait:
+    /// We have the parent args are the args for the parent trait:
     /// `[Vec<u8>, u8]` and `generic_args` are the arguments for the associated
-    /// type itself: `['a]`. The returned `SubstsRef` concatenates these two
+    /// type itself: `['a]`. The returned `GenericArgsRef` concatenates these two
     /// lists: `[Vec<u8>, u8, 'a]`.
     #[instrument(level = "debug", skip(self, span), ret)]
-    fn create_substs_for_ast_path<'a>(
+    fn create_args_for_ast_path<'a>(
         &self,
         span: Span,
         def_id: DefId,
-        parent_substs: &[subst::GenericArg<'tcx>],
+        parent_args: &[ty::GenericArg<'tcx>],
         seg: &hir::PathSegment<'_>,
         generic_args: &'a hir::GenericArgs<'_>,
         infer_args: bool,
         self_ty: Option<Ty<'tcx>>,
         constness: ty::BoundConstness,
-    ) -> (SubstsRef<'tcx>, GenericArgCountResult) {
+    ) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
         // If the type is parameterized by this region, then replace this
         // region with the current anon region binding (in other words,
         // whatever & would get replaced with).
@@ -369,7 +370,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             if generics.parent.is_some() {
                 // The parent is a trait so it should have at least one subst
                 // for the `Self` type.
-                assert!(!parent_substs.is_empty())
+                assert!(!parent_args.is_empty())
             } else {
                 // This item (presumably a trait) needs a self-type.
                 assert!(self_ty.is_some());
@@ -395,7 +396,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         // here and so associated type bindings will be handled regardless of whether there are any
         // non-`Self` generic parameters.
         if generics.params.is_empty() {
-            return (tcx.mk_substs(parent_substs), arg_count);
+            return (tcx.mk_args(parent_args), arg_count);
         }
 
         struct SubstsForAstPathCtxt<'a, 'tcx> {
@@ -421,7 +422,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 &mut self,
                 param: &ty::GenericParamDef,
                 arg: &GenericArg<'_>,
-            ) -> subst::GenericArg<'tcx> {
+            ) -> ty::GenericArg<'tcx> {
                 let tcx = self.astconv.tcx();
 
                 let mut handle_ty_args = |has_default, ty: &hir::Ty<'_>| {
@@ -483,10 +484,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
             fn inferred_kind(
                 &mut self,
-                substs: Option<&[subst::GenericArg<'tcx>]>,
+                args: Option<&[ty::GenericArg<'tcx>]>,
                 param: &ty::GenericParamDef,
                 infer_args: bool,
-            ) -> subst::GenericArg<'tcx> {
+            ) -> ty::GenericArg<'tcx> {
                 let tcx = self.astconv.tcx();
                 match param.kind {
                     GenericParamDefKind::Lifetime => self
@@ -506,15 +507,15 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     GenericParamDefKind::Type { has_default, .. } => {
                         if !infer_args && has_default {
                             // No type parameter provided, but a default exists.
-                            let substs = substs.unwrap();
-                            if substs.iter().any(|arg| match arg.unpack() {
+                            let args = args.unwrap();
+                            if args.iter().any(|arg| match arg.unpack() {
                                 GenericArgKind::Type(ty) => ty.references_error(),
                                 _ => false,
                             }) {
                                 // Avoid ICE #86756 when type error recovery goes awry.
                                 return Ty::new_misc_error(tcx).into();
                             }
-                            tcx.at(self.span).type_of(param.def_id).subst(tcx, substs).into()
+                            tcx.at(self.span).type_of(param.def_id).instantiate(tcx, args).into()
                         } else if infer_args {
                             self.astconv.ty_infer(Some(param), self.span).into()
                         } else {
@@ -532,7 +533,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             return ty::Const::new_error(tcx, guar, ty).into();
                         }
                         if !infer_args && has_default {
-                            tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into()
+                            tcx.const_param_default(param.def_id)
+                                .instantiate(tcx, args.unwrap())
+                                .into()
                         } else {
                             if infer_args {
                                 self.astconv.ct_infer(ty, Some(param), self.span).into()
@@ -546,7 +549,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
         }
 
-        let mut substs_ctx = SubstsForAstPathCtxt {
+        let mut args_ctx = SubstsForAstPathCtxt {
             astconv: self,
             def_id,
             span,
@@ -554,14 +557,14 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             inferred_params: vec![],
             infer_args,
         };
-        let substs = create_substs_for_generic_args(
+        let args = create_args_for_parent_generic_args(
             tcx,
             def_id,
-            parent_substs,
+            parent_args,
             self_ty.is_some(),
             self_ty,
             &arg_count,
-            &mut substs_ctx,
+            &mut args_ctx,
         );
 
         if let ty::BoundConstness::ConstIfConst = constness
@@ -570,7 +573,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             tcx.sess.emit_err(crate::errors::ConstBoundForNonConstTrait { span } );
         }
 
-        (substs, arg_count)
+        (args, arg_count)
     }
 
     fn create_assoc_bindings_for_generic_args<'a>(
@@ -617,21 +620,21 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         assoc_bindings
     }
 
-    pub fn create_substs_for_associated_item(
+    pub fn create_args_for_associated_item(
         &self,
         span: Span,
         item_def_id: DefId,
         item_segment: &hir::PathSegment<'_>,
-        parent_substs: SubstsRef<'tcx>,
-    ) -> SubstsRef<'tcx> {
+        parent_args: GenericArgsRef<'tcx>,
+    ) -> GenericArgsRef<'tcx> {
         debug!(
-            "create_substs_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
+            "create_args_for_associated_item(span: {:?}, item_def_id: {:?}, item_segment: {:?}",
             span, item_def_id, item_segment
         );
-        let (args, _) = self.create_substs_for_ast_path(
+        let (args, _) = self.create_args_for_ast_path(
             span,
             item_def_id,
-            parent_substs,
+            parent_args,
             item_segment,
             item_segment.args(),
             item_segment.infer_args,
@@ -687,7 +690,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         self_ty: Ty<'tcx>,
         only_self_bounds: OnlySelfBounds,
     ) -> GenericArgCountResult {
-        let (substs, arg_count) = self.create_substs_for_ast_path(
+        let (generic_args, arg_count) = self.create_args_for_ast_path(
             trait_ref_span,
             trait_def_id,
             &[],
@@ -704,8 +707,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
         let assoc_bindings = self.create_assoc_bindings_for_generic_args(args);
 
-        let poly_trait_ref =
-            ty::Binder::bind_with_vars(ty::TraitRef::new(tcx, trait_def_id, substs), bound_vars);
+        let poly_trait_ref = ty::Binder::bind_with_vars(
+            ty::TraitRef::new(tcx, trait_def_id, generic_args),
+            bound_vars,
+        );
 
         debug!(?poly_trait_ref, ?assoc_bindings);
         bounds.push_trait_bound(tcx, poly_trait_ref, span, constness, polarity);
@@ -846,7 +851,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         is_impl: bool,
         constness: ty::BoundConstness,
     ) -> ty::TraitRef<'tcx> {
-        let (substs, _) = self.create_substs_for_ast_trait_ref(
+        let (generic_args, _) = self.create_args_for_ast_trait_ref(
             span,
             trait_def_id,
             self_ty,
@@ -857,11 +862,11 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         if let Some(b) = trait_segment.args().bindings.first() {
             prohibit_assoc_ty_binding(self.tcx(), b.span, Some((trait_segment, span)));
         }
-        ty::TraitRef::new(self.tcx(), trait_def_id, substs)
+        ty::TraitRef::new(self.tcx(), trait_def_id, generic_args)
     }
 
     #[instrument(level = "debug", skip(self, span))]
-    fn create_substs_for_ast_trait_ref<'a>(
+    fn create_args_for_ast_trait_ref<'a>(
         &self,
         span: Span,
         trait_def_id: DefId,
@@ -869,10 +874,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         trait_segment: &'a hir::PathSegment<'a>,
         is_impl: bool,
         constness: ty::BoundConstness,
-    ) -> (SubstsRef<'tcx>, GenericArgCountResult) {
+    ) -> (GenericArgsRef<'tcx>, GenericArgCountResult) {
         self.complain_about_internal_fn_trait(span, trait_def_id, trait_segment, is_impl);
 
-        self.create_substs_for_ast_path(
+        self.create_args_for_ast_path(
             span,
             trait_def_id,
             &[],
@@ -902,7 +907,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         did: DefId,
         item_segment: &hir::PathSegment<'_>,
     ) -> Ty<'tcx> {
-        let substs = self.ast_path_substs_for_ty(span, did, item_segment);
+        let args = self.ast_path_args_for_ty(span, did, item_segment);
         let ty = self.tcx().at(span).type_of(did);
 
         if matches!(self.tcx().def_kind(did), DefKind::TyAlias)
@@ -911,10 +916,10 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             // Type aliases referring to types that contain opaque types (but aren't just directly
             // referencing a single opaque type) get encoded as a type alias that normalization will
             // then actually instantiate the where bounds of.
-            let alias_ty = self.tcx().mk_alias_ty(did, substs);
+            let alias_ty = self.tcx().mk_alias_ty(did, args);
             Ty::new_alias(self.tcx(), ty::Weak, alias_ty)
         } else {
-            ty.subst(self.tcx(), substs)
+            ty.instantiate(self.tcx(), args)
         }
     }
 
@@ -1383,7 +1388,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 };
 
                 self.one_bound_for_assoc_type(
-                    || traits::supertraits(tcx, ty::Binder::dummy(trait_ref.subst_identity())),
+                    || {
+                        traits::supertraits(
+                            tcx,
+                            ty::Binder::dummy(trait_ref.instantiate_identity()),
+                        )
+                    },
                     kw::SelfUpper,
                     assoc_ident,
                     span,
@@ -1620,8 +1630,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         let ocx = ObligationCtxt::new(&infcx);
                         ocx.register_obligations(obligations.clone());
 
-                        let impl_substs = infcx.fresh_substs_for_item(span, impl_);
-                        let impl_ty = tcx.type_of(impl_).subst(tcx, impl_substs);
+                        let impl_args = infcx.fresh_args_for_item(span, impl_);
+                        let impl_ty = tcx.type_of(impl_).instantiate(tcx, impl_args);
                         let impl_ty = ocx.normalize(&cause, param_env, impl_ty);
 
                         // Check that the self types can be related.
@@ -1633,7 +1643,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         }
 
                         // Check whether the impl imposes obligations we have to worry about.
-                        let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_substs);
+                        let impl_bounds = tcx.predicates_of(impl_).instantiate(tcx, impl_args);
                         let impl_bounds = ocx.normalize(&cause, param_env, impl_bounds);
                         let impl_obligations = traits::predicates_for_generics(
                             |_, _| cause.clone(),
@@ -1665,18 +1675,17 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         if let Some((impl_, (assoc_item, def_scope))) = applicable_candidates.pop() {
             self.check_assoc_ty(assoc_item, name, def_scope, block, span);
 
-            // FIXME(fmease): Currently creating throwaway `parent_substs` to please
-            // `create_substs_for_associated_item`. Modify the latter instead (or sth. similar) to
-            // not require the parent substs logic.
-            let parent_substs = InternalSubsts::identity_for_item(tcx, impl_);
-            let substs =
-                self.create_substs_for_associated_item(span, assoc_item, segment, parent_substs);
-            let substs = tcx.mk_substs_from_iter(
+            // FIXME(fmease): Currently creating throwaway `parent_args` to please
+            // `create_args_for_associated_item`. Modify the latter instead (or sth. similar) to
+            // not require the parent args logic.
+            let parent_args = ty::GenericArgs::identity_for_item(tcx, impl_);
+            let args = self.create_args_for_associated_item(span, assoc_item, segment, parent_args);
+            let args = tcx.mk_args_from_iter(
                 std::iter::once(ty::GenericArg::from(self_ty))
-                    .chain(substs.into_iter().skip(parent_substs.len())),
+                    .chain(args.into_iter().skip(parent_args.len())),
             );
 
-            let ty = Ty::new_alias(tcx, ty::Inherent, tcx.mk_alias_ty(assoc_item, substs));
+            let ty = Ty::new_alias(tcx, ty::Inherent, tcx.mk_alias_ty(assoc_item, args));
 
             return Ok(Some((ty, assoc_item)));
         }
@@ -1780,9 +1789,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         .any(|impl_def_id| {
                             let trait_ref = tcx.impl_trait_ref(impl_def_id);
                             trait_ref.is_some_and(|trait_ref| {
-                                let impl_ = trait_ref.subst(
+                                let impl_ = trait_ref.instantiate(
                                     tcx,
-                                    infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id),
+                                    infcx.fresh_args_for_item(DUMMY_SP, impl_def_id),
                                 );
                                 let value = tcx.fold_regions(qself_ty, |_, _| tcx.lifetimes.re_erased);
                                 // FIXME: Don't bother dealing with non-lifetime binders here...
@@ -1848,7 +1857,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             && tcx.impl_polarity(impl_def_id) != ty::ImplPolarity::Negative
                     })
                     .filter_map(|impl_def_id| tcx.impl_trait_ref(impl_def_id))
-                    .map(|impl_| impl_.subst_identity().self_ty())
+                    .map(|impl_| impl_.instantiate_identity().self_ty())
                     // We don't care about blanket impls.
                     .filter(|self_ty| !self_ty.has_non_region_param())
                     .map(|self_ty| tcx.erase_regions(self_ty).to_string())
@@ -1877,16 +1886,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             constness,
         );
 
-        let item_substs = self.create_substs_for_associated_item(
-            span,
-            item_def_id,
-            item_segment,
-            trait_ref.substs,
-        );
+        let item_args =
+            self.create_args_for_associated_item(span, item_def_id, item_segment, trait_ref.args);
 
         debug!("qpath_to_ty: trait_ref={:?}", trait_ref);
 
-        Ty::new_projection(tcx, item_def_id, item_substs)
+        Ty::new_projection(tcx, item_def_id, item_args)
     }
 
     pub fn prohibit_generics<'a>(
@@ -2148,8 +2153,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 self.prohibit_generics(item_segment.1.iter(), |err| {
                     err.note("`impl Trait` types can't have type parameters");
                 });
-                let substs = self.ast_path_substs_for_ty(span, did, item_segment.0);
-                Ty::new_opaque(tcx, did, substs)
+                let args = self.ast_path_args_for_ty(span, did, item_segment.0);
+                Ty::new_opaque(tcx, did, args)
             }
             Res::Def(
                 DefKind::Enum
@@ -2233,7 +2238,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 // `Self` in impl (we know the concrete type).
                 assert_eq!(opt_self_ty, None);
                 // Try to evaluate any array length constants.
-                let ty = tcx.at(span).type_of(def_id).subst_identity();
+                let ty = tcx.at(span).type_of(def_id).instantiate_identity();
                 let span_of_impl = tcx.span_of_impl(def_id);
                 self.prohibit_generics(path.segments.iter(), |err| {
                     let def_id = match *ty.kind() {
@@ -2471,7 +2476,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             }
             &hir::TyKind::Path(hir::QPath::LangItem(lang_item, span, _)) => {
                 let def_id = tcx.require_lang_item(lang_item, Some(span));
-                let (substs, _) = self.create_substs_for_ast_path(
+                let (args, _) = self.create_args_for_ast_path(
                     span,
                     def_id,
                     &[],
@@ -2481,7 +2486,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     None,
                     ty::BoundConstness::NotConst,
                 );
-                tcx.at(span).type_of(def_id).subst(tcx, substs)
+                tcx.at(span).type_of(def_id).instantiate(tcx, args)
             }
             hir::TyKind::Array(ty, length) => {
                 let length = match length {
@@ -2494,7 +2499,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 Ty::new_array_with_const_len(tcx, self.ast_ty_to_ty(ty), length)
             }
             hir::TyKind::Typeof(e) => {
-                let ty_erased = tcx.type_of(e.def_id).subst_identity();
+                let ty_erased = tcx.type_of(e.def_id).instantiate_identity();
                 let ty = tcx.fold_regions(ty_erased, |r, _| {
                     if r.is_erased() { tcx.lifetimes.re_static } else { r }
                 });
@@ -2536,7 +2541,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         let generics = tcx.generics_of(def_id);
 
         debug!("impl_trait_ty_to_ty: generics={:?}", generics);
-        let substs = InternalSubsts::for_item(tcx, def_id, |param, _| {
+        let args = ty::GenericArgs::for_item(tcx, def_id, |param, _| {
             // We use `generics.count() - lifetimes.len()` here instead of `generics.parent_count`
             // since return-position impl trait in trait squashes all of the generics from its source fn
             // into its own generics, so the opaque's "own" params isn't always just lifetimes.
@@ -2550,12 +2555,12 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 tcx.mk_param_from_def(param)
             }
         });
-        debug!("impl_trait_ty_to_ty: substs={:?}", substs);
+        debug!("impl_trait_ty_to_ty: args={:?}", args);
 
         if in_trait {
-            Ty::new_projection(tcx, def_id, substs)
+            Ty::new_projection(tcx, def_id, args)
         } else {
-            Ty::new_opaque(tcx, def_id, substs)
+            Ty::new_opaque(tcx, def_id, args)
         }
     }
 
@@ -2720,9 +2725,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             trait_ref.def_id,
         )?;
 
-        let fn_sig = tcx.fn_sig(assoc.def_id).subst(
+        let fn_sig = tcx.fn_sig(assoc.def_id).instantiate(
             tcx,
-            trait_ref.substs.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)),
+            trait_ref.args.extend_to(tcx, assoc.def_id, |param, _| tcx.mk_param_from_def(param)),
         );
         let fn_sig = tcx.liberate_late_bound_regions(fn_hir_id.expect_owner().to_def_id(), fn_sig);
 
diff --git a/compiler/rustc_hir_analysis/src/astconv/object_safety.rs b/compiler/rustc_hir_analysis/src/astconv/object_safety.rs
index 9227ee9345142..034f2e4da0194 100644
--- a/compiler/rustc_hir_analysis/src/astconv/object_safety.rs
+++ b/compiler/rustc_hir_analysis/src/astconv/object_safety.rs
@@ -262,8 +262,8 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let mut missing_type_params = vec![];
                 let mut references_self = false;
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let substs: Vec<_> = trait_ref
-                    .substs
+                let args: Vec<_> = trait_ref
+                    .args
                     .iter()
                     .enumerate()
                     .skip(1) // Remove `Self` for `ExistentialPredicate`.
@@ -279,7 +279,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         arg
                     })
                     .collect();
-                let substs = tcx.mk_substs(&substs);
+                let args = tcx.mk_args(&args);
 
                 let span = i.bottom().1;
                 let empty_generic_args = hir_trait_bounds.iter().any(|hir_bound| {
@@ -310,7 +310,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     err.emit();
                 }
 
-                ty::ExistentialTraitRef { def_id: trait_ref.def_id, substs }
+                ty::ExistentialTraitRef { def_id: trait_ref.def_id, args }
             })
         });
 
@@ -325,7 +325,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
 
                     // Like for trait refs, verify that `dummy_self` did not leak inside default type
                     // parameters.
-                    let references_self = b.projection_ty.substs.iter().skip(1).any(|arg| {
+                    let references_self = b.projection_ty.args.iter().skip(1).any(|arg| {
                         if arg.walk().any(|arg| arg == dummy_self.into()) {
                             return true;
                         }
@@ -336,9 +336,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                             span,
                             "trait object projection bounds reference `Self`",
                         );
-                        let substs: Vec<_> = b
+                        let args: Vec<_> = b
                             .projection_ty
-                            .substs
+                            .args
                             .iter()
                             .map(|arg| {
                                 if arg.walk().any(|arg| arg == dummy_self.into()) {
@@ -347,7 +347,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                                 arg
                             })
                             .collect();
-                        b.projection_ty.substs = tcx.mk_substs(&substs);
+                        b.projection_ty.args = tcx.mk_args(&args);
                     }
 
                     ty::ExistentialProjection::erase_self_ty(tcx, b)
diff --git a/compiler/rustc_hir_analysis/src/check/check.rs b/compiler/rustc_hir_analysis/src/check/check.rs
index 91c33b09082a2..a4ef8e43527ca 100644
--- a/compiler/rustc_hir_analysis/src/check/check.rs
+++ b/compiler/rustc_hir_analysis/src/check/check.rs
@@ -20,8 +20,8 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::stability::EvalResult;
 use rustc_middle::traits::DefiningAnchor;
 use rustc_middle::ty::layout::{LayoutError, MAX_SIMD_LANES};
-use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::util::{Discr, IntTypeExt};
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{
     self, AdtDef, ParamEnv, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
@@ -96,8 +96,8 @@ fn check_union(tcx: TyCtxt<'_>, def_id: LocalDefId) {
 
 /// Check that the fields of the `union` do not need dropping.
 fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> bool {
-    let item_type = tcx.type_of(item_def_id).subst_identity();
-    if let ty::Adt(def, substs) = item_type.kind() {
+    let item_type = tcx.type_of(item_def_id).instantiate_identity();
+    if let ty::Adt(def, args) = item_type.kind() {
         assert!(def.is_union());
 
         fn allowed_union_field<'tcx>(
@@ -128,7 +128,7 @@ fn check_union_fields(tcx: TyCtxt<'_>, span: Span, item_def_id: LocalDefId) -> b
 
         let param_env = tcx.param_env(item_def_id);
         for field in &def.non_enum_variant().fields {
-            let field_ty = tcx.normalize_erasing_regions(param_env, field.ty(tcx, substs));
+            let field_ty = tcx.normalize_erasing_regions(param_env, field.ty(tcx, args));
 
             if !allowed_union_field(field_ty, tcx, param_env) {
                 let (field_span, ty_span) = match tcx.hir().get_if_local(field.did) {
@@ -163,7 +163,7 @@ fn check_static_inhabited(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     // would be enough to check this for `extern` statics, as statics with an initializer will
     // have UB during initialization if they are uninhabited, but there also seems to be no good
     // reason to allow any statics to be uninhabited.
-    let ty = tcx.type_of(def_id).subst_identity();
+    let ty = tcx.type_of(def_id).instantiate_identity();
     let span = tcx.def_span(def_id);
     let layout = match tcx.layout_of(ParamEnv::reveal_all().and(ty)) {
         Ok(l) => l,
@@ -212,16 +212,16 @@ fn check_opaque(tcx: TyCtxt<'_>, id: hir::ItemId) {
         return;
     }
 
-    let substs = InternalSubsts::identity_for_item(tcx, item.owner_id);
+    let args = GenericArgs::identity_for_item(tcx, item.owner_id);
     let span = tcx.def_span(item.owner_id.def_id);
 
     if !tcx.features().impl_trait_projections {
         check_opaque_for_inheriting_lifetimes(tcx, item.owner_id.def_id, span);
     }
-    if tcx.type_of(item.owner_id.def_id).subst_identity().references_error() {
+    if tcx.type_of(item.owner_id.def_id).instantiate_identity().references_error() {
         return;
     }
-    if check_opaque_for_cycles(tcx, item.owner_id.def_id, substs, span, &origin).is_err() {
+    if check_opaque_for_cycles(tcx, item.owner_id.def_id, args, span, &origin).is_err() {
         return;
     }
 
@@ -305,8 +305,8 @@ pub(super) fn check_opaque_for_inheriting_lifetimes(
         ..
     }) = item.kind
     {
-        let substs = InternalSubsts::identity_for_item(tcx, def_id);
-        let opaque_identity_ty = Ty::new_opaque(tcx, def_id.to_def_id(), substs);
+        let args = GenericArgs::identity_for_item(tcx, def_id);
+        let opaque_identity_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args);
         let mut visitor = ProhibitOpaqueVisitor {
             opaque_identity_ty,
             parent_count: tcx.generics_of(def_id).parent_count as u32,
@@ -316,7 +316,7 @@ pub(super) fn check_opaque_for_inheriting_lifetimes(
         };
         let prohibit_opaque = tcx
             .explicit_item_bounds(def_id)
-            .subst_identity_iter_copied()
+            .instantiate_identity_iter_copied()
             .try_for_each(|(predicate, _)| predicate.visit_with(&mut visitor));
 
         if let Some(ty) = prohibit_opaque.break_value() {
@@ -355,11 +355,11 @@ pub(super) fn check_opaque_for_inheriting_lifetimes(
 pub(super) fn check_opaque_for_cycles<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     span: Span,
     origin: &hir::OpaqueTyOrigin,
 ) -> Result<(), ErrorGuaranteed> {
-    if tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs).is_err() {
+    if tcx.try_expand_impl_trait_type(def_id.to_def_id(), args).is_err() {
         let reported = match origin {
             hir::OpaqueTyOrigin::AsyncFn(..) => async_opaque_type_cycle_error(tcx, span),
             _ => opaque_type_cycle_error(tcx, def_id, span),
@@ -404,16 +404,16 @@ fn check_opaque_meets_bounds<'tcx>(
         .build();
     let ocx = ObligationCtxt::new(&infcx);
 
-    let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
-    let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), substs);
+    let args = GenericArgs::identity_for_item(tcx, def_id.to_def_id());
+    let opaque_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args);
 
-    // `ReErased` regions appear in the "parent_substs" of closures/generators.
+    // `ReErased` regions appear in the "parent_args" of closures/generators.
     // We're ignoring them here and replacing them with fresh region variables.
-    // See tests in ui/type-alias-impl-trait/closure_{parent_substs,wf_outlives}.rs.
+    // See tests in ui/type-alias-impl-trait/closure_{parent_args,wf_outlives}.rs.
     //
     // FIXME: Consider wrapping the hidden type in an existential `Binder` and instantiating it
     // here rather than using ReErased.
-    let hidden_ty = tcx.type_of(def_id.to_def_id()).subst(tcx, substs);
+    let hidden_ty = tcx.type_of(def_id.to_def_id()).instantiate(tcx, args);
     let hidden_ty = tcx.fold_regions(hidden_ty, |re, _dbi| match re.kind() {
         ty::ReErased => infcx.next_region_var(RegionVariableOrigin::MiscVariable(span)),
         _ => re,
@@ -472,7 +472,7 @@ fn check_opaque_meets_bounds<'tcx>(
 fn is_enum_of_nonnullable_ptr<'tcx>(
     tcx: TyCtxt<'tcx>,
     adt_def: AdtDef<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
 ) -> bool {
     if adt_def.repr().inhibit_enum_layout_opt() {
         return false;
@@ -484,14 +484,14 @@ fn is_enum_of_nonnullable_ptr<'tcx>(
     let (([], [field]) | ([field], [])) = (&var_one.fields.raw[..], &var_two.fields.raw[..]) else {
         return false;
     };
-    matches!(field.ty(tcx, substs).kind(), ty::FnPtr(..) | ty::Ref(..))
+    matches!(field.ty(tcx, args).kind(), ty::FnPtr(..) | ty::Ref(..))
 }
 
 fn check_static_linkage(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     if tcx.codegen_fn_attrs(def_id).import_linkage.is_some() {
-        if match tcx.type_of(def_id).subst_identity().kind() {
+        if match tcx.type_of(def_id).instantiate_identity().kind() {
             ty::RawPtr(_) => false,
-            ty::Adt(adt_def, substs) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *substs),
+            ty::Adt(adt_def, args) => !is_enum_of_nonnullable_ptr(tcx, *adt_def, *args),
             _ => true,
         } {
             tcx.sess.emit_err(LinkageType { span: tcx.def_span(def_id) });
@@ -525,7 +525,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
                 check_impl_items_against_trait(
                     tcx,
                     id.owner_id.def_id,
-                    impl_trait_ref.subst_identity(),
+                    impl_trait_ref.instantiate_identity(),
                 );
                 check_on_unimplemented(tcx, id);
             }
@@ -541,13 +541,13 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
                         fn_maybe_err(tcx, assoc_item.ident(tcx).span, abi);
                     }
                     ty::AssocKind::Type if assoc_item.defaultness(tcx).has_value() => {
-                        let trait_substs =
-                            InternalSubsts::identity_for_item(tcx, id.owner_id);
+                        let trait_args =
+                            GenericArgs::identity_for_item(tcx, id.owner_id);
                         let _: Result<_, rustc_errors::ErrorGuaranteed> = check_type_bounds(
                             tcx,
                             assoc_item,
                             assoc_item,
-                            ty::TraitRef::new(tcx, id.owner_id.to_def_id(), trait_substs),
+                            ty::TraitRef::new(tcx, id.owner_id.to_def_id(), trait_args),
                         );
                     }
                     _ => {}
@@ -572,7 +572,7 @@ fn check_item_type(tcx: TyCtxt<'_>, id: hir::ItemId) {
             }
         }
         DefKind::TyAlias => {
-            let pty_ty = tcx.type_of(id.owner_id).subst_identity();
+            let pty_ty = tcx.type_of(id.owner_id).instantiate_identity();
             let generics = tcx.generics_of(id.owner_id);
             check_type_params_are_used(tcx, &generics, pty_ty);
         }
@@ -886,8 +886,8 @@ fn check_impl_items_against_trait<'tcx>(
 }
 
 pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
-    let t = tcx.type_of(def_id).subst_identity();
-    if let ty::Adt(def, substs) = t.kind()
+    let t = tcx.type_of(def_id).instantiate_identity();
+    if let ty::Adt(def, args) = t.kind()
         && def.is_struct()
     {
         let fields = &def.non_enum_variant().fields;
@@ -895,8 +895,8 @@ pub fn check_simd(tcx: TyCtxt<'_>, sp: Span, def_id: LocalDefId) {
             struct_span_err!(tcx.sess, sp, E0075, "SIMD vector cannot be empty").emit();
             return;
         }
-        let e = fields[FieldIdx::from_u32(0)].ty(tcx, substs);
-        if !fields.iter().all(|f| f.ty(tcx, substs) == e) {
+        let e = fields[FieldIdx::from_u32(0)].ty(tcx, args);
+        if !fields.iter().all(|f| f.ty(tcx, args) == e) {
             struct_span_err!(tcx.sess, sp, E0076, "SIMD vector should be homogeneous")
                 .span_label(sp, "SIMD elements must have the same type")
                 .emit();
@@ -1003,7 +1003,7 @@ pub(super) fn check_packed(tcx: TyCtxt<'_>, sp: Span, def: ty::AdtDef<'_>) {
                             if first {
                                 format!(
                                     "`{}` contains a field of type `{}`",
-                                    tcx.type_of(def.did()).subst_identity(),
+                                    tcx.type_of(def.did()).instantiate_identity(),
                                     ident
                                 )
                             } else {
@@ -1025,7 +1025,7 @@ pub(super) fn check_packed_inner(
     def_id: DefId,
     stack: &mut Vec<DefId>,
 ) -> Option<Vec<(DefId, Span)>> {
-    if let ty::Adt(def, substs) = tcx.type_of(def_id).subst_identity().kind() {
+    if let ty::Adt(def, args) = tcx.type_of(def_id).instantiate_identity().kind() {
         if def.is_struct() || def.is_union() {
             if def.repr().align.is_some() {
                 return Some(vec![(def.did(), DUMMY_SP)]);
@@ -1033,7 +1033,7 @@ pub(super) fn check_packed_inner(
 
             stack.push(def_id);
             for field in &def.non_enum_variant().fields {
-                if let ty::Adt(def, _) = field.ty(tcx, substs).kind()
+                if let ty::Adt(def, _) = field.ty(tcx, args).kind()
                     && !stack.contains(&def.did())
                     && let Some(mut defs) = check_packed_inner(tcx, def.did(), stack)
                 {
@@ -1072,7 +1072,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
     // For each field, figure out if it's known to be a ZST and align(1), with "known"
     // respecting #[non_exhaustive] attributes.
     let field_infos = adt.all_fields().map(|field| {
-        let ty = field.ty(tcx, InternalSubsts::identity_for_item(tcx, field.did));
+        let ty = field.ty(tcx, GenericArgs::identity_for_item(tcx, field.did));
         let param_env = tcx.param_env(field.did);
         let layout = tcx.layout_of(param_env.and(ty));
         // We are currently checking the type this field came from, so it must be local
@@ -1086,7 +1086,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
         fn check_non_exhaustive<'tcx>(
             tcx: TyCtxt<'tcx>,
             t: Ty<'tcx>,
-        ) -> ControlFlow<(&'static str, DefId, SubstsRef<'tcx>, bool)> {
+        ) -> ControlFlow<(&'static str, DefId, GenericArgsRef<'tcx>, bool)> {
             match t.kind() {
                 ty::Tuple(list) => list.iter().try_for_each(|t| check_non_exhaustive(tcx, t)),
                 ty::Array(ty, _) => check_non_exhaustive(tcx, *ty),
@@ -1140,7 +1140,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
             .span_label(span, "has alignment larger than 1")
             .emit();
         }
-        if incompat && let Some((descr, def_id, substs, non_exhaustive)) = non_exhaustive {
+        if incompat && let Some((descr, def_id, args, non_exhaustive)) = non_exhaustive {
             tcx.struct_span_lint_hir(
                 REPR_TRANSPARENT_EXTERNAL_PRIVATE_FIELDS,
                 tcx.hir().local_def_id_to_hir_id(adt.did().expect_local()),
@@ -1152,7 +1152,7 @@ pub(super) fn check_transparent<'tcx>(tcx: TyCtxt<'tcx>, adt: ty::AdtDef<'tcx>)
                     } else {
                         "contains private fields"
                     };
-                    let field_ty = tcx.def_path_str_with_substs(def_id, substs);
+                    let field_ty = tcx.def_path_str_with_args(def_id, args);
                     lint
                         .note(format!("this {descr} contains `{field_ty}`, which {note}, \
                             and makes it not a breaking change to become non-zero-sized in the future."))
diff --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 22e576e345e1f..2075b1add393c 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
@@ -16,7 +16,7 @@ use rustc_infer::traits::util;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::util::ExplicitSelf;
 use rustc_middle::ty::{
-    self, InternalSubsts, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    self, GenericArgs, Ty, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
 };
 use rustc_middle::ty::{GenericParamDefKind, ToPredicate, TyCtxt};
 use rustc_span::{Span, DUMMY_SP};
@@ -96,15 +96,15 @@ fn check_method_is_structurally_compatible<'tcx>(
 /// For this we have to show that, assuming the bounds of the impl hold, the
 /// bounds of `trait_m` imply the bounds of `impl_m`.
 ///
-/// We start out with `trait_to_impl_substs`, that maps the trait
+/// We start out with `trait_to_impl_args`, that maps the trait
 /// type parameters to impl type parameters. This is taken from the
 /// impl trait reference:
 ///
 /// ```rust,ignore (pseudo-Rust)
-/// trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
+/// trait_to_impl_args = {'t => 'j, T => &'i U, Self => Foo}
 /// ```
 ///
-/// We create a mapping `dummy_substs` that maps from the impl type
+/// We create a mapping `dummy_args` that maps from the impl type
 /// parameters to fresh types and regions. For type parameters,
 /// this is the identity transform, but we could as well use any
 /// placeholder types. For regions, we convert from bound to free
@@ -112,10 +112,10 @@ fn check_method_is_structurally_compatible<'tcx>(
 /// declared on the impl or used in type parameter bounds).
 ///
 /// ```rust,ignore (pseudo-Rust)
-/// impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
+/// impl_to_placeholder_args = {'i => 'i0, U => U0, N => N0 }
 /// ```
 ///
-/// Now we can apply `placeholder_substs` to the type of the impl method
+/// Now we can apply `placeholder_args` to the type of the impl method
 /// to yield a new function type in terms of our fresh, placeholder
 /// types:
 ///
@@ -125,13 +125,13 @@ fn check_method_is_structurally_compatible<'tcx>(
 ///
 /// We now want to extract and substitute the type of the *trait*
 /// method and compare it. To do so, we must create a compound
-/// substitution by combining `trait_to_impl_substs` and
-/// `impl_to_placeholder_substs`, and also adding a mapping for the method
+/// substitution by combining `trait_to_impl_args` and
+/// `impl_to_placeholder_args`, and also adding a mapping for the method
 /// type parameters. We extend the mapping to also include
 /// the method parameters.
 ///
 /// ```rust,ignore (pseudo-Rust)
-/// trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
+/// trait_to_placeholder_args = { T => &'i0 U0, Self => Foo, M => N0 }
 /// ```
 ///
 /// Applying this to the trait method type yields:
@@ -148,8 +148,8 @@ fn check_method_is_structurally_compatible<'tcx>(
 /// satisfied by the implementation's method.
 ///
 /// We do this by creating a parameter environment which contains a
-/// substitution corresponding to `impl_to_placeholder_substs`. We then build
-/// `trait_to_placeholder_substs` and use it to convert the predicates contained
+/// substitution corresponding to `impl_to_placeholder_args`. We then build
+/// `trait_to_placeholder_args` and use it to convert the predicates contained
 /// in the `trait_m` generics to the placeholder form.
 ///
 /// Finally we register each of these predicates as an obligation and check that
@@ -162,7 +162,7 @@ fn compare_method_predicate_entailment<'tcx>(
     impl_trait_ref: ty::TraitRef<'tcx>,
     check_implied_wf: CheckImpliedWfMode,
 ) -> Result<(), ErrorGuaranteed> {
-    let trait_to_impl_substs = impl_trait_ref.substs;
+    let trait_to_impl_args = impl_trait_ref.args;
 
     // This node-id should be used for the `body_id` field on each
     // `ObligationCause` (and the `FnCtxt`).
@@ -182,12 +182,12 @@ fn compare_method_predicate_entailment<'tcx>(
     );
 
     // Create mapping from impl to placeholder.
-    let impl_to_placeholder_substs = InternalSubsts::identity_for_item(tcx, impl_m.def_id);
+    let impl_to_placeholder_args = GenericArgs::identity_for_item(tcx, impl_m.def_id);
 
     // Create mapping from trait to placeholder.
-    let trait_to_placeholder_substs =
-        impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_substs);
-    debug!("compare_impl_method: trait_to_placeholder_substs={:?}", trait_to_placeholder_substs);
+    let trait_to_placeholder_args =
+        impl_to_placeholder_args.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_args);
+    debug!("compare_impl_method: trait_to_placeholder_args={:?}", trait_to_placeholder_args);
 
     let impl_m_predicates = tcx.predicates_of(impl_m.def_id);
     let trait_m_predicates = tcx.predicates_of(trait_m.def_id);
@@ -211,7 +211,7 @@ fn compare_method_predicate_entailment<'tcx>(
     // if all constraints hold.
     hybrid_preds.predicates.extend(
         trait_m_predicates
-            .instantiate_own(tcx, trait_to_placeholder_substs)
+            .instantiate_own(tcx, trait_to_placeholder_args)
             .map(|(predicate, _)| predicate),
     );
 
@@ -231,7 +231,7 @@ fn compare_method_predicate_entailment<'tcx>(
 
     debug!("compare_impl_method: caller_bounds={:?}", param_env.caller_bounds());
 
-    let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_substs);
+    let impl_m_own_bounds = impl_m_predicates.instantiate_own(tcx, impl_to_placeholder_args);
     for (predicate, span) in impl_m_own_bounds {
         let normalize_cause = traits::ObligationCause::misc(span, impl_m_def_id);
         let predicate = ocx.normalize(&normalize_cause, param_env, predicate);
@@ -269,7 +269,7 @@ fn compare_method_predicate_entailment<'tcx>(
     let unnormalized_impl_sig = infcx.instantiate_binder_with_fresh_vars(
         impl_m_span,
         infer::HigherRankedType,
-        tcx.fn_sig(impl_m.def_id).subst_identity(),
+        tcx.fn_sig(impl_m.def_id).instantiate_identity(),
     );
     let unnormalized_impl_fty = Ty::new_fn_ptr(tcx, ty::Binder::dummy(unnormalized_impl_sig));
 
@@ -277,7 +277,7 @@ fn compare_method_predicate_entailment<'tcx>(
     let impl_sig = ocx.normalize(&norm_cause, param_env, unnormalized_impl_sig);
     debug!("compare_impl_method: impl_fty={:?}", impl_sig);
 
-    let trait_sig = tcx.fn_sig(trait_m.def_id).subst(tcx, trait_to_placeholder_substs);
+    let trait_sig = tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_placeholder_args);
     let trait_sig = tcx.liberate_late_bound_regions(impl_m.def_id, trait_sig);
 
     // Next, add all inputs and output as well-formed tys. Importantly,
@@ -615,14 +615,14 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     let impl_m = tcx.opt_associated_item(impl_m_def_id.to_def_id()).unwrap();
     let trait_m = tcx.opt_associated_item(impl_m.trait_item_def_id.unwrap()).unwrap();
     let impl_trait_ref =
-        tcx.impl_trait_ref(impl_m.impl_container(tcx).unwrap()).unwrap().subst_identity();
+        tcx.impl_trait_ref(impl_m.impl_container(tcx).unwrap()).unwrap().instantiate_identity();
     let param_env = tcx.param_env(impl_m_def_id);
 
     // First, check a few of the same things as `compare_impl_method`,
     // just so we don't ICE during substitution later.
     check_method_is_structurally_compatible(tcx, impl_m, trait_m, impl_trait_ref, true)?;
 
-    let trait_to_impl_substs = impl_trait_ref.substs;
+    let trait_to_impl_args = impl_trait_ref.args;
 
     let impl_m_hir_id = tcx.hir().local_def_id_to_hir_id(impl_m_def_id);
     let return_span = tcx.hir().fn_decl_by_hir_id(impl_m_hir_id).unwrap().output.span();
@@ -637,11 +637,11 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     );
 
     // Create mapping from impl to placeholder.
-    let impl_to_placeholder_substs = InternalSubsts::identity_for_item(tcx, impl_m.def_id);
+    let impl_to_placeholder_args = GenericArgs::identity_for_item(tcx, impl_m.def_id);
 
     // Create mapping from trait to placeholder.
-    let trait_to_placeholder_substs =
-        impl_to_placeholder_substs.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_substs);
+    let trait_to_placeholder_args =
+        impl_to_placeholder_args.rebase_onto(tcx, impl_m.container_id(tcx), trait_to_impl_args);
 
     let infcx = &tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(infcx);
@@ -651,7 +651,10 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     let impl_sig = ocx.normalize(
         &norm_cause,
         param_env,
-        tcx.liberate_late_bound_regions(impl_m.def_id, tcx.fn_sig(impl_m.def_id).subst_identity()),
+        tcx.liberate_late_bound_regions(
+            impl_m.def_id,
+            tcx.fn_sig(impl_m.def_id).instantiate_identity(),
+        ),
     );
     impl_sig.error_reported()?;
     let impl_return_ty = impl_sig.output();
@@ -665,7 +668,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
         .instantiate_binder_with_fresh_vars(
             return_span,
             infer::HigherRankedType,
-            tcx.fn_sig(trait_m.def_id).subst(tcx, trait_to_placeholder_substs),
+            tcx.fn_sig(trait_m.def_id).instantiate(tcx, trait_to_placeholder_args),
         )
         .fold_with(&mut collector);
 
@@ -758,47 +761,47 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
     ocx.resolve_regions_and_report_errors(impl_m_def_id, &outlives_env)?;
 
     let mut collected_tys = FxHashMap::default();
-    for (def_id, (ty, substs)) in collected_types {
-        match infcx.fully_resolve((ty, substs)) {
-            Ok((ty, substs)) => {
+    for (def_id, (ty, args)) in collected_types {
+        match infcx.fully_resolve((ty, args)) {
+            Ok((ty, args)) => {
                 // `ty` contains free regions that we created earlier while liberating the
                 // trait fn signature. However, projection normalization expects `ty` to
                 // contains `def_id`'s early-bound regions.
-                let id_substs = InternalSubsts::identity_for_item(tcx, def_id);
-                debug!(?id_substs, ?substs);
-                let map: FxHashMap<_, _> = std::iter::zip(substs, id_substs)
+                let id_args = GenericArgs::identity_for_item(tcx, def_id);
+                debug!(?id_args, ?args);
+                let map: FxHashMap<_, _> = std::iter::zip(args, id_args)
                     .skip(tcx.generics_of(trait_m.def_id).count())
                     .filter_map(|(a, b)| Some((a.as_region()?, b.as_region()?)))
                     .collect();
                 debug!(?map);
 
                 // NOTE(compiler-errors): RPITITs, like all other RPITs, have early-bound
-                // region substs that are synthesized during AST lowering. These are substs
-                // that are appended to the parent substs (trait and trait method). However,
+                // region args that are synthesized during AST lowering. These are args
+                // that are appended to the parent args (trait and trait method). However,
                 // we're trying to infer the unsubstituted type value of the RPITIT inside
-                // the *impl*, so we can later use the impl's method substs to normalize
+                // the *impl*, so we can later use the impl's method args to normalize
                 // an RPITIT to a concrete type (`confirm_impl_trait_in_trait_candidate`).
                 //
                 // Due to the design of RPITITs, during AST lowering, we have no idea that
                 // an impl method corresponds to a trait method with RPITITs in it. Therefore,
-                // we don't have a list of early-bound region substs for the RPITIT in the impl.
+                // we don't have a list of early-bound region args for the RPITIT in the impl.
                 // Since early region parameters are index-based, we can't just rebase these
-                // (trait method) early-bound region substs onto the impl, and there's no
-                // guarantee that the indices from the trait substs and impl substs line up.
-                // So to fix this, we subtract the number of trait substs and add the number of
-                // impl substs to *renumber* these early-bound regions to their corresponding
+                // (trait method) early-bound region args onto the impl, and there's no
+                // guarantee that the indices from the trait args and impl args line up.
+                // So to fix this, we subtract the number of trait args and add the number of
+                // impl args to *renumber* these early-bound regions to their corresponding
                 // indices in the impl's substitutions list.
                 //
-                // Also, we only need to account for a difference in trait and impl substs,
+                // Also, we only need to account for a difference in trait and impl args,
                 // since we previously enforce that the trait method and impl method have the
                 // same generics.
-                let num_trait_substs = trait_to_impl_substs.len();
-                let num_impl_substs = tcx.generics_of(impl_m.container_id(tcx)).params.len();
+                let num_trait_args = trait_to_impl_args.len();
+                let num_impl_args = tcx.generics_of(impl_m.container_id(tcx)).params.len();
                 let ty = match ty.try_fold_with(&mut RemapHiddenTyRegions {
                     tcx,
                     map,
-                    num_trait_substs,
-                    num_impl_substs,
+                    num_trait_args,
+                    num_impl_args,
                     def_id,
                     impl_def_id: impl_m.container_id(tcx),
                     ty,
@@ -824,7 +827,7 @@ pub(super) fn collect_return_position_impl_trait_in_trait_tys<'tcx>(
 
 struct ImplTraitInTraitCollector<'a, 'tcx> {
     ocx: &'a ObligationCtxt<'a, 'tcx>,
-    types: FxHashMap<DefId, (Ty<'tcx>, ty::SubstsRef<'tcx>)>,
+    types: FxHashMap<DefId, (Ty<'tcx>, ty::GenericArgsRef<'tcx>)>,
     span: Span,
     param_env: ty::ParamEnv<'tcx>,
     body_id: LocalDefId,
@@ -853,8 +856,8 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'_, 'tcx> {
             if let Some((ty, _)) = self.types.get(&proj.def_id) {
                 return *ty;
             }
-            //FIXME(RPITIT): Deny nested RPITIT in substs too
-            if proj.substs.has_escaping_bound_vars() {
+            //FIXME(RPITIT): Deny nested RPITIT in args too
+            if proj.args.has_escaping_bound_vars() {
                 bug!("FIXME(RPITIT): error here");
             }
             // Replace with infer var
@@ -862,9 +865,9 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'_, 'tcx> {
                 span: self.span,
                 kind: TypeVariableOriginKind::MiscVariable,
             });
-            self.types.insert(proj.def_id, (infer_ty, proj.substs));
+            self.types.insert(proj.def_id, (infer_ty, proj.args));
             // Recurse into bounds
-            for (pred, pred_span) in self.interner().explicit_item_bounds(proj.def_id).subst_iter_copied(self.interner(), proj.substs) {
+            for (pred, pred_span) in self.interner().explicit_item_bounds(proj.def_id).arg_iter_copied(self.interner(), proj.args) {
                 let pred = pred.fold_with(self);
                 let pred = self.ocx.normalize(
                     &ObligationCause::misc(self.span, self.body_id),
@@ -893,8 +896,8 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ImplTraitInTraitCollector<'_, 'tcx> {
 struct RemapHiddenTyRegions<'tcx> {
     tcx: TyCtxt<'tcx>,
     map: FxHashMap<ty::Region<'tcx>, ty::Region<'tcx>>,
-    num_trait_substs: usize,
-    num_impl_substs: usize,
+    num_trait_args: usize,
+    num_impl_args: usize,
     def_id: DefId,
     impl_def_id: DefId,
     ty: Ty<'tcx>,
@@ -909,16 +912,16 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
     }
 
     fn try_fold_ty(&mut self, t: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        if let ty::Alias(ty::Opaque, ty::AliasTy { substs, def_id, .. }) = *t.kind() {
-            let mut mapped_substs = Vec::with_capacity(substs.len());
-            for (arg, v) in std::iter::zip(substs, self.tcx.variances_of(def_id)) {
-                mapped_substs.push(match (arg.unpack(), v) {
-                    // Skip uncaptured opaque substs
+        if let ty::Alias(ty::Opaque, ty::AliasTy { args, def_id, .. }) = *t.kind() {
+            let mut mapped_args = Vec::with_capacity(args.len());
+            for (arg, v) in std::iter::zip(args, self.tcx.variances_of(def_id)) {
+                mapped_args.push(match (arg.unpack(), v) {
+                    // Skip uncaptured opaque args
                     (ty::GenericArgKind::Lifetime(_), ty::Bivariant) => arg,
                     _ => arg.try_fold_with(self)?,
                 });
             }
-            Ok(Ty::new_opaque(self.tcx, def_id, self.tcx.mk_substs(&mapped_substs)))
+            Ok(Ty::new_opaque(self.tcx, def_id, self.tcx.mk_args(&mapped_args)))
         } else {
             t.try_super_fold_with(self)
         }
@@ -975,7 +978,7 @@ impl<'tcx> ty::FallibleTypeFolder<TyCtxt<'tcx>> for RemapHiddenTyRegions<'tcx> {
             ty::EarlyBoundRegion {
                 def_id: e.def_id,
                 name: e.name,
-                index: (e.index as usize - self.num_trait_substs + self.num_impl_substs) as u32,
+                index: (e.index as usize - self.num_trait_args + self.num_impl_args) as u32,
             },
         ))
     }
@@ -1214,7 +1217,7 @@ fn compare_self_type<'tcx>(
             ty::ImplContainer => impl_trait_ref.self_ty(),
             ty::TraitContainer => tcx.types.self_param,
         };
-        let self_arg_ty = tcx.fn_sig(method.def_id).subst_identity().input(0);
+        let self_arg_ty = tcx.fn_sig(method.def_id).instantiate_identity().input(0);
         let param_env = ty::ParamEnv::reveal_all();
 
         let infcx = tcx.infer_ctxt().build();
@@ -1738,7 +1741,7 @@ fn compare_generic_param_kinds<'tcx>(
                     format!(
                         "{} const parameter of type `{}`",
                         prefix,
-                        tcx.type_of(param.def_id).subst_identity()
+                        tcx.type_of(param.def_id).instantiate_identity()
                     )
                 }
                 Type { .. } => format!("{} type parameter", prefix),
@@ -1769,7 +1772,7 @@ pub(super) fn compare_impl_const_raw(
     let impl_const_item = tcx.associated_item(impl_const_item_def);
     let trait_const_item = tcx.associated_item(trait_const_item_def);
     let impl_trait_ref =
-        tcx.impl_trait_ref(impl_const_item.container_id(tcx)).unwrap().subst_identity();
+        tcx.impl_trait_ref(impl_const_item.container_id(tcx)).unwrap().instantiate_identity();
     debug!("compare_const_impl(impl_trait_ref={:?})", impl_trait_ref);
 
     let impl_c_span = tcx.def_span(impl_const_item_def.to_def_id());
@@ -1783,13 +1786,13 @@ pub(super) fn compare_impl_const_raw(
     // because we shouldn't really have to deal with lifetimes or
     // predicates. In fact some of this should probably be put into
     // shared functions because of DRY violations...
-    let trait_to_impl_substs = impl_trait_ref.substs;
+    let trait_to_impl_args = impl_trait_ref.args;
 
     // Create a parameter environment that represents the implementation's
     // method.
     // Compute placeholder form of impl and trait const tys.
-    let impl_ty = tcx.type_of(impl_const_item_def.to_def_id()).subst_identity();
-    let trait_ty = tcx.type_of(trait_const_item_def).subst(tcx, trait_to_impl_substs);
+    let impl_ty = tcx.type_of(impl_const_item_def.to_def_id()).instantiate_identity();
+    let trait_ty = tcx.type_of(trait_const_item_def).instantiate(tcx, trait_to_impl_args);
     let mut cause = ObligationCause::new(
         impl_c_span,
         impl_const_item_def,
@@ -1885,16 +1888,16 @@ fn compare_type_predicate_entailment<'tcx>(
     trait_ty: ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let impl_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
-    let trait_to_impl_substs =
-        impl_substs.rebase_onto(tcx, impl_ty.container_id(tcx), impl_trait_ref.substs);
+    let impl_args = GenericArgs::identity_for_item(tcx, impl_ty.def_id);
+    let trait_to_impl_args =
+        impl_args.rebase_onto(tcx, impl_ty.container_id(tcx), impl_trait_ref.args);
 
     let impl_ty_predicates = tcx.predicates_of(impl_ty.def_id);
     let trait_ty_predicates = tcx.predicates_of(trait_ty.def_id);
 
     check_region_bounds_on_impl_item(tcx, impl_ty, trait_ty, false)?;
 
-    let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_substs);
+    let impl_ty_own_bounds = impl_ty_predicates.instantiate_own(tcx, impl_args);
     if impl_ty_own_bounds.len() == 0 {
         // Nothing to check.
         return Ok(());
@@ -1904,7 +1907,7 @@ fn compare_type_predicate_entailment<'tcx>(
     // `ObligationCause` (and the `FnCtxt`). This is what
     // `regionck_item` expects.
     let impl_ty_def_id = impl_ty.def_id.expect_local();
-    debug!("compare_type_predicate_entailment: trait_to_impl_substs={:?}", trait_to_impl_substs);
+    debug!("compare_type_predicate_entailment: trait_to_impl_args={:?}", trait_to_impl_args);
 
     // The predicates declared by the impl definition, the trait and the
     // associated type in the trait are assumed.
@@ -1912,7 +1915,7 @@ fn compare_type_predicate_entailment<'tcx>(
     let mut hybrid_preds = impl_predicates.instantiate_identity(tcx);
     hybrid_preds.predicates.extend(
         trait_ty_predicates
-            .instantiate_own(tcx, trait_to_impl_substs)
+            .instantiate_own(tcx, trait_to_impl_args)
             .map(|(predicate, _)| predicate),
     );
 
@@ -1990,9 +1993,9 @@ pub(super) fn check_type_bounds<'tcx>(
     // }
     //
     // - `impl_trait_ref` would be `<(A, B) as Foo<u32>>`
-    // - `normalize_impl_ty_substs` would be `[A, B, ^0.0]` (`^0.0` here is the bound var with db 0 and index 0)
+    // - `normalize_impl_ty_args` would be `[A, B, ^0.0]` (`^0.0` here is the bound var with db 0 and index 0)
     // - `normalize_impl_ty` would be `Wrapper<A, B, ^0.0>`
-    // - `rebased_substs` would be `[(A, B), u32, ^0.0]`, combining the substs from
+    // - `rebased_args` would be `[(A, B), u32, ^0.0]`, combining the args from
     //    the *trait* with the generic associated type parameters (as bound vars).
     //
     // A note regarding the use of bound vars here:
@@ -2022,9 +2025,11 @@ pub(super) fn check_type_bounds<'tcx>(
     // the trait (notably, that X: Eq and T: Family).
     let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
         smallvec::SmallVec::with_capacity(tcx.generics_of(impl_ty.def_id).params.len());
-    // Extend the impl's identity substs with late-bound GAT vars
-    let normalize_impl_ty_substs = ty::InternalSubsts::identity_for_item(tcx, container_id)
-        .extend_to(tcx, impl_ty.def_id, |param, _| match param.kind {
+    // Extend the impl's identity args with late-bound GAT vars
+    let normalize_impl_ty_args = ty::GenericArgs::identity_for_item(tcx, container_id).extend_to(
+        tcx,
+        impl_ty.def_id,
+        |param, _| match param.kind {
             GenericParamDefKind::Type { .. } => {
                 let kind = ty::BoundTyKind::Param(param.def_id, param.name);
                 let bound_var = ty::BoundVariableKind::Ty(kind);
@@ -2060,7 +2065,8 @@ pub(super) fn check_type_bounds<'tcx>(
                 )
                 .into()
             }
-        });
+        },
+    );
     // When checking something like
     //
     // trait X { type Y: PartialEq<<Self as X>::Y> }
@@ -2070,15 +2076,14 @@ pub(super) fn check_type_bounds<'tcx>(
     // we want <T as X>::Y to normalize to S. This is valid because we are
     // checking the default value specifically here. Add this equality to the
     // ParamEnv for normalization specifically.
-    let normalize_impl_ty = tcx.type_of(impl_ty.def_id).subst(tcx, normalize_impl_ty_substs);
-    let rebased_substs =
-        normalize_impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs);
+    let normalize_impl_ty = tcx.type_of(impl_ty.def_id).instantiate(tcx, normalize_impl_ty_args);
+    let rebased_args = normalize_impl_ty_args.rebase_onto(tcx, container_id, impl_trait_ref.args);
     let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);
     let normalize_param_env = {
         let mut predicates = param_env.caller_bounds().iter().collect::<Vec<_>>();
         match normalize_impl_ty.kind() {
             ty::Alias(ty::Projection, proj)
-                if proj.def_id == trait_ty.def_id && proj.substs == rebased_substs =>
+                if proj.def_id == trait_ty.def_id && proj.args == rebased_args =>
             {
                 // Don't include this predicate if the projected type is
                 // exactly the same as the projection. This can occur in
@@ -2089,7 +2094,7 @@ pub(super) fn check_type_bounds<'tcx>(
             _ => predicates.push(
                 ty::Binder::bind_with_vars(
                     ty::ProjectionPredicate {
-                        projection_ty: tcx.mk_alias_ty(trait_ty.def_id, rebased_substs),
+                        projection_ty: tcx.mk_alias_ty(trait_ty.def_id, rebased_args),
                         term: normalize_impl_ty.into(),
                     },
                     bound_vars,
@@ -2102,8 +2107,8 @@ pub(super) fn check_type_bounds<'tcx>(
     debug!(?normalize_param_env);
 
     let impl_ty_def_id = impl_ty.def_id.expect_local();
-    let impl_ty_substs = InternalSubsts::identity_for_item(tcx, impl_ty.def_id);
-    let rebased_substs = impl_ty_substs.rebase_onto(tcx, container_id, impl_trait_ref.substs);
+    let impl_ty_args = GenericArgs::identity_for_item(tcx, impl_ty.def_id);
+    let rebased_args = impl_ty_args.rebase_onto(tcx, container_id, impl_trait_ref.args);
 
     let infcx = tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(&infcx);
@@ -2144,7 +2149,7 @@ pub(super) fn check_type_bounds<'tcx>(
 
     let obligations: Vec<_> = tcx
         .explicit_item_bounds(trait_ty.def_id)
-        .subst_iter_copied(tcx, rebased_substs)
+        .arg_iter_copied(tcx, rebased_args)
         .map(|(concrete_ty_bound, span)| {
             debug!("check_type_bounds: concrete_ty_bound = {:?}", concrete_ty_bound);
             traits::Obligation::new(tcx, mk_cause(span), param_env, concrete_ty_bound)
diff --git a/compiler/rustc_hir_analysis/src/check/dropck.rs b/compiler/rustc_hir_analysis/src/check/dropck.rs
index 2bb4cc39f9267..4ac3a7c23aef0 100644
--- a/compiler/rustc_hir_analysis/src/check/dropck.rs
+++ b/compiler/rustc_hir_analysis/src/check/dropck.rs
@@ -5,8 +5,8 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{struct_span_err, ErrorGuaranteed};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
-use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::util::CheckRegions;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, TyCtxt};
 use rustc_trait_selection::traits::{self, ObligationCtxt};
 
@@ -44,21 +44,21 @@ pub fn check_drop_impl(tcx: TyCtxt<'_>, drop_impl_did: DefId) -> Result<(), Erro
             }));
         }
     }
-    let dtor_self_type = tcx.type_of(drop_impl_did).subst_identity();
+    let dtor_self_type = tcx.type_of(drop_impl_did).instantiate_identity();
     match dtor_self_type.kind() {
-        ty::Adt(adt_def, adt_to_impl_substs) => {
+        ty::Adt(adt_def, adt_to_impl_args) => {
             ensure_drop_params_and_item_params_correspond(
                 tcx,
                 drop_impl_did.expect_local(),
                 adt_def.did(),
-                adt_to_impl_substs,
+                adt_to_impl_args,
             )?;
 
             ensure_drop_predicates_are_implied_by_item_defn(
                 tcx,
                 drop_impl_did.expect_local(),
                 adt_def.did().expect_local(),
-                adt_to_impl_substs,
+                adt_to_impl_args,
             )
         }
         _ => {
@@ -79,9 +79,9 @@ fn ensure_drop_params_and_item_params_correspond<'tcx>(
     tcx: TyCtxt<'tcx>,
     drop_impl_did: LocalDefId,
     self_type_did: DefId,
-    adt_to_impl_substs: SubstsRef<'tcx>,
+    adt_to_impl_args: GenericArgsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
-    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_substs, CheckRegions::OnlyEarlyBound)
+    let Err(arg) = tcx.uses_unique_generic_params(adt_to_impl_args, CheckRegions::OnlyEarlyBound)
     else {
         return Ok(());
     };
@@ -115,12 +115,12 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
     tcx: TyCtxt<'tcx>,
     drop_impl_def_id: LocalDefId,
     adt_def_id: LocalDefId,
-    adt_to_impl_substs: SubstsRef<'tcx>,
+    adt_to_impl_args: GenericArgsRef<'tcx>,
 ) -> Result<(), ErrorGuaranteed> {
     let infcx = tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(&infcx);
 
-    // Take the param-env of the adt and substitute the substs that show up in
+    // Take the param-env of the adt and substitute the args that show up in
     // the implementation's self type. This gives us the assumptions that the
     // self ty of the implementation is allowed to know just from it being a
     // well-formed adt, since that's all we're allowed to assume while proving
@@ -130,7 +130,7 @@ fn ensure_drop_predicates_are_implied_by_item_defn<'tcx>(
     // substituting it with free params, so no additional param-env normalization
     // can occur on top of what has been done in the param_env query itself.
     let param_env = ty::EarlyBinder::bind(tcx.param_env(adt_def_id))
-        .subst(tcx, adt_to_impl_substs)
+        .instantiate(tcx, adt_to_impl_args)
         .with_constness(tcx.constness(drop_impl_def_id));
 
     for (pred, span) in tcx.predicates_of(drop_impl_def_id).instantiate_identity(tcx) {
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsic.rs b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
index 1248f991cc4c7..d5c9840887a6e 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsic.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsic.rs
@@ -60,7 +60,7 @@ fn equate_intrinsic_type<'tcx>(
             tcx,
             &cause,
             ty::ParamEnv::empty(), // FIXME: do all intrinsics have an empty param env?
-            Ty::new_fn_ptr(tcx, tcx.fn_sig(it.owner_id).subst_identity()),
+            Ty::new_fn_ptr(tcx, tcx.fn_sig(it.owner_id).instantiate_identity()),
             fty,
         );
     }
@@ -155,7 +155,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                 ty::INNERMOST,
                 ty::BoundRegion { var: ty::BoundVar::from_u32(1), kind: ty::BrEnv },
             );
-            let va_list_ty = tcx.type_of(did).subst(tcx, &[region.into()]);
+            let va_list_ty = tcx.type_of(did).instantiate(tcx, &[region.into()]);
             (Ty::new_ref(tcx, env_region, ty::TypeAndMut { ty: va_list_ty, mutbl }), va_list_ty)
         })
     };
@@ -238,7 +238,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                             ty: Ty::new_adt(
                                 tcx,
                                 tcx.adt_def(option_def_id),
-                                tcx.mk_substs_from_iter([ty::GenericArg::from(p0)].into_iter()),
+                                tcx.mk_args_from_iter([ty::GenericArg::from(p0)].into_iter()),
                             ),
                             mutbl: hir::Mutability::Not,
                         },
@@ -412,7 +412,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem<'_>) {
                         ty::Region::new_late_bound(tcx, ty::INNERMOST, br),
                         param(0),
                     )],
-                    Ty::new_projection(tcx, discriminant_def_id, tcx.mk_substs(&[param(0).into()])),
+                    Ty::new_projection(tcx, discriminant_def_id, tcx.mk_args(&[param(0).into()])),
                 )
             }
 
diff --git a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
index 15be441e947e8..8423a9550bac3 100644
--- a/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
+++ b/compiler/rustc_hir_analysis/src/check/intrinsicck.rs
@@ -81,9 +81,9 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
             ty::RawPtr(ty::TypeAndMut { ty, mutbl: _ }) if self.is_thin_ptr_ty(ty) => {
                 Some(asm_ty_isize)
             }
-            ty::Adt(adt, substs) if adt.repr().simd() => {
+            ty::Adt(adt, args) if adt.repr().simd() => {
                 let fields = &adt.non_enum_variant().fields;
-                let elem_ty = fields[FieldIdx::from_u32(0)].ty(self.tcx, substs);
+                let elem_ty = fields[FieldIdx::from_u32(0)].ty(self.tcx, args);
 
                 let (size, ty) = match elem_ty.kind() {
                     ty::Array(ty, len) => {
@@ -423,7 +423,7 @@ impl<'a, 'tcx> InlineAsmCtxt<'a, 'tcx> {
                 // Check that sym actually points to a function. Later passes
                 // depend on this.
                 hir::InlineAsmOperand::SymFn { anon_const } => {
-                    let ty = self.tcx.type_of(anon_const.def_id).subst_identity();
+                    let ty = self.tcx.type_of(anon_const.def_id).instantiate_identity();
                     match ty.kind() {
                         ty::Never | ty::Error(_) => {}
                         ty::FnDef(..) => {}
diff --git a/compiler/rustc_hir_analysis/src/check/mod.rs b/compiler/rustc_hir_analysis/src/check/mod.rs
index ce2da7cb1a325..1805a08bbb2ca 100644
--- a/compiler/rustc_hir_analysis/src/check/mod.rs
+++ b/compiler/rustc_hir_analysis/src/check/mod.rs
@@ -38,7 +38,7 @@ can be broken down into several distinct phases:
 
 While type checking a function, the intermediate types for the
 expressions, blocks, and so forth contained within the function are
-stored in `fcx.node_types` and `fcx.node_substs`. These types
+stored in `fcx.node_types` and `fcx.node_args`. These types
 may contain unresolved type variables. After type checking is
 complete, the functions in the writeback module are used to take the
 types from this table, resolve them, and then write them into their
@@ -80,7 +80,7 @@ use rustc_hir::intravisit::Visitor;
 use rustc_index::bit_set::BitSet;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, Ty, TyCtxt};
-use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_session::parse::feature_err;
 use rustc_span::source_map::DUMMY_SP;
 use rustc_span::symbol::{kw, Ident};
@@ -211,7 +211,7 @@ fn missing_items_err(
         let snippet = suggestion_signature(
             tcx,
             trait_item,
-            tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity(),
+            tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity(),
         );
         let code = format!("{}{}\n{}", padding, snippet, padding);
         if let Some(span) = tcx.hir().span_if_local(trait_item.def_id) {
@@ -408,7 +408,7 @@ fn fn_sig_suggestion<'tcx>(
     let asyncness = if tcx.asyncness(assoc.def_id).is_async() {
         output = if let ty::Alias(_, alias_ty) = *output.kind() {
             tcx.explicit_item_bounds(alias_ty.def_id)
-                .subst_iter_copied(tcx, alias_ty.substs)
+                .arg_iter_copied(tcx, alias_ty.args)
                 .find_map(|(bound, _)| bound.as_projection_clause()?.no_bound_vars()?.term.ty())
                 .unwrap_or_else(|| {
                     span_bug!(
@@ -461,10 +461,10 @@ fn suggestion_signature<'tcx>(
     assoc: ty::AssocItem,
     impl_trait_ref: ty::TraitRef<'tcx>,
 ) -> String {
-    let substs = ty::InternalSubsts::identity_for_item(tcx, assoc.def_id).rebase_onto(
+    let args = ty::GenericArgs::identity_for_item(tcx, assoc.def_id).rebase_onto(
         tcx,
         assoc.container_id(tcx),
-        impl_trait_ref.with_self_ty(tcx, tcx.types.self_param).substs,
+        impl_trait_ref.with_self_ty(tcx, tcx.types.self_param).args,
     );
 
     match assoc.kind {
@@ -472,21 +472,21 @@ fn suggestion_signature<'tcx>(
             tcx,
             tcx.liberate_late_bound_regions(
                 assoc.def_id,
-                tcx.fn_sig(assoc.def_id).subst(tcx, substs),
+                tcx.fn_sig(assoc.def_id).instantiate(tcx, args),
             ),
             assoc.ident(tcx),
-            tcx.predicates_of(assoc.def_id).instantiate_own(tcx, substs),
+            tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
             assoc,
         ),
         ty::AssocKind::Type => {
             let (generics, where_clauses) = bounds_from_generic_predicates(
                 tcx,
-                tcx.predicates_of(assoc.def_id).instantiate_own(tcx, substs),
+                tcx.predicates_of(assoc.def_id).instantiate_own(tcx, args),
             );
             format!("type {}{generics} = /* Type */{where_clauses};", assoc.name)
         }
         ty::AssocKind::Const => {
-            let ty = tcx.type_of(assoc.def_id).subst_identity();
+            let ty = tcx.type_of(assoc.def_id).instantiate_identity();
             let val = ty_kind_suggestion(ty).unwrap_or("todo!()");
             format!("const {}: {} = {};", assoc.name, ty, val)
         }
diff --git a/compiler/rustc_hir_analysis/src/check/wfcheck.rs b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
index d4748b7ef0be4..443d072f99244 100644
--- a/compiler/rustc_hir_analysis/src/check/wfcheck.rs
+++ b/compiler/rustc_hir_analysis/src/check/wfcheck.rs
@@ -18,7 +18,7 @@ use rustc_middle::ty::{
     self, AdtKind, GenericParamDefKind, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeSuperVisitable,
     TypeVisitable, TypeVisitableExt, TypeVisitor,
 };
-use rustc_middle::ty::{GenericArgKind, InternalSubsts};
+use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::{sym, Ident, Symbol};
 use rustc_span::{Span, DUMMY_SP};
@@ -290,7 +290,7 @@ fn check_trait_item(tcx: TyCtxt<'_>, trait_item: &hir::TraitItem<'_>) {
 
 /// Require that the user writes where clauses on GATs for the implicit
 /// outlives bounds involving trait parameters in trait functions and
-/// lifetimes passed as GAT substs. See `self-outlives-lint` test.
+/// lifetimes passed as GAT args. See `self-outlives-lint` test.
 ///
 /// We use the following trait as an example throughout this function:
 /// ```rust,ignore (this code fails due to this lint)
@@ -314,7 +314,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRe
         for gat_item in associated_items {
             let gat_def_id = gat_item.id.owner_id;
             let gat_item = tcx.associated_item(gat_def_id);
-            // If this item is not an assoc ty, or has no substs, then it's not a GAT
+            // If this item is not an assoc ty, or has no args, then it's not a GAT
             if gat_item.kind != ty::AssocKind::Type {
                 continue;
             }
@@ -345,7 +345,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRe
                         // `Self::Iter<'a>` is a GAT we want to gather any potential missing bounds from.
                         let sig: ty::FnSig<'_> = tcx.liberate_late_bound_regions(
                             item_def_id.to_def_id(),
-                            tcx.fn_sig(item_def_id).subst_identity(),
+                            tcx.fn_sig(item_def_id).instantiate_identity(),
                         );
                         gather_gat_bounds(
                             tcx,
@@ -374,7 +374,7 @@ fn check_gat_where_clauses(tcx: TyCtxt<'_>, associated_items: &[hir::TraitItemRe
                             param_env,
                             item_def_id,
                             tcx.explicit_item_bounds(item_def_id)
-                                .subst_identity_iter_copied()
+                                .instantiate_identity_iter_copied()
                                 .collect::<Vec<_>>(),
                             &FxIndexSet::default(),
                             gat_def_id.def_id,
@@ -737,7 +737,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for GATSubstCollector<'tcx> {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match t.kind() {
             ty::Alias(ty::Projection, p) if p.def_id == self.gat => {
-                for (idx, subst) in p.substs.iter().enumerate() {
+                for (idx, subst) in p.args.iter().enumerate() {
                     match subst.unpack() {
                         GenericArgKind::Lifetime(lt) if !lt.is_late_bound() => {
                             self.regions.insert((lt, idx));
@@ -836,7 +836,7 @@ fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {
 
         // Const parameters are well formed if their type is structural match.
         hir::GenericParamKind::Const { ty: hir_ty, default: _ } => {
-            let ty = tcx.type_of(param.def_id).subst_identity();
+            let ty = tcx.type_of(param.def_id).instantiate_identity();
 
             if tcx.features().adt_const_params {
                 enter_wf_checking_ctxt(tcx, hir_ty.span, param.def_id, |wfcx| {
@@ -910,17 +910,17 @@ fn check_associated_item(
 
         let self_ty = match item.container {
             ty::TraitContainer => tcx.types.self_param,
-            ty::ImplContainer => tcx.type_of(item.container_id(tcx)).subst_identity(),
+            ty::ImplContainer => tcx.type_of(item.container_id(tcx)).instantiate_identity(),
         };
 
         match item.kind {
             ty::AssocKind::Const => {
-                let ty = tcx.type_of(item.def_id).subst_identity();
+                let ty = tcx.type_of(item.def_id).instantiate_identity();
                 let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                 wfcx.register_wf_obligation(span, loc, ty.into());
             }
             ty::AssocKind::Fn => {
-                let sig = tcx.fn_sig(item.def_id).subst_identity();
+                let sig = tcx.fn_sig(item.def_id).instantiate_identity();
                 let hir_sig = sig_if_method.expect("bad signature for method");
                 check_fn_or_method(
                     wfcx,
@@ -936,7 +936,7 @@ fn check_associated_item(
                     check_associated_type_bounds(wfcx, item, span)
                 }
                 if item.defaultness(tcx).has_value() {
-                    let ty = tcx.type_of(item.def_id).subst_identity();
+                    let ty = tcx.type_of(item.def_id).instantiate_identity();
                     let ty = wfcx.normalize(span, Some(WellFormedLoc::Ty(item_id)), ty);
                     wfcx.register_wf_obligation(span, loc, ty.into());
                 }
@@ -969,7 +969,11 @@ fn check_type_defn<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: b
                 let field_id = field.did.expect_local();
                 let hir::FieldDef { ty: hir_ty, .. } =
                     tcx.hir().get_by_def_id(field_id).expect_field();
-                let ty = wfcx.normalize(hir_ty.span, None, tcx.type_of(field.did).subst_identity());
+                let ty = wfcx.normalize(
+                    hir_ty.span,
+                    None,
+                    tcx.type_of(field.did).instantiate_identity(),
+                );
                 wfcx.register_wf_obligation(
                     hir_ty.span,
                     Some(WellFormedLoc::Ty(field_id)),
@@ -981,7 +985,7 @@ fn check_type_defn<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: b
             // intermediate types must be sized.
             let needs_drop_copy = || {
                 packed && {
-                    let ty = tcx.type_of(variant.tail().did).subst_identity();
+                    let ty = tcx.type_of(variant.tail().did).instantiate_identity();
                     let ty = tcx.erase_regions(ty);
                     if ty.has_infer() {
                         tcx.sess
@@ -1003,7 +1007,11 @@ fn check_type_defn<'tcx>(tcx: TyCtxt<'tcx>, item: &hir::Item<'tcx>, all_sized: b
                 let field_id = field.did.expect_local();
                 let hir::FieldDef { ty: hir_ty, .. } =
                     tcx.hir().get_by_def_id(field_id).expect_field();
-                let ty = wfcx.normalize(hir_ty.span, None, tcx.type_of(field.did).subst_identity());
+                let ty = wfcx.normalize(
+                    hir_ty.span,
+                    None,
+                    tcx.type_of(field.did).instantiate_identity(),
+                );
                 wfcx.register_bound(
                     traits::ObligationCause::new(
                         hir_ty.span,
@@ -1083,16 +1091,17 @@ fn check_associated_type_bounds(wfcx: &WfCheckingCtxt<'_, '_>, item: ty::AssocIt
     let bounds = wfcx.tcx().explicit_item_bounds(item.def_id);
 
     debug!("check_associated_type_bounds: bounds={:?}", bounds);
-    let wf_obligations = bounds.subst_identity_iter_copied().flat_map(|(bound, bound_span)| {
-        let normalized_bound = wfcx.normalize(span, None, bound);
-        traits::wf::predicate_obligations(
-            wfcx.infcx,
-            wfcx.param_env,
-            wfcx.body_def_id,
-            normalized_bound.as_predicate(),
-            bound_span,
-        )
-    });
+    let wf_obligations =
+        bounds.instantiate_identity_iter_copied().flat_map(|(bound, bound_span)| {
+            let normalized_bound = wfcx.normalize(span, None, bound);
+            traits::wf::predicate_obligations(
+                wfcx.infcx,
+                wfcx.param_env,
+                wfcx.body_def_id,
+                normalized_bound.as_predicate(),
+                bound_span,
+            )
+        });
 
     wfcx.register_obligations(wf_obligations);
 }
@@ -1105,7 +1114,7 @@ fn check_item_fn(
     decl: &hir::FnDecl<'_>,
 ) {
     enter_wf_checking_ctxt(tcx, span, def_id, |wfcx| {
-        let sig = tcx.fn_sig(def_id).subst_identity();
+        let sig = tcx.fn_sig(def_id).instantiate_identity();
         check_fn_or_method(wfcx, ident.span, sig, decl, def_id);
     })
 }
@@ -1125,7 +1134,7 @@ fn check_item_type(
     debug!("check_item_type: {:?}", item_id);
 
     enter_wf_checking_ctxt(tcx, ty_span, item_id, |wfcx| {
-        let ty = tcx.type_of(item_id).subst_identity();
+        let ty = tcx.type_of(item_id).instantiate_identity();
         let item_ty = wfcx.normalize(ty_span, Some(WellFormedLoc::Ty(item_id)), ty);
 
         let forbid_unsized = match unsized_handling {
@@ -1178,7 +1187,7 @@ fn check_impl<'tcx>(
                 // `#[rustc_reservation_impl]` impls are not real impls and
                 // therefore don't need to be WF (the trait's `Self: Trait` predicate
                 // won't hold).
-                let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().subst_identity();
+                let trait_ref = tcx.impl_trait_ref(item.owner_id).unwrap().instantiate_identity();
                 let trait_ref = wfcx.normalize(
                     ast_trait_ref.path.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
@@ -1211,7 +1220,7 @@ fn check_impl<'tcx>(
                 wfcx.register_obligations(obligations);
             }
             None => {
-                let self_ty = tcx.type_of(item.owner_id).subst_identity();
+                let self_ty = tcx.type_of(item.owner_id).instantiate_identity();
                 let self_ty = wfcx.normalize(
                     item.span,
                     Some(WellFormedLoc::Ty(item.hir_id().expect_owner().def_id)),
@@ -1256,7 +1265,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
         match param.kind {
             GenericParamDefKind::Type { .. } => {
                 if is_our_default(param) {
-                    let ty = tcx.type_of(param.def_id).subst_identity();
+                    let ty = tcx.type_of(param.def_id).instantiate_identity();
                     // Ignore dependent defaults -- that is, where the default of one type
                     // parameter includes another (e.g., `<T, U = T>`). In those cases, we can't
                     // be sure if it will error or not as user might always specify the other.
@@ -1272,10 +1281,10 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             GenericParamDefKind::Const { .. } => {
                 if is_our_default(param) {
                     // FIXME(const_generics_defaults): This
-                    // is incorrect when dealing with unused substs, for example
+                    // is incorrect when dealing with unused args, for example
                     // for `struct Foo<const N: usize, const M: usize = { 1 - 2 }>`
                     // we should eagerly error.
-                    let default_ct = tcx.const_param_default(param.def_id).subst_identity();
+                    let default_ct = tcx.const_param_default(param.def_id).instantiate_identity();
                     if !default_ct.has_param() {
                         wfcx.register_wf_obligation(
                             tcx.def_span(param.def_id),
@@ -1298,7 +1307,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
     // For more examples see tests `defaults-well-formedness.rs` and `type-check-defaults.rs`.
     //
     // First we build the defaulted substitution.
-    let substs = InternalSubsts::for_item(tcx, def_id.to_def_id(), |param, _| {
+    let args = GenericArgs::for_item(tcx, def_id.to_def_id(), |param, _| {
         match param.kind {
             GenericParamDefKind::Lifetime => {
                 // All regions are identity.
@@ -1308,7 +1317,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             GenericParamDefKind::Type { .. } => {
                 // If the param has a default, ...
                 if is_our_default(param) {
-                    let default_ty = tcx.type_of(param.def_id).subst_identity();
+                    let default_ty = tcx.type_of(param.def_id).instantiate_identity();
                     // ... and it's not a dependent default, ...
                     if !default_ty.has_param() {
                         // ... then substitute it with the default.
@@ -1321,7 +1330,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             GenericParamDefKind::Const { .. } => {
                 // If the param has a default, ...
                 if is_our_default(param) {
-                    let default_ct = tcx.const_param_default(param.def_id).subst_identity();
+                    let default_ct = tcx.const_param_default(param.def_id).instantiate_identity();
                     // ... and it's not a dependent default, ...
                     if !default_ct.has_param() {
                         // ... then substitute it with the default.
@@ -1366,7 +1375,7 @@ fn check_where_clauses<'tcx>(wfcx: &WfCheckingCtxt<'_, 'tcx>, span: Span, def_id
             }
             let mut param_count = CountParams::default();
             let has_region = pred.visit_with(&mut param_count).is_break();
-            let substituted_pred = ty::EarlyBinder::bind(pred).subst(tcx, substs);
+            let substituted_pred = ty::EarlyBinder::bind(pred).instantiate(tcx, args);
             // Don't check non-defaulted params, dependent defaults (including lifetimes)
             // or preds with multiple params.
             if substituted_pred.has_non_region_param() || param_count.params.len() > 1 || has_region
@@ -1529,7 +1538,7 @@ fn check_return_position_impl_trait_in_trait_bounds<'tcx>(
 // strategy, we can't just call `check_associated_item` on the new RPITITs,
 // because tests like `tests/ui/async-await/in-trait/implied-bounds.rs` will fail.
 // That's because we need to check that the bounds of the RPITIT hold using
-// the special substs that we create during opaque type lowering, otherwise we're
+// the special args that we create during opaque type lowering, otherwise we're
 // getting a bunch of early bound and free regions mixed up... Haven't looked too
 // deep into this, though.
 struct ImplTraitInTraitFinder<'a, 'tcx> {
@@ -1558,7 +1567,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
             });
             for (bound, bound_span) in tcx
                 .explicit_item_bounds(opaque_ty.def_id)
-                .subst_iter_copied(tcx, opaque_ty.substs)
+                .arg_iter_copied(tcx, opaque_ty.args)
             {
                 let bound = self.wfcx.normalize(bound_span, None, bound);
                 self.wfcx.register_obligations(traits::wf::predicate_obligations(
@@ -1569,7 +1578,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
                     bound_span,
                 ));
                 // Set the debruijn index back to innermost here, since we already eagerly
-                // shifted the substs that we use to generate these bounds. This is unfortunately
+                // shifted the args that we use to generate these bounds. This is unfortunately
                 // subtly different behavior than the `ImplTraitInTraitFinder` we use in `param_env`,
                 // but that function doesn't actually need to normalize the bound it's visiting
                 // (whereas we have to do so here)...
@@ -1601,7 +1610,7 @@ fn check_method_receiver<'tcx>(
 
     let span = fn_sig.decl.inputs[0].span;
 
-    let sig = tcx.fn_sig(method.def_id).subst_identity();
+    let sig = tcx.fn_sig(method.def_id).instantiate_identity();
     let sig = tcx.liberate_late_bound_regions(method.def_id, sig);
     let sig = wfcx.normalize(span, None, sig);
 
@@ -1773,9 +1782,9 @@ fn check_variances_for_type_defn<'tcx>(
     item: &hir::Item<'tcx>,
     hir_generics: &hir::Generics<'_>,
 ) {
-    let identity_substs = ty::InternalSubsts::identity_for_item(tcx, item.owner_id);
+    let identity_args = ty::GenericArgs::identity_for_item(tcx, item.owner_id);
     for field in tcx.adt_def(item.owner_id).all_fields() {
-        if field.ty(tcx, identity_substs).references_error() {
+        if field.ty(tcx, identity_args).references_error() {
             return;
         }
     }
diff --git a/compiler/rustc_hir_analysis/src/coherence/builtin.rs b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
index 79cc43edff139..3f65adcd36ebd 100644
--- a/compiler/rustc_hir_analysis/src/coherence/builtin.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/builtin.rs
@@ -57,7 +57,7 @@ impl<'tcx> Checker<'tcx> {
 
 fn visit_implementation_of_drop(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
     // Destructors only work on local ADT types.
-    match tcx.type_of(impl_did).subst_identity().kind() {
+    match tcx.type_of(impl_did).instantiate_identity().kind() {
         ty::Adt(def, _) if def.did().is_local() => return,
         ty::Error(_) => return,
         _ => {}
@@ -71,7 +71,7 @@ fn visit_implementation_of_drop(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
 fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
     debug!("visit_implementation_of_copy: impl_did={:?}", impl_did);
 
-    let self_type = tcx.type_of(impl_did).subst_identity();
+    let self_type = tcx.type_of(impl_did).instantiate_identity();
     debug!("visit_implementation_of_copy: self_type={:?} (bound)", self_type);
 
     let param_env = tcx.param_env(impl_did);
@@ -100,7 +100,7 @@ fn visit_implementation_of_copy(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
 }
 
 fn visit_implementation_of_const_param_ty(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
-    let self_type = tcx.type_of(impl_did).subst_identity();
+    let self_type = tcx.type_of(impl_did).instantiate_identity();
     assert!(!self_type.has_escaping_bound_vars());
 
     let param_env = tcx.param_env(impl_did);
@@ -139,13 +139,13 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
 
     let dispatch_from_dyn_trait = tcx.require_lang_item(LangItem::DispatchFromDyn, Some(span));
 
-    let source = tcx.type_of(impl_did).subst_identity();
+    let source = tcx.type_of(impl_did).instantiate_identity();
     assert!(!source.has_escaping_bound_vars());
     let target = {
-        let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().subst_identity();
+        let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().instantiate_identity();
         assert_eq!(trait_ref.def_id, dispatch_from_dyn_trait);
 
-        trait_ref.substs.type_at(1)
+        trait_ref.args.type_at(1)
     };
 
     debug!("visit_implementation_of_dispatch_from_dyn: {:?} -> {:?}", source, target);
@@ -163,9 +163,7 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
             if infcx.at(&cause, param_env).eq(DefineOpaqueTypes::No, r_a, *r_b).is_ok()
                 && mutbl_a == *mutbl_b => {}
         (&RawPtr(tm_a), &RawPtr(tm_b)) if tm_a.mutbl == tm_b.mutbl => (),
-        (&Adt(def_a, substs_a), &Adt(def_b, substs_b))
-            if def_a.is_struct() && def_b.is_struct() =>
-        {
+        (&Adt(def_a, args_a), &Adt(def_b, args_b)) if def_a.is_struct() && def_b.is_struct() => {
             if def_a != def_b {
                 let source_path = tcx.def_path_str(def_a.did());
                 let target_path = tcx.def_path_str(def_b.did());
@@ -194,8 +192,8 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
             let coerced_fields = fields
                 .iter()
                 .filter(|field| {
-                    let ty_a = field.ty(tcx, substs_a);
-                    let ty_b = field.ty(tcx, substs_b);
+                    let ty_a = field.ty(tcx, args_a);
+                    let ty_b = field.ty(tcx, args_b);
 
                     if let Ok(layout) = tcx.layout_of(param_env.and(ty_a)) {
                         if layout.is_zst() && layout.align.abi.bytes() == 1 {
@@ -250,8 +248,8 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
                                 format!(
                                     "`{}` (`{}` to `{}`)",
                                     field.name,
-                                    field.ty(tcx, substs_a),
-                                    field.ty(tcx, substs_b),
+                                    field.ty(tcx, args_a),
+                                    field.ty(tcx, args_b),
                                 )
                             })
                             .collect::<Vec<_>>()
@@ -268,7 +266,7 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
                         ty::TraitRef::new(
                             tcx,
                             dispatch_from_dyn_trait,
-                            [field.ty(tcx, substs_a), field.ty(tcx, substs_b)],
+                            [field.ty(tcx, args_a), field.ty(tcx, args_b)],
                         ),
                     ));
                 }
@@ -300,10 +298,10 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) -> Coe
 
     let unsize_trait = tcx.require_lang_item(LangItem::Unsize, Some(span));
 
-    let source = tcx.type_of(impl_did).subst_identity();
-    let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().subst_identity();
+    let source = tcx.type_of(impl_did).instantiate_identity();
+    let trait_ref = tcx.impl_trait_ref(impl_did).unwrap().instantiate_identity();
     assert_eq!(trait_ref.def_id, coerce_unsized_trait);
-    let target = trait_ref.substs.type_at(1);
+    let target = trait_ref.args.type_at(1);
     debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target);
 
     let param_env = tcx.param_env(impl_did);
@@ -348,7 +346,7 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) -> Coe
             check_mutbl(mt_a, mt_b, &|ty| Ty::new_imm_ptr(tcx, ty))
         }
 
-        (&ty::Adt(def_a, substs_a), &ty::Adt(def_b, substs_b))
+        (&ty::Adt(def_a, args_a), &ty::Adt(def_b, args_b))
             if def_a.is_struct() && def_b.is_struct() =>
         {
             if def_a != def_b {
@@ -411,9 +409,9 @@ pub fn coerce_unsized_info<'tcx>(tcx: TyCtxt<'tcx>, impl_did: LocalDefId) -> Coe
             let diff_fields = fields
                 .iter_enumerated()
                 .filter_map(|(i, f)| {
-                    let (a, b) = (f.ty(tcx, substs_a), f.ty(tcx, substs_b));
+                    let (a, b) = (f.ty(tcx, args_a), f.ty(tcx, args_b));
 
-                    if tcx.type_of(f.did).subst_identity().is_phantom_data() {
+                    if tcx.type_of(f.did).instantiate_identity().is_phantom_data() {
                         // Ignore PhantomData fields
                         return None;
                     }
diff --git a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
index 3355902069248..f5326e50614fd 100644
--- a/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs
@@ -171,7 +171,7 @@ impl<'tcx> InherentCollect<'tcx> {
 
         let id = id.owner_id.def_id;
         let item_span = self.tcx.def_span(id);
-        let self_ty = self.tcx.type_of(id).subst_identity();
+        let self_ty = self.tcx.type_of(id).instantiate_identity();
         match *self_ty.kind() {
             ty::Adt(def, _) => self.check_def_id(id, self_ty, def.did()),
             ty::Foreign(did) => self.check_def_id(id, self_ty, did),
diff --git a/compiler/rustc_hir_analysis/src/coherence/mod.rs b/compiler/rustc_hir_analysis/src/coherence/mod.rs
index 5097f43607e85..fc8fab0eabc83 100644
--- a/compiler/rustc_hir_analysis/src/coherence/mod.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -122,7 +122,7 @@ fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) {
 
     let impls = tcx.hir().trait_impls(def_id);
     for &impl_def_id in impls {
-        let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity();
+        let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity();
 
         check_impl(tcx, impl_def_id, trait_ref);
         check_object_overlap(tcx, impl_def_id, trait_ref);
diff --git a/compiler/rustc_hir_analysis/src/coherence/orphan.rs b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
index 025bab140215e..05c78f5708814 100644
--- a/compiler/rustc_hir_analysis/src/coherence/orphan.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/orphan.rs
@@ -5,8 +5,8 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{struct_span_err, DelayDm};
 use rustc_errors::{Diagnostic, ErrorGuaranteed};
 use rustc_hir as hir;
-use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::util::CheckRegions;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{
     self, AliasKind, ImplPolarity, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
     TypeVisitor,
@@ -22,7 +22,7 @@ pub(crate) fn orphan_check_impl(
     tcx: TyCtxt<'_>,
     impl_def_id: LocalDefId,
 ) -> Result<(), ErrorGuaranteed> {
-    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity();
+    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity();
     trait_ref.error_reported()?;
 
     let ret = do_orphan_check_impl(tcx, trait_ref, impl_def_id);
@@ -488,10 +488,10 @@ fn lint_auto_trait_impl<'tcx>(
     trait_ref: ty::TraitRef<'tcx>,
     impl_def_id: LocalDefId,
 ) {
-    assert_eq!(trait_ref.substs.len(), 1);
+    assert_eq!(trait_ref.args.len(), 1);
     let self_ty = trait_ref.self_ty();
-    let (self_type_did, substs) = match self_ty.kind() {
-        ty::Adt(def, substs) => (def.did(), substs),
+    let (self_type_did, args) = match self_ty.kind() {
+        ty::Adt(def, args) => (def.did(), args),
         _ => {
             // FIXME: should also lint for stuff like `&i32` but
             // considering that auto traits are unstable, that
@@ -502,9 +502,9 @@ fn lint_auto_trait_impl<'tcx>(
     };
 
     // Impls which completely cover a given root type are fine as they
-    // disable auto impls entirely. So only lint if the substs
-    // are not a permutation of the identity substs.
-    let Err(arg) = tcx.uses_unique_generic_params(substs, CheckRegions::No) else {
+    // disable auto impls entirely. So only lint if the args
+    // are not a permutation of the identity args.
+    let Err(arg) = tcx.uses_unique_generic_params(args, CheckRegions::No) else {
         // ok
         return;
     };
@@ -585,14 +585,14 @@ fn fast_reject_auto_impl<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId, self_ty:
             }
 
             match t.kind() {
-                ty::Adt(def, substs) if def.is_phantom_data() => substs.visit_with(self),
-                ty::Adt(def, substs) => {
+                ty::Adt(def, args) if def.is_phantom_data() => args.visit_with(self),
+                ty::Adt(def, args) => {
                     // @lcnr: This is the only place where cycles can happen. We avoid this
                     // by only visiting each `DefId` once.
                     //
                     // This will be is incorrect in subtle cases, but I don't care :)
                     if self.seen.insert(def.did()) {
-                        for ty in def.all_fields().map(|field| field.ty(tcx, substs)) {
+                        for ty in def.all_fields().map(|field| field.ty(tcx, args)) {
                             ty.visit_with(self)?;
                         }
                     }
@@ -605,9 +605,7 @@ fn fast_reject_auto_impl<'tcx>(tcx: TyCtxt<'tcx>, trait_def_id: DefId, self_ty:
     }
 
     let self_ty_root = match self_ty.kind() {
-        ty::Adt(def, _) => {
-            Ty::new_adt(tcx, *def, InternalSubsts::identity_for_item(tcx, def.did()))
-        }
+        ty::Adt(def, _) => Ty::new_adt(tcx, *def, GenericArgs::identity_for_item(tcx, def.did())),
         _ => unimplemented!("unexpected self ty {:?}", self_ty),
     };
 
diff --git a/compiler/rustc_hir_analysis/src/coherence/unsafety.rs b/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
index c6b16171311fb..6b18b0ebe9d1a 100644
--- a/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
+++ b/compiler/rustc_hir_analysis/src/coherence/unsafety.rs
@@ -12,7 +12,7 @@ pub(super) fn check_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let impl_ = item.expect_impl();
 
     if let Some(trait_ref) = tcx.impl_trait_ref(item.owner_id) {
-        let trait_ref = trait_ref.subst_identity();
+        let trait_ref = trait_ref.instantiate_identity();
         let trait_def = tcx.trait_def(trait_ref.def_id);
         let unsafe_attr =
             impl_.generics.params.iter().find(|p| p.pure_wrt_drop).map(|_| "may_dangle");
diff --git a/compiler/rustc_hir_analysis/src/collect.rs b/compiler/rustc_hir_analysis/src/collect.rs
index d724dce89f458..c160cf2df6e5f 100644
--- a/compiler/rustc_hir_analysis/src/collect.rs
+++ b/compiler/rustc_hir_analysis/src/collect.rs
@@ -401,13 +401,13 @@ impl<'tcx> AstConv<'tcx> for ItemCtxt<'tcx> {
         poly_trait_ref: ty::PolyTraitRef<'tcx>,
     ) -> Ty<'tcx> {
         if let Some(trait_ref) = poly_trait_ref.no_bound_vars() {
-            let item_substs = self.astconv().create_substs_for_associated_item(
+            let item_args = self.astconv().create_args_for_associated_item(
                 span,
                 item_def_id,
                 item_segment,
-                trait_ref.substs,
+                trait_ref.args,
             );
-            Ty::new_projection(self.tcx(), item_def_id, item_substs)
+            Ty::new_projection(self.tcx(), item_def_id, item_args)
         } else {
             // There are no late-bound regions; we can just ignore the binder.
             let (mut mpart_sugg, mut inferred_sugg) = (None, None);
@@ -1145,8 +1145,8 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<ty::PolyFnSig<
         }
 
         Ctor(data) | Variant(hir::Variant { data, .. }) if data.ctor().is_some() => {
-            let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id)).subst_identity();
-            let inputs = data.fields().iter().map(|f| tcx.type_of(f.def_id).subst_identity());
+            let ty = tcx.type_of(tcx.hir().get_parent_item(hir_id)).instantiate_identity();
+            let inputs = data.fields().iter().map(|f| tcx.type_of(f.def_id).instantiate_identity());
             ty::Binder::dummy(tcx.mk_fn_sig(
                 inputs,
                 ty,
@@ -1161,15 +1161,13 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<ty::PolyFnSig<
             // signatures and cannot be accessed through `fn_sig`. For
             // example, a closure signature excludes the `self`
             // argument. In any case they are embedded within the
-            // closure type as part of the `ClosureSubsts`.
+            // closure type as part of the `ClosureArgs`.
             //
             // To get the signature of a closure, you should use the
-            // `sig` method on the `ClosureSubsts`:
+            // `sig` method on the `ClosureArgs`:
             //
-            //    substs.as_closure().sig(def_id, tcx)
-            bug!(
-                "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
-            );
+            //    args.as_closure().sig(def_id, tcx)
+            bug!("to get the signature of a closure, use `args.as_closure().sig()` not `fn_sig()`",);
         }
 
         x => {
@@ -1266,7 +1264,7 @@ fn suggest_impl_trait<'tcx>(
 ) -> Option<String> {
     let format_as_assoc: fn(_, _, _, _, _) -> _ =
         |tcx: TyCtxt<'tcx>,
-         _: ty::SubstsRef<'tcx>,
+         _: ty::GenericArgsRef<'tcx>,
          trait_def_id: DefId,
          assoc_item_def_id: DefId,
          item_ty: Ty<'tcx>| {
@@ -1276,12 +1274,12 @@ fn suggest_impl_trait<'tcx>(
         };
     let format_as_parenthesized: fn(_, _, _, _, _) -> _ =
         |tcx: TyCtxt<'tcx>,
-         substs: ty::SubstsRef<'tcx>,
+         args: ty::GenericArgsRef<'tcx>,
          trait_def_id: DefId,
          _: DefId,
          item_ty: Ty<'tcx>| {
             let trait_name = tcx.item_name(trait_def_id);
-            let args_tuple = substs.type_at(1);
+            let args_tuple = args.type_at(1);
             let ty::Tuple(types) = *args_tuple.kind() else {
                 return None;
             };
@@ -1328,24 +1326,23 @@ fn suggest_impl_trait<'tcx>(
         }
         let param_env = tcx.param_env(def_id);
         let infcx = tcx.infer_ctxt().build();
-        let substs = ty::InternalSubsts::for_item(tcx, trait_def_id, |param, _| {
+        let args = ty::GenericArgs::for_item(tcx, trait_def_id, |param, _| {
             if param.index == 0 { ret_ty.into() } else { infcx.var_for_def(span, param) }
         });
-        if !infcx.type_implements_trait(trait_def_id, substs, param_env).must_apply_modulo_regions()
-        {
+        if !infcx.type_implements_trait(trait_def_id, args, param_env).must_apply_modulo_regions() {
             continue;
         }
         let ocx = ObligationCtxt::new(&infcx);
         let item_ty = ocx.normalize(
             &ObligationCause::misc(span, def_id),
             param_env,
-            Ty::new_projection(tcx, assoc_item_def_id, substs),
+            Ty::new_projection(tcx, assoc_item_def_id, args),
         );
         // FIXME(compiler-errors): We may benefit from resolving regions here.
         if ocx.select_where_possible().is_empty()
             && let item_ty = infcx.resolve_vars_if_possible(item_ty)
             && let Some(item_ty) = item_ty.make_suggestable(tcx, false)
-            && let Some(sugg) = formatter(tcx, infcx.resolve_vars_if_possible(substs), trait_def_id, assoc_item_def_id, item_ty)
+            && let Some(sugg) = formatter(tcx, infcx.resolve_vars_if_possible(args), trait_def_id, assoc_item_def_id, item_ty)
         {
             return Some(sugg);
         }
@@ -1363,7 +1360,7 @@ fn impl_trait_ref(
         .of_trait
         .as_ref()
         .map(|ast_trait_ref| {
-            let selfty = tcx.type_of(def_id).subst_identity();
+            let selfty = tcx.type_of(def_id).instantiate_identity();
             icx.astconv().instantiate_mono_trait_ref(
                 ast_trait_ref,
                 selfty,
diff --git a/compiler/rustc_hir_analysis/src/collect/generics_of.rs b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
index ccc9f808411c3..edcb9527fe2f9 100644
--- a/compiler/rustc_hir_analysis/src/collect/generics_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/generics_of.rs
@@ -68,17 +68,17 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
                     //        ^ parent_def_id
                     //
                     // then we only want to return generics for params to the left of `N`. If we don't do that we
-                    // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, substs: [N#0])`.
+                    // end up with that const looking like: `ty::ConstKind::Unevaluated(def_id, args: [N#0])`.
                     //
-                    // This causes ICEs (#86580) when building the substs for Foo in `fn foo() -> Foo { .. }` as
-                    // we substitute the defaults with the partially built substs when we build the substs. Subst'ing
-                    // the `N#0` on the unevaluated const indexes into the empty substs we're in the process of building.
+                    // This causes ICEs (#86580) when building the args for Foo in `fn foo() -> Foo { .. }` as
+                    // we substitute the defaults with the partially built args when we build the args. Subst'ing
+                    // the `N#0` on the unevaluated const indexes into the empty args we're in the process of building.
                     //
                     // We fix this by having this function return the parent's generics ourselves and truncating the
                     // generics to only include non-forward declared params (with the exception of the `Self` ty)
                     //
-                    // For the above code example that means we want `substs: []`
-                    // For the following struct def we want `substs: [N#0]` when generics_of is called on
+                    // For the above code example that means we want `args: []`
+                    // For the following struct def we want `args: [N#0]` when generics_of is called on
                     // the def id of the `{ N + 1 }` anon const
                     // struct Foo<const N: usize, const M: usize = { N + 1 }>;
                     //
@@ -93,7 +93,7 @@ pub(super) fn generics_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Generics {
 
                     return ty::Generics {
                         // we set the parent of these generics to be our parent's parent so that we
-                        // dont end up with substs: [N, M, N] for the const default on a struct like this:
+                        // dont end up with args: [N, M, N] for the const default on a struct like this:
                         // struct Foo<const N: usize, const M: usize = { ... }>;
                         parent: generics.parent,
                         parent_count: generics.parent_count,
diff --git a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
index d6f33869a03f0..758e9dc723047 100644
--- a/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
+++ b/compiler/rustc_hir_analysis/src/collect/item_bounds.rs
@@ -2,7 +2,7 @@ use super::ItemCtxt;
 use crate::astconv::{AstConv, PredicateFilter};
 use rustc_hir as hir;
 use rustc_infer::traits::util;
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::def_id::{DefId, LocalDefId};
 use rustc_span::Span;
@@ -10,7 +10,7 @@ use rustc_span::Span;
 /// For associated types we include both bounds written on the type
 /// (`type X: Trait`) and predicates from the trait: `where Self::X: Trait`.
 ///
-/// Note that this filtering is done with the items identity substs to
+/// Note that this filtering is done with the items identity args to
 /// simplify checking that these bounds are met in impls. This means that
 /// a bound such as `for<'b> <Self as X<'b>>::U: Clone` can't be used, as in
 /// `hr-associated-type-bound-1.rs`.
@@ -23,7 +23,7 @@ fn associated_type_bounds<'tcx>(
     let item_ty = Ty::new_projection(
         tcx,
         assoc_item_def_id.to_def_id(),
-        InternalSubsts::identity_for_item(tcx, assoc_item_def_id),
+        GenericArgs::identity_for_item(tcx, assoc_item_def_id),
     );
 
     let icx = ItemCtxt::new(tcx, assoc_item_def_id);
@@ -95,7 +95,7 @@ pub(super) fn explicit_item_bounds(
                 Ty::new_projection(
                     tcx,
                     def_id.to_def_id(),
-                    ty::InternalSubsts::identity_for_item(tcx, def_id),
+                    ty::GenericArgs::identity_for_item(tcx, def_id),
                 ),
                 item.span,
             ));
@@ -117,8 +117,8 @@ pub(super) fn explicit_item_bounds(
             span,
             ..
         }) => {
-            let substs = InternalSubsts::identity_for_item(tcx, def_id);
-            let item_ty = Ty::new_opaque(tcx, def_id.to_def_id(), substs);
+            let args = GenericArgs::identity_for_item(tcx, def_id);
+            let item_ty = Ty::new_opaque(tcx, def_id.to_def_id(), args);
             opaque_type_bounds(tcx, def_id, bounds, item_ty, *span)
         }
         hir::Node::Item(hir::Item { kind: hir::ItemKind::TyAlias(..), .. }) => &[],
diff --git a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
index 81e4aa2542783..1c9070600dbe3 100644
--- a/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/predicates_of.rs
@@ -8,7 +8,6 @@ use rustc_hir as hir;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::intravisit::{self, Visitor};
-use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{GenericPredicates, Generics, ImplTraitInTraitData, ToPredicate};
 use rustc_span::symbol::{sym, Ident};
@@ -80,10 +79,9 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             // both to ensure that the RPITITs are only instantiated when the
             // parent predicates would hold, and also so that the param-env
             // inherits these predicates as assumptions.
-            let identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
-            predicates.extend(
-                tcx.explicit_predicates_of(fn_def_id).instantiate_own(tcx, identity_substs),
-            );
+            let identity_args = ty::GenericArgs::identity_for_item(tcx, def_id);
+            predicates
+                .extend(tcx.explicit_predicates_of(fn_def_id).instantiate_own(tcx, identity_args));
 
             // We also install bidirectional outlives predicates for the RPITIT
             // to keep the duplicates lifetimes from opaque lowering in sync.
@@ -108,15 +106,15 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
             let trait_assoc_predicates =
                 tcx.explicit_predicates_of(assoc_item.trait_item_def_id.unwrap());
 
-            let impl_assoc_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+            let impl_assoc_identity_args = ty::GenericArgs::identity_for_item(tcx, def_id);
             let impl_def_id = tcx.parent(fn_def_id);
-            let impl_trait_ref_substs =
-                tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity().substs;
+            let impl_trait_ref_args =
+                tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity().args;
 
-            let impl_assoc_substs =
-                impl_assoc_identity_substs.rebase_onto(tcx, impl_def_id, impl_trait_ref_substs);
+            let impl_assoc_args =
+                impl_assoc_identity_args.rebase_onto(tcx, impl_def_id, impl_trait_ref_args);
 
-            let impl_predicates = trait_assoc_predicates.instantiate_own(tcx, impl_assoc_substs);
+            let impl_predicates = trait_assoc_predicates.instantiate_own(tcx, impl_assoc_args);
 
             return ty::GenericPredicates {
                 parent: Some(impl_def_id),
@@ -150,8 +148,9 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
         Node::Item(item) => match item.kind {
             ItemKind::Impl(impl_) => {
                 if impl_.defaultness.is_default() {
-                    is_default_impl_trait =
-                        tcx.impl_trait_ref(def_id).map(|t| ty::Binder::dummy(t.subst_identity()));
+                    is_default_impl_trait = tcx
+                        .impl_trait_ref(def_id)
+                        .map(|t| ty::Binder::dummy(t.instantiate_identity()));
                 }
                 impl_.generics
             }
@@ -337,8 +336,8 @@ fn gather_explicit_predicates_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::Gen
     // in trait checking. See `setup_constraining_predicates`
     // for details.
     if let Node::Item(&Item { kind: ItemKind::Impl { .. }, .. }) = node {
-        let self_ty = tcx.type_of(def_id).subst_identity();
-        let trait_ref = tcx.impl_trait_ref(def_id).map(ty::EarlyBinder::subst_identity);
+        let self_ty = tcx.type_of(def_id).instantiate_identity();
+        let trait_ref = tcx.impl_trait_ref(def_id).map(ty::EarlyBinder::instantiate_identity);
         cgp::setup_constraining_predicates(
             tcx,
             &mut predicates,
@@ -397,7 +396,7 @@ fn compute_bidirectional_outlives_predicates<'tcx>(
         let orig_region = icx.astconv().ast_region_to_region(&arg, None);
         if !matches!(orig_region.kind(), ty::ReEarlyBound(..)) {
             // There is no late-bound lifetime to actually match up here, since the lifetime doesn't
-            // show up in the opaque's parent's substs.
+            // show up in the opaque's parent's args.
             continue;
         }
 
@@ -499,20 +498,20 @@ pub(super) fn explicit_predicates_of<'tcx>(
         // Remove bounds on associated types from the predicates, they will be
         // returned by `explicit_item_bounds`.
         let predicates_and_bounds = tcx.trait_explicit_predicates_and_bounds(def_id);
-        let trait_identity_substs = InternalSubsts::identity_for_item(tcx, def_id);
+        let trait_identity_args = ty::GenericArgs::identity_for_item(tcx, def_id);
 
         let is_assoc_item_ty = |ty: Ty<'tcx>| {
             // For a predicate from a where clause to become a bound on an
             // associated type:
-            // * It must use the identity substs of the item.
+            // * It must use the identity args of the item.
             //   * We're in the scope of the trait, so we can't name any
             //     parameters of the GAT. That means that all we need to
-            //     check are that the substs of the projection are the
-            //     identity substs of the trait.
+            //     check are that the args of the projection are the
+            //     identity args of the trait.
             // * It must be an associated type for this trait (*not* a
             //   supertrait).
             if let ty::Alias(ty::Projection, projection) = ty.kind() {
-                projection.substs == trait_identity_substs
+                projection.args == trait_identity_args
                     // FIXME(return_type_notation): This check should be more robust
                     && !tcx.is_impl_trait_in_trait(projection.def_id)
                     && tcx.associated_item(projection.def_id).container_id(tcx)
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index c0eba18f83850..44f116ef2da6c 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1721,7 +1721,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
                         },
                     ));
                     bound_vars
-                        .extend(self.tcx.fn_sig(assoc_fn.def_id).subst_identity().bound_vars());
+                        .extend(self.tcx.fn_sig(assoc_fn.def_id).instantiate_identity().bound_vars());
                     bound_vars
                 } else {
                     self.tcx.sess.delay_span_bug(
@@ -2038,12 +2038,12 @@ fn is_late_bound_map(
                     hir::Path { res: Res::Def(DefKind::TyAlias, alias_def), segments, span },
                 )) => {
                     // See comments on `ConstrainedCollectorPostAstConv` for why this arm does not just consider
-                    // substs to be unconstrained.
+                    // args to be unconstrained.
                     let generics = self.tcx.generics_of(alias_def);
                     let mut walker = ConstrainedCollectorPostAstConv {
                         arg_is_constrained: vec![false; generics.params.len()].into_boxed_slice(),
                     };
-                    walker.visit_ty(self.tcx.type_of(alias_def).subst_identity());
+                    walker.visit_ty(self.tcx.type_of(alias_def).instantiate_identity());
 
                     match segments.last() {
                         Some(hir::PathSegment { args: Some(args), .. }) => {
diff --git a/compiler/rustc_hir_analysis/src/collect/type_of.rs b/compiler/rustc_hir_analysis/src/collect/type_of.rs
index 3755342aef5df..c39edaa157787 100644
--- a/compiler/rustc_hir_analysis/src/collect/type_of.rs
+++ b/compiler/rustc_hir_analysis/src/collect/type_of.rs
@@ -3,7 +3,6 @@ use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_hir::HirId;
 use rustc_middle::ty::print::with_forced_trimmed_paths;
-use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::util::IntTypeExt;
 use rustc_middle::ty::{self, ImplTraitInTraitData, IsSuggestable, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::symbol::Ident;
@@ -338,8 +337,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
     let output = match tcx.hir().get(hir_id) {
         Node::TraitItem(item) => match item.kind {
             TraitItemKind::Fn(..) => {
-                let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
+                let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
             TraitItemKind::Const(ty, body_id) => body_id
                 .and_then(|body_id| {
@@ -363,8 +362,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
 
         Node::ImplItem(item) => match item.kind {
             ImplItemKind::Fn(..) => {
-                let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
+                let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
             ImplItemKind::Const(ty, body_id) => {
                 if is_suggestable_infer_ty(ty) {
@@ -426,13 +425,13 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
                     _ => icx.to_ty(*self_ty),
                 },
                 ItemKind::Fn(..) => {
-                    let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                    Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
+                    let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                    Ty::new_fn_def(tcx, def_id.to_def_id(), args)
                 }
                 ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) => {
                     let def = tcx.adt_def(def_id);
-                    let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                    Ty::new_adt(tcx, def, substs)
+                    let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                    Ty::new_adt(tcx, def, args)
                 }
                 ItemKind::OpaqueTy(OpaqueTy {
                     origin: hir::OpaqueTyOrigin::TyAlias { .. },
@@ -472,8 +471,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
 
         Node::ForeignItem(foreign_item) => match foreign_item.kind {
             ForeignItemKind::Fn(..) => {
-                let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
+                let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
             ForeignItemKind::Static(t, _) => icx.to_ty(t),
             ForeignItemKind::Type => Ty::new_foreign(tcx, def_id.to_def_id()),
@@ -481,11 +480,11 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
 
         Node::Ctor(def) | Node::Variant(Variant { data: def, .. }) => match def {
             VariantData::Unit(..) | VariantData::Struct(..) => {
-                tcx.type_of(tcx.hir().get_parent_item(hir_id)).subst_identity()
+                tcx.type_of(tcx.hir().get_parent_item(hir_id)).instantiate_identity()
             }
             VariantData::Tuple(..) => {
-                let substs = InternalSubsts::identity_for_item(tcx, def_id);
-                Ty::new_fn_def(tcx, def_id.to_def_id(), substs)
+                let args = ty::GenericArgs::identity_for_item(tcx, def_id);
+                Ty::new_fn_def(tcx, def_id.to_def_id(), args)
             }
         },
 
@@ -498,8 +497,8 @@ pub(super) fn type_of(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::EarlyBinder<Ty
         Node::AnonConst(_) => anon_const_type_of(tcx, def_id),
 
         Node::ConstBlock(_) => {
-            let substs = InternalSubsts::identity_for_item(tcx, def_id.to_def_id());
-            substs.as_inline_const().ty()
+            let args = ty::GenericArgs::identity_for_item(tcx, def_id.to_def_id());
+            args.as_inline_const().ty()
         }
 
         Node::GenericParam(param) => match &param.kind {
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check.rs b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
index d654b0be62045..62f22bda9f900 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check.rs
@@ -70,7 +70,7 @@ pub fn provide(providers: &mut Providers) {
 
 fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId) {
     // Every lifetime used in an associated type must be constrained.
-    let impl_self_ty = tcx.type_of(impl_def_id).subst_identity();
+    let impl_self_ty = tcx.type_of(impl_def_id).instantiate_identity();
     if impl_self_ty.references_error() {
         // Don't complain about unconstrained type params when self ty isn't known due to errors.
         // (#36836)
@@ -85,7 +85,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
     }
     let impl_generics = tcx.generics_of(impl_def_id);
     let impl_predicates = tcx.predicates_of(impl_def_id);
-    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::subst_identity);
+    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::instantiate_identity);
 
     let mut input_parameters = cgp::parameters_for_impl(impl_self_ty, impl_trait_ref);
     cgp::identify_constrained_generic_params(
@@ -104,7 +104,7 @@ fn enforce_impl_params_are_constrained(tcx: TyCtxt<'_>, impl_def_id: LocalDefId)
             match item.kind {
                 ty::AssocKind::Type => {
                     if item.defaultness(tcx).has_value() {
-                        cgp::parameters_for(&tcx.type_of(def_id).subst_identity(), true)
+                        cgp::parameters_for(&tcx.type_of(def_id).instantiate_identity(), true)
                     } else {
                         vec![]
                     }
diff --git a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
index c64fb469bb205..81993789bcf69 100644
--- a/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
+++ b/compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs
@@ -14,15 +14,15 @@
 //! To enforce this requirement on specializations we take the following
 //! approach:
 //!
-//! 1. Match up the substs for `impl2` so that the implemented trait and
+//! 1. Match up the args for `impl2` so that the implemented trait and
 //!    self-type match those for `impl1`.
-//! 2. Check for any direct use of `'static` in the substs of `impl2`.
+//! 2. Check for any direct use of `'static` in the args of `impl2`.
 //! 3. Check that all of the generic parameters of `impl1` occur at most once
-//!    in the *unconstrained* substs for `impl2`. A parameter is constrained if
+//!    in the *unconstrained* args for `impl2`. A parameter is constrained if
 //!    its value is completely determined by an associated type projection
 //!    predicate.
 //! 4. Check that all predicates on `impl1` either exist on `impl2` (after
-//!    matching substs), or are well-formed predicates for the trait's type
+//!    matching args), or are well-formed predicates for the trait's type
 //!    arguments.
 //!
 //! ## Example
@@ -74,13 +74,13 @@ use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::specialization_graph::Node;
-use rustc_middle::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 use rustc_middle::ty::trait_def::TraitSpecializationKind;
 use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use rustc_span::{ErrorGuaranteed, Span};
 use rustc_trait_selection::traits::error_reporting::TypeErrCtxtExt;
 use rustc_trait_selection::traits::outlives_bounds::InferCtxtExt as _;
-use rustc_trait_selection::traits::{self, translate_substs_with_cause, wf, ObligationCtxt};
+use rustc_trait_selection::traits::{self, translate_args_with_cause, wf, ObligationCtxt};
 
 pub(super) fn check_min_specialization(tcx: TyCtxt<'_>, impl_def_id: LocalDefId) {
     if let Some(node) = parent_specialization_node(tcx, impl_def_id) {
@@ -113,20 +113,20 @@ fn check_always_applicable(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node
     let span = tcx.def_span(impl1_def_id);
     check_has_items(tcx, impl1_def_id, impl2_node, span);
 
-    if let Ok((impl1_substs, impl2_substs)) = get_impl_substs(tcx, impl1_def_id, impl2_node) {
+    if let Ok((impl1_args, impl2_args)) = get_impl_args(tcx, impl1_def_id, impl2_node) {
         let impl2_def_id = impl2_node.def_id();
-        debug!(?impl2_def_id, ?impl2_substs);
+        debug!(?impl2_def_id, ?impl2_args);
 
-        let parent_substs = if impl2_node.is_from_trait() {
-            impl2_substs.to_vec()
+        let parent_args = if impl2_node.is_from_trait() {
+            impl2_args.to_vec()
         } else {
-            unconstrained_parent_impl_substs(tcx, impl2_def_id, impl2_substs)
+            unconstrained_parent_impl_args(tcx, impl2_def_id, impl2_args)
         };
 
         check_constness(tcx, impl1_def_id, impl2_node, span);
-        check_static_lifetimes(tcx, &parent_substs, span);
-        check_duplicate_params(tcx, impl1_substs, &parent_substs, span);
-        check_predicates(tcx, impl1_def_id, impl1_substs, impl2_node, impl2_substs, span);
+        check_static_lifetimes(tcx, &parent_args, span);
+        check_duplicate_params(tcx, impl1_args, &parent_args, span);
+        check_predicates(tcx, impl1_def_id, impl1_args, impl2_node, impl2_args, span);
     }
 }
 
@@ -167,23 +167,23 @@ fn check_constness(tcx: TyCtxt<'_>, impl1_def_id: LocalDefId, impl2_node: Node,
 /// ```
 ///
 /// Would return `S1 = [C]` and `S2 = [Vec<C>, C]`.
-fn get_impl_substs(
+fn get_impl_args(
     tcx: TyCtxt<'_>,
     impl1_def_id: LocalDefId,
     impl2_node: Node,
-) -> Result<(SubstsRef<'_>, SubstsRef<'_>), ErrorGuaranteed> {
+) -> Result<(GenericArgsRef<'_>, GenericArgsRef<'_>), ErrorGuaranteed> {
     let infcx = &tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(infcx);
     let param_env = tcx.param_env(impl1_def_id);
     let impl1_span = tcx.def_span(impl1_def_id);
     let assumed_wf_types = ocx.assumed_wf_types_and_report_errors(param_env, impl1_def_id)?;
 
-    let impl1_substs = InternalSubsts::identity_for_item(tcx, impl1_def_id);
-    let impl2_substs = translate_substs_with_cause(
+    let impl1_args = GenericArgs::identity_for_item(tcx, impl1_def_id);
+    let impl2_args = translate_args_with_cause(
         infcx,
         param_env,
         impl1_def_id.to_def_id(),
-        impl1_substs,
+        impl1_args,
         impl2_node,
         |_, span| {
             traits::ObligationCause::new(
@@ -203,12 +203,12 @@ fn get_impl_substs(
     let implied_bounds = infcx.implied_bounds_tys(param_env, impl1_def_id, assumed_wf_types);
     let outlives_env = OutlivesEnvironment::with_bounds(param_env, implied_bounds);
     let _ = ocx.resolve_regions_and_report_errors(impl1_def_id, &outlives_env);
-    let Ok(impl2_substs) = infcx.fully_resolve(impl2_substs) else {
+    let Ok(impl2_args) = infcx.fully_resolve(impl2_args) else {
         let span = tcx.def_span(impl1_def_id);
         let guar = tcx.sess.emit_err(SubstsOnOverriddenImpl { span });
         return Err(guar);
     };
-    Ok((impl1_substs, impl2_substs))
+    Ok((impl1_args, impl2_args))
 }
 
 /// Returns a list of all of the unconstrained subst of the given impl.
@@ -217,17 +217,17 @@ fn get_impl_substs(
 ///
 /// impl<'a, T, I> ... where &'a I: IntoIterator<Item=&'a T>
 ///
-/// This would return the substs corresponding to `['a, I]`, because knowing
+/// This would return the args corresponding to `['a, I]`, because knowing
 /// `'a` and `I` determines the value of `T`.
-fn unconstrained_parent_impl_substs<'tcx>(
+fn unconstrained_parent_impl_args<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl_def_id: DefId,
-    impl_substs: SubstsRef<'tcx>,
+    impl_args: GenericArgsRef<'tcx>,
 ) -> Vec<GenericArg<'tcx>> {
     let impl_generic_predicates = tcx.predicates_of(impl_def_id);
     let mut unconstrained_parameters = FxHashSet::default();
     let mut constrained_params = FxHashSet::default();
-    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::subst_identity);
+    let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).map(ty::EarlyBinder::instantiate_identity);
 
     // Unfortunately the functions in `constrained_generic_parameters` don't do
     // what we want here. We want only a list of constrained parameters while
@@ -255,7 +255,7 @@ fn unconstrained_parent_impl_substs<'tcx>(
         }
     }
 
-    impl_substs
+    impl_args
         .iter()
         .enumerate()
         .filter(|&(idx, _)| !constrained_params.contains(&(idx as u32)))
@@ -264,7 +264,7 @@ fn unconstrained_parent_impl_substs<'tcx>(
 }
 
 /// Check that parameters of the derived impl don't occur more than once in the
-/// equated substs of the base impl.
+/// equated args of the base impl.
 ///
 /// For example forbid the following:
 ///
@@ -280,19 +280,19 @@ fn unconstrained_parent_impl_substs<'tcx>(
 /// impl<T> Tr<T> for Vec<T> { }
 /// ```
 ///
-/// The substs for the parent impl here are `[T, Vec<T>]`, which repeats `T`,
-/// but `S` is constrained in the parent impl, so `parent_substs` is only
+/// The args for the parent impl here are `[T, Vec<T>]`, which repeats `T`,
+/// but `S` is constrained in the parent impl, so `parent_args` is only
 /// `[Vec<T>]`. This means we allow this impl.
 fn check_duplicate_params<'tcx>(
     tcx: TyCtxt<'tcx>,
-    impl1_substs: SubstsRef<'tcx>,
-    parent_substs: &Vec<GenericArg<'tcx>>,
+    impl1_args: GenericArgsRef<'tcx>,
+    parent_args: &Vec<GenericArg<'tcx>>,
     span: Span,
 ) {
-    let mut base_params = cgp::parameters_for(parent_substs, true);
+    let mut base_params = cgp::parameters_for(parent_args, true);
     base_params.sort_by_key(|param| param.0);
     if let (_, [duplicate, ..]) = base_params.partition_dedup() {
-        let param = impl1_substs[duplicate.0 as usize];
+        let param = impl1_args[duplicate.0 as usize];
         tcx.sess
             .struct_span_err(span, format!("specializing impl repeats parameter `{}`", param))
             .emit();
@@ -309,10 +309,10 @@ fn check_duplicate_params<'tcx>(
 /// ```
 fn check_static_lifetimes<'tcx>(
     tcx: TyCtxt<'tcx>,
-    parent_substs: &Vec<GenericArg<'tcx>>,
+    parent_args: &Vec<GenericArg<'tcx>>,
     span: Span,
 ) {
-    if tcx.any_free_region_meets(parent_substs, |r| r.is_static()) {
+    if tcx.any_free_region_meets(parent_args, |r| r.is_static()) {
         tcx.sess.emit_err(errors::StaticSpecialize { span });
     }
 }
@@ -331,14 +331,14 @@ fn check_static_lifetimes<'tcx>(
 fn check_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl1_def_id: LocalDefId,
-    impl1_substs: SubstsRef<'tcx>,
+    impl1_args: GenericArgsRef<'tcx>,
     impl2_node: Node,
-    impl2_substs: SubstsRef<'tcx>,
+    impl2_args: GenericArgsRef<'tcx>,
     span: Span,
 ) {
     let impl1_predicates: Vec<_> = traits::elaborate(
         tcx,
-        tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_substs).into_iter(),
+        tcx.predicates_of(impl1_def_id).instantiate(tcx, impl1_args).into_iter(),
     )
     .collect();
 
@@ -350,7 +350,7 @@ fn check_predicates<'tcx>(
         traits::elaborate(
             tcx,
             tcx.predicates_of(impl2_node.def_id())
-                .instantiate(tcx, impl2_substs)
+                .instantiate(tcx, impl2_args)
                 .into_iter()
                 .map(|(c, _s)| c.as_predicate()),
         )
@@ -385,7 +385,7 @@ fn check_predicates<'tcx>(
         .map(|(c, _span)| c.as_predicate());
 
     // Include the well-formed predicates of the type parameters of the impl.
-    for arg in tcx.impl_trait_ref(impl1_def_id).unwrap().subst_identity().substs {
+    for arg in tcx.impl_trait_ref(impl1_def_id).unwrap().instantiate_identity().args {
         let infcx = &tcx.infer_ctxt().build();
         let obligations =
             wf::obligations(infcx, tcx.param_env(impl1_def_id), impl1_def_id, 0, arg, span)
diff --git a/compiler/rustc_hir_analysis/src/lib.rs b/compiler/rustc_hir_analysis/src/lib.rs
index 8312ec74c437c..677d94f173144 100644
--- a/compiler/rustc_hir_analysis/src/lib.rs
+++ b/compiler/rustc_hir_analysis/src/lib.rs
@@ -178,12 +178,12 @@ fn require_same_types<'tcx>(
 }
 
 fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
-    let main_fnsig = tcx.fn_sig(main_def_id).subst_identity();
+    let main_fnsig = tcx.fn_sig(main_def_id).instantiate_identity();
     let main_span = tcx.def_span(main_def_id);
 
     fn main_fn_diagnostics_def_id(tcx: TyCtxt<'_>, def_id: DefId, sp: Span) -> LocalDefId {
         if let Some(local_def_id) = def_id.as_local() {
-            let hir_type = tcx.type_of(local_def_id).subst_identity();
+            let hir_type = tcx.type_of(local_def_id).instantiate_identity();
             if !matches!(hir_type.kind(), ty::FnDef(..)) {
                 span_bug!(sp, "main has a non-function type: found `{}`", hir_type);
             }
@@ -350,7 +350,7 @@ fn check_start_fn_ty(tcx: TyCtxt<'_>, start_def_id: DefId) {
     let start_def_id = start_def_id.expect_local();
     let start_id = tcx.hir().local_def_id_to_hir_id(start_def_id);
     let start_span = tcx.def_span(start_def_id);
-    let start_t = tcx.type_of(start_def_id).subst_identity();
+    let start_t = tcx.type_of(start_def_id).instantiate_identity();
     match start_t.kind() {
         ty::FnDef(..) => {
             if let Some(Node::Item(it)) = tcx.hir().find(start_id) {
@@ -421,7 +421,7 @@ fn check_start_fn_ty(tcx: TyCtxt<'_>, start_def_id: DefId) {
                 ),
                 ty::ParamEnv::empty(), // start should not have any where bounds.
                 se_ty,
-                Ty::new_fn_ptr(tcx, tcx.fn_sig(start_def_id).subst_identity()),
+                Ty::new_fn_ptr(tcx, tcx.fn_sig(start_def_id).instantiate_identity()),
             );
         }
         _ => {
diff --git a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
index 71dca918fc5e1..c17925471d983 100644
--- a/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/implicit_infer.rs
@@ -46,7 +46,7 @@ pub(super) fn infer_predicates(
                         // For field of type &'a T (reference) or Adt
                         // (struct/enum/union) there will be outlive
                         // requirements for adt_def.
-                        let field_ty = tcx.type_of(field_def.did).subst_identity();
+                        let field_ty = tcx.type_of(field_def.did).instantiate_identity();
                         let field_span = tcx.def_span(field_def.did);
                         insert_required_predicates_to_be_wf(
                             tcx,
@@ -117,7 +117,7 @@ fn insert_required_predicates_to_be_wf<'tcx>(
             // can load the current set of inferred and explicit
             // predicates from `global_inferred_outlives` and filter the
             // ones that are TypeOutlives.
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 // First check the inferred predicates
                 //
                 // Example 1:
@@ -146,7 +146,7 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                         // get `T: 'a` (or `predicate`):
                         let predicate = unsubstituted_predicates
                             .rebind(*unsubstituted_predicate)
-                            .subst(tcx, substs);
+                            .instantiate(tcx, args);
                         insert_outlives_predicate(
                             tcx,
                             predicate.0,
@@ -159,11 +159,11 @@ fn insert_required_predicates_to_be_wf<'tcx>(
 
                 // Check if the type has any explicit predicates that need
                 // to be added to `required_predicates`
-                // let _: () = substs.region_at(0);
+                // let _: () = args.region_at(0);
                 check_explicit_predicates(
                     tcx,
                     def.did(),
-                    substs,
+                    args,
                     required_predicates,
                     explicit_map,
                     None,
@@ -186,12 +186,11 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                     // predicates in `check_explicit_predicates` we
                     // need to ignore checking the explicit_map for
                     // Self type.
-                    let substs =
-                        ex_trait_ref.with_self_ty(tcx, tcx.types.usize).skip_binder().substs;
+                    let args = ex_trait_ref.with_self_ty(tcx, tcx.types.usize).skip_binder().args;
                     check_explicit_predicates(
                         tcx,
                         ex_trait_ref.skip_binder().def_id,
-                        substs,
+                        args,
                         required_predicates,
                         explicit_map,
                         Some(tcx.types.self_param),
@@ -206,7 +205,7 @@ fn insert_required_predicates_to_be_wf<'tcx>(
                 check_explicit_predicates(
                     tcx,
                     tcx.parent(obj.def_id),
-                    obj.substs,
+                    obj.args,
                     required_predicates,
                     explicit_map,
                     None,
@@ -239,18 +238,18 @@ fn insert_required_predicates_to_be_wf<'tcx>(
 fn check_explicit_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: DefId,
-    substs: &[GenericArg<'tcx>],
+    args: &[GenericArg<'tcx>],
     required_predicates: &mut RequiredPredicates<'tcx>,
     explicit_map: &mut ExplicitPredicatesMap<'tcx>,
     ignored_self_ty: Option<Ty<'tcx>>,
 ) {
     debug!(
         "check_explicit_predicates(def_id={:?}, \
-         substs={:?}, \
+         args={:?}, \
          explicit_map={:?}, \
          required_predicates={:?}, \
          ignored_self_ty={:?})",
-        def_id, substs, explicit_map, required_predicates, ignored_self_ty,
+        def_id, args, explicit_map, required_predicates, ignored_self_ty,
     );
     let explicit_predicates = explicit_map.explicit_predicates_of(tcx, def_id);
 
@@ -278,10 +277,10 @@ fn check_explicit_predicates<'tcx>(
         // that is represented by the `dyn Trait`, not to the `X` type parameter
         // (or any other generic parameter) declared on `MyStruct`.
         //
-        // Note that we do this check for self **before** applying `substs`. In the
-        // case that `substs` come from a `dyn Trait` type, our caller will have
+        // Note that we do this check for self **before** applying `args`. In the
+        // case that `args` come from a `dyn Trait` type, our caller will have
         // included `Self = usize` as the value for `Self`. If we were
-        // to apply the substs, and not filter this predicate, we might then falsely
+        // to apply the args, and not filter this predicate, we might then falsely
         // conclude that e.g., `X: 'x` was a reasonable inferred requirement.
         //
         // Another similar case is where we have an inferred
@@ -299,7 +298,7 @@ fn check_explicit_predicates<'tcx>(
             continue;
         }
 
-        let predicate = explicit_predicates.rebind(*outlives_predicate).subst(tcx, substs);
+        let predicate = explicit_predicates.rebind(*outlives_predicate).instantiate(tcx, args);
         debug!("predicate = {:?}", &predicate);
         insert_outlives_predicate(tcx, predicate.0, predicate.1, span, required_predicates);
     }
diff --git a/compiler/rustc_hir_analysis/src/outlives/mod.rs b/compiler/rustc_hir_analysis/src/outlives/mod.rs
index 48624cefe4d02..be9d076bd6eb0 100644
--- a/compiler/rustc_hir_analysis/src/outlives/mod.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/mod.rs
@@ -2,7 +2,7 @@ use hir::Node;
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, CratePredicatesMap, ToPredicate, TyCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
diff --git a/compiler/rustc_hir_analysis/src/outlives/utils.rs b/compiler/rustc_hir_analysis/src/outlives/utils.rs
index c5c5f63a108b3..a6410c944f778 100644
--- a/compiler/rustc_hir_analysis/src/outlives/utils.rs
+++ b/compiler/rustc_hir_analysis/src/outlives/utils.rs
@@ -1,6 +1,6 @@
 use rustc_infer::infer::outlives::components::{push_outlives_components, Component};
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, Region, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArg, GenericArgKind};
 use rustc_span::Span;
 use smallvec::smallvec;
 use std::collections::BTreeMap;
diff --git a/compiler/rustc_hir_analysis/src/variance/constraints.rs b/compiler/rustc_hir_analysis/src/variance/constraints.rs
index 6f0afae1b4c68..ec8889781f484 100644
--- a/compiler/rustc_hir_analysis/src/variance/constraints.rs
+++ b/compiler/rustc_hir_analysis/src/variance/constraints.rs
@@ -6,8 +6,8 @@
 use hir::def_id::{DefId, LocalDefId};
 use rustc_hir as hir;
 use rustc_hir::def::DefKind;
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef};
 
 use super::terms::VarianceTerm::*;
 use super::terms::*;
@@ -101,7 +101,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
 
         let inferred_start = self.terms_cx.inferred_starts[&def_id];
         let current_item = &CurrentItem { inferred_start };
-        match tcx.type_of(def_id).subst_identity().kind() {
+        match tcx.type_of(def_id).instantiate_identity().kind() {
             ty::Adt(def, _) => {
                 // Not entirely obvious: constraints on structs/enums do not
                 // affect the variance of their type parameters. See discussion
@@ -112,7 +112,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 for field in def.all_fields() {
                     self.add_constraints_from_ty(
                         current_item,
-                        tcx.type_of(field.did).subst_identity(),
+                        tcx.type_of(field.did).instantiate_identity(),
                         self.covariant,
                     );
                 }
@@ -121,7 +121,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             ty::FnDef(..) => {
                 self.add_constraints_from_sig(
                     current_item,
-                    tcx.fn_sig(def_id).subst_identity(),
+                    tcx.fn_sig(def_id).instantiate_identity(),
                     self.covariant,
                 );
             }
@@ -175,16 +175,16 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self, current))]
-    fn add_constraints_from_invariant_substs(
+    fn add_constraints_from_invariant_args(
         &mut self,
         current: &CurrentItem,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         variance: VarianceTermPtr<'a>,
     ) {
         // Trait are always invariant so we can take advantage of that.
         let variance_i = self.invariant(variance);
 
-        for k in substs {
+        for k in args {
             match k.unpack() {
                 GenericArgKind::Lifetime(lt) => {
                     self.add_constraints_from_region(current, lt, variance_i)
@@ -248,12 +248,12 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 }
             }
 
-            ty::Adt(def, substs) => {
-                self.add_constraints_from_substs(current, def.did(), substs, variance);
+            ty::Adt(def, args) => {
+                self.add_constraints_from_args(current, def.did(), args, variance);
             }
 
             ty::Alias(_, ref data) => {
-                self.add_constraints_from_invariant_substs(current, data.substs, variance);
+                self.add_constraints_from_invariant_args(current, data.args, variance);
             }
 
             ty::Dynamic(data, r, _) => {
@@ -261,9 +261,9 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
                 self.add_constraints_from_region(current, r, variance);
 
                 if let Some(poly_trait_ref) = data.principal() {
-                    self.add_constraints_from_invariant_substs(
+                    self.add_constraints_from_invariant_args(
                         current,
-                        poly_trait_ref.skip_binder().substs,
+                        poly_trait_ref.skip_binder().args,
                         variance,
                     );
                 }
@@ -305,20 +305,20 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
 
     /// Adds constraints appropriate for a nominal type (enum, struct,
     /// object, etc) appearing in a context with ambient variance `variance`
-    fn add_constraints_from_substs(
+    fn add_constraints_from_args(
         &mut self,
         current: &CurrentItem,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         variance: VarianceTermPtr<'a>,
     ) {
         debug!(
-            "add_constraints_from_substs(def_id={:?}, substs={:?}, variance={:?})",
-            def_id, substs, variance
+            "add_constraints_from_args(def_id={:?}, args={:?}, variance={:?})",
+            def_id, args, variance
         );
 
         // We don't record `inferred_starts` entries for empty generics.
-        if substs.is_empty() {
+        if args.is_empty() {
             return;
         }
 
@@ -328,7 +328,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             (None, Some(self.tcx().variances_of(def_id)))
         };
 
-        for (i, k) in substs.iter().enumerate() {
+        for (i, k) in args.iter().enumerate() {
             let variance_decl = if let Some(InferredIndex(start)) = local {
                 // Parameter on an item defined within current crate:
                 // variance not yet inferred, so return a symbolic
@@ -341,7 +341,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
             };
             let variance_i = self.xform(variance, variance_decl);
             debug!(
-                "add_constraints_from_substs: variance_decl={:?} variance_i={:?}",
+                "add_constraints_from_args: variance_decl={:?} variance_i={:?}",
                 variance_decl, variance_i
             );
             match k.unpack() {
@@ -368,7 +368,7 @@ impl<'a, 'tcx> ConstraintContext<'a, 'tcx> {
 
         match &c.kind() {
             ty::ConstKind::Unevaluated(uv) => {
-                self.add_constraints_from_invariant_substs(current, uv.substs, variance);
+                self.add_constraints_from_invariant_args(current, uv.args, variance);
             }
             _ => {}
         }
diff --git a/compiler/rustc_hir_analysis/src/variance/mod.rs b/compiler/rustc_hir_analysis/src/variance/mod.rs
index c703cb03515a8..199cdabb7e98a 100644
--- a/compiler/rustc_hir_analysis/src/variance/mod.rs
+++ b/compiler/rustc_hir_analysis/src/variance/mod.rs
@@ -7,7 +7,7 @@ use rustc_arena::DroplessArena;
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, CrateVariancesMap, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, CrateVariancesMap, GenericArgsRef, Ty, TyCtxt};
 use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable};
 use std::ops::ControlFlow;
 
@@ -83,17 +83,17 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
 
     impl<'tcx> OpaqueTypeLifetimeCollector<'tcx> {
         #[instrument(level = "trace", skip(self), ret)]
-        fn visit_opaque(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> ControlFlow<!> {
+        fn visit_opaque(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> ControlFlow<!> {
             if def_id != self.root_def_id && self.tcx.is_descendant_of(def_id, self.root_def_id) {
                 let child_variances = self.tcx.variances_of(def_id);
-                for (a, v) in substs.iter().zip(child_variances) {
+                for (a, v) in args.iter().zip(child_variances) {
                     if *v != ty::Bivariant {
                         a.visit_with(self)?;
                     }
                 }
                 ControlFlow::Continue(())
             } else {
-                substs.visit_with(self)
+                args.visit_with(self)
             }
         }
     }
@@ -110,10 +110,10 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
         #[instrument(level = "trace", skip(self), ret)]
         fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
             match t.kind() {
-                ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+                ty::Alias(_, ty::AliasTy { def_id, args, .. })
                     if matches!(self.tcx.def_kind(*def_id), DefKind::OpaqueTy) =>
                 {
-                    self.visit_opaque(*def_id, substs)
+                    self.visit_opaque(*def_id, args)
                 }
                 _ => t.super_visit_with(self),
             }
@@ -144,30 +144,30 @@ fn variance_of_opaque(tcx: TyCtxt<'_>, item_def_id: LocalDefId) -> &[ty::Varianc
 
     let mut collector =
         OpaqueTypeLifetimeCollector { tcx, root_def_id: item_def_id.to_def_id(), variances };
-    let id_substs = ty::InternalSubsts::identity_for_item(tcx, item_def_id);
-    for (pred, _) in tcx.explicit_item_bounds(item_def_id).subst_iter_copied(tcx, id_substs) {
+    let id_args = ty::GenericArgs::identity_for_item(tcx, item_def_id);
+    for (pred, _) in tcx.explicit_item_bounds(item_def_id).arg_iter_copied(tcx, id_args) {
         debug!(?pred);
 
-        // We only ignore opaque type substs if the opaque type is the outermost type.
+        // We only ignore opaque type args if the opaque type is the outermost type.
         // The opaque type may be nested within itself via recursion in e.g.
         // type Foo<'a> = impl PartialEq<Foo<'a>>;
         // which thus mentions `'a` and should thus accept hidden types that borrow 'a
         // instead of requiring an additional `+ 'a`.
         match pred.kind().skip_binder() {
             ty::ClauseKind::Trait(ty::TraitPredicate {
-                trait_ref: ty::TraitRef { def_id: _, substs, .. },
+                trait_ref: ty::TraitRef { def_id: _, args, .. },
                 constness: _,
                 polarity: _,
             }) => {
-                for subst in &substs[1..] {
+                for subst in &args[1..] {
                     subst.visit_with(&mut collector);
                 }
             }
             ty::ClauseKind::Projection(ty::ProjectionPredicate {
-                projection_ty: ty::AliasTy { substs, .. },
+                projection_ty: ty::AliasTy { args, .. },
                 term,
             }) => {
-                for subst in &substs[1..] {
+                for subst in &args[1..] {
                     subst.visit_with(&mut collector);
                 }
                 term.visit_with(&mut collector);
diff --git a/compiler/rustc_hir_analysis/src/variance/solve.rs b/compiler/rustc_hir_analysis/src/variance/solve.rs
index c27c176e35f58..54da327702675 100644
--- a/compiler/rustc_hir_analysis/src/variance/solve.rs
+++ b/compiler/rustc_hir_analysis/src/variance/solve.rs
@@ -103,7 +103,7 @@ impl<'a, 'tcx> SolveContext<'a, 'tcx> {
                 self.enforce_const_invariance(generics, variances);
 
                 // Functions are permitted to have unused generic parameters: make those invariant.
-                if let ty::FnDef(..) = tcx.type_of(def_id).subst_identity().kind() {
+                if let ty::FnDef(..) = tcx.type_of(def_id).instantiate_identity().kind() {
                     for variance in variances.iter_mut() {
                         if *variance == ty::Bivariant {
                             *variance = ty::Invariant;
diff --git a/compiler/rustc_hir_typeck/src/_match.rs b/compiler/rustc_hir_typeck/src/_match.rs
index 6a27e78c5947b..f2a43cc414d3b 100644
--- a/compiler/rustc_hir_typeck/src/_match.rs
+++ b/compiler/rustc_hir_typeck/src/_match.rs
@@ -535,12 +535,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 let sig = self.body_fn_sig()?;
 
-                let substs = sig.output().walk().find_map(|arg| {
+                let args = sig.output().walk().find_map(|arg| {
                     if let ty::GenericArgKind::Type(ty) = arg.unpack()
-                        && let ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) = *ty.kind()
+                        && let ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) = *ty.kind()
                         && def_id == rpit_def_id
                     {
-                        Some(substs)
+                        Some(args)
                     } else {
                         None
                     }
@@ -551,26 +551,24 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
 
                 for ty in [first_ty, second_ty] {
-                    for (clause, _) in self
-                        .tcx
-                        .explicit_item_bounds(rpit_def_id)
-                        .subst_iter_copied(self.tcx, substs)
+                    for (clause, _) in
+                        self.tcx.explicit_item_bounds(rpit_def_id).arg_iter_copied(self.tcx, args)
                     {
                         let pred = clause.kind().rebind(match clause.kind().skip_binder() {
                             ty::ClauseKind::Trait(trait_pred) => {
                                 // FIXME(rpitit): This will need to be fixed when we move to associated types
                                 assert!(matches!(
                                     *trait_pred.trait_ref.self_ty().kind(),
-                                    ty::Alias(_, ty::AliasTy { def_id, substs: alias_substs, .. })
-                                    if def_id == rpit_def_id && substs == alias_substs
+                                    ty::Alias(_, ty::AliasTy { def_id, args: alias_args, .. })
+                                    if def_id == rpit_def_id && args == alias_args
                                 ));
                                 ty::ClauseKind::Trait(trait_pred.with_self_ty(self.tcx, ty))
                             }
                             ty::ClauseKind::Projection(mut proj_pred) => {
                                 assert!(matches!(
                                     *proj_pred.projection_ty.self_ty().kind(),
-                                    ty::Alias(_, ty::AliasTy { def_id, substs: alias_substs, .. })
-                                    if def_id == rpit_def_id && substs == alias_substs
+                                    ty::Alias(_, ty::AliasTy { def_id, args: alias_args, .. })
+                                    if def_id == rpit_def_id && args == alias_args
                                 ));
                                 proj_pred = proj_pred.with_self_ty(self.tcx, ty);
                                 ty::ClauseKind::Projection(proj_pred)
diff --git a/compiler/rustc_hir_typeck/src/callee.rs b/compiler/rustc_hir_typeck/src/callee.rs
index eb695d6b85931..a24d1ff077f38 100644
--- a/compiler/rustc_hir_typeck/src/callee.rs
+++ b/compiler/rustc_hir_typeck/src/callee.rs
@@ -21,7 +21,7 @@ use rustc_infer::{
 use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
 };
-use rustc_middle::ty::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::symbol::{sym, Ident};
@@ -149,14 +149,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 return Some(CallStep::Builtin(adjusted_ty));
             }
 
-            ty::Closure(def_id, substs) => {
+            ty::Closure(def_id, args) => {
                 let def_id = def_id.expect_local();
 
                 // Check whether this is a call to a closure where we
                 // haven't yet decided on whether the closure is fn vs
                 // fnmut vs fnonce. If so, we have to defer further processing.
-                if self.closure_kind(substs).is_none() {
-                    let closure_sig = substs.as_closure().sig();
+                if self.closure_kind(args).is_none() {
+                    let closure_sig = args.as_closure().sig();
                     let closure_sig = self.instantiate_binder_with_fresh_vars(
                         call_expr.span,
                         infer::FnCall,
@@ -171,7 +171,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             adjusted_ty,
                             adjustments,
                             fn_sig: closure_sig,
-                            closure_substs: substs,
+                            closure_args: args,
                         },
                     );
                     return Some(CallStep::DeferredClosure(def_id, closure_sig));
@@ -380,16 +380,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Expectation<'tcx>,
     ) -> Ty<'tcx> {
         let (fn_sig, def_id) = match *callee_ty.kind() {
-            ty::FnDef(def_id, substs) => {
-                self.enforce_context_effects(call_expr.hir_id, call_expr.span, def_id, substs);
-                let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, substs);
+            ty::FnDef(def_id, args) => {
+                self.enforce_context_effects(call_expr.hir_id, call_expr.span, def_id, args);
+                let fn_sig = self.tcx.fn_sig(def_id).instantiate(self.tcx, args);
 
                 // Unit testing: function items annotated with
                 // `#[rustc_evaluate_where_clauses]` trigger special output
                 // to let us test the trait evaluation system.
                 if self.tcx.has_attr(def_id, sym::rustc_evaluate_where_clauses) {
                     let predicates = self.tcx.predicates_of(def_id);
-                    let predicates = predicates.instantiate(self.tcx, substs);
+                    let predicates = predicates.instantiate(self.tcx, args);
                     for (predicate, predicate_span) in predicates {
                         let obligation = Obligation::new(
                             self.tcx,
@@ -751,7 +751,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         call_expr_hir: HirId,
         span: Span,
         callee_did: DefId,
-        callee_substs: SubstsRef<'tcx>,
+        callee_args: GenericArgsRef<'tcx>,
     ) {
         let tcx = self.tcx;
 
@@ -774,18 +774,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let effect = match const_context {
             Some(hir::ConstContext::Static(_) | hir::ConstContext::Const) => tcx.consts.false_,
             Some(hir::ConstContext::ConstFn) => {
-                let substs = ty::InternalSubsts::identity_for_item(tcx, context);
-                substs.host_effect_param().expect("ConstContext::Maybe must have host effect param")
+                let args = ty::GenericArgs::identity_for_item(tcx, context);
+                args.host_effect_param().expect("ConstContext::Maybe must have host effect param")
             }
             None => tcx.consts.true_,
         };
 
         let generics = tcx.generics_of(callee_did);
 
-        trace!(?effect, ?generics, ?callee_substs);
+        trace!(?effect, ?generics, ?callee_args);
 
         if let Some(idx) = generics.host_effect_index {
-            let param = callee_substs.const_at(idx);
+            let param = callee_args.const_at(idx);
             let cause = self.misc(span);
             match self.at(&cause, self.param_env).eq(infer::DefineOpaqueTypes::No, effect, param) {
                 Ok(infer::InferOk { obligations, value: () }) => {
@@ -827,7 +827,7 @@ pub struct DeferredCallResolution<'tcx> {
     adjusted_ty: Ty<'tcx>,
     adjustments: Vec<Adjustment<'tcx>>,
     fn_sig: ty::FnSig<'tcx>,
-    closure_substs: SubstsRef<'tcx>,
+    closure_args: GenericArgsRef<'tcx>,
 }
 
 impl<'a, 'tcx> DeferredCallResolution<'tcx> {
@@ -836,7 +836,7 @@ impl<'a, 'tcx> DeferredCallResolution<'tcx> {
 
         // we should not be invoked until the closure kind has been
         // determined by upvar inference
-        assert!(fcx.closure_kind(self.closure_substs).is_some());
+        assert!(fcx.closure_kind(self.closure_args).is_some());
 
         // We may now know enough to figure out fn vs fnmut etc.
         match fcx.try_overloaded_call_traits(self.call_expr, self.adjusted_ty, None) {
diff --git a/compiler/rustc_hir_typeck/src/cast.rs b/compiler/rustc_hir_typeck/src/cast.rs
index 633933317c0b5..7597ce88f9342 100644
--- a/compiler/rustc_hir_typeck/src/cast.rs
+++ b/compiler/rustc_hir_typeck/src/cast.rs
@@ -103,10 +103,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         Ok(match *t.kind() {
             ty::Slice(_) | ty::Str => Some(PointerKind::Length),
             ty::Dynamic(ref tty, _, ty::Dyn) => Some(PointerKind::VTable(tty.principal_def_id())),
-            ty::Adt(def, substs) if def.is_struct() => match def.non_enum_variant().tail_opt() {
+            ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
                 None => Some(PointerKind::Thin),
                 Some(f) => {
-                    let field_ty = self.field_ty(span, f, substs);
+                    let field_ty = self.field_ty(span, f, args);
                     self.pointer_kind(field_ty, span)?
                 }
             },
diff --git a/compiler/rustc_hir_typeck/src/check.rs b/compiler/rustc_hir_typeck/src/check.rs
index 8b57e311fc04d..53bae315d7862 100644
--- a/compiler/rustc_hir_typeck/src/check.rs
+++ b/compiler/rustc_hir_typeck/src/check.rs
@@ -80,7 +80,7 @@ pub(super) fn check_fn<'a, 'tcx>(
         let va_list_did = tcx.require_lang_item(LangItem::VaList, Some(span));
         let region = fcx.next_region_var(RegionVariableOrigin::MiscVariable(span));
 
-        tcx.type_of(va_list_did).subst(tcx, &[region.into()])
+        tcx.type_of(va_list_did).instantiate(tcx, &[region.into()])
     });
 
     // Add formal parameters.
diff --git a/compiler/rustc_hir_typeck/src/closure.rs b/compiler/rustc_hir_typeck/src/closure.rs
index 78a9ac49de2a2..e7df9ecf383ed 100644
--- a/compiler/rustc_hir_typeck/src/closure.rs
+++ b/compiler/rustc_hir_typeck/src/closure.rs
@@ -10,8 +10,8 @@ use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKi
 use rustc_infer::infer::{DefineOpaqueTypes, LateBoundRegionConversionTime};
 use rustc_infer::infer::{InferOk, InferResult};
 use rustc_macros::{TypeFoldable, TypeVisitable};
-use rustc_middle::ty::subst::InternalSubsts;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitor};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Span;
@@ -93,7 +93,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             false,
         );
 
-        let parent_substs = InternalSubsts::identity_for_item(
+        let parent_args = GenericArgs::identity_for_item(
             self.tcx,
             self.tcx.typeck_root_def_id(expr_def_id.to_def_id()),
         );
@@ -105,10 +105,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         if let Some(GeneratorTypes { resume_ty, yield_ty, interior, movability }) = generator_types
         {
-            let generator_substs = ty::GeneratorSubsts::new(
+            let generator_args = ty::GeneratorArgs::new(
                 self.tcx,
-                ty::GeneratorSubstsParts {
-                    parent_substs,
+                ty::GeneratorArgsParts {
+                    parent_args,
                     resume_ty,
                     yield_ty,
                     return_ty: liberated_sig.output(),
@@ -120,7 +120,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return Ty::new_generator(
                 self.tcx,
                 expr_def_id.to_def_id(),
-                generator_substs.substs,
+                generator_args.args,
                 movability,
             );
         }
@@ -151,17 +151,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }),
         };
 
-        let closure_substs = ty::ClosureSubsts::new(
+        let closure_args = ty::ClosureArgs::new(
             self.tcx,
-            ty::ClosureSubstsParts {
-                parent_substs,
+            ty::ClosureArgsParts {
+                parent_args,
                 closure_kind_ty,
                 closure_sig_as_fn_ptr_ty: Ty::new_fn_ptr(self.tcx, sig),
                 tupled_upvars_ty,
             },
         );
 
-        Ty::new_closure(self.tcx, expr_def_id.to_def_id(), closure_substs.substs)
+        Ty::new_closure(self.tcx, expr_def_id.to_def_id(), closure_args.args)
     }
 
     /// Given the expected type, figures out what it can about this closure we
@@ -172,12 +172,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected_ty: Ty<'tcx>,
     ) -> (Option<ExpectedSig<'tcx>>, Option<ty::ClosureKind>) {
         match *expected_ty.kind() {
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => self
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => self
                 .deduce_closure_signature_from_predicates(
                     expected_ty,
                     self.tcx
                         .explicit_item_bounds(def_id)
-                        .subst_iter_copied(self.tcx, substs)
+                        .arg_iter_copied(self.tcx, args)
                         .map(|(c, s)| (c.as_predicate(), s)),
                 ),
             ty::Dynamic(ref object_type, ..) => {
@@ -315,7 +315,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let input_tys = if is_fn {
-            let arg_param_ty = projection.skip_binder().projection_ty.substs.type_at(1);
+            let arg_param_ty = projection.skip_binder().projection_ty.args.type_at(1);
             let arg_param_ty = self.resolve_vars_if_possible(arg_param_ty);
             debug!(?arg_param_ty);
 
@@ -717,16 +717,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     get_future_output(obligation.predicate, obligation.cause.span)
                 })?
             }
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => self
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => self
                 .tcx
                 .explicit_item_bounds(def_id)
-                .subst_iter_copied(self.tcx, substs)
+                .arg_iter_copied(self.tcx, args)
                 .find_map(|(p, s)| get_future_output(p.as_predicate(), s))?,
             ty::Error(_) => return None,
             ty::Alias(ty::Projection, proj) if self.tcx.is_impl_trait_in_trait(proj.def_id) => self
                 .tcx
                 .explicit_item_bounds(proj.def_id)
-                .subst_iter_copied(self.tcx, proj.substs)
+                .arg_iter_copied(self.tcx, proj.args)
                 .find_map(|(p, s)| get_future_output(p.as_predicate(), s))?,
             _ => span_bug!(
                 self.tcx.def_span(expr_def_id),
diff --git a/compiler/rustc_hir_typeck/src/coercion.rs b/compiler/rustc_hir_typeck/src/coercion.rs
index 9ef01e37ac1c1..3b1d9c8905b40 100644
--- a/compiler/rustc_hir_typeck/src/coercion.rs
+++ b/compiler/rustc_hir_typeck/src/coercion.rs
@@ -51,8 +51,8 @@ use rustc_middle::ty::adjustment::{
 };
 use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::relate::RelateResult;
-use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::visit::TypeVisitableExt;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TypeAndMut};
 use rustc_session::parse::feature_err;
 use rustc_span::symbol::sym;
@@ -251,11 +251,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                 // unsafe qualifier.
                 self.coerce_from_fn_pointer(a, a_f, b)
             }
-            ty::Closure(closure_def_id_a, substs_a) => {
+            ty::Closure(closure_def_id_a, args_a) => {
                 // Non-capturing closures are coercible to
                 // function pointers or unsafe function pointers.
                 // It cannot convert closures that require unsafe.
-                self.coerce_closure_to_fn(a, closure_def_id_a, substs_a, b)
+                self.coerce_closure_to_fn(a, closure_def_id_a, args_a, b)
             }
             _ => {
                 // Otherwise, just use unification rules.
@@ -639,7 +639,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                     let trait_pred = self.resolve_vars_if_possible(trait_pred);
                     if unsize_did == trait_pred.def_id() {
                         let self_ty = trait_pred.self_ty();
-                        let unsize_ty = trait_pred.trait_ref.substs[1].expect_ty();
+                        let unsize_ty = trait_pred.trait_ref.args[1].expect_ty();
                         if let (ty::Dynamic(ref data_a, ..), ty::Dynamic(ref data_b, ..)) =
                             (self_ty.kind(), unsize_ty.kind())
                             && data_a.principal_def_id() != data_b.principal_def_id()
@@ -664,7 +664,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                 Ok(None) => {
                     if trait_pred.def_id() == unsize_did {
                         let self_ty = trait_pred.self_ty();
-                        let unsize_ty = trait_pred.trait_ref.substs[1].expect_ty();
+                        let unsize_ty = trait_pred.trait_ref.args[1].expect_ty();
                         debug!("coerce_unsized: ambiguous unsize case for {:?}", trait_pred);
                         match (self_ty.kind(), unsize_ty.kind()) {
                             (&ty::Infer(ty::TyVar(v)), ty::Dynamic(..))
@@ -916,7 +916,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
         &self,
         a: Ty<'tcx>,
         closure_def_id_a: DefId,
-        substs_a: SubstsRef<'tcx>,
+        args_a: GenericArgsRef<'tcx>,
         b: Ty<'tcx>,
     ) -> CoerceResult<'tcx> {
         //! Attempts to coerce from the type of a non-capturing closure
@@ -927,7 +927,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
 
         match b.kind() {
             // At this point we haven't done capture analysis, which means
-            // that the ClosureSubsts just contains an inference variable instead
+            // that the ClosureArgs just contains an inference variable instead
             // of tuple of captured types.
             //
             // All we care here is if any variable is being captured and not the exact paths,
@@ -944,7 +944,7 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
                 //     `fn(arg0,arg1,...) -> _`
                 // or
                 //     `unsafe fn(arg0,arg1,...) -> _`
-                let closure_sig = substs_a.as_closure().sig();
+                let closure_sig = args_a.as_closure().sig();
                 let unsafety = fn_ty.unsafety();
                 let pointer_ty =
                     Ty::new_fn_ptr(self.tcx, self.tcx.signature_unclosure(closure_sig, unsafety));
@@ -1109,10 +1109,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         // Special-case that coercion alone cannot handle:
-        // Function items or non-capturing closures of differing IDs or InternalSubsts.
+        // Function items or non-capturing closures of differing IDs or GenericArgs.
         let (a_sig, b_sig) = {
             let is_capturing_closure = |ty: Ty<'tcx>| {
-                if let &ty::Closure(closure_def_id, _substs) = ty.kind() {
+                if let &ty::Closure(closure_def_id, _args) = ty.kind() {
                     self.tcx.upvars_mentioned(closure_def_id.expect_local()).is_some()
                 } else {
                     false
@@ -1139,30 +1139,30 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             }
                         }
                     }
-                    (ty::Closure(_, substs), ty::FnDef(..)) => {
+                    (ty::Closure(_, args), ty::FnDef(..)) => {
                         let b_sig = new_ty.fn_sig(self.tcx);
-                        let a_sig = self
-                            .tcx
-                            .signature_unclosure(substs.as_closure().sig(), b_sig.unsafety());
+                        let a_sig =
+                            self.tcx.signature_unclosure(args.as_closure().sig(), b_sig.unsafety());
                         (Some(a_sig), Some(b_sig))
                     }
-                    (ty::FnDef(..), ty::Closure(_, substs)) => {
+                    (ty::FnDef(..), ty::Closure(_, args)) => {
                         let a_sig = prev_ty.fn_sig(self.tcx);
-                        let b_sig = self
-                            .tcx
-                            .signature_unclosure(substs.as_closure().sig(), a_sig.unsafety());
+                        let b_sig =
+                            self.tcx.signature_unclosure(args.as_closure().sig(), a_sig.unsafety());
                         (Some(a_sig), Some(b_sig))
                     }
-                    (ty::Closure(_, substs_a), ty::Closure(_, substs_b)) => (
-                        Some(self.tcx.signature_unclosure(
-                            substs_a.as_closure().sig(),
-                            hir::Unsafety::Normal,
-                        )),
-                        Some(self.tcx.signature_unclosure(
-                            substs_b.as_closure().sig(),
-                            hir::Unsafety::Normal,
-                        )),
-                    ),
+                    (ty::Closure(_, args_a), ty::Closure(_, args_b)) => {
+                        (
+                            Some(self.tcx.signature_unclosure(
+                                args_a.as_closure().sig(),
+                                hir::Unsafety::Normal,
+                            )),
+                            Some(self.tcx.signature_unclosure(
+                                args_b.as_closure().sig(),
+                                hir::Unsafety::Normal,
+                            )),
+                        )
+                    }
                     _ => (None, None),
                 }
             }
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index 80db01e08dbc7..8fecb82259fef 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -712,7 +712,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .filter(|c| c.item.def_id != pick.item.def_id)
             .map(|c| {
                 let m = c.item;
-                let substs = ty::InternalSubsts::for_item(self.tcx, m.def_id, |param, _| {
+                let generic_args = ty::GenericArgs::for_item(self.tcx, m.def_id, |param, _| {
                     self.var_for_def(deref.span, param)
                 });
                 let mutability =
@@ -727,7 +727,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         format!(
                             "{}({}",
                             with_no_trimmed_paths!(
-                                self.tcx.def_path_str_with_substs(m.def_id, substs,)
+                                self.tcx.def_path_str_with_args(m.def_id, generic_args,)
                             ),
                             mutability,
                         ),
@@ -824,10 +824,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         found: Ty<'tcx>,
     ) -> bool {
-        let ty::Adt(e, substs_e) = expected.kind() else {
+        let ty::Adt(e, args_e) = expected.kind() else {
             return false;
         };
-        let ty::Adt(f, substs_f) = found.kind() else {
+        let ty::Adt(f, args_f) = found.kind() else {
             return false;
         };
         if e.did() != f.did() {
@@ -846,8 +846,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             return false;
         }
-        let e = substs_e.type_at(1);
-        let f = substs_f.type_at(1);
+        let e = args_e.type_at(1);
+        let f = args_f.type_at(1);
         if self
             .infcx
             .type_implements_trait(
@@ -880,7 +880,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Ty<'tcx>,
         expr_ty: Ty<'tcx>,
     ) -> bool {
-        if let ty::Adt(expected_adt, substs) = expected.kind() {
+        if let ty::Adt(expected_adt, args) = expected.kind() {
             if let hir::ExprKind::Field(base, ident) = expr.kind {
                 let base_ty = self.typeck_results.borrow().expr_ty(base);
                 if self.can_eq(self.param_env, base_ty, expected)
@@ -979,7 +979,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     let note_about_variant_field_privacy = (field_is_local && !field_is_accessible)
                         .then(|| " (its field is private, but it's local to this crate and its privacy can be changed)".to_string());
 
-                    let sole_field_ty = sole_field.ty(self.tcx, substs);
+                    let sole_field_ty = sole_field.ty(self.tcx, args);
                     if self.can_coerce(expr_ty, sole_field_ty) {
                         let variant_path =
                             with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
@@ -1072,9 +1072,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let tcx = self.tcx;
         let (adt, unwrap) = match expected.kind() {
             // In case Option<NonZero*> is wanted, but * is provided, suggest calling new
-            ty::Adt(adt, substs) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
+            ty::Adt(adt, args) if tcx.is_diagnostic_item(sym::Option, adt.did()) => {
                 // Unwrap option
-                let ty::Adt(adt, _) = substs.type_at(0).kind() else {
+                let ty::Adt(adt, _) = args.type_at(0).kind() else {
                     return false;
                 };
 
diff --git a/compiler/rustc_hir_typeck/src/expr.rs b/compiler/rustc_hir_typeck/src/expr.rs
index 6e3c117dd9e05..29488c9011a19 100644
--- a/compiler/rustc_hir_typeck/src/expr.rs
+++ b/compiler/rustc_hir_typeck/src/expr.rs
@@ -44,7 +44,7 @@ use rustc_infer::traits::ObligationCause;
 use rustc_middle::middle::stability;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AllowTwoPhase};
 use rustc_middle::ty::error::TypeError::FieldMisMatch;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, AdtKind, Ty, TypeVisitableExt};
 use rustc_session::errors::ExprParenthesesNeeded;
 use rustc_session::parse::feature_err;
@@ -593,8 +593,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // We always require that the type provided as the value for
         // a type parameter outlives the moment of instantiation.
-        let substs = self.typeck_results.borrow().node_substs(expr.hir_id);
-        self.add_wf_bounds(substs, expr);
+        let args = self.typeck_results.borrow().node_args(expr.hir_id);
+        self.add_wf_bounds(args, expr);
 
         ty
     }
@@ -1281,7 +1281,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // We could add a "consider `foo::<params>`" suggestion here, but I wasn't able to
                 // trigger this codepath causing `structurally_resolve_type` to emit an error.
 
-                self.enforce_context_effects(expr.hir_id, expr.span, method.def_id, method.substs);
+                self.enforce_context_effects(expr.hir_id, expr.span, method.def_id, method.args);
                 self.write_method_call(expr.hir_id, method);
                 Ok(method)
             }
@@ -1620,7 +1620,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // re-link the regions that EIfEO can erase.
         self.demand_eqtype(span, adt_ty_hint, adt_ty);
 
-        let ty::Adt(adt, substs) = adt_ty.kind() else {
+        let ty::Adt(adt, args) = adt_ty.kind() else {
             span_bug!(span, "non-ADT passed to check_expr_struct_fields");
         };
         let adt_kind = adt.adt_kind();
@@ -1649,7 +1649,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     tcx.check_stability(v_field.did, Some(expr_id), field.span, None);
                 }
 
-                self.field_ty(field.span, v_field, substs)
+                self.field_ty(field.span, v_field, args)
             } else {
                 error_happened = true;
                 let guar = if let Some(prev_span) = seen_fields.get(&ident) {
@@ -1681,7 +1681,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             if let Some(mut diag) = diag {
                 if idx == ast_fields.len() - 1 {
                     if remaining_fields.is_empty() {
-                        self.suggest_fru_from_range(field, variant, substs, &mut diag);
+                        self.suggest_fru_from_range(field, variant, args, &mut diag);
                         diag.emit();
                     } else {
                         diag.stash(field.span, StashKey::MaybeFruTypo);
@@ -1721,7 +1721,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let fru_tys = if self.tcx.features().type_changing_struct_update {
                 if adt.is_struct() {
                     // Make some fresh substitutions for our ADT type.
-                    let fresh_substs = self.fresh_substs_for_item(base_expr.span, adt.did());
+                    let fresh_args = self.fresh_args_for_item(base_expr.span, adt.did());
                     // We do subtyping on the FRU fields first, so we can
                     // learn exactly what types we expect the base expr
                     // needs constrained to be compatible with the struct
@@ -1730,13 +1730,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .fields
                         .iter()
                         .map(|f| {
-                            let fru_ty = self.normalize(
-                                expr_span,
-                                self.field_ty(base_expr.span, f, fresh_substs),
-                            );
+                            let fru_ty = self
+                                .normalize(expr_span, self.field_ty(base_expr.span, f, fresh_args));
                             let ident = self.tcx.adjust_ident(f.ident(self.tcx), variant.def_id);
                             if let Some(_) = remaining_fields.remove(&ident) {
-                                let target_ty = self.field_ty(base_expr.span, f, substs);
+                                let target_ty = self.field_ty(base_expr.span, f, args);
                                 let cause = self.misc(base_expr.span);
                                 match self.at(&cause, self.param_env).sup(
                                     DefineOpaqueTypes::No,
@@ -1763,7 +1761,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             self.resolve_vars_if_possible(fru_ty)
                         })
                         .collect();
-                    // The use of fresh substs that we have subtyped against
+                    // The use of fresh args that we have subtyped against
                     // our base ADT type's fields allows us to guide inference
                     // along so that, e.g.
                     // ```
@@ -1781,7 +1779,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // `MyStruct<'a, _, F2, C>`, as opposed to just `_`...
                     // This is important to allow coercions to happen in
                     // `other_struct` itself. See `coerce-in-base-expr.rs`.
-                    let fresh_base_ty = Ty::new_adt(self.tcx, *adt, fresh_substs);
+                    let fresh_base_ty = Ty::new_adt(self.tcx, *adt, fresh_args);
                     self.check_expr_has_type_or_error(
                         base_expr,
                         self.resolve_vars_if_possible(fresh_base_ty),
@@ -1813,10 +1811,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 });
                 match adt_ty.kind() {
-                    ty::Adt(adt, substs) if adt.is_struct() => variant
+                    ty::Adt(adt, args) if adt.is_struct() => variant
                         .fields
                         .iter()
-                        .map(|f| self.normalize(expr_span, f.ty(self.tcx, substs)))
+                        .map(|f| self.normalize(expr_span, f.ty(self.tcx, args)))
                         .collect(),
                     _ => {
                         self.tcx
@@ -1844,7 +1842,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     remaining_fields,
                     variant,
                     ast_fields,
-                    substs,
+                    args,
                 );
             }
         }
@@ -1881,7 +1879,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         remaining_fields: FxHashMap<Ident, (FieldIdx, &ty::FieldDef)>,
         variant: &'tcx ty::VariantDef,
         ast_fields: &'tcx [hir::ExprField<'tcx>],
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) {
         let len = remaining_fields.len();
 
@@ -1920,7 +1918,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         err.span_label(span, format!("missing {remaining_fields_names}{truncated_fields_error}"));
 
         if let Some(last) = ast_fields.last() {
-            self.suggest_fru_from_range(last, variant, substs, &mut err);
+            self.suggest_fru_from_range(last, variant, args, &mut err);
         }
 
         err.emit();
@@ -1932,7 +1930,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         last_expr_field: &hir::ExprField<'tcx>,
         variant: &ty::VariantDef,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         err: &mut Diagnostic,
     ) {
         // I don't use 'is_range_literal' because only double-sided, half-open ranges count.
@@ -1945,7 +1943,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 variant.fields.iter().find(|field| field.ident(self.tcx) == last_expr_field.ident)
             && let range_def_id = self.tcx.lang_items().range_struct()
             && variant_field
-                .and_then(|field| field.ty(self.tcx, substs).ty_adt_def())
+                .and_then(|field| field.ty(self.tcx, args).ty_adt_def())
                 .map(|adt| adt.did())
                 != range_def_id
         {
@@ -2268,7 +2266,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         while let Some((deref_base_ty, _)) = autoderef.next() {
             debug!("deref_base_ty: {:?}", deref_base_ty);
             match deref_base_ty.kind() {
-                ty::Adt(base_def, substs) if !base_def.is_enum() => {
+                ty::Adt(base_def, args) if !base_def.is_enum() => {
                     debug!("struct named {:?}", deref_base_ty);
                     let body_hir_id = self.tcx.hir().local_def_id_to_hir_id(self.body_id);
                     let (ident, def_scope) =
@@ -2278,7 +2276,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .iter_enumerated()
                         .find(|(_, f)| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
                     {
-                        let field_ty = self.field_ty(expr.span, field, substs);
+                        let field_ty = self.field_ty(expr.span, field, args);
                         // Save the index of all fields regardless of their visibility in case
                         // of error recovery.
                         self.write_field_index(expr.hir_id, index);
@@ -2716,7 +2714,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // try to add a suggestion in case the field is a nested field of a field of the Adt
         let mod_id = self.tcx.parent_module(id).to_def_id();
-        if let Some((fields, substs)) =
+        if let Some((fields, args)) =
             self.get_field_candidates_considering_privacy(span, expr_t, mod_id)
         {
             let candidate_fields: Vec<_> = fields
@@ -2725,7 +2723,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         span,
                         &|candidate_field, _| candidate_field.ident(self.tcx()) == field,
                         candidate_field,
-                        substs,
+                        args,
                         vec![],
                         mod_id,
                     )
@@ -2780,12 +2778,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         base_ty: Ty<'tcx>,
         mod_id: DefId,
-    ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, SubstsRef<'tcx>)> {
+    ) -> Option<(impl Iterator<Item = &'tcx ty::FieldDef> + 'tcx, GenericArgsRef<'tcx>)> {
         debug!("get_field_candidates(span: {:?}, base_t: {:?}", span, base_ty);
 
         for (base_t, _) in self.autoderef(span, base_ty) {
             match base_t.kind() {
-                ty::Adt(base_def, substs) if !base_def.is_enum() => {
+                ty::Adt(base_def, args) if !base_def.is_enum() => {
                     let tcx = self.tcx;
                     let fields = &base_def.non_enum_variant().fields;
                     // Some struct, e.g. some that impl `Deref`, have all private fields
@@ -2800,7 +2798,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             .filter(move |field| field.vis.is_accessible_from(mod_id, tcx))
                             // For compile-time reasons put a limit on number of fields we search
                             .take(100),
-                        substs,
+                        args,
                     ));
                 }
                 _ => {}
@@ -2816,7 +2814,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         span: Span,
         matches: &impl Fn(&ty::FieldDef, Ty<'tcx>) -> bool,
         candidate_field: &ty::FieldDef,
-        subst: SubstsRef<'tcx>,
+        subst: GenericArgsRef<'tcx>,
         mut field_path: Vec<Ident>,
         mod_id: DefId,
     ) -> Option<Vec<Ident>> {
@@ -2975,9 +2973,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         self.commit_if_ok(|_| {
             let ocx = ObligationCtxt::new(self);
-            let impl_substs = self.fresh_substs_for_item(base_expr.span, impl_def_id);
+            let impl_args = self.fresh_args_for_item(base_expr.span, impl_def_id);
             let impl_trait_ref =
-                self.tcx.impl_trait_ref(impl_def_id).unwrap().subst(self.tcx, impl_substs);
+                self.tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(self.tcx, impl_args);
             let cause = self.misc(base_expr.span);
 
             // Match the impl self type against the base ty. If this fails,
@@ -3009,7 +3007,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     )
                 },
                 self.param_env,
-                self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_substs),
+                self.tcx.predicates_of(impl_def_id).instantiate(self.tcx, impl_args),
             ));
 
             // Normalize the output type, which we can use later on as the
@@ -3017,7 +3015,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let element_ty = ocx.normalize(
                 &cause,
                 self.param_env,
-                Ty::new_projection(self.tcx, index_trait_output_def_id, impl_trait_ref.substs),
+                Ty::new_projection(self.tcx, index_trait_output_def_id, impl_trait_ref.args),
             );
 
             let errors = ocx.select_where_possible();
@@ -3025,7 +3023,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // will still delay a span bug in `report_fulfillment_errors`.
             Ok::<_, NoSolution>((
                 self.err_ctxt().report_fulfillment_errors(&errors),
-                impl_trait_ref.substs.type_at(1),
+                impl_trait_ref.args.type_at(1),
                 element_ty,
             ))
         })
@@ -3157,7 +3155,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let container = self.structurally_resolve_type(expr.span, current_container);
 
             match container.kind() {
-                ty::Adt(container_def, substs) if !container_def.is_enum() => {
+                ty::Adt(container_def, args) if !container_def.is_enum() => {
                     let block = self.tcx.hir().local_def_id_to_hir_id(self.body_id);
                     let (ident, def_scope) =
                         self.tcx.adjust_ident_and_get_scope(field, container_def.did(), block);
@@ -3167,7 +3165,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .iter_enumerated()
                         .find(|(_, f)| f.ident(self.tcx).normalize_to_macros_2_0() == ident)
                     {
-                        let field_ty = self.field_ty(expr.span, field, substs);
+                        let field_ty = self.field_ty(expr.span, field, args);
 
                         // FIXME: DSTs with static alignment should be allowed
                         self.require_type_is_sized(field_ty, expr.span, traits::MiscObligation);
diff --git a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
index 0d2e0602e1cdd..a59061cbf6752 100644
--- a/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
+++ b/compiler/rustc_hir_typeck/src/expr_use_visitor.rs
@@ -549,7 +549,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
         // Select just those fields of the `with`
         // expression that will actually be used
         match with_place.place.ty().kind() {
-            ty::Adt(adt, substs) if adt.is_struct() => {
+            ty::Adt(adt, args) if adt.is_struct() => {
                 // Consume those fields of the with expression that are needed.
                 for (f_index, with_field) in adt.non_enum_variant().fields.iter_enumerated() {
                     let is_mentioned = fields
@@ -559,7 +559,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                         let field_place = self.mc.cat_projection(
                             &*with_expr,
                             with_place.clone(),
-                            with_field.ty(self.tcx(), substs),
+                            with_field.ty(self.tcx(), args),
                             ProjectionKind::Field(f_index, FIRST_VARIANT),
                         );
                         self.delegate_consume(&field_place, field_place.hir_id);
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
index 9a80a9c9303e3..bd7e7a671e6b9 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs
@@ -12,7 +12,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_hir::{ExprKind, GenericArg, Node, QPath};
 use rustc_hir_analysis::astconv::generics::{
-    check_generic_arg_count_for_call, create_substs_for_generic_args,
+    check_generic_arg_count_for_call, create_args_for_parent_generic_args,
 };
 use rustc_hir_analysis::astconv::{
     AstConv, CreateSubstsForGenericArgsCtxt, ExplicitLateBound, GenericArgCountMismatch,
@@ -28,7 +28,7 @@ use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{
     self, AdtKind, CanonicalUserType, GenericParamDefKind, Ty, TyCtxt, UserType,
 };
-use rustc_middle::ty::{GenericArgKind, SubstsRef, UserSelfTy, UserSubsts};
+use rustc_middle::ty::{GenericArgKind, GenericArgsRef, UserArgs, UserSelfTy};
 use rustc_session::lint;
 use rustc_span::def_id::LocalDefId;
 use rustc_span::hygiene::DesugaringKind;
@@ -169,18 +169,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     #[instrument(level = "debug", skip(self))]
     pub fn write_method_call(&self, hir_id: hir::HirId, method: MethodCallee<'tcx>) {
         self.write_resolution(hir_id, Ok((DefKind::AssocFn, method.def_id)));
-        self.write_substs(hir_id, method.substs);
+        self.write_args(hir_id, method.args);
     }
 
-    pub fn write_substs(&self, node_id: hir::HirId, substs: SubstsRef<'tcx>) {
-        if !substs.is_empty() {
-            debug!("write_substs({:?}, {:?}) in fcx {}", node_id, substs, self.tag());
+    pub fn write_args(&self, node_id: hir::HirId, args: GenericArgsRef<'tcx>) {
+        if !args.is_empty() {
+            debug!("write_args({:?}, {:?}) in fcx {}", node_id, args, self.tag());
 
-            self.typeck_results.borrow_mut().node_substs_mut().insert(node_id, substs);
+            self.typeck_results.borrow_mut().node_args_mut().insert(node_id, args);
         }
     }
 
-    /// Given the substs that we just converted from the HIR, try to
+    /// Given the args that we just converted from the HIR, try to
     /// canonicalize them and store them as user-given substitutions
     /// (i.e., substitutions that must be respected by the NLL check).
     ///
@@ -188,19 +188,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// occurred**, so that annotations like `Vec<_>` are preserved
     /// properly.
     #[instrument(skip(self), level = "debug")]
-    pub fn write_user_type_annotation_from_substs(
+    pub fn write_user_type_annotation_from_args(
         &self,
         hir_id: hir::HirId,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         user_self_ty: Option<UserSelfTy<'tcx>>,
     ) {
         debug!("fcx {}", self.tag());
 
-        if Self::can_contain_user_lifetime_bounds((substs, user_self_ty)) {
+        if Self::can_contain_user_lifetime_bounds((args, user_self_ty)) {
             let canonicalized = self.canonicalize_user_type_annotation(UserType::TypeOf(
                 def_id,
-                UserSubsts { substs, user_self_ty },
+                UserArgs { args, user_self_ty },
             ));
             debug!(?canonicalized);
             self.write_user_type_annotation(hir_id, canonicalized);
@@ -221,7 +221,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .user_provided_types_mut()
                 .insert(hir_id, canonical_user_type_annotation);
         } else {
-            debug!("skipping identity substs");
+            debug!("skipping identity args");
         }
     }
 
@@ -306,12 +306,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         span: Span,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> ty::InstantiatedPredicates<'tcx> {
         let bounds = self.tcx.predicates_of(def_id);
-        let result = bounds.instantiate(self.tcx, substs);
+        let result = bounds.instantiate(self.tcx, args);
         let result = self.normalize(span, result);
-        debug!("instantiate_bounds(bounds={:?}, substs={:?}) = {:?}", bounds, substs, result);
+        debug!("instantiate_bounds(bounds={:?}, args={:?}) = {:?}", bounds, args, result);
         result
     }
 
@@ -397,11 +397,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ty.normalized
     }
 
-    pub(super) fn user_substs_for_adt(ty: RawTy<'tcx>) -> UserSubsts<'tcx> {
+    pub(super) fn user_args_for_adt(ty: RawTy<'tcx>) -> UserArgs<'tcx> {
         match (ty.raw.kind(), ty.normalized.kind()) {
-            (ty::Adt(_, substs), _) => UserSubsts { substs, user_self_ty: None },
-            (_, ty::Adt(adt, substs)) => UserSubsts {
-                substs,
+            (ty::Adt(_, args), _) => UserArgs { args, user_self_ty: None },
+            (_, ty::Adt(adt, args)) => UserArgs {
+                args,
                 user_self_ty: Some(UserSelfTy { impl_def_id: adt.did(), self_ty: ty.raw }),
             },
             _ => bug!("non-adt type {:?}", ty),
@@ -489,9 +489,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ));
     }
 
-    /// Registers obligations that all `substs` are well-formed.
-    pub fn add_wf_bounds(&self, substs: SubstsRef<'tcx>, expr: &hir::Expr<'_>) {
-        for arg in substs.iter().filter(|arg| {
+    /// Registers obligations that all `args` are well-formed.
+    pub fn add_wf_bounds(&self, args: GenericArgsRef<'tcx>, expr: &hir::Expr<'_>) {
+        for arg in args.iter().filter(|arg| {
             matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
         }) {
             self.register_wf_obligation(arg, expr.span, traits::WellFormed(None));
@@ -505,9 +505,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         span: Span,
         field: &'tcx ty::FieldDef,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        self.normalize(span, field.ty(self.tcx, substs))
+        self.normalize(span, field.ty(self.tcx, args))
     }
 
     pub(in super::super) fn resolve_rvalue_scopes(&self, def_id: DefId) {
@@ -554,11 +554,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             debug!(?expr_def_id);
 
             // Create the `GeneratorWitness` type that we will unify with `interior`.
-            let substs = ty::InternalSubsts::identity_for_item(
+            let args = ty::GenericArgs::identity_for_item(
                 self.tcx,
                 self.tcx.typeck_root_def_id(expr_def_id.to_def_id()),
             );
-            let witness = Ty::new_generator_witness_mir(self.tcx, expr_def_id.to_def_id(), substs);
+            let witness = Ty::new_generator_witness_mir(self.tcx, expr_def_id.to_def_id(), args);
 
             // Unify `interior` with `witness` and collect all the resulting obligations.
             let span = self.tcx.hir().body(body_id).value.span;
@@ -737,7 +737,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // tests/ui/impl-trait/hidden-type-is-opaque-2.rs for examples that hit this path.
         if formal_ret.has_infer_types() {
             for ty in ret_ty.walk() {
-                if let ty::subst::GenericArgKind::Type(ty) = ty.unpack()
+                if let ty::GenericArgKind::Type(ty) = ty.unpack()
                     && let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *ty.kind()
                     && let Some(def_id) = def_id.as_local()
                     && self.opaque_type_origin(def_id).is_some() {
@@ -784,8 +784,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         } else {
             self.tcx.type_of(def_id)
         };
-        let substs = self.fresh_substs_for_item(span, def_id);
-        let ty = item_ty.subst(self.tcx, substs);
+        let args = self.fresh_args_for_item(span, def_id);
+        let ty = item_ty.instantiate(self.tcx, args);
 
         self.write_resolution(hir_id, Ok((def_kind, def_id)));
 
@@ -802,9 +802,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ => None,
         };
         if let Some(code) = code {
-            self.add_required_obligations_with_code(span, def_id, substs, move |_, _| code.clone());
+            self.add_required_obligations_with_code(span, def_id, args, move |_, _| code.clone());
         } else {
-            self.add_required_obligations_for_hir(span, def_id, substs, hir_id);
+            self.add_required_obligations_for_hir(span, def_id, args, hir_id);
         }
 
         (Res::Def(def_kind, def_id), ty)
@@ -1205,8 +1205,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let has_self =
             path_segs.last().is_some_and(|PathSeg(def_id, _)| tcx.generics_of(*def_id).has_self);
 
-        let (res, self_ctor_substs) = if let Res::SelfCtor(impl_def_id) = res {
-            let ty = self.handle_raw_ty(span, tcx.at(span).type_of(impl_def_id).subst_identity());
+        let (res, self_ctor_args) = if let Res::SelfCtor(impl_def_id) = res {
+            let ty =
+                self.handle_raw_ty(span, tcx.at(span).type_of(impl_def_id).instantiate_identity());
             match ty.normalized.ty_adt_def() {
                 Some(adt_def) if adt_def.has_ctor() => {
                     let (ctor_kind, ctor_def_id) = adt_def.non_enum_variant().ctor.unwrap();
@@ -1217,9 +1218,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             .emit_err(CtorIsPrivate { span, def: tcx.def_path_str(adt_def.did()) });
                     }
                     let new_res = Res::Def(DefKind::Ctor(CtorOf::Struct, ctor_kind), ctor_def_id);
-                    let user_substs = Self::user_substs_for_adt(ty);
-                    user_self_ty = user_substs.user_self_ty;
-                    (new_res, Some(user_substs.substs))
+                    let user_args = Self::user_args_for_adt(ty);
+                    user_self_ty = user_args.user_self_ty;
+                    (new_res, Some(user_args.args))
                 }
                 _ => {
                     let mut err = tcx.sess.struct_span_err(
@@ -1324,7 +1325,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             fn inferred_kind(
                 &mut self,
-                substs: Option<&[ty::GenericArg<'tcx>]>,
+                args: Option<&[ty::GenericArg<'tcx>]>,
                 param: &ty::GenericParamDef,
                 infer_args: bool,
             ) -> ty::GenericArg<'tcx> {
@@ -1338,7 +1339,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             // If we have a default, then we it doesn't matter that we're not
                             // inferring the type arguments: we provide the default where any
                             // is missing.
-                            tcx.type_of(param.def_id).subst(tcx, substs.unwrap()).into()
+                            tcx.type_of(param.def_id).instantiate(tcx, args.unwrap()).into()
                         } else {
                             // If no type arguments were provided, we have to infer them.
                             // This case also occurs as a result of some malformed input, e.g.
@@ -1349,7 +1350,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                     GenericParamDefKind::Const { has_default } => {
                         if !infer_args && has_default {
-                            tcx.const_param_default(param.def_id).subst(tcx, substs.unwrap()).into()
+                            tcx.const_param_default(param.def_id)
+                                .instantiate(tcx, args.unwrap())
+                                .into()
                         } else {
                             self.fcx.var_for_def(self.span, param)
                         }
@@ -1358,8 +1361,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         }
 
-        let substs_raw = self_ctor_substs.unwrap_or_else(|| {
-            create_substs_for_generic_args(
+        let args_raw = self_ctor_args.unwrap_or_else(|| {
+            create_args_for_parent_generic_args(
                 tcx,
                 def_id,
                 &[],
@@ -1376,20 +1379,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             )
         });
 
-        // First, store the "user substs" for later.
-        self.write_user_type_annotation_from_substs(hir_id, def_id, substs_raw, user_self_ty);
+        // First, store the "user args" for later.
+        self.write_user_type_annotation_from_args(hir_id, def_id, args_raw, user_self_ty);
 
         // Normalize only after registering type annotations.
-        let substs = self.normalize(span, substs_raw);
+        let args = self.normalize(span, args_raw);
 
-        self.add_required_obligations_for_hir(span, def_id, &substs, hir_id);
+        self.add_required_obligations_for_hir(span, def_id, &args, hir_id);
 
         // Substitute the values for the type parameters into the type of
         // the referenced item.
         let ty = tcx.type_of(def_id);
-        assert!(!substs.has_escaping_bound_vars());
+        assert!(!args.has_escaping_bound_vars());
         assert!(!ty.skip_binder().has_escaping_bound_vars());
-        let ty_substituted = self.normalize(span, ty.subst(tcx, substs));
+        let ty_substituted = self.normalize(span, ty.instantiate(tcx, args));
 
         if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
             // In the case of `Foo<T>::method` and `<Foo<T>>::method`, if `method`
@@ -1397,7 +1400,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // type parameters, which we can infer by unifying the provided `Self`
             // with the substituted impl type.
             // This also occurs for an enum variant on a type alias.
-            let impl_ty = self.normalize(span, tcx.type_of(impl_def_id).subst(tcx, substs));
+            let impl_ty = self.normalize(span, tcx.type_of(impl_def_id).instantiate(tcx, args));
             let self_ty = self.normalize(span, self_ty);
             match self.at(&self.misc(span), self.param_env).eq(
                 DefineOpaqueTypes::No,
@@ -1419,7 +1422,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         debug!("instantiate_value_path: type of {:?} is {:?}", hir_id, ty_substituted);
-        self.write_substs(hir_id, substs);
+        self.write_args(hir_id, args);
 
         (ty_substituted, res)
     }
@@ -1429,10 +1432,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         &self,
         span: Span,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         hir_id: hir::HirId,
     ) {
-        self.add_required_obligations_with_code(span, def_id, substs, |idx, span| {
+        self.add_required_obligations_with_code(span, def_id, args, |idx, span| {
             if span.is_dummy() {
                 ObligationCauseCode::ExprItemObligation(def_id, hir_id, idx)
             } else {
@@ -1441,17 +1444,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         })
     }
 
-    #[instrument(level = "debug", skip(self, code, span, substs))]
+    #[instrument(level = "debug", skip(self, code, span, args))]
     fn add_required_obligations_with_code(
         &self,
         span: Span,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         code: impl Fn(usize, Span) -> ObligationCauseCode<'tcx>,
     ) {
         let param_env = self.param_env;
 
-        let bounds = self.instantiate_bounds(span, def_id, &substs);
+        let bounds = self.instantiate_bounds(span, def_id, &args);
 
         for obligation in traits::predicates_for_generics(
             |idx, predicate_span| {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
index b3ee284d8d70f..15ca5808a93ab 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs
@@ -37,9 +37,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let generics = self.tcx.generics_of(def_id);
-        let predicate_substs = match unsubstituted_pred.kind().skip_binder() {
-            ty::ClauseKind::Trait(pred) => pred.trait_ref.substs.to_vec(),
-            ty::ClauseKind::Projection(pred) => pred.projection_ty.substs.to_vec(),
+        let predicate_args = match unsubstituted_pred.kind().skip_binder() {
+            ty::ClauseKind::Trait(pred) => pred.trait_ref.args.to_vec(),
+            ty::ClauseKind::Projection(pred) => pred.projection_ty.args.to_vec(),
             ty::ClauseKind::ConstArgHasType(arg, ty) => {
                 vec![ty.into(), arg.into()]
             }
@@ -48,7 +48,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
 
         let find_param_matching = |matches: &dyn Fn(ty::ParamTerm) -> bool| {
-            predicate_substs.iter().find_map(|arg| {
+            predicate_args.iter().find_map(|arg| {
                 arg.walk().find_map(|arg| {
                     if let ty::GenericArgKind::Type(ty) = arg.unpack()
                         && let ty::Param(param_ty) = *ty.kind()
@@ -238,12 +238,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         param_to_point_at: ty::GenericArg<'tcx>,
         segment: &hir::PathSegment<'tcx>,
     ) -> bool {
-        let own_substs = self
+        let own_args = self
             .tcx
             .generics_of(def_id)
-            .own_substs(ty::InternalSubsts::identity_for_item(self.tcx, def_id));
+            .own_args(ty::GenericArgs::identity_for_item(self.tcx, def_id));
         let Some((index, _)) =
-            own_substs.iter().enumerate().find(|(_, arg)| **arg == param_to_point_at)
+            own_args.iter().enumerate().find(|(_, arg)| **arg == param_to_point_at)
         else {
             return false;
         };
@@ -271,7 +271,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         origin.kind
                     && let generics = self.0.tcx.generics_of(self.1)
                     && let Some(index) = generics.param_def_id_to_index(self.0.tcx, def_id)
-                    && let Some(subst) = ty::InternalSubsts::identity_for_item(self.0.tcx, self.1)
+                    && let Some(subst) = ty::GenericArgs::identity_for_item(self.0.tcx, self.1)
                         .get(index as usize)
                 {
                     ControlFlow::Break(*subst)
@@ -311,13 +311,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Option<(&'tcx hir::Expr<'tcx>, Ty<'tcx>)> {
         let def = self.tcx.adt_def(def_id);
 
-        let identity_substs = ty::InternalSubsts::identity_for_item(self.tcx, def_id);
+        let identity_args = ty::GenericArgs::identity_for_item(self.tcx, def_id);
         let fields_referencing_param: Vec<_> = def
             .variant_with_id(variant_def_id)
             .fields
             .iter()
             .filter(|field| {
-                let field_ty = field.ty(self.tcx, identity_substs);
+                let field_ty = field.ty(self.tcx, identity_args);
                 find_param_in_ty(field_ty.into(), param_to_point_at)
             })
             .collect();
@@ -328,7 +328,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // same rules that check_expr_struct uses for macro hygiene.
                 if self.tcx.adjust_ident(expr_field.ident, variant_def_id) == field.ident(self.tcx)
                 {
-                    return Some((expr_field.expr, self.tcx.type_of(field.did).subst_identity()));
+                    return Some((
+                        expr_field.expr,
+                        self.tcx.type_of(field.did).instantiate_identity(),
+                    ));
                 }
             }
         }
@@ -355,7 +358,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         receiver: Option<&'tcx hir::Expr<'tcx>>,
         args: &'tcx [hir::Expr<'tcx>],
     ) -> bool {
-        let ty = self.tcx.type_of(def_id).subst_identity();
+        let ty = self.tcx.type_of(def_id).instantiate_identity();
         if !ty.is_fn() {
             return false;
         }
@@ -497,7 +500,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ty::TraitRef::new(
                 self.tcx,
                 obligation.impl_or_alias_def_id,
-                ty::InternalSubsts::identity_for_item(self.tcx, obligation.impl_or_alias_def_id),
+                ty::GenericArgs::identity_for_item(self.tcx, obligation.impl_or_alias_def_id),
             )
         } else {
             self.tcx
@@ -861,7 +864,7 @@ fn find_param_in_ty<'tcx>(
                 // This logic may seem a bit strange, but typically when
                 // we have a projection type in a function signature, the
                 // argument that's being passed into that signature is
-                // not actually constraining that projection's substs in
+                // not actually constraining that projection's args in
                 // a meaningful way. So we skip it, and see improvements
                 // in some UI tests.
                 walk.skip_current_subtree();
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
index 5c5aef334136f..a9610009db1ee 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs
@@ -93,7 +93,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expected: Expectation<'tcx>,
     ) -> Ty<'tcx> {
         let has_error = match method {
-            Ok(method) => method.substs.references_error() || method.sig.references_error(),
+            Ok(method) => method.args.references_error() || method.sig.references_error(),
             Err(_) => true,
         };
         if has_error {
@@ -1366,7 +1366,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             Res::Def(DefKind::Variant, _) => match ty.normalized.ty_adt_def() {
                 Some(adt) => {
-                    Some((adt.variant_of_res(def), adt.did(), Self::user_substs_for_adt(ty)))
+                    Some((adt.variant_of_res(def), adt.did(), Self::user_args_for_adt(ty)))
                 }
                 _ => bug!("unexpected type: {:?}", ty.normalized),
             },
@@ -1374,21 +1374,21 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             | Res::SelfTyParam { .. }
             | Res::SelfTyAlias { .. } => match ty.normalized.ty_adt_def() {
                 Some(adt) if !adt.is_enum() => {
-                    Some((adt.non_enum_variant(), adt.did(), Self::user_substs_for_adt(ty)))
+                    Some((adt.non_enum_variant(), adt.did(), Self::user_args_for_adt(ty)))
                 }
                 _ => None,
             },
             _ => bug!("unexpected definition: {:?}", def),
         };
 
-        if let Some((variant, did, ty::UserSubsts { substs, user_self_ty })) = variant {
-            debug!("check_struct_path: did={:?} substs={:?}", did, substs);
+        if let Some((variant, did, ty::UserArgs { args, user_self_ty })) = variant {
+            debug!("check_struct_path: did={:?} args={:?}", did, args);
 
             // Register type annotation.
-            self.write_user_type_annotation_from_substs(hir_id, did, substs, user_self_ty);
+            self.write_user_type_annotation_from_args(hir_id, did, args, user_self_ty);
 
             // Check bounds on type arguments used in the path.
-            self.add_required_obligations_for_hir(path_span, did, substs, hir_id);
+            self.add_required_obligations_for_hir(path_span, did, args, hir_id);
 
             Ok((variant, ty.normalized))
         } else {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
index 20b34df99b275..1e8af6c6ed733 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs
@@ -288,14 +288,14 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
             poly_trait_ref,
         );
 
-        let item_substs = self.astconv().create_substs_for_associated_item(
+        let item_args = self.astconv().create_args_for_associated_item(
             span,
             item_def_id,
             item_segment,
-            trait_ref.substs,
+            trait_ref.args,
         );
 
-        Ty::new_projection(self.tcx(), item_def_id, item_substs)
+        Ty::new_projection(self.tcx(), item_def_id, item_args)
     }
 
     fn probe_adt(&self, span: Span, ty: Ty<'tcx>) -> Option<ty::AdtDef<'tcx>> {
diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
index 5d80137f212d1..92cae84afd931 100644
--- a/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
+++ b/compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs
@@ -481,23 +481,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         found_ty: Ty<'tcx>,
         expected_ty: Ty<'tcx>,
     ) -> Option<(Ty<'tcx>, Ty<'tcx>, Option<(Ty<'tcx>, Ty<'tcx>)>)> {
-        let ty::Adt(found_adt, found_substs) = found_ty.peel_refs().kind() else {
+        let ty::Adt(found_adt, found_args) = found_ty.peel_refs().kind() else {
             return None;
         };
-        let ty::Adt(expected_adt, expected_substs) = expected_ty.kind() else {
+        let ty::Adt(expected_adt, expected_args) = expected_ty.kind() else {
             return None;
         };
         if self.tcx.is_diagnostic_item(sym::Option, found_adt.did())
             && self.tcx.is_diagnostic_item(sym::Option, expected_adt.did())
         {
-            Some((found_substs.type_at(0), expected_substs.type_at(0), None))
+            Some((found_args.type_at(0), expected_args.type_at(0), None))
         } else if self.tcx.is_diagnostic_item(sym::Result, found_adt.did())
             && self.tcx.is_diagnostic_item(sym::Result, expected_adt.did())
         {
             Some((
-                found_substs.type_at(0),
-                expected_substs.type_at(0),
-                Some((found_substs.type_at(1), expected_substs.type_at(1))),
+                found_args.type_at(0),
+                expected_args.type_at(0),
+                Some((found_args.type_at(1), expected_args.type_at(1))),
             ))
         } else {
             None
@@ -763,9 +763,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 if let Some(found) = found.make_suggestable(self.tcx, false) {
                     err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: found.to_string() });
                     return true;
-                } else if let ty::Closure(_, substs) = found.kind()
+                } else if let ty::Closure(_, args) = found.kind()
                     // FIXME(compiler-errors): Get better at printing binders...
-                    && let closure = substs.as_closure()
+                    && let closure = args.as_closure()
                     && closure.sig().is_suggestable(self.tcx, false)
                 {
                     err.subdiagnostic(AddReturnTypeSuggestion::Add { span, found: closure.print_as_impl_trait().to_string() });
@@ -1092,10 +1092,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expr_ty: Ty<'tcx>,
         expected_ty: Ty<'tcx>,
     ) -> bool {
-        let ty::Adt(adt_def, substs) = expr_ty.kind() else {
+        let ty::Adt(adt_def, args) = expr_ty.kind() else {
             return false;
         };
-        let ty::Adt(expected_adt_def, expected_substs) = expected_ty.kind() else {
+        let ty::Adt(expected_adt_def, expected_args) = expected_ty.kind() else {
             return false;
         };
         if adt_def != expected_adt_def {
@@ -1103,8 +1103,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         }
 
         let mut suggest_copied_or_cloned = || {
-            let expr_inner_ty = substs.type_at(0);
-            let expected_inner_ty = expected_substs.type_at(0);
+            let expr_inner_ty = args.type_at(0);
+            let expected_inner_ty = expected_args.type_at(0);
             if let &ty::Ref(_, ty, hir::Mutability::Not) = expr_inner_ty.kind()
                 && self.can_eq(self.param_env, ty, expected_inner_ty)
             {
@@ -1144,7 +1144,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if let Some(result_did) = self.tcx.get_diagnostic_item(sym::Result)
             && adt_def.did() == result_did
             // Check that the error types are equal
-            && self.can_eq(self.param_env, substs.type_at(1), expected_substs.type_at(1))
+            && self.can_eq(self.param_env, args.type_at(1), expected_args.type_at(1))
         {
             return suggest_copied_or_cloned();
         } else if let Some(option_did) = self.tcx.get_diagnostic_item(sym::Option)
@@ -1475,7 +1475,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Same item
             return false;
         }
-        let item_ty = self.tcx.type_of(item.def_id).subst_identity();
+        let item_ty = self.tcx.type_of(item.def_id).instantiate_identity();
         // FIXME(compiler-errors): This check is *so* rudimentary
         if item_ty.has_param() {
             return false;
diff --git a/compiler/rustc_hir_typeck/src/intrinsicck.rs b/compiler/rustc_hir_typeck/src/intrinsicck.rs
index e58efc9d1e38d..2d85451c9e185 100644
--- a/compiler/rustc_hir_typeck/src/intrinsicck.rs
+++ b/compiler/rustc_hir_typeck/src/intrinsicck.rs
@@ -11,7 +11,7 @@ use super::FnCtxt;
 /// If the type is `Option<T>`, it will return `T`, otherwise
 /// the type itself. Works on most `Option`-like types.
 fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
-    let ty::Adt(def, substs) = *ty.kind() else { return ty };
+    let ty::Adt(def, args) = *ty.kind() else { return ty };
 
     if def.variants().len() == 2 && !def.repr().c() && def.repr().int.is_none() {
         let data_idx;
@@ -28,7 +28,7 @@ fn unpack_option_like<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
         }
 
         if def.variant(data_idx).fields.len() == 1 {
-            return def.variant(data_idx).single_field().ty(tcx, substs);
+            return def.variant(data_idx).single_field().ty(tcx, args);
         }
     }
 
diff --git a/compiler/rustc_hir_typeck/src/lib.rs b/compiler/rustc_hir_typeck/src/lib.rs
index b1130430b3993..28e7f29073785 100644
--- a/compiler/rustc_hir_typeck/src/lib.rs
+++ b/compiler/rustc_hir_typeck/src/lib.rs
@@ -144,7 +144,7 @@ fn used_trait_imports(tcx: TyCtxt<'_>, def_id: LocalDefId) -> &UnordSet<LocalDef
 }
 
 fn typeck<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &ty::TypeckResults<'tcx> {
-    let fallback = move || tcx.type_of(def_id.to_def_id()).subst_identity();
+    let fallback = move || tcx.type_of(def_id.to_def_id()).instantiate_identity();
     typeck_with_fallback(tcx, def_id, fallback)
 }
 
@@ -194,7 +194,7 @@ fn typeck_with_fallback<'tcx>(
         let fn_sig = if rustc_hir_analysis::collect::get_infer_ret_ty(&decl.output).is_some() {
             fcx.astconv().ty_of_fn(id, header.unsafety, header.abi, decl, None, None)
         } else {
-            tcx.fn_sig(def_id).subst_identity()
+            tcx.fn_sig(def_id).instantiate_identity()
         };
 
         check_abi(tcx, id, span, fn_sig.abi());
diff --git a/compiler/rustc_hir_typeck/src/mem_categorization.rs b/compiler/rustc_hir_typeck/src/mem_categorization.rs
index a1aa090841a70..0700e2e05546c 100644
--- a/compiler/rustc_hir_typeck/src/mem_categorization.rs
+++ b/compiler/rustc_hir_typeck/src/mem_categorization.rs
@@ -595,7 +595,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx> {
     fn total_fields_in_tuple(&self, pat_hir_id: hir::HirId, span: Span) -> McResult<usize> {
         let ty = self.typeck_results.node_type(pat_hir_id);
         match ty.kind() {
-            ty::Tuple(substs) => Ok(substs.len()),
+            ty::Tuple(args) => Ok(args.len()),
             _ => {
                 self.tcx().sess.delay_span_bug(span, "tuple pattern not applied to a tuple");
                 Err(())
diff --git a/compiler/rustc_hir_typeck/src/method/confirm.rs b/compiler/rustc_hir_typeck/src/method/confirm.rs
index 168eb3a6cdc75..6835782b5bd8f 100644
--- a/compiler/rustc_hir_typeck/src/method/confirm.rs
+++ b/compiler/rustc_hir_typeck/src/method/confirm.rs
@@ -5,7 +5,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_hir::GenericArg;
 use rustc_hir_analysis::astconv::generics::{
-    check_generic_arg_count_for_call, create_substs_for_generic_args,
+    check_generic_arg_count_for_call, create_args_for_parent_generic_args,
 };
 use rustc_hir_analysis::astconv::{AstConv, CreateSubstsForGenericArgsCtxt, IsMethodCall};
 use rustc_infer::infer::{self, DefineOpaqueTypes, InferOk};
@@ -13,9 +13,9 @@ use rustc_middle::traits::{ObligationCauseCode, UnifyReceiverContext};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::adjustment::{AllowTwoPhase, AutoBorrow, AutoBorrowMutability};
 use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::subst::{self, SubstsRef};
-use rustc_middle::ty::{self, GenericParamDefKind, Ty, TyCtxt};
-use rustc_middle::ty::{InternalSubsts, UserSubsts, UserType};
+use rustc_middle::ty::{
+    self, GenericArgs, GenericArgsRef, GenericParamDefKind, Ty, TyCtxt, UserArgs, UserType,
+};
 use rustc_span::{Span, DUMMY_SP};
 use rustc_trait_selection::traits;
 
@@ -96,13 +96,13 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         let self_ty = self.adjust_self_ty(unadjusted_self_ty, &pick);
 
         // Create substitutions for the method's type parameters.
-        let rcvr_substs = self.fresh_receiver_substs(self_ty, &pick);
-        let all_substs = self.instantiate_method_substs(&pick, segment, rcvr_substs);
+        let rcvr_args = self.fresh_receiver_args(self_ty, &pick);
+        let all_args = self.instantiate_method_args(&pick, segment, rcvr_args);
 
-        debug!("rcvr_substs={rcvr_substs:?}, all_substs={all_substs:?}");
+        debug!("rcvr_args={rcvr_args:?}, all_args={all_args:?}");
 
         // Create the final signature for the method, replacing late-bound regions.
-        let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_substs);
+        let (method_sig, method_predicates) = self.instantiate_method_sig(&pick, all_args);
 
         // If there is a `Self: Sized` bound and `Self` is a trait object, it is possible that
         // something which derefs to `Self` actually implements the trait and the caller
@@ -112,10 +112,10 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // In that case, we'll error anyway, but we'll also re-run the search with all traits
         // in scope, and if we find another method which can be used, we'll output an
         // appropriate hint suggesting to import the trait.
-        let filler_substs = rcvr_substs
+        let filler_args = rcvr_args
             .extend_to(self.tcx, pick.item.def_id, |def, _| self.tcx.mk_param_from_def(def));
         let illegal_sized_bound = self.predicates_require_illegal_sized_bound(
-            self.tcx.predicates_of(pick.item.def_id).instantiate(self.tcx, filler_substs),
+            self.tcx.predicates_of(pick.item.def_id).instantiate(self.tcx, filler_args),
         );
 
         // Unify the (adjusted) self type with what the method expects.
@@ -129,7 +129,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             "confirm: self_ty={:?} method_sig_rcvr={:?} method_sig={:?} method_predicates={:?}",
             self_ty, method_sig_rcvr, method_sig, method_predicates
         );
-        self.unify_receivers(self_ty, method_sig_rcvr, &pick, all_substs);
+        self.unify_receivers(self_ty, method_sig_rcvr, &pick, all_args);
 
         let (method_sig, method_predicates) =
             self.normalize(self.span, (method_sig, method_predicates));
@@ -144,7 +144,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         if illegal_sized_bound.is_none() {
             self.add_obligations(
                 Ty::new_fn_ptr(self.tcx, method_sig),
-                all_substs,
+                all_args,
                 method_predicates,
                 pick.item.def_id,
             );
@@ -153,7 +153,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // Create the final `MethodCallee`.
         let callee = MethodCallee {
             def_id: pick.item.def_id,
-            substs: all_substs,
+            args: all_args,
             sig: method_sig.skip_binder(),
         };
         ConfirmResult { callee, illegal_sized_bound }
@@ -252,11 +252,11 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
     ///
     /// Note that this substitution may include late-bound regions from the impl level. If so,
     /// these are instantiated later in the `instantiate_method_sig` routine.
-    fn fresh_receiver_substs(
+    fn fresh_receiver_args(
         &mut self,
         self_ty: Ty<'tcx>,
         pick: &probe::Pick<'tcx>,
-    ) -> SubstsRef<'tcx> {
+    ) -> GenericArgsRef<'tcx> {
         match pick.kind {
             probe::InherentImplPick => {
                 let impl_def_id = pick.item.container_id(self.tcx);
@@ -265,7 +265,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                     "impl {:?} is not an inherent impl",
                     impl_def_id
                 );
-                self.fresh_substs_for_item(self.span, impl_def_id)
+                self.fresh_args_for_item(self.span, impl_def_id)
             }
 
             probe::ObjectPick => {
@@ -289,7 +289,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                         "original_poly_trait_ref={:?} upcast_trait_ref={:?} target_trait={:?}",
                         original_poly_trait_ref, upcast_trait_ref, trait_def_id
                     );
-                    upcast_trait_ref.substs
+                    upcast_trait_ref.args
                 })
             }
 
@@ -301,13 +301,13 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                 // the process we will unify the transformed-self-type
                 // of the method with the actual type in order to
                 // unify some of these variables.
-                self.fresh_substs_for_item(self.span, trait_def_id)
+                self.fresh_args_for_item(self.span, trait_def_id)
             }
 
             probe::WhereClausePick(poly_trait_ref) => {
                 // Where clauses can have bound regions in them. We need to instantiate
                 // those to convert from a poly-trait-ref to a trait-ref.
-                self.instantiate_binder_with_fresh_vars(poly_trait_ref).substs
+                self.instantiate_binder_with_fresh_vars(poly_trait_ref).args
             }
         }
     }
@@ -344,12 +344,12 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             })
     }
 
-    fn instantiate_method_substs(
+    fn instantiate_method_args(
         &mut self,
         pick: &probe::Pick<'tcx>,
         seg: &hir::PathSegment<'_>,
-        parent_substs: SubstsRef<'tcx>,
-    ) -> SubstsRef<'tcx> {
+        parent_args: GenericArgsRef<'tcx>,
+    ) -> GenericArgsRef<'tcx> {
         // Determine the values for the generic parameters of the method.
         // If they were not explicitly supplied, just construct fresh
         // variables.
@@ -366,7 +366,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
         // Create subst for early-bound lifetime parameters, combining
         // parameters from the type and those from the method.
-        assert_eq!(generics.parent_count, parent_substs.len());
+        assert_eq!(generics.parent_count, parent_args.len());
 
         struct MethodSubstsCtxt<'a, 'tcx> {
             cfcx: &'a ConfirmContext<'a, 'tcx>,
@@ -390,7 +390,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
                 &mut self,
                 param: &ty::GenericParamDef,
                 arg: &GenericArg<'_>,
-            ) -> subst::GenericArg<'tcx> {
+            ) -> ty::GenericArg<'tcx> {
                 match (&param.kind, arg) {
                     (GenericParamDefKind::Lifetime, GenericArg::Lifetime(lt)) => {
                         self.cfcx.fcx.astconv().ast_region_to_region(lt, Some(param)).into()
@@ -422,31 +422,31 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
             fn inferred_kind(
                 &mut self,
-                _substs: Option<&[subst::GenericArg<'tcx>]>,
+                _args: Option<&[ty::GenericArg<'tcx>]>,
                 param: &ty::GenericParamDef,
                 _infer_args: bool,
-            ) -> subst::GenericArg<'tcx> {
+            ) -> ty::GenericArg<'tcx> {
                 self.cfcx.var_for_def(self.cfcx.span, param)
             }
         }
 
-        let substs = create_substs_for_generic_args(
+        let args = create_args_for_parent_generic_args(
             self.tcx,
             pick.item.def_id,
-            parent_substs,
+            parent_args,
             false,
             None,
             &arg_count_correct,
             &mut MethodSubstsCtxt { cfcx: self, pick, seg },
         );
 
-        // When the method is confirmed, the `substs` includes
+        // When the method is confirmed, the `args` includes
         // parameters from not just the method, but also the impl of
         // the method -- in particular, the `Self` type will be fully
         // resolved. However, those are not something that the "user
         // specified" -- i.e., those types come from the inferred type
         // of the receiver, not something the user wrote. So when we
-        // create the user-substs, we want to replace those earlier
+        // create the user-args, we want to replace those earlier
         // types with just the types that the user actually wrote --
         // that is, those that appear on the *method itself*.
         //
@@ -454,15 +454,15 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         // `foo.bar::<u32>(...)` -- the `Self` type here will be the
         // type of `foo` (possibly adjusted), but we don't want to
         // include that. We want just the `[_, u32]` part.
-        if !substs.is_empty() && !generics.params.is_empty() {
+        if !args.is_empty() && !generics.params.is_empty() {
             let user_type_annotation = self.probe(|_| {
-                let user_substs = UserSubsts {
-                    substs: InternalSubsts::for_item(self.tcx, pick.item.def_id, |param, _| {
+                let user_args = UserArgs {
+                    args: GenericArgs::for_item(self.tcx, pick.item.def_id, |param, _| {
                         let i = param.index as usize;
                         if i < generics.parent_count {
                             self.fcx.var_for_def(DUMMY_SP, param)
                         } else {
-                            substs[i]
+                            args[i]
                         }
                     }),
                     user_self_ty: None, // not relevant here
@@ -470,18 +470,18 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
                 self.fcx.canonicalize_user_type_annotation(UserType::TypeOf(
                     pick.item.def_id,
-                    user_substs,
+                    user_args,
                 ))
             });
 
-            debug!("instantiate_method_substs: user_type_annotation={:?}", user_type_annotation);
+            debug!("instantiate_method_args: user_type_annotation={:?}", user_type_annotation);
 
             if !self.skip_record_for_diagnostics {
                 self.fcx.write_user_type_annotation(self.call_expr.hir_id, user_type_annotation);
             }
         }
 
-        self.normalize(self.span, substs)
+        self.normalize(self.span, args)
     }
 
     fn unify_receivers(
@@ -489,7 +489,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
         self_ty: Ty<'tcx>,
         method_self_ty: Ty<'tcx>,
         pick: &probe::Pick<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) {
         debug!(
             "unify_receivers: self_ty={:?} method_self_ty={:?} span={:?} pick={:?}",
@@ -500,7 +500,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             ObligationCauseCode::UnifyReceiver(Box::new(UnifyReceiverContext {
                 assoc_item: pick.item,
                 param_env: self.param_env,
-                substs,
+                args,
             })),
         );
         match self.at(&cause, self.param_env).sup(DefineOpaqueTypes::No, method_self_ty, self_ty) {
@@ -510,7 +510,7 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
             Err(terr) => {
                 // FIXME(arbitrary_self_types): We probably should limit the
                 // situations where this can occur by adding additional restrictions
-                // to the feature, like the self type can't reference method substs.
+                // to the feature, like the self type can't reference method args.
                 if self.tcx.features().arbitrary_self_types {
                     self.err_ctxt()
                         .report_mismatched_types(&cause, method_self_ty, self_ty, terr)
@@ -533,19 +533,19 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
     fn instantiate_method_sig(
         &mut self,
         pick: &probe::Pick<'tcx>,
-        all_substs: SubstsRef<'tcx>,
+        all_args: GenericArgsRef<'tcx>,
     ) -> (ty::FnSig<'tcx>, ty::InstantiatedPredicates<'tcx>) {
-        debug!("instantiate_method_sig(pick={:?}, all_substs={:?})", pick, all_substs);
+        debug!("instantiate_method_sig(pick={:?}, all_args={:?})", pick, all_args);
 
         // Instantiate the bounds on the method with the
         // type/early-bound-regions substitutions performed. There can
         // be no late-bound regions appearing here.
         let def_id = pick.item.def_id;
-        let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_substs);
+        let method_predicates = self.tcx.predicates_of(def_id).instantiate(self.tcx, all_args);
 
         debug!("method_predicates after subst = {:?}", method_predicates);
 
-        let sig = self.tcx.fn_sig(def_id).subst(self.tcx, all_substs);
+        let sig = self.tcx.fn_sig(def_id).instantiate(self.tcx, all_args);
         debug!("type scheme substituted, sig={:?}", sig);
 
         let sig = self.instantiate_binder_with_fresh_vars(sig);
@@ -557,18 +557,18 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
     fn add_obligations(
         &mut self,
         fty: Ty<'tcx>,
-        all_substs: SubstsRef<'tcx>,
+        all_args: GenericArgsRef<'tcx>,
         method_predicates: ty::InstantiatedPredicates<'tcx>,
         def_id: DefId,
     ) {
         debug!(
-            "add_obligations: fty={:?} all_substs={:?} method_predicates={:?} def_id={:?}",
-            fty, all_substs, method_predicates, def_id
+            "add_obligations: fty={:?} all_args={:?} method_predicates={:?} def_id={:?}",
+            fty, all_args, method_predicates, def_id
         );
 
         // FIXME: could replace with the following, but we already calculated `method_predicates`,
         // so we just call `predicates_for_generics` directly to avoid redoing work.
-        // `self.add_required_obligations(self.span, def_id, &all_substs);`
+        // `self.add_required_obligations(self.span, def_id, &all_args);`
         for obligation in traits::predicates_for_generics(
             |idx, span| {
                 let code = if span.is_dummy() {
@@ -591,10 +591,10 @@ impl<'a, 'tcx> ConfirmContext<'a, 'tcx> {
 
         // this is a projection from a trait reference, so we have to
         // make sure that the trait reference inputs are well-formed.
-        self.add_wf_bounds(all_substs, self.call_expr);
+        self.add_wf_bounds(all_args, self.call_expr);
 
         // the function type must also be well-formed (this is not
-        // implied by the substs being well-formed because of inherent
+        // implied by the args being well-formed because of inherent
         // impls and late-bound regions - see issue #28609).
         self.register_wf_obligation(fty.into(), self.span, traits::WellFormed(None));
     }
diff --git a/compiler/rustc_hir_typeck/src/method/mod.rs b/compiler/rustc_hir_typeck/src/method/mod.rs
index c59e9e315b129..356e7022aea11 100644
--- a/compiler/rustc_hir_typeck/src/method/mod.rs
+++ b/compiler/rustc_hir_typeck/src/method/mod.rs
@@ -19,8 +19,8 @@ use rustc_hir::def_id::DefId;
 use rustc_infer::infer::{self, InferOk};
 use rustc_middle::query::Providers;
 use rustc_middle::traits::ObligationCause;
-use rustc_middle::ty::subst::{InternalSubsts, SubstsRef};
 use rustc_middle::ty::{self, GenericParamDefKind, Ty, TypeVisitableExt};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_span::symbol::Ident;
 use rustc_span::Span;
 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
@@ -36,7 +36,7 @@ pub fn provide(providers: &mut Providers) {
 pub struct MethodCallee<'tcx> {
     /// Impl method ID, for inherent methods, or trait method ID, otherwise.
     pub def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 
     /// Instantiated method signature, i.e., it has been
     /// substituted, normalized, and has had late-bound
@@ -321,9 +321,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         trait_def_id: DefId,
         self_ty: Ty<'tcx>,
         opt_input_types: Option<&[Ty<'tcx>]>,
-    ) -> (traits::PredicateObligation<'tcx>, &'tcx ty::List<ty::subst::GenericArg<'tcx>>) {
+    ) -> (traits::PredicateObligation<'tcx>, &'tcx ty::List<ty::GenericArg<'tcx>>) {
         // Construct a trait-reference `self_ty : Trait<input_tys>`
-        let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
+        let args = GenericArgs::for_item(self.tcx, trait_def_id, |param, _| {
             match param.kind {
                 GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => {}
                 GenericParamDefKind::Type { .. } => {
@@ -337,7 +337,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             self.var_for_def(cause.span, param)
         });
 
-        let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, substs);
+        let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, args);
 
         // Construct an obligation
         let poly_trait_ref = ty::Binder::dummy(trait_ref);
@@ -348,7 +348,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 self.param_env,
                 poly_trait_ref.without_const(),
             ),
-            substs,
+            args,
         )
     }
 
@@ -366,9 +366,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         self_ty: Ty<'tcx>,
         opt_input_types: Option<&[Ty<'tcx>]>,
     ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
-        let (obligation, substs) =
+        let (obligation, args) =
             self.obligation_for_method(cause, trait_def_id, self_ty, opt_input_types);
-        self.construct_obligation_for_trait(m_name, trait_def_id, obligation, substs)
+        self.construct_obligation_for_trait(m_name, trait_def_id, obligation, args)
     }
 
     // FIXME(#18741): it seems likely that we can consolidate some of this
@@ -379,7 +379,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         m_name: Ident,
         trait_def_id: DefId,
         obligation: traits::PredicateObligation<'tcx>,
-        substs: &'tcx ty::List<ty::subst::GenericArg<'tcx>>,
+        args: &'tcx ty::List<ty::GenericArg<'tcx>>,
     ) -> Option<InferOk<'tcx, MethodCallee<'tcx>>> {
         debug!(?obligation);
 
@@ -425,7 +425,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // N.B., instantiate late-bound regions before normalizing the
         // function signature so that normalization does not need to deal
         // with bound regions.
-        let fn_sig = tcx.fn_sig(def_id).subst(self.tcx, substs);
+        let fn_sig = tcx.fn_sig(def_id).instantiate(self.tcx, args);
         let fn_sig =
             self.instantiate_binder_with_fresh_vars(obligation.cause.span, infer::FnCall, fn_sig);
 
@@ -444,7 +444,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         //
         // Note that as the method comes from a trait, it should not have
         // any late-bound regions appearing in its bounds.
-        let bounds = self.tcx.predicates_of(def_id).instantiate(self.tcx, substs);
+        let bounds = self.tcx.predicates_of(def_id).instantiate(self.tcx, args);
 
         let InferOk { value, obligations: o } =
             self.at(&obligation.cause, self.param_env).normalize(bounds);
@@ -477,7 +477,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ))),
         ));
 
-        let callee = MethodCallee { def_id, substs, sig: fn_sig };
+        let callee = MethodCallee { def_id, args, sig: fn_sig };
 
         debug!("callee = {:?}", callee);
 
diff --git a/compiler/rustc_hir_typeck/src/method/probe.rs b/compiler/rustc_hir_typeck/src/method/probe.rs
index 45c9f15c0d555..9ef97243c5e0f 100644
--- a/compiler/rustc_hir_typeck/src/method/probe.rs
+++ b/compiler/rustc_hir_typeck/src/method/probe.rs
@@ -22,7 +22,7 @@ use rustc_middle::ty::AssocItem;
 use rustc_middle::ty::GenericParamDefKind;
 use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
-use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_session::lint;
 use rustc_span::def_id::DefId;
 use rustc_span::def_id::LocalDefId;
@@ -100,10 +100,10 @@ impl<'a, 'tcx> Deref for ProbeContext<'a, 'tcx> {
 #[derive(Debug, Clone)]
 pub(crate) struct Candidate<'tcx> {
     // Candidates are (I'm not quite sure, but they are mostly) basically
-    // some metadata on top of a `ty::AssocItem` (without substs).
+    // some metadata on top of a `ty::AssocItem` (without args).
     //
     // However, method probing wants to be able to evaluate the predicates
-    // for a function with the substs applied - for example, if a function
+    // for a function with the args applied - for example, if a function
     // has `where Self: Sized`, we don't want to consider it unless `Self`
     // is actually `Sized`, and similarly, return-type suggestions want
     // to consider the "actual" return type.
@@ -140,7 +140,7 @@ pub(crate) struct Candidate<'tcx> {
 #[derive(Debug, Clone)]
 pub(crate) enum CandidateKind<'tcx> {
     InherentImplCandidate(
-        SubstsRef<'tcx>,
+        GenericArgsRef<'tcx>,
         // Normalize obligations
         Vec<traits::PredicateObligation<'tcx>>,
     ),
@@ -738,13 +738,13 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 continue;
             }
 
-            let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
-            let impl_ty = impl_ty.subst(self.tcx, impl_substs);
+            let (impl_ty, impl_args) = self.impl_ty_and_args(impl_def_id);
+            let impl_ty = impl_ty.instantiate(self.tcx, impl_args);
 
             debug!("impl_ty: {:?}", impl_ty);
 
             // Determine the receiver type that the method itself expects.
-            let (xform_self_ty, xform_ret_ty) = self.xform_self_ty(item, impl_ty, impl_substs);
+            let (xform_self_ty, xform_ret_ty) = self.xform_self_ty(item, impl_ty, impl_args);
             debug!("xform_self_ty: {:?}, xform_ret_ty: {:?}", xform_self_ty, xform_ret_ty);
 
             // We can't use normalize_associated_types_in as it will pollute the
@@ -770,7 +770,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     xform_self_ty,
                     xform_ret_ty,
                     item,
-                    kind: InherentImplCandidate(impl_substs, obligations),
+                    kind: InherentImplCandidate(impl_args, obligations),
                     import_ids: smallvec![],
                 },
                 true,
@@ -813,7 +813,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             let new_trait_ref = this.erase_late_bound_regions(new_trait_ref);
 
             let (xform_self_ty, xform_ret_ty) =
-                this.xform_self_ty(item, new_trait_ref.self_ty(), new_trait_ref.substs);
+                this.xform_self_ty(item, new_trait_ref.self_ty(), new_trait_ref.args);
             this.push_candidate(
                 Candidate {
                     xform_self_ty,
@@ -859,7 +859,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             );
 
             let (xform_self_ty, xform_ret_ty) =
-                this.xform_self_ty(item, trait_ref.self_ty(), trait_ref.substs);
+                this.xform_self_ty(item, trait_ref.self_ty(), trait_ref.args);
 
             this.push_candidate(
                 Candidate {
@@ -929,8 +929,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     ) -> bool {
         match method.kind {
             ty::AssocKind::Fn => self.probe(|_| {
-                let substs = self.fresh_substs_for_item(self.span, method.def_id);
-                let fty = self.tcx.fn_sig(method.def_id).subst(self.tcx, substs);
+                let args = self.fresh_args_for_item(self.span, method.def_id);
+                let fty = self.tcx.fn_sig(method.def_id).instantiate(self.tcx, args);
                 let fty = self.instantiate_binder_with_fresh_vars(self.span, infer::FnCall, fty);
 
                 if let Some(self_ty) = self_ty {
@@ -954,8 +954,8 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         trait_def_id: DefId,
     ) {
         debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})", trait_def_id);
-        let trait_substs = self.fresh_substs_for_item(self.span, trait_def_id);
-        let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, trait_substs);
+        let trait_args = self.fresh_args_for_item(self.span, trait_def_id);
+        let trait_ref = ty::TraitRef::new(self.tcx, trait_def_id, trait_args);
 
         if self.tcx.is_trait_alias(trait_def_id) {
             // For trait aliases, recursively assume all explicitly named traits are relevant
@@ -977,7 +977,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                         );
 
                         let (xform_self_ty, xform_ret_ty) =
-                            self.xform_self_ty(item, new_trait_ref.self_ty(), new_trait_ref.substs);
+                            self.xform_self_ty(item, new_trait_ref.self_ty(), new_trait_ref.args);
                         self.push_candidate(
                             Candidate {
                                 xform_self_ty,
@@ -1005,7 +1005,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 }
 
                 let (xform_self_ty, xform_ret_ty) =
-                    self.xform_self_ty(item, trait_ref.self_ty(), trait_substs);
+                    self.xform_self_ty(item, trait_ref.self_ty(), trait_args);
                 self.push_candidate(
                     Candidate {
                         xform_self_ty,
@@ -1510,7 +1510,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
             // match as well (or at least may match, sometimes we
             // don't have enough information to fully evaluate).
             match probe.kind {
-                InherentImplCandidate(ref substs, ref ref_obligations) => {
+                InherentImplCandidate(ref args, ref ref_obligations) => {
                     // `xform_ret_ty` hasn't been normalized yet, only `xform_self_ty`,
                     // see the reasons mentioned in the comments in `assemble_inherent_impl_probe`
                     // for why this is necessary
@@ -1524,7 +1524,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     // Check whether the impl imposes obligations we have to worry about.
                     let impl_def_id = probe.item.container_id(self.tcx);
                     let impl_bounds = self.tcx.predicates_of(impl_def_id);
-                    let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
+                    let impl_bounds = impl_bounds.instantiate(self.tcx, args);
 
                     let InferOk { value: impl_bounds, obligations: norm_obligations } =
                         self.fcx.at(&cause, self.param_env).normalize(impl_bounds);
@@ -1843,10 +1843,10 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         &self,
         item: ty::AssocItem,
         impl_ty: Ty<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> (Ty<'tcx>, Option<Ty<'tcx>>) {
         if item.kind == ty::AssocKind::Fn && self.mode == Mode::MethodCall {
-            let sig = self.xform_method_sig(item.def_id, substs);
+            let sig = self.xform_method_sig(item.def_id, args);
             (sig.inputs()[0], Some(sig.output()))
         } else {
             (impl_ty, None)
@@ -1854,11 +1854,11 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
     }
 
     #[instrument(level = "debug", skip(self))]
-    fn xform_method_sig(&self, method: DefId, substs: SubstsRef<'tcx>) -> ty::FnSig<'tcx> {
+    fn xform_method_sig(&self, method: DefId, args: GenericArgsRef<'tcx>) -> ty::FnSig<'tcx> {
         let fn_sig = self.tcx.fn_sig(method);
         debug!(?fn_sig);
 
-        assert!(!substs.has_escaping_bound_vars());
+        assert!(!args.has_escaping_bound_vars());
 
         // It is possible for type parameters or early-bound lifetimes
         // to appear in the signature of `self`. The substitutions we
@@ -1866,15 +1866,15 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
         // method yet. So create fresh variables here for those too,
         // if there are any.
         let generics = self.tcx.generics_of(method);
-        assert_eq!(substs.len(), generics.parent_count as usize);
+        assert_eq!(args.len(), generics.parent_count as usize);
 
         let xform_fn_sig = if generics.params.is_empty() {
-            fn_sig.subst(self.tcx, substs)
+            fn_sig.instantiate(self.tcx, args)
         } else {
-            let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
+            let args = GenericArgs::for_item(self.tcx, method, |param, _| {
                 let i = param.index as usize;
-                if i < substs.len() {
-                    substs[i]
+                if i < args.len() {
+                    args[i]
                 } else {
                     match param.kind {
                         GenericParamDefKind::Lifetime => {
@@ -1887,18 +1887,18 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     }
                 }
             });
-            fn_sig.subst(self.tcx, substs)
+            fn_sig.instantiate(self.tcx, args)
         };
 
         self.erase_late_bound_regions(xform_fn_sig)
     }
 
     /// Gets the type of an impl and generate substitutions with inference vars.
-    fn impl_ty_and_substs(
+    fn impl_ty_and_args(
         &self,
         impl_def_id: DefId,
-    ) -> (ty::EarlyBinder<Ty<'tcx>>, SubstsRef<'tcx>) {
-        (self.tcx.type_of(impl_def_id), self.fresh_substs_for_item(self.span, impl_def_id))
+    ) -> (ty::EarlyBinder<Ty<'tcx>>, GenericArgsRef<'tcx>) {
+        (self.tcx.type_of(impl_def_id), self.fresh_args_for_item(self.span, impl_def_id))
     }
 
     /// Replaces late-bound-regions bound by `value` with `'static` using
@@ -2040,8 +2040,8 @@ impl<'tcx> Candidate<'tcx> {
                     // means they are safe to put into the
                     // `WhereClausePick`.
                     assert!(
-                        !trait_ref.skip_binder().substs.has_infer()
-                            && !trait_ref.skip_binder().substs.has_placeholders()
+                        !trait_ref.skip_binder().args.has_infer()
+                            && !trait_ref.skip_binder().args.has_placeholders()
                     );
 
                     WhereClausePick(*trait_ref)
diff --git a/compiler/rustc_hir_typeck/src/method/suggest.rs b/compiler/rustc_hir_typeck/src/method/suggest.rs
index a30e6479ca6fe..e3e0eff23d219 100644
--- a/compiler/rustc_hir_typeck/src/method/suggest.rs
+++ b/compiler/rustc_hir_typeck/src/method/suggest.rs
@@ -650,13 +650,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         // `<Foo as Iterator>::Item = String`.
                         let projection_ty = pred.skip_binder().projection_ty;
 
-                        let substs_with_infer_self = tcx.mk_substs_from_iter(
+                        let args_with_infer_self = tcx.mk_args_from_iter(
                             iter::once(Ty::new_var(tcx, ty::TyVid::from_u32(0)).into())
-                                .chain(projection_ty.substs.iter().skip(1)),
+                                .chain(projection_ty.args.iter().skip(1)),
                         );
 
                         let quiet_projection_ty =
-                            tcx.mk_alias_ty(projection_ty.def_id, substs_with_infer_self);
+                            tcx.mk_alias_ty(projection_ty.def_id, args_with_infer_self);
 
                         let term = pred.skip_binder().term;
 
@@ -995,9 +995,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                         // different from the received one
                                         // So we avoid suggestion method with Box<Self>
                                         // for instance
-                                        self.tcx.at(span).type_of(*def_id).subst_identity()
+                                        self.tcx.at(span).type_of(*def_id).instantiate_identity()
                                             != rcvr_ty
-                                            && self.tcx.at(span).type_of(*def_id).subst_identity()
+                                            && self
+                                                .tcx
+                                                .at(span)
+                                                .type_of(*def_id)
+                                                .instantiate_identity()
                                                 != rcvr_ty
                                     }
                                     (Mode::Path, false, _) => true,
@@ -1020,7 +1024,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             .map(|impl_item| {
                                 format!(
                                     "- `{}`",
-                                    self.tcx.at(span).type_of(*impl_item).subst_identity()
+                                    self.tcx.at(span).type_of(*impl_item).instantiate_identity()
                                 )
                             })
                             .collect::<Vec<_>>()
@@ -1199,7 +1203,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         None
                     };
 
-                    let impl_ty = self.tcx.at(span).type_of(impl_did).subst_identity();
+                    let impl_ty = self.tcx.at(span).type_of(impl_did).instantiate_identity();
 
                     let insertion = match self.tcx.impl_trait_ref(impl_did) {
                         None => String::new(),
@@ -1245,7 +1249,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             ty::AssocKind::Fn => self
                                 .tcx
                                 .fn_sig(item.def_id)
-                                .subst_identity()
+                                .instantiate_identity()
                                 .inputs()
                                 .skip_binder()
                                 .get(0)
@@ -1328,7 +1332,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // When the "method" is resolved through dereferencing, we really want the
             // original type that has the associated function for accurate suggestions.
             // (#61411)
-            let impl_ty = self.tcx.type_of(*impl_did).subst_identity();
+            let impl_ty = self.tcx.type_of(*impl_did).instantiate_identity();
             let target_ty = self
                 .autoderef(sugg_span, rcvr_ty)
                 .find(|(rcvr_ty, _)| {
@@ -1337,10 +1341,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 })
                 .map_or(impl_ty, |(ty, _)| ty)
                 .peel_refs();
-            if let ty::Adt(def, substs) = target_ty.kind() {
+            if let ty::Adt(def, args) = target_ty.kind() {
                 // If there are any inferred arguments, (`{integer}`), we should replace
                 // them with underscores to allow the compiler to infer them
-                let infer_substs = self.tcx.mk_substs_from_iter(substs.into_iter().map(|arg| {
+                let infer_args = self.tcx.mk_args_from_iter(args.into_iter().map(|arg| {
                     if !arg.is_suggestable(self.tcx, true) {
                         has_unsuggestable_args = true;
                         match arg.unpack() {
@@ -1370,7 +1374,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
                 }));
 
-                self.tcx.value_path_str_with_substs(def.did(), infer_substs)
+                self.tcx.value_path_str_with_args(def.did(), infer_args)
             } else {
                 self.ty_to_value_string(target_ty)
             }
@@ -1382,7 +1386,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 && let Some(assoc) = self.associated_value(*impl_did, item_name)
                 && assoc.kind == ty::AssocKind::Fn
             {
-                let sig = self.tcx.fn_sig(assoc.def_id).subst_identity();
+                let sig = self.tcx.fn_sig(assoc.def_id).instantiate_identity();
                 sig.inputs().skip_binder().get(0).and_then(|first| if first.peel_refs() == rcvr_ty.peel_refs() {
                     None
                 } else {
@@ -1447,11 +1451,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> bool {
         let tcx = self.tcx;
         let field_receiver = self.autoderef(span, rcvr_ty).find_map(|(ty, _)| match ty.kind() {
-            ty::Adt(def, substs) if !def.is_enum() => {
+            ty::Adt(def, args) if !def.is_enum() => {
                 let variant = &def.non_enum_variant();
                 tcx.find_field_index(item_name, variant).map(|index| {
                     let field = &variant.fields[index];
-                    let field_ty = field.ty(tcx, substs);
+                    let field_ty = field.ty(tcx, args);
                     (field, field_ty)
                 })
             }
@@ -1548,7 +1552,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     }
 
                     let range_def_id = self.tcx.require_lang_item(lang_item.unwrap(), None);
-                    let range_ty = self.tcx.type_of(range_def_id).subst(self.tcx, &[actual.into()]);
+                    let range_ty =
+                        self.tcx.type_of(range_def_id).instantiate(self.tcx, &[actual.into()]);
 
                     let pick = self.lookup_probe_for_diagnostic(
                         item_name,
@@ -1772,7 +1777,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         if let SelfSource::MethodCall(expr) = source
         && let mod_id = self.tcx.parent_module(expr.hir_id).to_def_id()
-        && let Some((fields, substs)) =
+        && let Some((fields, args)) =
             self.get_field_candidates_considering_privacy(span, actual, mod_id)
         {
             let call_expr = self.tcx.hir().expect_expr(self.tcx.hir().parent_id(expr.hir_id));
@@ -1807,7 +1812,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             })
                         },
                         candidate_field,
-                        substs,
+                        args,
                         vec![],
                         mod_id,
                     )
@@ -1850,7 +1855,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
         let call_expr = tcx.hir().expect_expr(tcx.hir().parent_id(expr.hir_id));
 
-        let ty::Adt(kind, substs) = actual.kind() else {
+        let ty::Adt(kind, args) = actual.kind() else {
             return;
         };
         match kind.adt_kind() {
@@ -1862,7 +1867,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         let [field] = &variant.fields.raw[..] else {
                             return None;
                         };
-                        let field_ty = field.ty(tcx, substs);
+                        let field_ty = field.ty(tcx, args);
 
                         // Skip `_`, since that'll just lead to ambiguity.
                         if self.resolve_vars_if_possible(field_ty).is_ty_var() {
@@ -1897,7 +1902,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
                 match &matching_variants[..] {
                     [(_, field, pick)] => {
-                        let self_ty = field.ty(tcx, substs);
+                        let self_ty = field.ty(tcx, args);
                         err.span_note(
                             tcx.def_span(pick.item.def_id),
                             format!("the method `{item_name}` exists on the type `{self_ty}`"),
@@ -1939,7 +1944,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Target wrapper types - types that wrap or pretend to wrap another type,
             // perhaps this inner type is meant to be called?
             ty::AdtKind::Struct | ty::AdtKind::Union => {
-                let [first] = ***substs else {
+                let [first] = ***args else {
                     return;
                 };
                 let ty::GenericArgKind::Type(ty) = first.unpack() else {
@@ -2234,7 +2239,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     // just changing the path.
                     && pick.item.fn_has_self_parameter
                     && let Some(self_ty) =
-                        self.tcx.fn_sig(pick.item.def_id).subst_identity().inputs().skip_binder().get(0)
+                        self.tcx.fn_sig(pick.item.def_id).instantiate_identity().inputs().skip_binder().get(0)
                     && self_ty.is_ref()
                 {
                     let suggested_path = match deref_ty.kind() {
@@ -2275,7 +2280,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /// Print out the type for use in value namespace.
     fn ty_to_value_string(&self, ty: Ty<'tcx>) -> String {
         match ty.kind() {
-            ty::Adt(def, substs) => self.tcx.def_path_str_with_substs(def.did(), substs),
+            ty::Adt(def, args) => self.tcx.def_path_str_with_args(def.did(), args),
             _ => self.ty_to_string(ty),
         }
     }
@@ -2772,7 +2777,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             self.tcx.impl_polarity(*imp_did) == ty::ImplPolarity::Negative
                         })
                         .any(|imp_did| {
-                            let imp = self.tcx.impl_trait_ref(imp_did).unwrap().subst_identity();
+                            let imp =
+                                self.tcx.impl_trait_ref(imp_did).unwrap().instantiate_identity();
                             let imp_simp =
                                 simplify_type(self.tcx, imp.self_ty(), TreatParams::ForLookup);
                             imp_simp.is_some_and(|s| s == simp_rcvr_ty)
diff --git a/compiler/rustc_hir_typeck/src/pat.rs b/compiler/rustc_hir_typeck/src/pat.rs
index 69c8cc8c59031..8bf95d4bf9a6c 100644
--- a/compiler/rustc_hir_typeck/src/pat.rs
+++ b/compiler/rustc_hir_typeck/src/pat.rs
@@ -1094,12 +1094,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if subpats.len() == variant.fields.len()
             || subpats.len() < variant.fields.len() && ddpos.as_opt_usize().is_some()
         {
-            let ty::Adt(_, substs) = pat_ty.kind() else {
+            let ty::Adt(_, args) = pat_ty.kind() else {
                 bug!("unexpected pattern type {:?}", pat_ty);
             };
             for (i, subpat) in subpats.iter().enumerate_and_adjust(variant.fields.len(), ddpos) {
                 let field = &variant.fields[FieldIdx::from_usize(i)];
-                let field_ty = self.field_ty(subpat.span, field, substs);
+                let field_ty = self.field_ty(subpat.span, field, args);
                 self.check_pat(subpat, field_ty, def_bm, ti);
 
                 self.tcx.check_stability(
@@ -1182,10 +1182,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`.
         let missing_parentheses = match (&expected.kind(), fields, had_err) {
             // #67037: only do this if we could successfully type-check the expected type against
-            // the tuple struct pattern. Otherwise the substs could get out of range on e.g.,
+            // the tuple struct pattern. Otherwise the args could get out of range on e.g.,
             // `let P() = U;` where `P != U` with `struct P<T>(T);`.
-            (ty::Adt(_, substs), [field], false) => {
-                let field_ty = self.field_ty(pat_span, field, substs);
+            (ty::Adt(_, args), [field], false) => {
+                let field_ty = self.field_ty(pat_span, field, args);
                 match field_ty.kind() {
                     ty::Tuple(fields) => fields.len() == subpats.len(),
                     _ => false,
@@ -1335,7 +1335,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> bool {
         let tcx = self.tcx;
 
-        let ty::Adt(adt, substs) = adt_ty.kind() else {
+        let ty::Adt(adt, args) = adt_ty.kind() else {
             span_bug!(pat.span, "struct pattern is not an ADT");
         };
 
@@ -1368,7 +1368,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                         .map(|(i, f)| {
                             self.write_field_index(field.hir_id, *i);
                             self.tcx.check_stability(f.did, Some(pat.hir_id), span, None);
-                            self.field_ty(span, f, substs)
+                            self.field_ty(span, f, args)
                         })
                         .unwrap_or_else(|| {
                             inexistent_fields.push(field);
@@ -1396,7 +1396,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 &inexistent_fields,
                 &mut unmentioned_fields,
                 variant,
-                substs,
+                args,
             ))
         } else {
             None
@@ -1566,7 +1566,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         inexistent_fields: &[&hir::PatField<'tcx>],
         unmentioned_fields: &mut Vec<(&'tcx ty::FieldDef, Ident)>,
         variant: &ty::VariantDef,
-        substs: &'tcx ty::List<ty::subst::GenericArg<'tcx>>,
+        args: &'tcx ty::List<ty::GenericArg<'tcx>>,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
         let tcx = self.tcx;
         let (field_names, t, plural) = if inexistent_fields.len() == 1 {
@@ -1636,7 +1636,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 self.field_ty(
                                     unmentioned_fields[0].1.span,
                                     unmentioned_fields[0].0,
-                                    substs,
+                                    args,
                                 ),
                             ) => {}
                         _ => {
diff --git a/compiler/rustc_hir_typeck/src/place_op.rs b/compiler/rustc_hir_typeck/src/place_op.rs
index fd43b475e3af4..1eb84eb163754 100644
--- a/compiler/rustc_hir_typeck/src/place_op.rs
+++ b/compiler/rustc_hir_typeck/src/place_op.rs
@@ -392,7 +392,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // We also could not use `expr_ty_adjusted` of index_expr because reborrowing
                 // during coercions can also cause type of index_expr to differ from `T`,
                 // which can potentially cause regionck failure (#74933).
-                Some(self.typeck_results.borrow().node_substs(expr.hir_id).type_at(1))
+                Some(self.typeck_results.borrow().node_args(expr.hir_id).type_at(1))
             }
         };
         let arg_tys = arg_ty.as_slice();
diff --git a/compiler/rustc_hir_typeck/src/upvar.rs b/compiler/rustc_hir_typeck/src/upvar.rs
index a3838275dc5cd..f77a4d16b5f7c 100644
--- a/compiler/rustc_hir_typeck/src/upvar.rs
+++ b/compiler/rustc_hir_typeck/src/upvar.rs
@@ -42,7 +42,7 @@ use rustc_infer::infer::UpvarRegion;
 use rustc_middle::hir::place::{Place, PlaceBase, PlaceWithHirId, Projection, ProjectionKind};
 use rustc_middle::mir::FakeReadCause;
 use rustc_middle::ty::{
-    self, ClosureSizeProfileData, Ty, TyCtxt, TypeckResults, UpvarCapture, UpvarSubsts,
+    self, ClosureSizeProfileData, Ty, TyCtxt, TypeckResults, UpvarArgs, UpvarCapture,
 };
 use rustc_session::lint;
 use rustc_span::sym;
@@ -169,9 +169,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) {
         // Extract the type of the closure.
         let ty = self.node_ty(closure_hir_id);
-        let (closure_def_id, substs) = match *ty.kind() {
-            ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs)),
-            ty::Generator(def_id, substs, _) => (def_id, UpvarSubsts::Generator(substs)),
+        let (closure_def_id, args) = match *ty.kind() {
+            ty::Closure(def_id, args) => (def_id, UpvarArgs::Closure(args)),
+            ty::Generator(def_id, args, _) => (def_id, UpvarArgs::Generator(args)),
             ty::Error(_) => {
                 // #51714: skip analysis when we have already encountered type errors
                 return;
@@ -187,8 +187,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         };
         let closure_def_id = closure_def_id.expect_local();
 
-        let infer_kind = if let UpvarSubsts::Closure(closure_substs) = substs {
-            self.closure_kind(closure_substs).is_none().then_some(closure_substs)
+        let infer_kind = if let UpvarArgs::Closure(closure_args) = args {
+            self.closure_kind(closure_args).is_none().then_some(closure_args)
         } else {
             None
         };
@@ -257,10 +257,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let before_feature_tys = self.final_upvar_tys(closure_def_id);
 
-        if let Some(closure_substs) = infer_kind {
+        if let Some(closure_args) = infer_kind {
             // Unify the (as yet unbound) type variable in the closure
-            // substs with the kind we inferred.
-            let closure_kind_ty = closure_substs.as_closure().kind_ty();
+            // args with the kind we inferred.
+            let closure_kind_ty = closure_args.as_closure().kind_ty();
             self.demand_eqtype(span, closure_kind.to_ty(self.tcx), closure_kind_ty);
 
             // If we have an origin, store it.
@@ -295,14 +295,14 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Equate the type variables for the upvars with the actual types.
         let final_upvar_tys = self.final_upvar_tys(closure_def_id);
         debug!(
-            "analyze_closure: id={:?} substs={:?} final_upvar_tys={:?}",
-            closure_hir_id, substs, final_upvar_tys
+            "analyze_closure: id={:?} args={:?} final_upvar_tys={:?}",
+            closure_hir_id, args, final_upvar_tys
         );
 
         // Build a tuple (U0..Un) of the final upvar types U0..Un
         // and unify the upvar tuple type in the closure with it:
         let final_tupled_upvars_type = Ty::new_tup(self.tcx, &final_upvar_tys);
-        self.demand_suptype(span, substs.tupled_upvars_ty(), final_tupled_upvars_type);
+        self.demand_suptype(span, args.tupled_upvars_ty(), final_tupled_upvars_type);
 
         let fake_reads = delegate
             .fake_reads
@@ -1383,7 +1383,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ty::Ref(..) => unreachable!(),
             ty::RawPtr(..) => unreachable!(),
 
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 // Multi-variant enums are captured in entirety,
                 // which would've been handled in the case of single empty slice in `captured_by_move_projs`.
                 assert_eq!(def.variants().len(), 1);
@@ -1410,7 +1410,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             })
                             .collect();
 
-                        let after_field_ty = field.ty(self.tcx, substs);
+                        let after_field_ty = field.ty(self.tcx, args);
                         self.has_significant_drop_outside_of_captures(
                             closure_def_id,
                             closure_span,
diff --git a/compiler/rustc_hir_typeck/src/writeback.rs b/compiler/rustc_hir_typeck/src/writeback.rs
index fab6090ff195a..cf6c7f70de3f1 100644
--- a/compiler/rustc_hir_typeck/src/writeback.rs
+++ b/compiler/rustc_hir_typeck/src/writeback.rs
@@ -40,9 +40,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // This attribute causes us to dump some writeback information
         // in the form of errors, which is used for unit tests.
-        let rustc_dump_user_substs = self.tcx.has_attr(item_def_id, sym::rustc_dump_user_substs);
+        let rustc_dump_user_args = self.tcx.has_attr(item_def_id, sym::rustc_dump_user_args);
 
-        let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_substs);
+        let mut wbcx = WritebackCx::new(self, body, rustc_dump_user_args);
         for param in body.params {
             wbcx.visit_node_id(param.pat.span, param.hir_id);
         }
@@ -100,14 +100,14 @@ struct WritebackCx<'cx, 'tcx> {
 
     body: &'tcx hir::Body<'tcx>,
 
-    rustc_dump_user_substs: bool,
+    rustc_dump_user_args: bool,
 }
 
 impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
     fn new(
         fcx: &'cx FnCtxt<'cx, 'tcx>,
         body: &'tcx hir::Body<'tcx>,
-        rustc_dump_user_substs: bool,
+        rustc_dump_user_args: bool,
     ) -> WritebackCx<'cx, 'tcx> {
         let owner = body.id().hir_id.owner;
 
@@ -115,7 +115,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
             fcx,
             typeck_results: ty::TypeckResults::new(owner),
             body,
-            rustc_dump_user_substs,
+            rustc_dump_user_args,
         };
 
         // HACK: We specifically don't want the (opaque) error from tainting our
@@ -152,7 +152,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
                 if inner_ty.is_scalar() {
                     self.typeck_results.type_dependent_defs_mut().remove(e.hir_id);
-                    self.typeck_results.node_substs_mut().remove(e.hir_id);
+                    self.typeck_results.node_args_mut().remove(e.hir_id);
                 }
             }
             hir::ExprKind::Binary(ref op, lhs, rhs) | hir::ExprKind::AssignOp(ref op, lhs, rhs) => {
@@ -161,7 +161,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
 
                 if lhs_ty.is_scalar() && rhs_ty.is_scalar() {
                     self.typeck_results.type_dependent_defs_mut().remove(e.hir_id);
-                    self.typeck_results.node_substs_mut().remove(e.hir_id);
+                    self.typeck_results.node_args_mut().remove(e.hir_id);
 
                     match e.kind {
                         hir::ExprKind::Binary(..) => {
@@ -239,7 +239,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                 if self.is_builtin_index(e, base_ty_inner, index_ty) {
                     // Remove the method call record
                     self.typeck_results.type_dependent_defs_mut().remove(e.hir_id);
-                    self.typeck_results.node_substs_mut().remove(e.hir_id);
+                    self.typeck_results.node_args_mut().remove(e.hir_id);
 
                     if let Some(a) = self.typeck_results.adjustments_mut().get_mut(base.hir_id) {
                         // Discard the need for a mutable borrow
@@ -477,7 +477,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
         let common_hir_owner = fcx_typeck_results.hir_owner;
 
-        if self.rustc_dump_user_substs {
+        if self.rustc_dump_user_args {
             let sorted_user_provided_types =
                 fcx_typeck_results.user_provided_types().items_in_stable_order();
 
@@ -485,7 +485,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
             for (local_id, c_ty) in sorted_user_provided_types {
                 let hir_id = hir::HirId { owner: common_hir_owner, local_id };
 
-                if let ty::UserType::TypeOf(_, user_substs) = c_ty.value {
+                if let ty::UserType::TypeOf(_, user_args) = c_ty.value {
                     // This is a unit-testing mechanism.
                     let span = self.tcx().hir().span(hir_id);
                     // We need to buffer the errors in order to guarantee a consistent
@@ -493,7 +493,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
                     let err = self
                         .tcx()
                         .sess
-                        .struct_span_err(span, format!("user substs: {:?}", user_substs));
+                        .struct_span_err(span, format!("user args: {:?}", user_args));
                     err.buffer(&mut errors_buffer);
                 }
             }
@@ -631,11 +631,11 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         debug!(?n_ty);
 
         // Resolve any substitutions
-        if let Some(substs) = self.fcx.typeck_results.borrow().node_substs_opt(hir_id) {
-            let substs = self.resolve(substs, &span);
-            debug!("write_substs_to_tcx({:?}, {:?})", hir_id, substs);
-            assert!(!substs.has_infer() && !substs.has_placeholders());
-            self.typeck_results.node_substs_mut().insert(hir_id, substs);
+        if let Some(args) = self.fcx.typeck_results.borrow().node_args_opt(hir_id) {
+            let args = self.resolve(args, &span);
+            debug!("write_args_to_tcx({:?}, {:?})", hir_id, args);
+            assert!(!args.has_infer() && !args.has_placeholders());
+            self.typeck_results.node_args_mut().insert(hir_id, args);
         }
     }
 
diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index e57532e2de20a..1fd5d2adf8098 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -11,7 +11,7 @@ use crate::infer::canonical::{
 use crate::infer::InferCtxt;
 use rustc_middle::ty::flags::FlagComputation;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use rustc_middle::ty::subst::GenericArg;
+use rustc_middle::ty::GenericArg;
 use rustc_middle::ty::{self, BoundVar, InferConst, List, Ty, TyCtxt, TypeFlags, TypeVisitableExt};
 use std::sync::atomic::Ordering;
 
diff --git a/compiler/rustc_infer/src/infer/canonical/mod.rs b/compiler/rustc_infer/src/infer/canonical/mod.rs
index f765c41a36714..8ca2e40304345 100644
--- a/compiler/rustc_infer/src/infer/canonical/mod.rs
+++ b/compiler/rustc_infer/src/infer/canonical/mod.rs
@@ -25,7 +25,7 @@ use crate::infer::{ConstVariableOrigin, ConstVariableOriginKind};
 use crate::infer::{InferCtxt, RegionVariableOrigin, TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_index::IndexVec;
 use rustc_middle::ty::fold::TypeFoldable;
-use rustc_middle::ty::subst::GenericArg;
+use rustc_middle::ty::GenericArg;
 use rustc_middle::ty::{self, List, Ty, TyCtxt};
 use rustc_span::source_map::Span;
 
@@ -88,7 +88,7 @@ impl<'tcx> InferCtxt<'tcx> {
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> CanonicalVarValues<'tcx> {
         CanonicalVarValues {
-            var_values: self.tcx.mk_substs_from_iter(
+            var_values: self.tcx.mk_args_from_iter(
                 variables
                     .iter()
                     .map(|info| self.instantiate_canonical_var(span, info, &universe_map)),
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs
index 9c3ab04deae9d..ed101082130c6 100644
--- a/compiler/rustc_infer/src/infer/canonical/query_response.rs
+++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs
@@ -25,8 +25,8 @@ use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::relate::TypeRelation;
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, BoundVar, ToPredicate, Ty, TyCtxt};
+use rustc_middle::ty::{GenericArg, GenericArgKind};
 use rustc_span::{Span, Symbol};
 use std::fmt::Debug;
 use std::iter;
@@ -484,7 +484,7 @@ impl<'tcx> InferCtxt<'tcx> {
         // given variable in the loop above, use that. Otherwise, use
         // a fresh inference variable.
         let result_subst = CanonicalVarValues {
-            var_values: self.tcx.mk_substs_from_iter(
+            var_values: self.tcx.mk_args_from_iter(
                 query_response.variables.iter().enumerate().map(|(index, info)| {
                     if info.is_existential() {
                         match opt_values[BoundVar::new(index)] {
@@ -520,7 +520,7 @@ impl<'tcx> InferCtxt<'tcx> {
                 self.at(cause, param_env)
                     .eq(
                         DefineOpaqueTypes::Yes,
-                        Ty::new_opaque(self.tcx, a.def_id.to_def_id(), a.substs),
+                        Ty::new_opaque(self.tcx, a.def_id.to_def_id(), a.args),
                         b,
                     )?
                     .obligations,
diff --git a/compiler/rustc_infer/src/infer/canonical/substitute.rs b/compiler/rustc_infer/src/infer/canonical/substitute.rs
index cac3b40725158..f368b30fbd193 100644
--- a/compiler/rustc_infer/src/infer/canonical/substitute.rs
+++ b/compiler/rustc_infer/src/infer/canonical/substitute.rs
@@ -8,7 +8,7 @@
 
 use crate::infer::canonical::{Canonical, CanonicalVarValues};
 use rustc_middle::ty::fold::{FnMutDelegate, TypeFoldable};
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, TyCtxt};
 
 /// FIXME(-Ztrait-solver=next): This or public because it is shared with the
diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index a9cdb8c51cf7c..38f8ad744a6ad 100644
--- a/compiler/rustc_infer/src/infer/combine.rs
+++ b/compiler/rustc_infer/src/infer/combine.rs
@@ -254,7 +254,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// in `ct` with `ct` itself.
     ///
     /// This is especially important as unevaluated consts use their parents generics.
-    /// They therefore often contain unused substs, making these errors far more likely.
+    /// They therefore often contain unused args, making these errors far more likely.
     ///
     /// A good example of this is the following:
     ///
@@ -272,12 +272,12 @@ impl<'tcx> InferCtxt<'tcx> {
     /// ```
     ///
     /// Here `3 + 4` ends up as `ConstKind::Unevaluated` which uses the generics
-    /// of `fn bind` (meaning that its substs contain `N`).
+    /// of `fn bind` (meaning that its args contain `N`).
     ///
     /// `bind(arr)` now infers that the type of `arr` must be `[u8; N]`.
     /// The assignment `arr = bind(arr)` now tries to equate `N` with `3 + 4`.
     ///
-    /// As `3 + 4` contains `N` in its substs, this must not succeed.
+    /// As `3 + 4` contains `N` in its args, this must not succeed.
     ///
     /// See `tests/ui/const-generics/occurs-check/` for more examples where this is relevant.
     #[instrument(level = "debug", skip(self))]
diff --git a/compiler/rustc_infer/src/infer/equate.rs b/compiler/rustc_infer/src/infer/equate.rs
index 495c250a77d07..1dbab48fd6ceb 100644
--- a/compiler/rustc_infer/src/infer/equate.rs
+++ b/compiler/rustc_infer/src/infer/equate.rs
@@ -5,7 +5,7 @@ use super::combine::{CombineFields, ObligationEmittingRelation};
 use super::Subtype;
 
 use rustc_middle::ty::relate::{self, Relate, RelateResult, TypeRelation};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::TyVar;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
 
@@ -43,12 +43,12 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
         self.a_is_expected
     }
 
-    fn relate_item_substs(
+    fn relate_item_args(
         &mut self,
         _item_def_id: DefId,
-        a_subst: SubstsRef<'tcx>,
-        b_subst: SubstsRef<'tcx>,
-    ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
+        a_arg: GenericArgsRef<'tcx>,
+        b_arg: GenericArgsRef<'tcx>,
+    ) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
         // N.B., once we are equating types, we don't care about
         // variance, so don't try to lookup the variance here. This
         // also avoids some cycles (e.g., #41849) since looking up
@@ -56,7 +56,7 @@ impl<'tcx> TypeRelation<'tcx> for Equate<'_, '_, 'tcx> {
         // performing trait matching (which then performs equality
         // unification).
 
-        relate::relate_substs(self, a_subst, b_subst)
+        relate::relate_args(self, a_arg, b_arg)
     }
 
     fn relate_with_variance<T: Relate<'tcx>>(
diff --git a/compiler/rustc_infer/src/infer/error_reporting/mod.rs b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
index 37249b62e8bfe..bf46f9881d47b 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/mod.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/mod.rs
@@ -315,7 +315,7 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
     let mut err = tcx.sess.create_err(errors::OpaqueCapturesLifetime {
         span,
-        opaque_ty: Ty::new_opaque(tcx, opaque_ty_key.def_id.to_def_id(), opaque_ty_key.substs),
+        opaque_ty: Ty::new_opaque(tcx, opaque_ty_key.def_id.to_def_id(), opaque_ty_key.args),
         opaque_ty_span: tcx.def_span(opaque_ty_key.def_id),
     });
 
@@ -386,16 +386,16 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
 
 impl<'tcx> InferCtxt<'tcx> {
     pub fn get_impl_future_output_ty(&self, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
-        let (def_id, substs) = match *ty.kind() {
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+        let (def_id, args) = match *ty.kind() {
+            ty::Alias(_, ty::AliasTy { def_id, args, .. })
                 if matches!(self.tcx.def_kind(def_id), DefKind::OpaqueTy) =>
             {
-                (def_id, substs)
+                (def_id, args)
             }
-            ty::Alias(_, ty::AliasTy { def_id, substs, .. })
+            ty::Alias(_, ty::AliasTy { def_id, args, .. })
                 if self.tcx.is_impl_trait_in_trait(def_id) =>
             {
-                (def_id, substs)
+                (def_id, args)
             }
             _ => return None,
         };
@@ -403,7 +403,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let future_trait = self.tcx.require_lang_item(LangItem::Future, None);
         let item_def_id = self.tcx.associated_item_def_ids(future_trait)[0];
 
-        self.tcx.explicit_item_bounds(def_id).subst_iter_copied(self.tcx, substs).find_map(
+        self.tcx.explicit_item_bounds(def_id).arg_iter_copied(self.tcx, args).find_map(
             |(predicate, _)| {
                 predicate
                     .kind()
@@ -573,7 +573,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         use hir::def_id::CrateNum;
         use rustc_hir::definitions::DisambiguatedDefPathData;
         use ty::print::Printer;
-        use ty::subst::GenericArg;
+        use ty::GenericArg;
 
         struct AbsolutePathPrinter<'tcx> {
             tcx: TyCtxt<'tcx>,
@@ -711,10 +711,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 {
                     // don't show type `_`
                     if span.desugaring_kind() == Some(DesugaringKind::ForLoop)
-                        && let ty::Adt(def, substs) = ty.kind()
+                        && let ty::Adt(def, args) = ty.kind()
                         && Some(def.did()) == self.tcx.get_diagnostic_item(sym::Option)
                     {
-                        err.span_label(span, format!("this is an iterator with items of type `{}`", substs.type_at(0)));
+                        err.span_label(span, format!("this is an iterator with items of type `{}`", args.type_at(0)));
                     } else {
                     err.span_label(span, format!("this expression has type `{}`", ty));
                 }
@@ -908,7 +908,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         value: &mut DiagnosticStyledString,
         other_value: &mut DiagnosticStyledString,
         name: String,
-        sub: ty::subst::SubstsRef<'tcx>,
+        sub: ty::GenericArgsRef<'tcx>,
         pos: usize,
         other_ty: Ty<'tcx>,
     ) {
@@ -986,9 +986,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         other_path: String,
         other_ty: Ty<'tcx>,
     ) -> Option<()> {
-        // FIXME/HACK: Go back to `SubstsRef` to use its inherent methods,
+        // FIXME/HACK: Go back to `GenericArgsRef` to use its inherent methods,
         // ideally that shouldn't be necessary.
-        let sub = self.tcx.mk_substs(sub);
+        let sub = self.tcx.mk_args(sub);
         for (i, ta) in sub.types().enumerate() {
             if ta == other_ty {
                 self.highlight_outer(&mut t1_out, &mut t2_out, path, sub, i, other_ty);
@@ -1180,9 +1180,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 let did1 = def1.did();
                 let did2 = def2.did();
                 let sub_no_defaults_1 =
-                    self.tcx.generics_of(did1).own_substs_no_defaults(self.tcx, sub1);
+                    self.tcx.generics_of(did1).own_args_no_defaults(self.tcx, sub1);
                 let sub_no_defaults_2 =
-                    self.tcx.generics_of(did2).own_substs_no_defaults(self.tcx, sub2);
+                    self.tcx.generics_of(did2).own_args_no_defaults(self.tcx, sub2);
                 let mut values = (DiagnosticStyledString::new(), DiagnosticStyledString::new());
                 let path1 = self.tcx.def_path_str(did1);
                 let path2 = self.tcx.def_path_str(did2);
@@ -1403,11 +1403,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             }
 
             // When encountering tuples of the same size, highlight only the differing types
-            (&ty::Tuple(substs1), &ty::Tuple(substs2)) if substs1.len() == substs2.len() => {
+            (&ty::Tuple(args1), &ty::Tuple(args2)) if args1.len() == args2.len() => {
                 let mut values =
                     (DiagnosticStyledString::normal("("), DiagnosticStyledString::normal("("));
-                let len = substs1.len();
-                for (i, (left, right)) in substs1.iter().zip(substs2).enumerate() {
+                let len = args1.len();
+                for (i, (left, right)) in args1.iter().zip(args2).enumerate() {
                     let (x1, x2) = self.cmp(left, right);
                     (values.0).0.extend(x1.0);
                     (values.1).0.extend(x2.0);
@@ -1423,35 +1423,34 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 values
             }
 
-            (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
-                let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
-                let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
+            (ty::FnDef(did1, args1), ty::FnDef(did2, args2)) => {
+                let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
+                let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
                 let mut values = self.cmp_fn_sig(&sig1, &sig2);
-                let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did1, substs1));
-                let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_substs(*did2, substs2));
+                let path1 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did1, args1));
+                let path2 = format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2));
                 let same_path = path1 == path2;
                 values.0.push(path1, !same_path);
                 values.1.push(path2, !same_path);
                 values
             }
 
-            (ty::FnDef(did1, substs1), ty::FnPtr(sig2)) => {
-                let sig1 = self.tcx.fn_sig(*did1).subst(self.tcx, substs1);
+            (ty::FnDef(did1, args1), ty::FnPtr(sig2)) => {
+                let sig1 = self.tcx.fn_sig(*did1).instantiate(self.tcx, args1);
                 let mut values = self.cmp_fn_sig(&sig1, sig2);
                 values.0.push_highlighted(format!(
                     " {{{}}}",
-                    self.tcx.def_path_str_with_substs(*did1, substs1)
+                    self.tcx.def_path_str_with_args(*did1, args1)
                 ));
                 values
             }
 
-            (ty::FnPtr(sig1), ty::FnDef(did2, substs2)) => {
-                let sig2 = self.tcx.fn_sig(*did2).subst(self.tcx, substs2);
+            (ty::FnPtr(sig1), ty::FnDef(did2, args2)) => {
+                let sig2 = self.tcx.fn_sig(*did2).instantiate(self.tcx, args2);
                 let mut values = self.cmp_fn_sig(sig1, &sig2);
-                values.1.push_normal(format!(
-                    " {{{}}}",
-                    self.tcx.def_path_str_with_substs(*did2, substs2)
-                ));
+                values
+                    .1
+                    .push_normal(format!(" {{{}}}", self.tcx.def_path_str_with_args(*did2, args2)));
                 values
             }
 
diff --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index d192624b17e1a..b4d8205fd6d6d 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
@@ -18,7 +18,7 @@ use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKin
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
 use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter, Print, Printer};
 use rustc_middle::ty::{self, InferConst};
-use rustc_middle::ty::{GenericArg, GenericArgKind, SubstsRef};
+use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_middle::ty::{IsSuggestable, Ty, TyCtxt, TypeckResults};
 use rustc_span::symbol::{kw, sym, Ident};
 use rustc_span::{BytePos, Span};
@@ -226,8 +226,8 @@ fn ty_to_string<'tcx>(
 /// something users are familiar with. Directly printing the `fn_sig` of closures also
 /// doesn't work as they actually use the "rust-call" API.
 fn closure_as_fn_str<'tcx>(infcx: &InferCtxt<'tcx>, ty: Ty<'tcx>) -> String {
-    let ty::Closure(_, substs) = ty.kind() else { unreachable!() };
-    let fn_sig = substs.as_closure().sig();
+    let ty::Closure(_, args) = ty.kind() else { unreachable!() };
+    let fn_sig = args.as_closure().sig();
     let args = fn_sig
         .inputs()
         .skip_binder()
@@ -524,9 +524,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     });
                 }
             }
-            InferSourceKind::FullyQualifiedMethodCall { receiver, successor, substs, def_id } => {
+            InferSourceKind::FullyQualifiedMethodCall { receiver, successor, args, def_id } => {
                 let printer = fmt_printer(self, Namespace::ValueNS);
-                let def_path = printer.print_def_path(def_id, substs).unwrap().into_buffer();
+                let def_path = printer.print_def_path(def_id, args).unwrap().into_buffer();
 
                 // We only care about whether we have to add `&` or `&mut ` for now.
                 // This is the case if the last adjustment is a borrow and the
@@ -659,7 +659,7 @@ enum InferSourceKind<'tcx> {
         /// If the method has other arguments, this is ", " and the start of the first argument,
         /// while for methods without arguments this is ")" and the end of the method call.
         successor: (&'static str, BytePos),
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         def_id: DefId,
     },
     ClosureReturn {
@@ -710,7 +710,7 @@ impl<'tcx> InferSourceKind<'tcx> {
 #[derive(Debug)]
 struct InsertableGenericArgs<'tcx> {
     insert_span: Span,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     generics_def_id: DefId,
     def_id: DefId,
     have_turbofish: bool,
@@ -774,11 +774,11 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                     ty::Closure(..) => 1000,
                     ty::FnDef(..) => 150,
                     ty::FnPtr(..) => 30,
-                    ty::Adt(def, substs) => {
+                    ty::Adt(def, args) => {
                         5 + self
                             .tcx
                             .generics_of(def.did())
-                            .own_substs_no_defaults(self.tcx, substs)
+                            .own_args_no_defaults(self.tcx, args)
                             .iter()
                             .map(|&arg| self.arg_cost(arg))
                             .sum::<usize>()
@@ -805,8 +805,8 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                 };
                 variant_cost + generic_args.iter().map(|&arg| ctx.arg_cost(arg)).sum::<usize>()
             }
-            InferSourceKind::FullyQualifiedMethodCall { substs, .. } => {
-                20 + substs.iter().map(|arg| ctx.arg_cost(arg)).sum::<usize>()
+            InferSourceKind::FullyQualifiedMethodCall { args, .. } => {
+                20 + args.iter().map(|arg| ctx.arg_cost(arg)).sum::<usize>()
             }
             InferSourceKind::ClosureReturn { ty, should_wrap_expr, .. } => {
                 30 + ctx.ty_cost(ty) + if should_wrap_expr.is_some() { 10 } else { 0 }
@@ -840,9 +840,9 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         }
     }
 
-    fn node_substs_opt(&self, hir_id: HirId) -> Option<SubstsRef<'tcx>> {
-        let substs = self.typeck_results.node_substs_opt(hir_id);
-        self.infcx.resolve_vars_if_possible(substs)
+    fn node_args_opt(&self, hir_id: HirId) -> Option<GenericArgsRef<'tcx>> {
+        let args = self.typeck_results.node_args_opt(hir_id);
+        self.infcx.resolve_vars_if_possible(args)
     }
 
     fn opt_node_type(&self, hir_id: HirId) -> Option<Ty<'tcx>> {
@@ -923,15 +923,15 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         false
     }
 
-    fn expr_inferred_subst_iter(
+    fn expr_inferred_arg_iter(
         &self,
         expr: &'tcx hir::Expr<'tcx>,
     ) -> Box<dyn Iterator<Item = InsertableGenericArgs<'tcx>> + 'a> {
         let tcx = self.infcx.tcx;
         match expr.kind {
             hir::ExprKind::Path(ref path) => {
-                if let Some(substs) = self.node_substs_opt(expr.hir_id) {
-                    return self.path_inferred_subst_iter(expr.hir_id, substs, path);
+                if let Some(args) = self.node_args_opt(expr.hir_id) {
+                    return self.path_inferred_arg_iter(expr.hir_id, args, path);
                 }
             }
             // FIXME(#98711): Ideally we would also deal with type relative
@@ -943,7 +943,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
             // However, the `type_dependent_def_id` for `Self::Output` in an
             // impl is currently the `DefId` of `Output` in the trait definition
             // which makes this somewhat difficult and prevents us from just
-            // using `self.path_inferred_subst_iter` here.
+            // using `self.path_inferred_arg_iter` here.
             hir::ExprKind::Struct(&hir::QPath::Resolved(_self_ty, path), _, _)
             // FIXME(TaKO8Ki): Ideally we should support this. For that
             // we have to map back from the self type to the
@@ -953,9 +953,9 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
             // a example.
             if !matches!(path.res, Res::Def(DefKind::TyAlias, _)) => {
                 if let Some(ty) = self.opt_node_type(expr.hir_id)
-                    && let ty::Adt(_, substs) = ty.kind()
+                    && let ty::Adt(_, args) = ty.kind()
                 {
-                    return Box::new(self.resolved_path_inferred_subst_iter(path, substs));
+                    return Box::new(self.resolved_path_inferred_arg_iter(path, args));
                 }
             }
             hir::ExprKind::MethodCall(segment, ..) => {
@@ -965,12 +965,12 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                         if generics.has_impl_trait() {
                             None?
                         }
-                        let substs = self.node_substs_opt(expr.hir_id)?;
+                        let args = self.node_args_opt(expr.hir_id)?;
                         let span = tcx.hir().span(segment.hir_id);
                         let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                         InsertableGenericArgs {
                             insert_span,
-                            substs,
+                            args,
                             generics_def_id: def_id,
                             def_id,
                             have_turbofish: false,
@@ -985,10 +985,10 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
         Box::new(iter::empty())
     }
 
-    fn resolved_path_inferred_subst_iter(
+    fn resolved_path_inferred_arg_iter(
         &self,
         path: &'tcx hir::Path<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> impl Iterator<Item = InsertableGenericArgs<'tcx>> + 'a {
         let tcx = self.infcx.tcx;
         let have_turbofish = path.segments.iter().any(|segment| {
@@ -1009,7 +1009,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                 path.segments.last().unwrap().ident.span.shrink_to_hi().with_hi(path.span.hi());
             InsertableGenericArgs {
                 insert_span,
-                substs,
+                args,
                 generics_def_id,
                 def_id: path.res.def_id(),
                 have_turbofish,
@@ -1029,7 +1029,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                 let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                 Some(InsertableGenericArgs {
                     insert_span,
-                    substs,
+                    args,
                     generics_def_id,
                     def_id: res.def_id(),
                     have_turbofish,
@@ -1038,16 +1038,16 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
             .chain(last_segment_using_path_data)
     }
 
-    fn path_inferred_subst_iter(
+    fn path_inferred_arg_iter(
         &self,
         hir_id: HirId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         qpath: &'tcx hir::QPath<'tcx>,
     ) -> Box<dyn Iterator<Item = InsertableGenericArgs<'tcx>> + 'a> {
         let tcx = self.infcx.tcx;
         match qpath {
             hir::QPath::Resolved(_self_ty, path) => {
-                Box::new(self.resolved_path_inferred_subst_iter(path, substs))
+                Box::new(self.resolved_path_inferred_arg_iter(path, args))
             }
             hir::QPath::TypeRelative(ty, segment) => {
                 let Some(def_id) = self.typeck_results.type_dependent_def_id(hir_id) else {
@@ -1063,7 +1063,7 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                     let insert_span = segment.ident.span.shrink_to_hi().with_hi(span.hi());
                     InsertableGenericArgs {
                         insert_span,
-                        substs,
+                        args,
                         generics_def_id: def_id,
                         def_id,
                         have_turbofish: false,
@@ -1072,10 +1072,10 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
 
                 let parent_def_id = generics.parent.unwrap();
                 if let DefKind::Impl { .. } = tcx.def_kind(parent_def_id) {
-                    let parent_ty = tcx.type_of(parent_def_id).subst(tcx, substs);
+                    let parent_ty = tcx.type_of(parent_def_id).instantiate(tcx, args);
                     match (parent_ty.kind(), &ty.kind) {
                         (
-                            ty::Adt(def, substs),
+                            ty::Adt(def, args),
                             hir::TyKind::Path(hir::QPath::Resolved(_self_ty, path)),
                         ) => {
                             if tcx.res_generics_def_id(path.res) != Some(def.did()) {
@@ -1092,14 +1092,13 @@ impl<'a, 'tcx> FindInferSourceVisitor<'a, 'tcx> {
                                     // so there's nothing for us to do here.
                                     Res::SelfTyParam { .. } | Res::SelfTyAlias { .. } => {}
                                     _ => warn!(
-                                        "unexpected path: def={:?} substs={:?} path={:?}",
-                                        def, substs, path,
+                                        "unexpected path: def={:?} args={:?} path={:?}",
+                                        def, args, path,
                                     ),
                                 }
                             } else {
                                 return Box::new(
-                                    self.resolved_path_inferred_subst_iter(path, substs)
-                                        .chain(segment),
+                                    self.resolved_path_inferred_arg_iter(path, args).chain(segment),
                                 );
                             }
                         }
@@ -1187,27 +1186,27 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
             _ => intravisit::walk_expr(self, expr),
         }
 
-        for args in self.expr_inferred_subst_iter(expr) {
+        for args in self.expr_inferred_arg_iter(expr) {
             debug!(?args);
             let InsertableGenericArgs {
                 insert_span,
-                substs,
+                args,
                 generics_def_id,
                 def_id,
                 have_turbofish,
             } = args;
             let generics = tcx.generics_of(generics_def_id);
             if let Some(mut argument_index) = generics
-                .own_substs(substs)
+                .own_args(args)
                 .iter()
                 .position(|&arg| self.generic_arg_contains_target(arg))
             {
                 if generics.parent.is_none() && generics.has_self {
                     argument_index += 1;
                 }
-                let substs = self.infcx.resolve_vars_if_possible(substs);
-                let generic_args = &generics.own_substs_no_defaults(tcx, substs)
-                    [generics.own_counts().lifetimes..];
+                let args = self.infcx.resolve_vars_if_possible(args);
+                let generic_args =
+                    &generics.own_args_no_defaults(tcx, args)[generics.own_counts().lifetimes..];
                 let span = match expr.kind {
                     ExprKind::MethodCall(path, ..) => path.ident.span,
                     _ => expr.span,
@@ -1230,10 +1229,10 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
         if let Some(node_ty) = self.opt_node_type(expr.hir_id) {
             if let (
                 &ExprKind::Closure(&Closure { fn_decl, body, fn_decl_span, .. }),
-                ty::Closure(_, substs),
+                ty::Closure(_, args),
             ) = (&expr.kind, node_ty.kind())
             {
-                let output = substs.as_closure().sig().output().skip_binder();
+                let output = args.as_closure().sig().output().skip_binder();
                 if self.generic_arg_contains_target(output.into()) {
                     let body = self.infcx.tcx.hir().body(body);
                     let should_wrap_expr = if matches!(body.value.kind, ExprKind::Block(..)) {
@@ -1259,22 +1258,22 @@ impl<'a, 'tcx> Visitor<'tcx> for FindInferSourceVisitor<'a, 'tcx> {
             })
             .any(|generics| generics.has_impl_trait())
         };
-        if let ExprKind::MethodCall(path, receiver, args, span) = expr.kind
-            && let Some(substs) = self.node_substs_opt(expr.hir_id)
-            && substs.iter().any(|arg| self.generic_arg_contains_target(arg))
+        if let ExprKind::MethodCall(path, receiver, method_args, span) = expr.kind
+            && let Some(args) = self.node_args_opt(expr.hir_id)
+            && args.iter().any(|arg| self.generic_arg_contains_target(arg))
             && let Some(def_id) = self.typeck_results.type_dependent_def_id(expr.hir_id)
             && self.infcx.tcx.trait_of_item(def_id).is_some()
             && !has_impl_trait(def_id)
         {
             let successor =
-                args.get(0).map_or_else(|| (")", span.hi()), |arg| (", ", arg.span.lo()));
-            let substs = self.infcx.resolve_vars_if_possible(substs);
+                method_args.get(0).map_or_else(|| (")", span.hi()), |arg| (", ", arg.span.lo()));
+            let args = self.infcx.resolve_vars_if_possible(args);
             self.update_infer_source(InferSource {
                 span: path.ident.span,
                 kind: InferSourceKind::FullyQualifiedMethodCall {
                     receiver,
                     successor,
-                    substs,
+                    args,
                     def_id,
                 }
             })
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs
index d46dd8f326830..6901955af65fd 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/mismatched_static_lifetime.rs
@@ -74,7 +74,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             };
 
             // Next, let's figure out the set of trait objects with implicit static bounds
-            let ty = self.tcx().type_of(*impl_def_id).subst_identity();
+            let ty = self.tcx().type_of(*impl_def_id).instantiate_identity();
             let mut v = super::static_impl_trait::TraitObjectVisitor(FxIndexSet::default());
             v.visit_ty(ty);
             let mut traits = vec![];
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
index 0b3bc1ce6b38d..f903f7a49ef85 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/placeholder_error.rs
@@ -13,7 +13,7 @@ use rustc_hir::def::Namespace;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::error::ExpectedFound;
 use rustc_middle::ty::print::{FmtPrinter, Print, RegionHighlightMode};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, RePlaceholder, Region, TyCtxt};
 
 use std::fmt;
@@ -196,11 +196,11 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         sup_placeholder: Option<Region<'tcx>>,
         value_pairs: &ValuePairs<'tcx>,
     ) -> Option<DiagnosticBuilder<'tcx, ErrorGuaranteed>> {
-        let (expected_substs, found_substs, trait_def_id) = match value_pairs {
+        let (expected_args, found_args, trait_def_id) = match value_pairs {
             ValuePairs::TraitRefs(ExpectedFound { expected, found })
                 if expected.def_id == found.def_id =>
             {
-                (expected.substs, found.substs, expected.def_id)
+                (expected.args, found.args, expected.def_id)
             }
             ValuePairs::PolyTraitRefs(ExpectedFound { expected, found })
                 if expected.def_id() == found.def_id() =>
@@ -208,7 +208,7 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
                 // It's possible that the placeholders come from a binder
                 // outside of this value pair. Use `no_bound_vars` as a
                 // simple heuristic for that.
-                (expected.no_bound_vars()?.substs, found.no_bound_vars()?.substs, expected.def_id())
+                (expected.no_bound_vars()?.args, found.no_bound_vars()?.args, expected.def_id())
             }
             _ => return None,
         };
@@ -219,8 +219,8 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             sub_placeholder,
             sup_placeholder,
             trait_def_id,
-            expected_substs,
-            found_substs,
+            expected_args,
+            found_args,
         ))
     }
 
@@ -241,8 +241,8 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         sub_placeholder: Option<Region<'tcx>>,
         sup_placeholder: Option<Region<'tcx>>,
         trait_def_id: DefId,
-        expected_substs: SubstsRef<'tcx>,
-        actual_substs: SubstsRef<'tcx>,
+        expected_args: GenericArgsRef<'tcx>,
+        actual_args: GenericArgsRef<'tcx>,
     ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
         let span = cause.span();
 
@@ -264,12 +264,12 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
         let expected_trait_ref = self.cx.resolve_vars_if_possible(ty::TraitRef::new(
             self.cx.tcx,
             trait_def_id,
-            expected_substs,
+            expected_args,
         ));
         let actual_trait_ref = self.cx.resolve_vars_if_possible(ty::TraitRef::new(
             self.cx.tcx,
             trait_def_id,
-            actual_substs,
+            actual_args,
         ));
 
         // Search the expected and actual trait references to see (a)
@@ -413,9 +413,9 @@ impl<'tcx> NiceRegionError<'_, 'tcx> {
             if self_ty.value.is_closure() && self.tcx().is_fn_trait(expected_trait_ref.value.def_id)
             {
                 let closure_sig = self_ty.map(|closure| {
-                    if let ty::Closure(_, substs) = closure.kind() {
+                    if let ty::Closure(_, args) = closure.kind() {
                         self.tcx().signature_unclosure(
-                            substs.as_closure().sig(),
+                            args.as_closure().sig(),
                             rustc_hir::Unsafety::Normal,
                         )
                     } else {
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
index d70fea20cf406..cc92bfbfdfeb2 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs
@@ -288,7 +288,7 @@ pub fn suggest_new_region_bound(
 
                 // Get the identity type for this RPIT
                 let did = item_id.owner_id.to_def_id();
-                let ty = Ty::new_opaque(tcx, did, ty::InternalSubsts::identity_for_item(tcx, did));
+                let ty = Ty::new_opaque(tcx, did, ty::GenericArgs::identity_for_item(tcx, did));
 
                 if let Some(span) = opaque.bounds.iter().find_map(|arg| match arg {
                     GenericBound::Outlives(Lifetime {
@@ -493,7 +493,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             tcx,
             ctxt.param_env,
             ctxt.assoc_item.def_id,
-            self.cx.resolve_vars_if_possible(ctxt.substs),
+            self.cx.resolve_vars_if_possible(ctxt.args),
         ) else {
             return false;
         };
diff --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs
index c5ef48fe3da25..2775b5ded038e 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs
@@ -65,7 +65,7 @@ pub fn find_param_with_region<'tcx>(
 
     let owner_id = hir.body_owner(body_id);
     let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap();
-    let poly_fn_sig = tcx.fn_sig(id).subst_identity();
+    let poly_fn_sig = tcx.fn_sig(id).instantiate_identity();
 
     let fn_sig = tcx.liberate_late_bound_regions(id, poly_fn_sig);
     let body = hir.body(body_id);
@@ -123,7 +123,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
         br: ty::BoundRegionKind,
         hir_sig: &hir::FnSig<'_>,
     ) -> Option<Span> {
-        let fn_ty = self.tcx().type_of(scope_def_id).subst_identity();
+        let fn_ty = self.tcx().type_of(scope_def_id).instantiate_identity();
         if let ty::FnDef(_, _) = fn_ty.kind() {
             let ret_ty = fn_ty.fn_sig(self.tcx()).output();
             let span = hir_sig.decl.output.span();
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note.rs b/compiler/rustc_infer/src/infer/error_reporting/note.rs
index 6517b90440428..7144084c78ebe 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note.rs
@@ -302,18 +302,18 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         let Some(trait_ref) = self.tcx.impl_trait_ref(impl_def_id) else {
             return;
         };
-        let trait_substs = trait_ref
-            .subst_identity()
+        let trait_args = trait_ref
+            .instantiate_identity()
             // Replace the explicit self type with `Self` for better suggestion rendering
             .with_self_ty(self.tcx, Ty::new_param(self.tcx, 0, kw::SelfUpper))
-            .substs;
-        let trait_item_substs = ty::InternalSubsts::identity_for_item(self.tcx, impl_item_def_id)
-            .rebase_onto(self.tcx, impl_def_id, trait_substs);
+            .args;
+        let trait_item_args = ty::GenericArgs::identity_for_item(self.tcx, impl_item_def_id)
+            .rebase_onto(self.tcx, impl_def_id, trait_args);
 
         let Ok(trait_predicates) =
             self.tcx
                 .explicit_predicates_of(trait_item_def_id)
-                .instantiate_own(self.tcx, trait_item_substs)
+                .instantiate_own(self.tcx, trait_item_args)
                 .map(|(pred, _)| {
                     if pred.is_suggestable(self.tcx, false) {
                         Ok(pred.to_string())
diff --git a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
index 63613b59020fb..8e3f6b97e8f55 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/note_and_explain.rs
@@ -100,9 +100,9 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                         {
                             // Synthesize the associated type restriction `Add<Output = Expected>`.
                             // FIXME: extract this logic for use in other diagnostics.
-                            let (trait_ref, assoc_substs) = proj.trait_ref_and_own_substs(tcx);
+                            let (trait_ref, assoc_args) = proj.trait_ref_and_own_args(tcx);
                             let item_name = tcx.item_name(proj.def_id);
-                            let item_args = self.format_generic_args(assoc_substs);
+                            let item_args = self.format_generic_args(assoc_args);
 
                             // Here, we try to see if there's an existing
                             // trait implementation that matches the one that
@@ -316,7 +316,7 @@ impl<T> Trait<T> for X {
     ) -> bool {
         let tcx = self.tcx;
         let assoc = tcx.associated_item(proj_ty.def_id);
-        let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(tcx);
+        let (trait_ref, assoc_args) = proj_ty.trait_ref_and_own_args(tcx);
         if let Some(item) = tcx.hir().get_if_local(body_owner_def_id) {
             if let Some(hir_generics) = item.generics() {
                 // Get the `DefId` for the type parameter corresponding to `A` in `<A as T>::Foo`.
@@ -339,7 +339,7 @@ impl<T> Trait<T> for X {
                         &trait_ref,
                         pred.bounds,
                         assoc,
-                        assoc_substs,
+                        assoc_args,
                         ty,
                         &msg,
                         false,
@@ -488,14 +488,14 @@ fn foo(&self) -> Self::T { String::new() }
                 return false;
             };
 
-            let (trait_ref, assoc_substs) = proj_ty.trait_ref_and_own_substs(tcx);
+            let (trait_ref, assoc_args) = proj_ty.trait_ref_and_own_args(tcx);
 
             self.constrain_generic_bound_associated_type_structured_suggestion(
                 diag,
                 &trait_ref,
                 opaque_hir_ty.bounds,
                 assoc,
-                assoc_substs,
+                assoc_args,
                 ty,
                 msg,
                 true,
@@ -527,7 +527,7 @@ fn foo(&self) -> Self::T { String::new() }
                     && !tcx.is_doc_hidden(item.def_id)
             })
             .filter_map(|item| {
-                let method = tcx.fn_sig(item.def_id).subst_identity();
+                let method = tcx.fn_sig(item.def_id).instantiate_identity();
                 match *method.output().skip_binder().kind() {
                     ty::Alias(ty::Projection, ty::AliasTy { def_id: item_def_id, .. })
                         if item_def_id == proj_ty_item_def_id =>
@@ -597,7 +597,7 @@ fn foo(&self) -> Self::T { String::new() }
                             if let hir::Defaultness::Default { has_value: true } =
                                 tcx.defaultness(item.id.owner_id)
                             {
-                                let assoc_ty = tcx.type_of(item.id.owner_id).subst_identity();
+                                let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity();
                                 if self.infcx.can_eq(param_env, assoc_ty, found) {
                                     diag.span_label(
                                         item.span,
@@ -618,7 +618,7 @@ fn foo(&self) -> Self::T { String::new() }
             })) => {
                 for item in &items[..] {
                     if let hir::AssocItemKind::Type = item.kind {
-                        let assoc_ty = tcx.type_of(item.id.owner_id).subst_identity();
+                        let assoc_ty = tcx.type_of(item.id.owner_id).instantiate_identity();
 
                         if self.infcx.can_eq(param_env, assoc_ty, found) {
                             diag.span_label(item.span, "expected this associated type");
@@ -645,7 +645,7 @@ fn foo(&self) -> Self::T { String::new() }
         trait_ref: &ty::TraitRef<'tcx>,
         bounds: hir::GenericBounds<'_>,
         assoc: ty::AssocItem,
-        assoc_substs: &[ty::GenericArg<'tcx>],
+        assoc_args: &[ty::GenericArg<'tcx>],
         ty: Ty<'tcx>,
         msg: impl Fn() -> String,
         is_bound_surely_present: bool,
@@ -671,14 +671,7 @@ fn foo(&self) -> Self::T { String::new() }
             _ => return false,
         };
 
-        self.constrain_associated_type_structured_suggestion(
-            diag,
-            span,
-            assoc,
-            assoc_substs,
-            ty,
-            msg,
-        )
+        self.constrain_associated_type_structured_suggestion(diag, span, assoc, assoc_args, ty, msg)
     }
 
     /// Given a span corresponding to a bound, provide a structured suggestion to set an
@@ -688,7 +681,7 @@ fn foo(&self) -> Self::T { String::new() }
         diag: &mut Diagnostic,
         span: Span,
         assoc: ty::AssocItem,
-        assoc_substs: &[ty::GenericArg<'tcx>],
+        assoc_args: &[ty::GenericArg<'tcx>],
         ty: Ty<'tcx>,
         msg: impl Fn() -> String,
     ) -> bool {
@@ -702,7 +695,7 @@ fn foo(&self) -> Self::T { String::new() }
                 let span = Span::new(pos, pos, span.ctxt(), span.parent());
                 (span, format!(", {} = {}", assoc.ident(tcx), ty))
             } else {
-                let item_args = self.format_generic_args(assoc_substs);
+                let item_args = self.format_generic_args(assoc_args);
                 (span.shrink_to_hi(), format!("<{}{} = {}>", assoc.ident(tcx), item_args, ty))
             };
             diag.span_suggestion_verbose(span, msg(), sugg, MaybeIncorrect);
diff --git a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
index aac2a43648b75..ce5d3791a48f3 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
+++ b/compiler/rustc_infer/src/infer/error_reporting/suggest.rs
@@ -105,7 +105,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         // Heavily inspired by `FnCtxt::suggest_compatible_variants`, with
         // some modifications due to that being in typeck and this being in infer.
         if let ObligationCauseCode::Pattern { .. } = cause.code() {
-            if let ty::Adt(expected_adt, substs) = exp_found.expected.kind() {
+            if let ty::Adt(expected_adt, args) = exp_found.expected.kind() {
                 let compatible_variants: Vec<_> = expected_adt
                     .variants()
                     .iter()
@@ -114,7 +114,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     })
                     .filter_map(|variant| {
                         let sole_field = &variant.single_field();
-                        let sole_field_ty = sole_field.ty(self.tcx, substs);
+                        let sole_field_ty = sole_field.ty(self.tcx, args);
                         if self.same_type_modulo_infer(sole_field_ty, exp_found.found) {
                             let variant_path =
                                 with_no_trimmed_paths!(self.tcx.def_path_str(variant.def_id));
@@ -260,7 +260,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             "suggest_accessing_field_where_appropriate(cause={:?}, exp_found={:?})",
             cause, exp_found
         );
-        if let ty::Adt(expected_def, expected_substs) = exp_found.expected.kind() {
+        if let ty::Adt(expected_def, expected_args) = exp_found.expected.kind() {
             if expected_def.is_enum() {
                 return;
             }
@@ -270,7 +270,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 .fields
                 .iter()
                 .filter(|field| field.vis.is_accessible_from(field.did, self.tcx))
-                .map(|field| (field.name, field.ty(self.tcx, expected_substs)))
+                .map(|field| (field.name, field.ty(self.tcx, expected_args)))
                 .find(|(_, ty)| self.same_type_modulo_infer(*ty, exp_found.found))
             {
                 if let ObligationCauseCode::Pattern { span: Some(span), .. } = *cause.code() {
@@ -304,12 +304,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             return;
         }
         match (&expected_inner.kind(), &found_inner.kind()) {
-            (ty::FnPtr(sig), ty::FnDef(did, substs)) => {
+            (ty::FnPtr(sig), ty::FnDef(did, args)) => {
                 let expected_sig = &(self.normalize_fn_sig)(*sig);
                 let found_sig =
-                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did).subst(self.tcx, substs));
+                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did).instantiate(self.tcx, args));
 
-                let fn_name = self.tcx.def_path_str_with_substs(*did, substs);
+                let fn_name = self.tcx.def_path_str_with_args(*did, args);
 
                 if !self.same_type_modulo_infer(*found_sig, *expected_sig)
                     || !sig.is_suggestable(self.tcx, true)
@@ -332,11 +332,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 };
                 diag.subdiagnostic(sugg);
             }
-            (ty::FnDef(did1, substs1), ty::FnDef(did2, substs2)) => {
+            (ty::FnDef(did1, args1), ty::FnDef(did2, args2)) => {
                 let expected_sig =
-                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did1).subst(self.tcx, substs1));
+                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did1).instantiate(self.tcx, args1));
                 let found_sig =
-                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did2).subst(self.tcx, substs2));
+                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did2).instantiate(self.tcx, args2));
 
                 if self.same_type_modulo_infer(*expected_sig, *found_sig) {
                     diag.subdiagnostic(FnUniqTypes);
@@ -351,7 +351,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     return;
                 }
 
-                let fn_name = self.tcx.def_path_str_with_substs(*did2, substs2);
+                let fn_name = self.tcx.def_path_str_with_args(*did2, args2);
                 let sug = if found.is_ref() {
                     FunctionPointerSuggestion::CastBothRef {
                         span,
@@ -370,16 +370,16 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
 
                 diag.subdiagnostic(sug);
             }
-            (ty::FnDef(did, substs), ty::FnPtr(sig)) => {
+            (ty::FnDef(did, args), ty::FnPtr(sig)) => {
                 let expected_sig =
-                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did).subst(self.tcx, substs));
+                    &(self.normalize_fn_sig)(self.tcx.fn_sig(*did).instantiate(self.tcx, args));
                 let found_sig = &(self.normalize_fn_sig)(*sig);
 
                 if !self.same_type_modulo_infer(*found_sig, *expected_sig) {
                     return;
                 }
 
-                let fn_name = self.tcx.def_path_str_with_substs(*did, substs);
+                let fn_name = self.tcx.def_path_str_with_args(*did, args);
 
                 let casting = if expected.is_ref() {
                     format!("&({fn_name} as {found_sig})")
@@ -400,10 +400,10 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         expected: Ty<'tcx>,
         found: Ty<'tcx>,
     ) -> Option<SuggestAsRefKind> {
-        if let (ty::Adt(exp_def, exp_substs), ty::Ref(_, found_ty, _)) =
+        if let (ty::Adt(exp_def, exp_args), ty::Ref(_, found_ty, _)) =
             (expected.kind(), found.kind())
         {
-            if let ty::Adt(found_def, found_substs) = *found_ty.kind() {
+            if let ty::Adt(found_def, found_args) = *found_ty.kind() {
                 if exp_def == &found_def {
                     let have_as_ref = &[
                         (sym::Option, SuggestAsRefKind::Option),
@@ -414,7 +414,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     }) {
                         let mut show_suggestion = true;
                         for (exp_ty, found_ty) in
-                            std::iter::zip(exp_substs.types(), found_substs.types())
+                            std::iter::zip(exp_args.types(), found_args.types())
                         {
                             match *exp_ty.kind() {
                                 ty::Ref(_, exp_ty, _) => {
@@ -535,12 +535,12 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
         };
         let hir::Body { params, .. } = self.tcx.hir().body(*body);
 
-        // 1. Get the substs of the closure.
+        // 1. Get the args of the closure.
         // 2. Assume exp_found is FnOnce / FnMut / Fn, we can extract function parameters from [1].
-        let Some(expected) = exp_found.expected.skip_binder().substs.get(1) else {
+        let Some(expected) = exp_found.expected.skip_binder().args.get(1) else {
             return;
         };
-        let Some(found) = exp_found.found.skip_binder().substs.get(1) else {
+        let Some(found) = exp_found.found.skip_binder().args.get(1) else {
             return;
         };
         let expected = expected.unpack();
@@ -631,8 +631,8 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 ty::Alias(ty::Opaque, ty::AliasTy { def_id: exp_def_id, .. }),
             ) if last_def_id == exp_def_id => StatementAsExpression::CorrectType,
             (
-                ty::Alias(ty::Opaque, ty::AliasTy { def_id: last_def_id, substs: last_bounds, .. }),
-                ty::Alias(ty::Opaque, ty::AliasTy { def_id: exp_def_id, substs: exp_bounds, .. }),
+                ty::Alias(ty::Opaque, ty::AliasTy { def_id: last_def_id, args: last_bounds, .. }),
+                ty::Alias(ty::Opaque, ty::AliasTy { def_id: exp_def_id, args: exp_bounds, .. }),
             ) => {
                 debug!(
                     "both opaque, likely future {:?} {:?} {:?} {:?}",
diff --git a/compiler/rustc_infer/src/infer/freshen.rs b/compiler/rustc_infer/src/infer/freshen.rs
index 05769b7907a2e..689945d644c48 100644
--- a/compiler/rustc_infer/src/infer/freshen.rs
+++ b/compiler/rustc_infer/src/infer/freshen.rs
@@ -11,7 +11,7 @@
 //!
 //! To handle closures, freshened types also have to contain the signature and kind of any
 //! closure in the local inference context, as otherwise the cache key might be invalidated.
-//! The way this is done is somewhat hacky - the closure signature is appended to the substs,
+//! The way this is done is somewhat hacky - the closure signature is appended to the args,
 //! as well as the closure kind "encoded" as a type. Also, special handling is needed when
 //! the closure signature contains a reference to the original closure.
 //!
diff --git a/compiler/rustc_infer/src/infer/generalize.rs b/compiler/rustc_infer/src/infer/generalize.rs
index 78025016757c6..cf674d5dda65d 100644
--- a/compiler/rustc_infer/src/infer/generalize.rs
+++ b/compiler/rustc_infer/src/infer/generalize.rs
@@ -173,21 +173,21 @@ where
         true
     }
 
-    fn relate_item_substs(
+    fn relate_item_args(
         &mut self,
         item_def_id: DefId,
-        a_subst: ty::SubstsRef<'tcx>,
-        b_subst: ty::SubstsRef<'tcx>,
-    ) -> RelateResult<'tcx, ty::SubstsRef<'tcx>> {
+        a_subst: ty::GenericArgsRef<'tcx>,
+        b_subst: ty::GenericArgsRef<'tcx>,
+    ) -> RelateResult<'tcx, ty::GenericArgsRef<'tcx>> {
         if self.ambient_variance == ty::Variance::Invariant {
             // Avoid fetching the variance if we are in an invariant
             // context; no need, and it can induce dependency cycles
             // (e.g., #41849).
-            relate::relate_substs(self, a_subst, b_subst)
+            relate::relate_args(self, a_subst, b_subst)
         } else {
             let tcx = self.tcx();
             let opt_variances = tcx.variances_of(item_def_id);
-            relate::relate_substs_with_variances(
+            relate::relate_args_with_variances(
                 self,
                 item_def_id,
                 opt_variances,
@@ -405,16 +405,16 @@ where
             }
             // FIXME: remove this branch once `structurally_relate_consts` is fully
             // structural.
-            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => {
-                let substs = self.relate_with_variance(
+            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args }) => {
+                let args = self.relate_with_variance(
                     ty::Variance::Invariant,
                     ty::VarianceDiagInfo::default(),
-                    substs,
-                    substs,
+                    args,
+                    args,
                 )?;
                 Ok(ty::Const::new_unevaluated(
                     self.tcx(),
-                    ty::UnevaluatedConst { def, substs },
+                    ty::UnevaluatedConst { def, args },
                     c.ty(),
                 ))
             }
diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs
index a123effd0f0b7..a73e84f94c4ca 100644
--- a/compiler/rustc_infer/src/infer/mod.rs
+++ b/compiler/rustc_infer/src/infer/mod.rs
@@ -30,11 +30,11 @@ use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::BoundVarReplacerDelegate;
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::relate::RelateResult;
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 pub use rustc_middle::ty::IntVarValue;
 use rustc_middle::ty::{self, GenericParamDefKind, InferConst, InferTy, Ty, TyCtxt};
 use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
+use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgs, GenericArgsRef};
 use rustc_span::symbol::Symbol;
 use rustc_span::Span;
 
@@ -1184,8 +1184,8 @@ impl<'tcx> InferCtxt<'tcx> {
 
     /// Given a set of generics defined on a type or impl, returns a substitution mapping each
     /// type/region parameter to a fresh inference variable.
-    pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
-        InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
+    pub fn fresh_args_for_item(&self, span: Span, def_id: DefId) -> GenericArgsRef<'tcx> {
+        GenericArgs::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
     }
 
     /// Returns `true` if errors have been reported since this infcx was
@@ -1474,8 +1474,8 @@ impl<'tcx> InferCtxt<'tcx> {
     /// Obtains the latest type of the given closure; this may be a
     /// closure in the current function, in which case its
     /// `ClosureKind` may not yet be known.
-    pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
-        let closure_kind_ty = closure_substs.as_closure().kind_ty();
+    pub fn closure_kind(&self, closure_args: GenericArgsRef<'tcx>) -> Option<ty::ClosureKind> {
+        let closure_kind_ty = closure_args.as_closure().kind_ty();
         let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
         closure_kind_ty.to_opt_closure_kind()
     }
@@ -1534,7 +1534,7 @@ impl<'tcx> InferCtxt<'tcx> {
     /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
     /// returned.
     ///
-    /// This handles inferences variables within both `param_env` and `substs` by
+    /// This handles inferences variables within both `param_env` and `args` by
     /// performing the operation on their respective canonical forms.
     #[instrument(skip(self), level = "debug")]
     pub fn const_eval_resolve(
@@ -1543,34 +1543,34 @@ impl<'tcx> InferCtxt<'tcx> {
         unevaluated: ty::UnevaluatedConst<'tcx>,
         span: Option<Span>,
     ) -> EvalToValTreeResult<'tcx> {
-        let mut substs = self.resolve_vars_if_possible(unevaluated.substs);
-        debug!(?substs);
+        let mut args = self.resolve_vars_if_possible(unevaluated.args);
+        debug!(?args);
 
-        // Postpone the evaluation of constants whose substs depend on inference
+        // Postpone the evaluation of constants whose args depend on inference
         // variables
         let tcx = self.tcx;
-        if substs.has_non_region_infer() {
+        if args.has_non_region_infer() {
             if let Some(ct) = tcx.thir_abstract_const(unevaluated.def)? {
-                let ct = tcx.expand_abstract_consts(ct.subst(tcx, substs));
+                let ct = tcx.expand_abstract_consts(ct.instantiate(tcx, args));
                 if let Err(e) = ct.error_reported() {
                     return Err(ErrorHandled::Reported(e.into()));
                 } else if ct.has_non_region_infer() || ct.has_non_region_param() {
                     return Err(ErrorHandled::TooGeneric);
                 } else {
-                    substs = replace_param_and_infer_substs_with_placeholder(tcx, substs);
+                    args = replace_param_and_infer_args_with_placeholder(tcx, args);
                 }
             } else {
-                substs = InternalSubsts::identity_for_item(tcx, unevaluated.def);
+                args = GenericArgs::identity_for_item(tcx, unevaluated.def);
                 param_env = tcx.param_env(unevaluated.def);
             }
         }
 
         let param_env_erased = tcx.erase_regions(param_env);
-        let substs_erased = tcx.erase_regions(substs);
+        let args_erased = tcx.erase_regions(args);
         debug!(?param_env_erased);
-        debug!(?substs_erased);
+        debug!(?args_erased);
 
-        let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, substs: substs_erased };
+        let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, args: args_erased };
 
         // The return value is the evaluated value which doesn't contain any reference to inference
         // variables, thus we don't need to substitute back the original values.
@@ -1959,13 +1959,13 @@ impl RegionVariableOrigin {
     }
 }
 
-/// Replaces substs that reference param or infer variables with suitable
+/// Replaces args that reference param or infer variables with suitable
 /// placeholders. This function is meant to remove these param and infer
-/// substs when they're not actually needed to evaluate a constant.
-fn replace_param_and_infer_substs_with_placeholder<'tcx>(
+/// args when they're not actually needed to evaluate a constant.
+fn replace_param_and_infer_args_with_placeholder<'tcx>(
     tcx: TyCtxt<'tcx>,
-    substs: SubstsRef<'tcx>,
-) -> SubstsRef<'tcx> {
+    args: GenericArgsRef<'tcx>,
+) -> GenericArgsRef<'tcx> {
     struct ReplaceParamAndInferWithPlaceholder<'tcx> {
         tcx: TyCtxt<'tcx>,
         idx: u32,
@@ -2023,5 +2023,5 @@ fn replace_param_and_infer_substs_with_placeholder<'tcx>(
         }
     }
 
-    substs.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
+    args.fold_with(&mut ReplaceParamAndInferWithPlaceholder { tcx, idx: 0 })
 }
diff --git a/compiler/rustc_infer/src/infer/opaque_types.rs b/compiler/rustc_infer/src/infer/opaque_types.rs
index 5927f79a18333..90f0b4ce401da 100644
--- a/compiler/rustc_infer/src/infer/opaque_types.rs
+++ b/compiler/rustc_infer/src/infer/opaque_types.rs
@@ -103,7 +103,7 @@ impl<'tcx> InferCtxt<'tcx> {
         }
         let (a, b) = if a_is_expected { (a, b) } else { (b, a) };
         let process = |a: Ty<'tcx>, b: Ty<'tcx>, a_is_expected| match *a.kind() {
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) if def_id.is_local() => {
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) if def_id.is_local() => {
                 let def_id = def_id.expect_local();
                 match self.defining_use_anchor {
                     DefiningAnchor::Bind(_) => {
@@ -165,7 +165,7 @@ impl<'tcx> InferCtxt<'tcx> {
                     }
                 }
                 Some(self.register_hidden_type(
-                    OpaqueTypeKey { def_id, substs },
+                    OpaqueTypeKey { def_id, args },
                     cause.clone(),
                     param_env,
                     b,
@@ -214,12 +214,12 @@ impl<'tcx> InferCtxt<'tcx> {
     /// fn foo<'a, 'b>(..) -> (Foo1<'a>, Foo2<'b>) { .. }
     ///                    //  ^^^^ ^^
     ///                    //  |    |
-    ///                    //  |    substs
+    ///                    //  |    args
     ///                    //  def_id
     /// ```
     ///
     /// As indicating in the comments above, each of those references
-    /// is (in the compiler) basically a substitution (`substs`)
+    /// is (in the compiler) basically a substitution (`args`)
     /// applied to the type of a suitable `def_id` (which identifies
     /// `Foo1` or `Foo2`).
     ///
@@ -278,7 +278,7 @@ impl<'tcx> InferCtxt<'tcx> {
     ///
     /// We generally prefer to make `<=` constraints, since they
     /// integrate best into the region solver. To do that, we find the
-    /// "minimum" of all the arguments that appear in the substs: that
+    /// "minimum" of all the arguments that appear in the args: that
     /// is, some region which is less than all the others. In the case
     /// of `Foo1<'a>`, that would be `'a` (it's the only choice, after
     /// all). Then we apply that as a least bound to the variables
@@ -350,7 +350,7 @@ impl<'tcx> InferCtxt<'tcx> {
         // opaque type definition.
         let choice_regions: Lrc<Vec<ty::Region<'tcx>>> = Lrc::new(
             opaque_type_key
-                .substs
+                .args
                 .iter()
                 .enumerate()
                 .filter(|(i, _)| variances[*i] == ty::Variance::Invariant)
@@ -445,28 +445,28 @@ where
         }
 
         match ty.kind() {
-            ty::Closure(_, ref substs) => {
+            ty::Closure(_, ref args) => {
                 // Skip lifetime parameters of the enclosing item(s)
 
-                substs.as_closure().tupled_upvars_ty().visit_with(self);
-                substs.as_closure().sig_as_fn_ptr_ty().visit_with(self);
+                args.as_closure().tupled_upvars_ty().visit_with(self);
+                args.as_closure().sig_as_fn_ptr_ty().visit_with(self);
             }
 
-            ty::Generator(_, ref substs, _) => {
+            ty::Generator(_, ref args, _) => {
                 // Skip lifetime parameters of the enclosing item(s)
                 // Also skip the witness type, because that has no free regions.
 
-                substs.as_generator().tupled_upvars_ty().visit_with(self);
-                substs.as_generator().return_ty().visit_with(self);
-                substs.as_generator().yield_ty().visit_with(self);
-                substs.as_generator().resume_ty().visit_with(self);
+                args.as_generator().tupled_upvars_ty().visit_with(self);
+                args.as_generator().return_ty().visit_with(self);
+                args.as_generator().yield_ty().visit_with(self);
+                args.as_generator().resume_ty().visit_with(self);
             }
 
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, ref substs, .. }) => {
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, ref args, .. }) => {
                 // Skip lifetime parameters that are not captures.
                 let variances = self.tcx.variances_of(*def_id);
 
-                for (v, s) in std::iter::zip(variances, substs.iter()) {
+                for (v, s) in std::iter::zip(variances, args.iter()) {
                     if *v != ty::Variance::Bivariant {
                         s.visit_with(self);
                     }
@@ -519,7 +519,7 @@ impl<'tcx> InferCtxt<'tcx> {
 
         self.add_item_bounds_for_hidden_type(
             opaque_type_key.def_id.to_def_id(),
-            opaque_type_key.substs,
+            opaque_type_key.args,
             cause,
             param_env,
             hidden_ty,
@@ -582,7 +582,7 @@ impl<'tcx> InferCtxt<'tcx> {
     pub fn add_item_bounds_for_hidden_type(
         &self,
         def_id: DefId,
-        substs: ty::SubstsRef<'tcx>,
+        args: ty::GenericArgsRef<'tcx>,
         cause: ObligationCause<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         hidden_ty: Ty<'tcx>,
@@ -591,7 +591,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let tcx = self.tcx;
         let item_bounds = tcx.explicit_item_bounds(def_id);
 
-        for (predicate, _) in item_bounds.subst_iter_copied(tcx, substs) {
+        for (predicate, _) in item_bounds.arg_iter_copied(tcx, args) {
             let predicate = predicate.fold_with(&mut BottomUpFolder {
                 tcx,
                 ty_op: |ty| match *ty.kind() {
@@ -614,17 +614,18 @@ impl<'tcx> InferCtxt<'tcx> {
                     }
                     // Replace all other mentions of the same opaque type with the hidden type,
                     // as the bounds must hold on the hidden type after all.
-                    ty::Alias(ty::Opaque, ty::AliasTy { def_id: def_id2, substs: substs2, .. })
-                        if def_id == def_id2 && substs == substs2 =>
+                    ty::Alias(ty::Opaque, ty::AliasTy { def_id: def_id2, args: args2, .. })
+                        if def_id == def_id2 && args == args2 =>
                     {
                         hidden_ty
                     }
                     // FIXME(RPITIT): This can go away when we move to associated types
                     // FIXME(inherent_associated_types): Extend this to support `ty::Inherent`, too.
-                    ty::Alias(
-                        ty::Projection,
-                        ty::AliasTy { def_id: def_id2, substs: substs2, .. },
-                    ) if def_id == def_id2 && substs == substs2 => hidden_ty,
+                    ty::Alias(ty::Projection, ty::AliasTy { def_id: def_id2, args: args2, .. })
+                        if def_id == def_id2 && args == args2 =>
+                    {
+                        hidden_ty
+                    }
                     _ => ty,
                 },
                 lt_op: |lt| lt,
diff --git a/compiler/rustc_infer/src/infer/outlives/components.rs b/compiler/rustc_infer/src/infer/outlives/components.rs
index cb63d2f18b634..2ac9568f60be7 100644
--- a/compiler/rustc_infer/src/infer/outlives/components.rs
+++ b/compiler/rustc_infer/src/infer/outlives/components.rs
@@ -3,8 +3,8 @@
 // RFC for reference.
 
 use rustc_data_structures::sso::SsoHashSet;
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{GenericArg, GenericArgKind};
 use smallvec::{smallvec, SmallVec};
 
 #[derive(Debug)]
@@ -71,15 +71,15 @@ fn compute_components<'tcx>(
     // in the `subtys` iterator (e.g., when encountering a
     // projection).
     match *ty.kind() {
-            ty::FnDef(_, substs) => {
-                // HACK(eddyb) ignore lifetimes found shallowly in `substs`.
-                // This is inconsistent with `ty::Adt` (including all substs)
-                // and with `ty::Closure` (ignoring all substs other than
+            ty::FnDef(_, args) => {
+                // HACK(eddyb) ignore lifetimes found shallowly in `args`.
+                // This is inconsistent with `ty::Adt` (including all args)
+                // and with `ty::Closure` (ignoring all args other than
                 // upvars, of which a `ty::FnDef` doesn't have any), but
                 // consistent with previous (accidental) behavior.
                 // See https://github.com/rust-lang/rust/issues/70917
                 // for further background and discussion.
-                for child in substs {
+                for child in args {
                     match child.unpack() {
                         GenericArgKind::Type(ty) => {
                             compute_components(tcx, ty, out, visited);
@@ -97,14 +97,14 @@ fn compute_components<'tcx>(
                 compute_components(tcx, element, out, visited);
             }
 
-            ty::Closure(_, ref substs) => {
-                let tupled_ty = substs.as_closure().tupled_upvars_ty();
+            ty::Closure(_, ref args) => {
+                let tupled_ty = args.as_closure().tupled_upvars_ty();
                 compute_components(tcx, tupled_ty, out, visited);
             }
 
-            ty::Generator(_, ref substs, _) => {
+            ty::Generator(_, ref args, _) => {
                 // Same as the closure case
-                let tupled_ty = substs.as_generator().tupled_upvars_ty();
+                let tupled_ty = args.as_generator().tupled_upvars_ty();
                 compute_components(tcx, tupled_ty, out, visited);
 
                 // We ignore regions in the generator interior as we don't
@@ -189,7 +189,7 @@ fn compute_components<'tcx>(
         }
 }
 
-/// Collect [Component]s for *all* the substs of `parent`.
+/// Collect [Component]s for *all* the args of `parent`.
 ///
 /// This should not be used to get the components of `parent` itself.
 /// Use [push_outlives_components] instead.
@@ -201,7 +201,7 @@ pub(super) fn compute_alias_components_recursive<'tcx>(
 ) {
     let ty::Alias(kind, alias_ty) = alias_ty.kind() else { bug!() };
     let opt_variances = if *kind == ty::Opaque { tcx.variances_of(alias_ty.def_id) } else { &[] };
-    for (index, child) in alias_ty.substs.iter().enumerate() {
+    for (index, child) in alias_ty.args.iter().enumerate() {
         if opt_variances.get(index) == Some(&ty::Bivariant) {
             continue;
         }
@@ -225,7 +225,7 @@ pub(super) fn compute_alias_components_recursive<'tcx>(
     }
 }
 
-/// Collect [Component]s for *all* the substs of `parent`.
+/// Collect [Component]s for *all* the args of `parent`.
 ///
 /// This should not be used to get the components of `parent` itself.
 /// Use [push_outlives_components] instead.
diff --git a/compiler/rustc_infer/src/infer/outlives/obligations.rs b/compiler/rustc_infer/src/infer/outlives/obligations.rs
index 73df6d03f86cb..0681f414ce900 100644
--- a/compiler/rustc_infer/src/infer/outlives/obligations.rs
+++ b/compiler/rustc_infer/src/infer/outlives/obligations.rs
@@ -68,8 +68,8 @@ use crate::infer::{
 use crate::traits::{ObligationCause, ObligationCauseCode};
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_middle::mir::ConstraintCategory;
-use rustc_middle::ty::subst::GenericArgKind;
-use rustc_middle::ty::{self, Region, SubstsRef, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::GenericArgKind;
+use rustc_middle::ty::{self, GenericArgsRef, Region, Ty, TyCtxt, TypeVisitableExt};
 use smallvec::smallvec;
 
 use super::env::OutlivesEnvironment;
@@ -279,7 +279,7 @@ where
         alias_ty: ty::AliasTy<'tcx>,
     ) {
         // An optimization for a common case with opaque types.
-        if alias_ty.substs.is_empty() {
+        if alias_ty.args.is_empty() {
             return;
         }
 
@@ -348,7 +348,7 @@ where
         {
             debug!("no declared bounds");
             let opt_variances = is_opaque.then(|| self.tcx.variances_of(alias_ty.def_id));
-            self.substs_must_outlive(alias_ty.substs, origin, region, opt_variances);
+            self.args_must_outlive(alias_ty.args, origin, region, opt_variances);
             return;
         }
 
@@ -395,15 +395,15 @@ where
     }
 
     #[instrument(level = "debug", skip(self))]
-    fn substs_must_outlive(
+    fn args_must_outlive(
         &mut self,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         origin: infer::SubregionOrigin<'tcx>,
         region: ty::Region<'tcx>,
         opt_variances: Option<&[ty::Variance]>,
     ) {
         let constraint = origin.to_constraint_category();
-        for (index, k) in substs.iter().enumerate() {
+        for (index, k) in args.iter().enumerate() {
             match k.unpack() {
                 GenericArgKind::Lifetime(lt) => {
                     let variance = if let Some(variances) = opt_variances {
diff --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
index cd2462d3c3123..fefa8959545ab 100644
--- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
+++ b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
@@ -157,7 +157,7 @@ impl<'tcx> TypeRelation<'tcx> for Match<'tcx> {
         a: T,
         b: T,
     ) -> RelateResult<'tcx, T> {
-        // Opaque types substs have lifetime parameters.
+        // Opaque types args have lifetime parameters.
         // We must not check them to be equal, as we never insert anything to make them so.
         if variance != ty::Bivariant { self.relate(a, b) } else { Ok(a) }
     }
diff --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index 1a5e2b520b80b..1e1ecd3fb9478 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/compiler/rustc_infer/src/infer/outlives/verify.rs
@@ -295,7 +295,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
         let bounds = tcx.item_bounds(alias_ty.def_id);
         trace!("{:#?}", bounds.skip_binder());
         bounds
-            .subst_iter(tcx, alias_ty.substs)
+            .arg_iter(tcx, alias_ty.args)
             .filter_map(|p| p.as_type_outlives_clause())
             .filter_map(|p| p.no_bound_vars())
             .map(|OutlivesPredicate(_, r)| r)
diff --git a/compiler/rustc_infer/src/infer/type_variable.rs b/compiler/rustc_infer/src/infer/type_variable.rs
index 01c11d16345fe..bc83f8d3f9676 100644
--- a/compiler/rustc_infer/src/infer/type_variable.rs
+++ b/compiler/rustc_infer/src/infer/type_variable.rs
@@ -125,7 +125,7 @@ pub enum TypeVariableOriginKind {
     OpaqueTypeInference(DefId),
     TypeParameterDefinition(Symbol, DefId),
 
-    /// One of the upvars or closure kind parameters in a `ClosureSubsts`
+    /// One of the upvars or closure kind parameters in a `ClosureArgs`
     /// (before it has been determined).
     // FIXME(eddyb) distinguish upvar inference variables from the rest.
     ClosureSynthetic,
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 03835f8151cee..84aca80b0dec0 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -61,7 +61,7 @@ use rustc_hir::{Body, FnDecl, ForeignItemKind, GenericParamKind, Node, PatKind,
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, VariantDef};
 use rustc_session::config::ExpectedValues;
@@ -181,9 +181,11 @@ impl<'tcx> LateLintPass<'tcx> for BoxPointers {
             | hir::ItemKind::TyAlias(..)
             | hir::ItemKind::Enum(..)
             | hir::ItemKind::Struct(..)
-            | hir::ItemKind::Union(..) => {
-                self.check_heap_type(cx, it.span, cx.tcx.type_of(it.owner_id).subst_identity())
-            }
+            | hir::ItemKind::Union(..) => self.check_heap_type(
+                cx,
+                it.span,
+                cx.tcx.type_of(it.owner_id).instantiate_identity(),
+            ),
             _ => (),
         }
 
@@ -194,7 +196,7 @@ impl<'tcx> LateLintPass<'tcx> for BoxPointers {
                     self.check_heap_type(
                         cx,
                         field.span,
-                        cx.tcx.type_of(field.def_id).subst_identity(),
+                        cx.tcx.type_of(field.def_id).instantiate_identity(),
                     );
                 }
             }
@@ -591,7 +593,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingDoc {
             // If the method is an impl for an item with docs_hidden, don't doc.
             MethodLateContext::PlainImpl => {
                 let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
-                let impl_ty = cx.tcx.type_of(parent).subst_identity();
+                let impl_ty = cx.tcx.type_of(parent).instantiate_identity();
                 let outerdef = match impl_ty.kind() {
                     ty::Adt(def, _) => Some(def.did()),
                     ty::Foreign(def_id) => Some(*def_id),
@@ -700,7 +702,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingCopyImplementations {
         // and recommending Copy might be a bad idea.
         for field in def.all_fields() {
             let did = field.did;
-            if cx.tcx.type_of(did).subst_identity().is_unsafe_ptr() {
+            if cx.tcx.type_of(did).instantiate_identity().is_unsafe_ptr() {
                 return;
             }
         }
@@ -798,7 +800,7 @@ impl<'tcx> LateLintPass<'tcx> for MissingDebugImplementations {
         if self.impling_types.is_none() {
             let mut impls = LocalDefIdSet::default();
             cx.tcx.for_each_impl(debug, |d| {
-                if let Some(ty_def) = cx.tcx.type_of(d).subst_identity().ty_adt_def() {
+                if let Some(ty_def) = cx.tcx.type_of(d).instantiate_identity().ty_adt_def() {
                     if let Some(def_id) = ty_def.did().as_local() {
                         impls.insert(def_id);
                     }
@@ -2455,12 +2457,12 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
             cx: &LateContext<'tcx>,
             ty: Ty<'tcx>,
             variant: &VariantDef,
-            substs: ty::SubstsRef<'tcx>,
+            args: ty::GenericArgsRef<'tcx>,
             descr: &str,
             init: InitKind,
         ) -> Option<InitError> {
             let mut field_err = variant.fields.iter().find_map(|field| {
-                ty_find_init_error(cx, field.ty(cx.tcx, substs), init).map(|mut err| {
+                ty_find_init_error(cx, field.ty(cx.tcx, args), init).map(|mut err| {
                     if !field.did.is_local() {
                         err
                     } else if err.span.is_none() {
@@ -2537,14 +2539,14 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
                     Some("raw pointers must be initialized".into())
                 }
                 // Recurse and checks for some compound types. (but not unions)
-                Adt(adt_def, substs) if !adt_def.is_union() => {
+                Adt(adt_def, args) if !adt_def.is_union() => {
                     // Handle structs.
                     if adt_def.is_struct() {
                         return variant_find_init_error(
                             cx,
                             ty,
                             adt_def.non_enum_variant(),
-                            substs,
+                            args,
                             "struct field",
                             init,
                         );
@@ -2554,7 +2556,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
                     let mut potential_variants = adt_def.variants().iter().filter_map(|variant| {
                         let definitely_inhabited = match variant
                             .inhabited_predicate(cx.tcx, *adt_def)
-                            .subst(cx.tcx, substs)
+                            .instantiate(cx.tcx, args)
                             .apply_any_module(cx.tcx, cx.param_env)
                         {
                             // Entirely skip uninhabited variants.
@@ -2578,7 +2580,7 @@ impl<'tcx> LateLintPass<'tcx> for InvalidValue {
                             cx,
                             ty,
                             &first_variant.0,
-                            substs,
+                            args,
                             "field of the only potentially inhabited enum variant",
                             init,
                         );
@@ -2778,7 +2780,7 @@ impl ClashingExternDeclarations {
             // type unless the newtype makes the type non-null.
             let non_transparent_ty = |mut ty: Ty<'tcx>| -> Ty<'tcx> {
                 loop {
-                    if let ty::Adt(def, substs) = *ty.kind() {
+                    if let ty::Adt(def, args) = *ty.kind() {
                         let is_transparent = def.repr().transparent();
                         let is_non_null = crate::types::nonnull_optimization_guaranteed(tcx, def);
                         debug!(
@@ -2791,7 +2793,7 @@ impl ClashingExternDeclarations {
                             // continue with `ty`'s non-ZST field,
                             // otherwise `ty` is a ZST and we can return
                             if let Some(field) = transparent_newtype_field(tcx, v) {
-                                ty = field.ty(tcx, substs);
+                                ty = field.ty(tcx, args);
                                 continue;
                             }
                         }
@@ -2857,8 +2859,8 @@ impl ClashingExternDeclarations {
                                     structurally_same_type_impl(
                                         seen_types,
                                         cx,
-                                        tcx.type_of(a_did).subst_identity(),
-                                        tcx.type_of(b_did).subst_identity(),
+                                        tcx.type_of(a_did).instantiate_identity(),
+                                        tcx.type_of(b_did).instantiate_identity(),
                                         ckind,
                                     )
                                 },
@@ -2905,8 +2907,8 @@ impl ClashingExternDeclarations {
                                     ckind,
                                 )
                         }
-                        (Tuple(a_substs), Tuple(b_substs)) => {
-                            a_substs.iter().eq_by(b_substs.iter(), |a_ty, b_ty| {
+                        (Tuple(a_args), Tuple(b_args)) => {
+                            a_args.iter().eq_by(b_args.iter(), |a_ty, b_ty| {
                                 structurally_same_type_impl(seen_types, cx, a_ty, b_ty, ckind)
                             })
                         }
@@ -2960,7 +2962,7 @@ impl<'tcx> LateLintPass<'tcx> for ClashingExternDeclarations {
             let tcx = cx.tcx;
             if let Some(existing_did) = self.insert(tcx, this_fi) {
                 let existing_decl_ty = tcx.type_of(existing_did).skip_binder();
-                let this_decl_ty = tcx.type_of(this_fi.owner_id).subst_identity();
+                let this_decl_ty = tcx.type_of(this_fi.owner_id).instantiate_identity();
                 debug!(
                     "ClashingExternDeclarations: Comparing existing {:?}: {:?} to this {:?}: {:?}",
                     existing_did, existing_decl_ty, this_fi.owner_id, this_decl_ty
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 4770ed6639312..6522e449386c7 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -35,7 +35,7 @@ use rustc_middle::middle::privacy::EffectiveVisibilities;
 use rustc_middle::middle::stability;
 use rustc_middle::ty::layout::{LayoutError, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self, print::Printer, subst::GenericArg, RegisteredTools, Ty, TyCtxt};
+use rustc_middle::ty::{self, print::Printer, GenericArg, RegisteredTools, Ty, TyCtxt};
 use rustc_session::config::ExpectedValues;
 use rustc_session::lint::{BuiltinLintDiagnostics, LintExpectationId};
 use rustc_session::lint::{FutureIncompatibleInfo, Level, Lint, LintBuffer, LintId};
@@ -1273,8 +1273,8 @@ impl<'tcx> LateContext<'tcx> {
                 trait_ref: Option<ty::TraitRef<'tcx>>,
             ) -> Result<Self::Path, Self::Error> {
                 if trait_ref.is_none() {
-                    if let ty::Adt(def, substs) = self_ty.kind() {
-                        return self.print_def_path(def.did(), substs);
+                    if let ty::Adt(def, args) = self_ty.kind() {
+                        return self.print_def_path(def.did(), args);
                     }
                 }
 
diff --git a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
index ccf95992a6e6e..851c6493daf9b 100644
--- a/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
+++ b/compiler/rustc_lint/src/deref_into_dyn_supertrait.rs
@@ -59,7 +59,7 @@ impl<'tcx> LateLintPass<'tcx> for DerefIntoDynSupertrait {
         // `Deref` is being implemented for `t`
         if let hir::ItemKind::Impl(impl_) = item.kind
             && let Some(trait_) = &impl_.of_trait
-            && let t = cx.tcx.type_of(item.owner_id).subst_identity()
+            && let t = cx.tcx.type_of(item.owner_id).instantiate_identity()
             && let opt_did @ Some(did) = trait_.trait_def_id()
             && opt_did == cx.tcx.lang_items().deref_trait()
             // `t` is `dyn t_principal`
diff --git a/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
index 2ce28f3a049e8..05fe64830d17e 100644
--- a/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
+++ b/compiler/rustc_lint/src/enum_intrinsics_non_enums.rs
@@ -51,7 +51,7 @@ fn enforce_mem_discriminant(
     expr_span: Span,
     args_span: Span,
 ) {
-    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    let ty_param = cx.typeck_results().node_args(func_expr.hir_id).type_at(0);
     if is_non_enum(ty_param) {
         cx.emit_spanned_lint(
             ENUM_INTRINSICS_NON_ENUMS,
@@ -62,7 +62,7 @@ fn enforce_mem_discriminant(
 }
 
 fn enforce_mem_variant_count(cx: &LateContext<'_>, func_expr: &hir::Expr<'_>, span: Span) {
-    let ty_param = cx.typeck_results().node_substs(func_expr.hir_id).type_at(0);
+    let ty_param = cx.typeck_results().node_args(func_expr.hir_id).type_at(0);
     if is_non_enum(ty_param) {
         cx.emit_spanned_lint(
             ENUM_INTRINSICS_NON_ENUMS,
diff --git a/compiler/rustc_lint/src/for_loops_over_fallibles.rs b/compiler/rustc_lint/src/for_loops_over_fallibles.rs
index 71832c1b7af5d..c299e38842acf 100644
--- a/compiler/rustc_lint/src/for_loops_over_fallibles.rs
+++ b/compiler/rustc_lint/src/for_loops_over_fallibles.rs
@@ -51,7 +51,7 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
 
         let ty = cx.typeck_results().expr_ty(arg);
 
-        let &ty::Adt(adt, substs) = ty.kind() else { return };
+        let &ty::Adt(adt, args) = ty.kind() else { return };
 
         let (article, ty, var) = match adt.did() {
             did if cx.tcx.is_diagnostic_item(sym::Option, did) => ("an", "Option", "Some"),
@@ -66,7 +66,7 @@ impl<'tcx> LateLintPass<'tcx> for ForLoopsOverFallibles {
             } else {
                 ForLoopsOverFalliblesLoopSub::UseWhileLet { start_span: expr.span.with_hi(pat.span.lo()), end_span: pat.span.between(arg.span), var }
             } ;
-        let question_mark = suggest_question_mark(cx, adt, substs, expr.span)
+        let question_mark = suggest_question_mark(cx, adt, args, expr.span)
             .then(|| ForLoopsOverFalliblesQuestionMark { suggestion: arg.span.shrink_to_hi() });
         let suggestion = ForLoopsOverFalliblesSuggestion {
             var,
@@ -115,7 +115,7 @@ fn extract_iterator_next_call<'tcx>(
 fn suggest_question_mark<'tcx>(
     cx: &LateContext<'tcx>,
     adt: ty::AdtDef<'tcx>,
-    substs: &List<ty::GenericArg<'tcx>>,
+    args: &List<ty::GenericArg<'tcx>>,
     span: Span,
 ) -> bool {
     let Some(body_id) = cx.enclosing_body else { return false };
@@ -137,7 +137,7 @@ fn suggest_question_mark<'tcx>(
         }
     }
 
-    let ty = substs.type_at(0);
+    let ty = args.type_at(0);
     let infcx = cx.tcx.infer_ctxt().build();
     let ocx = ObligationCtxt::new(&infcx);
 
diff --git a/compiler/rustc_lint/src/internal.rs b/compiler/rustc_lint/src/internal.rs
index 6f773e04a97d7..4b803621f71ce 100644
--- a/compiler/rustc_lint/src/internal.rs
+++ b/compiler/rustc_lint/src/internal.rs
@@ -52,20 +52,20 @@ impl LateLintPass<'_> for DefaultHashTypes {
 }
 
 /// Helper function for lints that check for expressions with calls and use typeck results to
-/// get the `DefId` and `SubstsRef` of the function.
+/// get the `DefId` and `GenericArgsRef` of the function.
 fn typeck_results_of_method_fn<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &Expr<'_>,
-) -> Option<(Span, DefId, ty::subst::SubstsRef<'tcx>)> {
+) -> Option<(Span, DefId, ty::GenericArgsRef<'tcx>)> {
     match expr.kind {
         ExprKind::MethodCall(segment, ..)
             if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) =>
         {
-            Some((segment.ident.span, def_id, cx.typeck_results().node_substs(expr.hir_id)))
+            Some((segment.ident.span, def_id, cx.typeck_results().node_args(expr.hir_id)))
         },
         _ => {
             match cx.typeck_results().node_type(expr.hir_id).kind() {
-                &ty::FnDef(def_id, substs) => Some((expr.span, def_id, substs)),
+                &ty::FnDef(def_id, args) => Some((expr.span, def_id, args)),
                 _ => None,
             }
         }
@@ -89,8 +89,8 @@ declare_lint_pass!(QueryStability => [POTENTIAL_QUERY_INSTABILITY]);
 
 impl LateLintPass<'_> for QueryStability {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
-        if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs) {
+        let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
+        if let Ok(Some(instance)) = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, args) {
             let def_id = instance.def_id();
             if cx.tcx.has_attr(def_id, sym::rustc_lint_query_instability) {
                 cx.emit_spanned_lint(
@@ -232,7 +232,7 @@ fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
         }
         // Only lint on `&Ty` and `&TyCtxt` if it is used outside of a trait.
         Res::SelfTyAlias { alias_to: did, is_trait_impl: false, .. } => {
-            if let ty::Adt(adt, substs) = cx.tcx.type_of(did).subst_identity().kind() {
+            if let ty::Adt(adt, args) = cx.tcx.type_of(did).instantiate_identity().kind() {
                 if let Some(name @ (sym::Ty | sym::TyCtxt)) = cx.tcx.get_diagnostic_name(adt.did())
                 {
                     // NOTE: This path is currently unreachable as `Ty<'tcx>` is
@@ -241,7 +241,7 @@ fn is_ty_or_ty_ctxt(cx: &LateContext<'_>, path: &Path<'_>) -> Option<String> {
                     //
                     // I(@lcnr) still kept this branch in so we don't miss this
                     // if we ever change it in the future.
-                    return Some(format!("{}<{}>", name, substs[0]));
+                    return Some(format!("{}<{}>", name, args[0]));
                 }
             }
         }
@@ -379,9 +379,9 @@ declare_lint_pass!(Diagnostics => [ UNTRANSLATABLE_DIAGNOSTIC, DIAGNOSTIC_OUTSID
 
 impl LateLintPass<'_> for Diagnostics {
     fn check_expr(&mut self, cx: &LateContext<'_>, expr: &Expr<'_>) {
-        let Some((span, def_id, substs)) = typeck_results_of_method_fn(cx, expr) else { return };
-        debug!(?span, ?def_id, ?substs);
-        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, substs)
+        let Some((span, def_id, args)) = typeck_results_of_method_fn(cx, expr) else { return };
+        debug!(?span, ?def_id, ?args);
+        let has_attr = ty::Instance::resolve(cx.tcx, cx.param_env, def_id, args)
             .ok()
             .flatten()
             .is_some_and(|inst| cx.tcx.has_attr(inst.def_id(), sym::rustc_lint_diagnostics));
@@ -414,7 +414,7 @@ impl LateLintPass<'_> for Diagnostics {
         }
 
         let mut found_diagnostic_message = false;
-        for ty in substs.types() {
+        for ty in args.types() {
             debug!(?ty);
             if let Some(adt_def) = ty.ty_adt_def() &&
                 let Some(name) =  cx.tcx.get_diagnostic_name(adt_def.did()) &&
diff --git a/compiler/rustc_lint/src/methods.rs b/compiler/rustc_lint/src/methods.rs
index 4c25d94a1f372..5b63b19c53c8a 100644
--- a/compiler/rustc_lint/src/methods.rs
+++ b/compiler/rustc_lint/src/methods.rs
@@ -53,9 +53,9 @@ fn lint_cstring_as_ptr(
     unwrap: &rustc_hir::Expr<'_>,
 ) {
     let source_type = cx.typeck_results().expr_ty(source);
-    if let ty::Adt(def, substs) = source_type.kind() {
+    if let ty::Adt(def, args) = source_type.kind() {
         if cx.tcx.is_diagnostic_item(sym::Result, def.did()) {
-            if let ty::Adt(adt, _) = substs.type_at(0).kind() {
+            if let ty::Adt(adt, _) = args.type_at(0).kind() {
                 if cx.tcx.is_diagnostic_item(sym::cstring_type, adt.did()) {
                     cx.emit_spanned_lint(
                         TEMPORARY_CSTRING_AS_PTR,
diff --git a/compiler/rustc_lint/src/noop_method_call.rs b/compiler/rustc_lint/src/noop_method_call.rs
index 79430393a647e..13f650c200826 100644
--- a/compiler/rustc_lint/src/noop_method_call.rs
+++ b/compiler/rustc_lint/src/noop_method_call.rs
@@ -93,11 +93,11 @@ impl<'tcx> LateLintPass<'tcx> for NoopMethodCall {
             return;
         };
 
-        let substs = cx
+        let args = cx
             .tcx
-            .normalize_erasing_regions(cx.param_env, cx.typeck_results().node_substs(expr.hir_id));
+            .normalize_erasing_regions(cx.param_env, cx.typeck_results().node_args(expr.hir_id));
         // Resolve the trait method instance.
-        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, cx.param_env, did, substs) else { return };
+        let Ok(Some(i)) = ty::Instance::resolve(cx.tcx, cx.param_env, did, args) else { return };
         // (Re)check that it implements the noop diagnostic.
         let Some(name) = cx.tcx.get_diagnostic_name(i.def_id()) else { return };
 
diff --git a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
index 5fd42942e3024..d5f0290767ac6 100644
--- a/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
+++ b/compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs
@@ -76,7 +76,9 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
         // For every projection predicate in the opaque type's explicit bounds,
         // check that the type that we're assigning actually satisfies the bounds
         // of the associated type.
-        for (pred, pred_span) in cx.tcx.explicit_item_bounds(def_id).subst_identity_iter_copied() {
+        for (pred, pred_span) in
+            cx.tcx.explicit_item_bounds(def_id).instantiate_identity_iter_copied()
+        {
             // Liberate bound regions in the predicate since we
             // don't actually care about lifetimes in this check.
             let predicate = cx.tcx.liberate_late_bound_regions(def_id, pred.kind());
@@ -99,7 +101,7 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
             }
 
             let proj_ty =
-                Ty::new_projection(cx.tcx, proj.projection_ty.def_id, proj.projection_ty.substs);
+                Ty::new_projection(cx.tcx, proj.projection_ty.def_id, proj.projection_ty.args);
             // For every instance of the projection type in the bounds,
             // replace them with the term we're assigning to the associated
             // type in our opaque type.
@@ -115,7 +117,7 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
             for (assoc_pred, assoc_pred_span) in cx
                 .tcx
                 .explicit_item_bounds(proj.projection_ty.def_id)
-                .subst_iter_copied(cx.tcx, &proj.projection_ty.substs)
+                .arg_iter_copied(cx.tcx, &proj.projection_ty.args)
             {
                 let assoc_pred = assoc_pred.fold_with(proj_replacer);
                 let Ok(assoc_pred) = traits::fully_normalize(
@@ -154,7 +156,7 @@ impl<'tcx> LateLintPass<'tcx> for OpaqueHiddenInferredBound {
                             ty: Ty::new_opaque(
                                 cx.tcx,
                                 def_id,
-                                ty::InternalSubsts::identity_for_item(cx.tcx, def_id),
+                                ty::GenericArgs::identity_for_item(cx.tcx, def_id),
                             ),
                             proj_ty: proj_term,
                             assoc_pred_span,
diff --git a/compiler/rustc_lint/src/pass_by_value.rs b/compiler/rustc_lint/src/pass_by_value.rs
index 2bb2a3aab5527..cad2cd7fa4c8b 100644
--- a/compiler/rustc_lint/src/pass_by_value.rs
+++ b/compiler/rustc_lint/src/pass_by_value.rs
@@ -50,9 +50,9 @@ fn path_for_pass_by_value(cx: &LateContext<'_>, ty: &hir::Ty<'_>) -> Option<Stri
                 return Some(format!("{}{}", name, gen_args(cx, path_segment)));
             }
             Res::SelfTyAlias { alias_to: did, is_trait_impl: false, .. } => {
-                if let ty::Adt(adt, substs) = cx.tcx.type_of(did).subst_identity().kind() {
+                if let ty::Adt(adt, args) = cx.tcx.type_of(did).instantiate_identity().kind() {
                     if cx.tcx.has_attr(adt.did(), sym::rustc_pass_by_value) {
-                        return Some(cx.tcx.def_path_str_with_substs(adt.did(), substs));
+                        return Some(cx.tcx.def_path_str_with_args(adt.did(), args));
                     }
                 }
             }
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs
index 0e30d9c86048e..cc8a34080040a 100644
--- a/compiler/rustc_lint/src/types.rs
+++ b/compiler/rustc_lint/src/types.rs
@@ -17,7 +17,7 @@ use rustc_errors::DiagnosticMessage;
 use rustc_hir as hir;
 use rustc_hir::{is_range_literal, Expr, ExprKind, Node};
 use rustc_middle::ty::layout::{IntegerExt, LayoutOf, SizeSkeleton};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{
     self, AdtKind, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt,
 };
@@ -808,7 +808,7 @@ pub fn transparent_newtype_field<'a, 'tcx>(
 ) -> Option<&'a ty::FieldDef> {
     let param_env = tcx.param_env(variant.def_id);
     variant.fields.iter().find(|field| {
-        let field_ty = tcx.type_of(field.did).subst_identity();
+        let field_ty = tcx.type_of(field.did).instantiate_identity();
         let is_zst = tcx.layout_of(param_env.and(field_ty)).is_ok_and(|layout| layout.is_zst());
         !is_zst
     })
@@ -821,7 +821,7 @@ fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKi
         ty::FnPtr(_) => true,
         ty::Ref(..) => true,
         ty::Adt(def, _) if def.is_box() && matches!(mode, CItemKind::Definition) => true,
-        ty::Adt(def, substs) if def.repr().transparent() && !def.is_union() => {
+        ty::Adt(def, args) if def.repr().transparent() && !def.is_union() => {
             let marked_non_null = nonnull_optimization_guaranteed(tcx, *def);
 
             if marked_non_null {
@@ -836,7 +836,7 @@ fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKi
             def.variants()
                 .iter()
                 .filter_map(|variant| transparent_newtype_field(cx.tcx, variant))
-                .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, substs), mode))
+                .any(|field| ty_is_known_nonnull(cx, field.ty(tcx, args), mode))
         }
         _ => false,
     }
@@ -847,7 +847,7 @@ fn ty_is_known_nonnull<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, mode: CItemKi
 fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'tcx>> {
     let tcx = cx.tcx;
     Some(match *ty.kind() {
-        ty::Adt(field_def, field_substs) => {
+        ty::Adt(field_def, field_args) => {
             let inner_field_ty = {
                 let mut first_non_zst_ty = field_def
                     .variants()
@@ -861,7 +861,7 @@ fn get_nullable_type<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<Ty<'t
                 first_non_zst_ty
                     .next_back()
                     .expect("No non-zst fields in transparent type.")
-                    .ty(tcx, field_substs)
+                    .ty(tcx, field_args)
             };
             return get_nullable_type(cx, inner_field_ty);
         }
@@ -900,10 +900,10 @@ pub(crate) fn repr_nullable_ptr<'tcx>(
     ckind: CItemKind,
 ) -> Option<Ty<'tcx>> {
     debug!("is_repr_nullable_ptr(cx, ty = {:?})", ty);
-    if let ty::Adt(ty_def, substs) = ty.kind() {
+    if let ty::Adt(ty_def, args) = ty.kind() {
         let field_ty = match &ty_def.variants().raw[..] {
             [var_one, var_two] => match (&var_one.fields.raw[..], &var_two.fields.raw[..]) {
-                ([], [field]) | ([field], []) => field.ty(cx.tcx, substs),
+                ([], [field]) | ([field], []) => field.ty(cx.tcx, args),
                 _ => return None,
             },
             _ => return None,
@@ -963,9 +963,9 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         &self,
         cache: &mut FxHashSet<Ty<'tcx>>,
         field: &ty::FieldDef,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> FfiResult<'tcx> {
-        let field_ty = field.ty(self.cx.tcx, substs);
+        let field_ty = field.ty(self.cx.tcx, args);
         if field_ty.has_opaque_types() {
             self.check_type_for_ffi(cache, field_ty)
         } else {
@@ -981,7 +981,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         ty: Ty<'tcx>,
         def: ty::AdtDef<'tcx>,
         variant: &ty::VariantDef,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> FfiResult<'tcx> {
         use FfiResult::*;
 
@@ -989,7 +989,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
             // Can assume that at most one field is not a ZST, so only check
             // that field's type for FFI-safety.
             if let Some(field) = transparent_newtype_field(self.cx.tcx, variant) {
-                return self.check_field_type_for_ffi(cache, field, substs);
+                return self.check_field_type_for_ffi(cache, field, args);
             } else {
                 // All fields are ZSTs; this means that the type should behave
                 // like (), which is FFI-unsafe... except if all fields are PhantomData,
@@ -1001,7 +1001,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         // actually safe.
         let mut all_phantom = !variant.fields.is_empty();
         for field in &variant.fields {
-            match self.check_field_type_for_ffi(cache, &field, substs) {
+            match self.check_field_type_for_ffi(cache, &field, args) {
                 FfiSafe => {
                     all_phantom = false;
                 }
@@ -1036,7 +1036,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
         }
 
         match *ty.kind() {
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 if def.is_box() && matches!(self.mode, CItemKind::Definition) {
                     if ty.boxed_ty().is_sized(tcx, self.cx.param_env) {
                         return FfiSafe;
@@ -1099,7 +1099,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                             };
                         }
 
-                        self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), substs)
+                        self.check_variant_for_ffi(cache, ty, def, def.non_enum_variant(), args)
                     }
                     AdtKind::Enum => {
                         if def.variants().is_empty() {
@@ -1140,7 +1140,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
                                 };
                             }
 
-                            match self.check_variant_for_ffi(cache, ty, def, variant, substs) {
+                            match self.check_variant_for_ffi(cache, ty, def, variant, args) {
                                 FfiSafe => (),
                                 r => return r,
                             }
@@ -1387,7 +1387,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
     /// For a external ABI function, argument types and the result type are walked to find fn-ptr
     /// types that have external ABIs, as these still need checked.
     fn check_fn(&mut self, def_id: LocalDefId, decl: &'tcx hir::FnDecl<'_>) {
-        let sig = self.cx.tcx.fn_sig(def_id).subst_identity();
+        let sig = self.cx.tcx.fn_sig(def_id).instantiate_identity();
         let sig = self.cx.tcx.erase_late_bound_regions(sig);
 
         for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
@@ -1405,7 +1405,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
 
     /// Check if a function's argument types and result type are "ffi-safe".
     fn check_foreign_fn(&mut self, def_id: LocalDefId, decl: &'tcx hir::FnDecl<'_>) {
-        let sig = self.cx.tcx.fn_sig(def_id).subst_identity();
+        let sig = self.cx.tcx.fn_sig(def_id).instantiate_identity();
         let sig = self.cx.tcx.erase_late_bound_regions(sig);
 
         for (input_ty, input_hir) in iter::zip(sig.inputs(), decl.inputs) {
@@ -1418,7 +1418,7 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> {
     }
 
     fn check_foreign_static(&mut self, id: hir::OwnerId, span: Span) {
-        let ty = self.cx.tcx.type_of(id).subst_identity();
+        let ty = self.cx.tcx.type_of(id).instantiate_identity();
         self.check_type_for_ffi_and_report_errors(span, ty, true, false);
     }
 
@@ -1524,7 +1524,7 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
                 self.check_ty_maybe_containing_foreign_fnptr(
                     cx,
                     ty,
-                    cx.tcx.type_of(item.owner_id).subst_identity(),
+                    cx.tcx.type_of(item.owner_id).instantiate_identity(),
                 );
             }
             // See `check_fn`..
@@ -1549,7 +1549,7 @@ impl<'tcx> LateLintPass<'tcx> for ImproperCTypesDefinitions {
         self.check_ty_maybe_containing_foreign_fnptr(
             cx,
             field.ty,
-            cx.tcx.type_of(field.def_id).subst_identity(),
+            cx.tcx.type_of(field.def_id).instantiate_identity(),
         );
     }
 
@@ -1584,7 +1584,7 @@ declare_lint_pass!(VariantSizeDifferences => [VARIANT_SIZE_DIFFERENCES]);
 impl<'tcx> LateLintPass<'tcx> for VariantSizeDifferences {
     fn check_item(&mut self, cx: &LateContext<'_>, it: &hir::Item<'_>) {
         if let hir::ItemKind::Enum(ref enum_definition, _) = it.kind {
-            let t = cx.tcx.type_of(it.owner_id).subst_identity();
+            let t = cx.tcx.type_of(it.owner_id).instantiate_identity();
             let ty = cx.tcx.erase_regions(t);
             let Ok(layout) = cx.layout_of(ty) else { return };
             let Variants::Multiple { tag_encoding: TagEncoding::Direct, tag, ref variants, .. } =
@@ -1704,7 +1704,7 @@ impl InvalidAtomicOrdering {
             && recognized_names.contains(&method_path.ident.name)
             && let Some(m_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id)
             && let Some(impl_did) = cx.tcx.impl_of_method(m_def_id)
-            && let Some(adt) = cx.tcx.type_of(impl_did).subst_identity().ty_adt_def()
+            && let Some(adt) = cx.tcx.type_of(impl_did).instantiate_identity().ty_adt_def()
             // skip extension traits, only lint functions from the standard library
             && cx.tcx.trait_id_of_impl(impl_did).is_none()
             && let parent = cx.tcx.parent(adt.did())
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index e35cc8de66fbc..f78da284a3a16 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -286,22 +286,25 @@ impl<'tcx> LateLintPass<'tcx> for UnusedResults {
                 }
                 ty::Adt(def, _) => is_def_must_use(cx, def.did(), span),
                 ty::Alias(ty::Opaque, ty::AliasTy { def_id: def, .. }) => {
-                    elaborate(cx.tcx, cx.tcx.explicit_item_bounds(def).subst_identity_iter_copied())
-                        // We only care about self bounds for the impl-trait
-                        .filter_only_self()
-                        .find_map(|(pred, _span)| {
-                            // We only look at the `DefId`, so it is safe to skip the binder here.
-                            if let ty::ClauseKind::Trait(ref poly_trait_predicate) =
-                                pred.kind().skip_binder()
-                            {
-                                let def_id = poly_trait_predicate.trait_ref.def_id;
-
-                                is_def_must_use(cx, def_id, span)
-                            } else {
-                                None
-                            }
-                        })
-                        .map(|inner| MustUsePath::Opaque(Box::new(inner)))
+                    elaborate(
+                        cx.tcx,
+                        cx.tcx.explicit_item_bounds(def).instantiate_identity_iter_copied(),
+                    )
+                    // We only care about self bounds for the impl-trait
+                    .filter_only_self()
+                    .find_map(|(pred, _span)| {
+                        // We only look at the `DefId`, so it is safe to skip the binder here.
+                        if let ty::ClauseKind::Trait(ref poly_trait_predicate) =
+                            pred.kind().skip_binder()
+                        {
+                            let def_id = poly_trait_predicate.trait_ref.def_id;
+
+                            is_def_must_use(cx, def_id, span)
+                        } else {
+                            None
+                        }
+                    })
+                    .map(|inner| MustUsePath::Opaque(Box::new(inner)))
                 }
                 ty::Dynamic(binders, _, _) => binders.iter().find_map(|predicate| {
                     if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate.skip_binder()
diff --git a/compiler/rustc_metadata/src/native_libs.rs b/compiler/rustc_metadata/src/native_libs.rs
index 0dd7b11979168..9e0bf81d58dc8 100644
--- a/compiler/rustc_metadata/src/native_libs.rs
+++ b/compiler/rustc_metadata/src/native_libs.rs
@@ -480,7 +480,7 @@ impl<'tcx> Collector<'tcx> {
         let argument_types: &List<Ty<'_>> = self.tcx.erase_late_bound_regions(
             self.tcx
                 .type_of(item.id.owner_id)
-                .subst_identity()
+                .instantiate_identity()
                 .fn_sig(self.tcx)
                 .inputs()
                 .map_bound(|slice| self.tcx.mk_type_list(slice)),
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index fc1062a48b45c..0056769cabbc6 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1924,7 +1924,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             if of_trait && let Some(trait_ref) = tcx.impl_trait_ref(def_id) {
                 record!(self.tables.impl_trait_ref[def_id] <- trait_ref);
 
-                let trait_ref = trait_ref.subst_identity();
+                let trait_ref = trait_ref.instantiate_identity();
                 let simplified_self_ty =
                     fast_reject::simplify_type(self.tcx, trait_ref.self_ty(), TreatParams::AsCandidateKey);
                 fx_hash_map
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index d5e8330b3f6fa..81823118ab810 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -23,7 +23,7 @@
 
 use crate::infer::MemberConstraint;
 use crate::mir::ConstraintCategory;
-use crate::ty::subst::GenericArg;
+use crate::ty::GenericArg;
 use crate::ty::{self, BoundVar, List, Region, Ty, TyCtxt};
 use rustc_macros::HashStable;
 use smallvec::SmallVec;
@@ -63,7 +63,7 @@ impl<'tcx> ty::TypeFoldable<TyCtxt<'tcx>> for CanonicalVarInfos<'tcx> {
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyDecodable, TyEncodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct CanonicalVarValues<'tcx> {
-    pub var_values: ty::SubstsRef<'tcx>,
+    pub var_values: ty::GenericArgsRef<'tcx>,
 }
 
 impl CanonicalVarValues<'_> {
@@ -429,7 +429,7 @@ impl<'tcx> CanonicalVarValues<'tcx> {
         infos: CanonicalVarInfos<'tcx>,
     ) -> CanonicalVarValues<'tcx> {
         CanonicalVarValues {
-            var_values: tcx.mk_substs_from_iter(infos.iter().enumerate().map(
+            var_values: tcx.mk_args_from_iter(infos.iter().enumerate().map(
                 |(i, info)| -> ty::GenericArg<'tcx> {
                     match info.kind {
                         CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
diff --git a/compiler/rustc_middle/src/infer/mod.rs b/compiler/rustc_middle/src/infer/mod.rs
index 2db59f37f4072..493bb8a682333 100644
--- a/compiler/rustc_middle/src/infer/mod.rs
+++ b/compiler/rustc_middle/src/infer/mod.rs
@@ -15,7 +15,7 @@ use rustc_span::Span;
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct MemberConstraint<'tcx> {
-    /// The `DefId` and substs of the opaque type causing this constraint.
+    /// The `DefId` and args of the opaque type causing this constraint.
     /// Used for error reporting.
     pub key: OpaqueTypeKey<'tcx>,
 
diff --git a/compiler/rustc_middle/src/middle/exported_symbols.rs b/compiler/rustc_middle/src/middle/exported_symbols.rs
index 9041da9a0604d..f19812619b213 100644
--- a/compiler/rustc_middle/src/middle/exported_symbols.rs
+++ b/compiler/rustc_middle/src/middle/exported_symbols.rs
@@ -1,4 +1,4 @@
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_macros::HashStable;
@@ -41,7 +41,7 @@ pub struct SymbolExportInfo {
 #[derive(Eq, PartialEq, Debug, Copy, Clone, TyEncodable, TyDecodable, HashStable)]
 pub enum ExportedSymbol<'tcx> {
     NonGeneric(DefId),
-    Generic(DefId, SubstsRef<'tcx>),
+    Generic(DefId, GenericArgsRef<'tcx>),
     DropGlue(Ty<'tcx>),
     ThreadLocalShim(DefId),
     NoDefId(ty::SymbolName<'tcx>),
@@ -53,15 +53,15 @@ impl<'tcx> ExportedSymbol<'tcx> {
     pub fn symbol_name_for_local_instance(&self, tcx: TyCtxt<'tcx>) -> ty::SymbolName<'tcx> {
         match *self {
             ExportedSymbol::NonGeneric(def_id) => tcx.symbol_name(ty::Instance::mono(tcx, def_id)),
-            ExportedSymbol::Generic(def_id, substs) => {
-                tcx.symbol_name(ty::Instance::new(def_id, substs))
+            ExportedSymbol::Generic(def_id, args) => {
+                tcx.symbol_name(ty::Instance::new(def_id, args))
             }
             ExportedSymbol::DropGlue(ty) => {
                 tcx.symbol_name(ty::Instance::resolve_drop_in_place(tcx, ty))
             }
             ExportedSymbol::ThreadLocalShim(def_id) => tcx.symbol_name(ty::Instance {
                 def: ty::InstanceDef::ThreadLocalShim(def_id),
-                substs: ty::InternalSubsts::empty(),
+                args: ty::GenericArgs::empty(),
             }),
             ExportedSymbol::NoDefId(symbol_name) => symbol_name,
         }
diff --git a/compiler/rustc_middle/src/mir/interpret/error.rs b/compiler/rustc_middle/src/mir/interpret/error.rs
index 2435bc59ec034..372452ea29a8d 100644
--- a/compiler/rustc_middle/src/mir/interpret/error.rs
+++ b/compiler/rustc_middle/src/mir/interpret/error.rs
@@ -22,7 +22,7 @@ pub enum ErrorHandled {
     /// *guaranteed* to fail. Warnings/lints *must not* produce `Reported`.
     Reported(ReportedErrorInfo),
     /// Don't emit an error, the evaluation failed because the MIR was generic
-    /// and the substs didn't fully monomorphize it.
+    /// and the args didn't fully monomorphize it.
     TooGeneric,
 }
 
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index 2d2cfee1b213b..fbd667a87fead 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -138,7 +138,7 @@ use rustc_target::abi::{AddressSpace, Endian, HasDataLayout};
 
 use crate::mir;
 use crate::ty::codec::{TyDecoder, TyEncoder};
-use crate::ty::subst::GenericArgKind;
+use crate::ty::GenericArgKind;
 use crate::ty::{self, Instance, Ty, TyCtxt};
 
 pub use self::error::{
@@ -559,7 +559,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // However, formatting code relies on function identity (see #58320), so we only do
         // this for generic functions. Lifetime parameters are ignored.
         let is_generic = instance
-            .substs
+            .args
             .into_iter()
             .any(|kind| !matches!(kind.unpack(), GenericArgKind::Lifetime(_)));
         if is_generic {
diff --git a/compiler/rustc_middle/src/mir/interpret/queries.rs b/compiler/rustc_middle/src/mir/interpret/queries.rs
index 9c97431f3614a..c9db0e7c11d2b 100644
--- a/compiler/rustc_middle/src/mir/interpret/queries.rs
+++ b/compiler/rustc_middle/src/mir/interpret/queries.rs
@@ -2,8 +2,8 @@ use super::{ErrorHandled, EvalToConstValueResult, EvalToValTreeResult, GlobalId}
 
 use crate::mir;
 use crate::query::{TyCtxtAt, TyCtxtEnsure};
-use crate::ty::subst::InternalSubsts;
 use crate::ty::visit::TypeVisitableExt;
+use crate::ty::GenericArgs;
 use crate::ty::{self, TyCtxt};
 use rustc_hir::def::DefKind;
 use rustc_hir::def_id::DefId;
@@ -20,8 +20,8 @@ impl<'tcx> TyCtxt<'tcx> {
         // to be used. So we can't use `Instance::mono`, instead we feed unresolved substitutions
         // into `const_eval` which will return `ErrorHandled::ToGeneric` if any of them are
         // encountered.
-        let substs = InternalSubsts::identity_for_item(self, def_id);
-        let instance = ty::Instance::new(def_id, substs);
+        let args = GenericArgs::identity_for_item(self, def_id);
+        let instance = ty::Instance::new(def_id, args);
         let cid = GlobalId { instance, promoted: None };
         let param_env = self.param_env(def_id).with_reveal_all_normalized(self);
         self.const_eval_global_id(param_env, cid, None)
@@ -48,14 +48,14 @@ impl<'tcx> TyCtxt<'tcx> {
         //
         // When trying to evaluate constants containing inference variables,
         // use `Infcx::const_eval_resolve` instead.
-        if ct.substs.has_non_region_infer() {
+        if ct.args.has_non_region_infer() {
             bug!("did not expect inference variables here");
         }
 
         match ty::Instance::resolve(
             self, param_env,
             // FIXME: maybe have a separate version for resolving mir::UnevaluatedConst?
-            ct.def, ct.substs,
+            ct.def, ct.args,
         ) {
             Ok(Some(instance)) => {
                 let cid = GlobalId { instance, promoted: ct.promoted };
@@ -79,11 +79,11 @@ impl<'tcx> TyCtxt<'tcx> {
         //
         // When trying to evaluate constants containing inference variables,
         // use `Infcx::const_eval_resolve` instead.
-        if ct.substs.has_non_region_infer() {
+        if ct.args.has_non_region_infer() {
             bug!("did not expect inference variables here");
         }
 
-        match ty::Instance::resolve(self, param_env, ct.def, ct.substs) {
+        match ty::Instance::resolve(self, param_env, ct.def, ct.args) {
             Ok(Some(instance)) => {
                 let cid = GlobalId { instance, promoted: None };
                 self.const_eval_global_id_for_typeck(param_env, cid, span).inspect(|_| {
@@ -94,7 +94,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     // @lcnr believes that successfully evaluating even though there are
                     // used generic parameters is a bug of evaluation, so checking for it
                     // here does feel somewhat sensible.
-                    if !self.features().generic_const_exprs && ct.substs.has_non_region_param() {
+                    if !self.features().generic_const_exprs && ct.args.has_non_region_param() {
                         let def_kind = self.def_kind(instance.def_id());
                         assert!(
                             matches!(
@@ -221,8 +221,8 @@ impl<'tcx> TyCtxtEnsure<'tcx> {
         // to be used. So we can't use `Instance::mono`, instead we feed unresolved substitutions
         // into `const_eval` which will return `ErrorHandled::ToGeneric` if any of them are
         // encountered.
-        let substs = InternalSubsts::identity_for_item(self.tcx, def_id);
-        let instance = ty::Instance::new(def_id, substs);
+        let args = GenericArgs::identity_for_item(self.tcx, def_id);
+        let instance = ty::Instance::new(def_id, args);
         let cid = GlobalId { instance, promoted: None };
         let param_env =
             self.tcx.param_env(def_id).with_reveal_all_normalized(self.tcx).with_const();
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index 28c50587800c0..97f53a59fd66c 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -12,7 +12,7 @@ use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::visit::TypeVisitableExt;
 use crate::ty::{self, List, Ty, TyCtxt};
 use crate::ty::{AdtDef, InstanceDef, ScalarInt, UserTypeAnnotationIndex};
-use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
+use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 
 use rustc_data_structures::captures::Captures;
 use rustc_errors::{DiagnosticArgValue, DiagnosticMessage, ErrorGuaranteed, IntoDiagnosticArg};
@@ -1905,15 +1905,15 @@ impl<'tcx> Debug for Operand<'tcx> {
 
 impl<'tcx> Operand<'tcx> {
     /// Convenience helper to make a constant that refers to the fn
-    /// with given `DefId` and substs. Since this is used to synthesize
+    /// with given `DefId` and args. Since this is used to synthesize
     /// MIR, assumes `user_ty` is None.
     pub fn function_handle(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        substs: impl IntoIterator<Item = GenericArg<'tcx>>,
+        args: impl IntoIterator<Item = GenericArg<'tcx>>,
         span: Span,
     ) -> Self {
-        let ty = Ty::new_fn_def(tcx, def_id, substs);
+        let ty = Ty::new_fn_def(tcx, def_id, args);
         Operand::Constant(Box::new(Constant {
             span,
             user_ty: None,
@@ -1981,9 +1981,9 @@ impl<'tcx> Operand<'tcx> {
     ///
     /// While this is unlikely in general, it's the normal case of what you'll
     /// find as the `func` in a [`TerminatorKind::Call`].
-    pub fn const_fn_def(&self) -> Option<(DefId, SubstsRef<'tcx>)> {
+    pub fn const_fn_def(&self) -> Option<(DefId, GenericArgsRef<'tcx>)> {
         let const_ty = self.constant()?.literal.ty();
-        if let ty::FnDef(def_id, substs) = *const_ty.kind() { Some((def_id, substs)) } else { None }
+        if let ty::FnDef(def_id, args) = *const_ty.kind() { Some((def_id, args)) } else { None }
     }
 }
 
@@ -2137,12 +2137,12 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         }
                     }
 
-                    AggregateKind::Adt(adt_did, variant, substs, _user_ty, _) => {
+                    AggregateKind::Adt(adt_did, variant, args, _user_ty, _) => {
                         ty::tls::with(|tcx| {
                             let variant_def = &tcx.adt_def(adt_did).variant(variant);
-                            let substs = tcx.lift(substs).expect("could not lift for printing");
+                            let args = tcx.lift(args).expect("could not lift for printing");
                             let name = FmtPrinter::new(tcx, Namespace::ValueNS)
-                                .print_def_path(variant_def.def_id, substs)?
+                                .print_def_path(variant_def.def_id, args)?
                                 .into_buffer();
 
                             match variant_def.ctor_kind() {
@@ -2159,10 +2159,10 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                         })
                     }
 
-                    AggregateKind::Closure(def_id, substs) => ty::tls::with(|tcx| {
+                    AggregateKind::Closure(def_id, args) => ty::tls::with(|tcx| {
                         let name = if tcx.sess.opts.unstable_opts.span_free_formats {
-                            let substs = tcx.lift(substs).unwrap();
-                            format!("[closure@{}]", tcx.def_path_str_with_substs(def_id, substs),)
+                            let args = tcx.lift(args).unwrap();
+                            format!("[closure@{}]", tcx.def_path_str_with_args(def_id, args),)
                         } else {
                             let span = tcx.def_span(def_id);
                             format!(
@@ -2493,7 +2493,7 @@ impl<'tcx> ConstantKind<'tcx> {
         };
         debug!("expr.kind: {:?}", expr.kind);
 
-        let ty = tcx.type_of(def).subst_identity();
+        let ty = tcx.type_of(def).instantiate_identity();
         debug!(?ty);
 
         // FIXME(const_generics): We currently have to special case parameters because `min_const_generics`
@@ -2521,23 +2521,22 @@ impl<'tcx> ConstantKind<'tcx> {
         }
 
         let hir_id = tcx.hir().local_def_id_to_hir_id(def);
-        let parent_substs = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id)
+        let parent_args = if let Some(parent_hir_id) = tcx.hir().opt_parent_id(hir_id)
             && let Some(parent_did) = parent_hir_id.as_owner()
         {
-            InternalSubsts::identity_for_item(tcx, parent_did)
+            GenericArgs::identity_for_item(tcx, parent_did)
         } else {
             List::empty()
         };
-        debug!(?parent_substs);
+        debug!(?parent_args);
 
         let did = def.to_def_id();
-        let child_substs = InternalSubsts::identity_for_item(tcx, did);
-        let substs =
-            tcx.mk_substs_from_iter(parent_substs.into_iter().chain(child_substs.into_iter()));
-        debug!(?substs);
+        let child_args = GenericArgs::identity_for_item(tcx, did);
+        let args = tcx.mk_args_from_iter(parent_args.into_iter().chain(child_args.into_iter()));
+        debug!(?args);
 
         let span = tcx.def_span(def);
-        let uneval = UnevaluatedConst::new(did, substs);
+        let uneval = UnevaluatedConst::new(did, args);
         debug!(?span, ?param_env);
 
         match tcx.const_eval_resolve(param_env, uneval, Some(span)) {
@@ -2552,7 +2551,7 @@ impl<'tcx> ConstantKind<'tcx> {
                 Self::Unevaluated(
                     UnevaluatedConst {
                         def: did,
-                        substs: InternalSubsts::identity_for_item(tcx, did),
+                        args: GenericArgs::identity_for_item(tcx, did),
                         promoted: None,
                     },
                     ty,
@@ -2578,7 +2577,7 @@ impl<'tcx> ConstantKind<'tcx> {
 #[derive(Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct UnevaluatedConst<'tcx> {
     pub def: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
     pub promoted: Option<Promoted>,
 }
 
@@ -2586,14 +2585,14 @@ impl<'tcx> UnevaluatedConst<'tcx> {
     #[inline]
     pub fn shrink(self) -> ty::UnevaluatedConst<'tcx> {
         assert_eq!(self.promoted, None);
-        ty::UnevaluatedConst { def: self.def, substs: self.substs }
+        ty::UnevaluatedConst { def: self.def, args: self.args }
     }
 }
 
 impl<'tcx> UnevaluatedConst<'tcx> {
     #[inline]
-    pub fn new(def: DefId, substs: SubstsRef<'tcx>) -> UnevaluatedConst<'tcx> {
-        UnevaluatedConst { def, substs, promoted: Default::default() }
+    pub fn new(def: DefId, args: GenericArgsRef<'tcx>) -> UnevaluatedConst<'tcx> {
+        UnevaluatedConst { def, args, promoted: Default::default() }
     }
 }
 
@@ -2906,15 +2905,15 @@ fn pretty_print_const_value<'tcx>(
                         ty::Adt(def, _) if def.variants().is_empty() => {
                             fmt.write_str(&format!("{{unreachable(): {}}}", ty))?;
                         }
-                        ty::Adt(def, substs) => {
+                        ty::Adt(def, args) => {
                             let variant_idx = contents
                                 .variant
                                 .expect("destructed mir constant of adt without variant idx");
                             let variant_def = &def.variant(variant_idx);
-                            let substs = tcx.lift(substs).unwrap();
+                            let args = tcx.lift(args).unwrap();
                             let mut cx = FmtPrinter::new(tcx, Namespace::ValueNS);
                             cx.print_alloc_ids = true;
-                            let cx = cx.print_value_path(variant_def.def_id, substs)?;
+                            let cx = cx.print_value_path(variant_def.def_id, args)?;
                             fmt.write_str(&cx.into_buffer())?;
 
                             match variant_def.ctor_kind() {
diff --git a/compiler/rustc_middle/src/mir/mono.rs b/compiler/rustc_middle/src/mir/mono.rs
index ca735d5231465..ca3cd943d3d5d 100644
--- a/compiler/rustc_middle/src/mir/mono.rs
+++ b/compiler/rustc_middle/src/mir/mono.rs
@@ -1,5 +1,5 @@
 use crate::dep_graph::{DepNode, WorkProduct, WorkProductId};
-use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
+use crate::ty::{GenericArgs, Instance, InstanceDef, SymbolName, TyCtxt};
 use rustc_attr::InlineAttr;
 use rustc_data_structures::base_n;
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -71,7 +71,7 @@ impl<'tcx> MonoItem<'tcx> {
 
     pub fn is_generic_fn(&self) -> bool {
         match *self {
-            MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
+            MonoItem::Fn(ref instance) => instance.args.non_erasable_generics().next().is_some(),
             MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
         }
     }
@@ -168,14 +168,14 @@ impl<'tcx> MonoItem<'tcx> {
     /// which will never be accessed) in its place.
     pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
         debug!("is_instantiable({:?})", self);
-        let (def_id, substs) = match *self {
-            MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
-            MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
+        let (def_id, args) = match *self {
+            MonoItem::Fn(ref instance) => (instance.def_id(), instance.args),
+            MonoItem::Static(def_id) => (def_id, GenericArgs::empty()),
             // global asm never has predicates
             MonoItem::GlobalAsm(..) => return true,
         };
 
-        !tcx.subst_and_check_impossible_predicates((def_id, &substs))
+        !tcx.subst_and_check_impossible_predicates((def_id, &args))
     }
 
     pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
@@ -216,7 +216,7 @@ impl<'tcx> fmt::Display for MonoItem<'tcx> {
         match *self {
             MonoItem::Fn(instance) => write!(f, "fn {}", instance),
             MonoItem::Static(def_id) => {
-                write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty()))
+                write!(f, "static {}", Instance::new(def_id, GenericArgs::empty()))
             }
             MonoItem::GlobalAsm(..) => write!(f, "global_asm"),
         }
diff --git a/compiler/rustc_middle/src/mir/pretty.rs b/compiler/rustc_middle/src/mir/pretty.rs
index ffa7a5400d358..8cbab31451b2f 100644
--- a/compiler/rustc_middle/src/mir/pretty.rs
+++ b/compiler/rustc_middle/src/mir/pretty.rs
@@ -477,7 +477,7 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
                 ConstantKind::Ty(ct) => match ct.kind() {
                     ty::ConstKind::Param(p) => format!("Param({})", p),
                     ty::ConstKind::Unevaluated(uv) => {
-                        format!("Unevaluated({}, {:?})", self.tcx.def_path_str(uv.def), uv.substs,)
+                        format!("Unevaluated({}, {:?})", self.tcx.def_path_str(uv.def), uv.args,)
                     }
                     ty::ConstKind::Value(val) => format!("Value({})", fmt_valtree(&val)),
                     ty::ConstKind::Error(_) => "Error".to_string(),
@@ -491,7 +491,7 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
                     format!(
                         "Unevaluated({}, {:?}, {:?})",
                         self.tcx.def_path_str(uv.def),
-                        uv.substs,
+                        uv.args,
                         uv.promoted,
                     )
                 }
@@ -512,16 +512,16 @@ impl<'tcx> Visitor<'tcx> for ExtraComments<'tcx> {
         self.super_rvalue(rvalue, location);
         if let Rvalue::Aggregate(kind, _) = rvalue {
             match **kind {
-                AggregateKind::Closure(def_id, substs) => {
+                AggregateKind::Closure(def_id, args) => {
                     self.push("closure");
                     self.push(&format!("+ def_id: {:?}", def_id));
-                    self.push(&format!("+ substs: {:#?}", substs));
+                    self.push(&format!("+ args: {:#?}", args));
                 }
 
-                AggregateKind::Generator(def_id, substs, movability) => {
+                AggregateKind::Generator(def_id, args, movability) => {
                     self.push("generator");
                     self.push(&format!("+ def_id: {:?}", def_id));
-                    self.push(&format!("+ substs: {:#?}", substs));
+                    self.push(&format!("+ args: {:#?}", args));
                     self.push(&format!("+ movability: {:?}", movability));
                 }
 
diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 613b132ff2d5c..e8cb9860ee594 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -194,7 +194,7 @@ impl Debug for GeneratorLayout<'_> {
         }
         impl Debug for GenVariantPrinter {
             fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-                let variant_name = ty::GeneratorSubsts::variant_name(self.0);
+                let variant_name = ty::GeneratorArgs::variant_name(self.0);
                 if fmt.alternate() {
                     write!(fmt, "{:9}({:?})", variant_name, self.0)
                 } else {
@@ -265,10 +265,10 @@ pub struct ConstQualifs {
 /// `UniversalRegions::closure_mapping`.) Note the free regions in the
 /// closure's signature and captures are erased.
 ///
-/// Example: If type check produces a closure with the closure substs:
+/// Example: If type check produces a closure with the closure args:
 ///
 /// ```text
-/// ClosureSubsts = [
+/// ClosureArgs = [
 ///     'a,                                         // From the parent.
 ///     'b,
 ///     i8,                                         // the "closure kind"
@@ -280,7 +280,7 @@ pub struct ConstQualifs {
 /// We would "renumber" each free region to a unique vid, as follows:
 ///
 /// ```text
-/// ClosureSubsts = [
+/// ClosureArgs = [
 ///     '1,                                         // From the parent.
 ///     '2,
 ///     i8,                                         // the "closure kind"
diff --git a/compiler/rustc_middle/src/mir/syntax.rs b/compiler/rustc_middle/src/mir/syntax.rs
index 8c8efc36a2ff9..be27bf75dbd15 100644
--- a/compiler/rustc_middle/src/mir/syntax.rs
+++ b/compiler/rustc_middle/src/mir/syntax.rs
@@ -8,7 +8,7 @@ use super::{BasicBlock, Constant, Local, SwitchTargets, UserTypeProjection};
 use crate::mir::coverage::{CodeRegion, CoverageKind};
 use crate::traits::Reveal;
 use crate::ty::adjustment::PointerCoercion;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, List, Ty};
 use crate::ty::{Region, UserTypeAnnotationIndex};
 
@@ -1268,10 +1268,10 @@ pub enum AggregateKind<'tcx> {
     /// active field number and is present only for union expressions
     /// -- e.g., for a union expression `SomeUnion { c: .. }`, the
     /// active field index would identity the field `c`
-    Adt(DefId, VariantIdx, SubstsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<FieldIdx>),
+    Adt(DefId, VariantIdx, GenericArgsRef<'tcx>, Option<UserTypeAnnotationIndex>, Option<FieldIdx>),
 
-    Closure(DefId, SubstsRef<'tcx>),
-    Generator(DefId, SubstsRef<'tcx>, hir::Movability),
+    Closure(DefId, GenericArgsRef<'tcx>),
+    Generator(DefId, GenericArgsRef<'tcx>, hir::Movability),
 }
 
 #[derive(Clone, Debug, PartialEq, Eq, TyEncodable, TyDecodable, Hash, HashStable)]
diff --git a/compiler/rustc_middle/src/mir/tcx.rs b/compiler/rustc_middle/src/mir/tcx.rs
index 8618a53152792..f79697936d28c 100644
--- a/compiler/rustc_middle/src/mir/tcx.rs
+++ b/compiler/rustc_middle/src/mir/tcx.rs
@@ -35,7 +35,7 @@ impl<'tcx> PlaceTy<'tcx> {
     #[instrument(level = "debug", skip(tcx), ret)]
     pub fn field_ty(self, tcx: TyCtxt<'tcx>, f: FieldIdx) -> Ty<'tcx> {
         match self.ty.kind() {
-            ty::Adt(adt_def, substs) => {
+            ty::Adt(adt_def, args) => {
                 let variant_def = match self.variant_index {
                     None => adt_def.non_enum_variant(),
                     Some(variant_index) => {
@@ -44,7 +44,7 @@ impl<'tcx> PlaceTy<'tcx> {
                     }
                 };
                 let field_def = &variant_def.fields[f];
-                field_def.ty(tcx, substs)
+                field_def.ty(tcx, args)
             }
             ty::Tuple(tys) => tys[f.index()],
             _ => bug!("extracting field of non-tuple non-adt: {:?}", self),
@@ -198,10 +198,10 @@ impl<'tcx> Rvalue<'tcx> {
                 AggregateKind::Tuple => {
                     Ty::new_tup_from_iter(tcx, ops.iter().map(|op| op.ty(local_decls, tcx)))
                 }
-                AggregateKind::Adt(did, _, substs, _, _) => tcx.type_of(did).subst(tcx, substs),
-                AggregateKind::Closure(did, substs) => Ty::new_closure(tcx, did, substs),
-                AggregateKind::Generator(did, substs, movability) => {
-                    Ty::new_generator(tcx, did, substs, movability)
+                AggregateKind::Adt(did, _, args, _, _) => tcx.type_of(did).instantiate(tcx, args),
+                AggregateKind::Closure(did, args) => Ty::new_closure(tcx, did, args),
+                AggregateKind::Generator(did, args, movability) => {
+                    Ty::new_generator(tcx, did, args, movability)
                 }
             },
             Rvalue::ShallowInitBox(_, ty) => Ty::new_box(tcx, ty),
diff --git a/compiler/rustc_middle/src/mir/visit.rs b/compiler/rustc_middle/src/mir/visit.rs
index 205dc9ec7465e..64bc4fa7926d9 100644
--- a/compiler/rustc_middle/src/mir/visit.rs
+++ b/compiler/rustc_middle/src/mir/visit.rs
@@ -63,7 +63,7 @@
 //! `is_cleanup` above.
 
 use crate::mir::*;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, CanonicalUserTypeAnnotation, Ty};
 use rustc_span::Span;
 
@@ -245,12 +245,12 @@ macro_rules! make_mir_visitor {
                 self.super_region(region);
             }
 
-            fn visit_substs(
+            fn visit_args(
                 &mut self,
-                substs: & $($mutability)? SubstsRef<'tcx>,
+                args: & $($mutability)? GenericArgsRef<'tcx>,
                 _: Location,
             ) {
-                self.super_substs(substs);
+                self.super_args(args);
             }
 
             fn visit_local_decl(
@@ -335,7 +335,7 @@ macro_rules! make_mir_visitor {
 
                     self.visit_span($(& $mutability)? *callsite_span);
 
-                    let ty::Instance { def: callee_def, substs: callee_substs } = callee;
+                    let ty::Instance { def: callee_def, args: callee_args } = callee;
                     match callee_def {
                         ty::InstanceDef::Item(_def_id) => {}
 
@@ -355,7 +355,7 @@ macro_rules! make_mir_visitor {
                             self.visit_ty($(& $mutability)? *ty, TyContext::Location(location));
                         }
                     }
-                    self.visit_substs(callee_substs, location);
+                    self.visit_args(callee_args, location);
                 }
                 if let Some(inlined_parent_scope) = inlined_parent_scope {
                     self.visit_source_scope($(& $mutability)? *inlined_parent_scope);
@@ -721,24 +721,24 @@ macro_rules! make_mir_visitor {
                             AggregateKind::Adt(
                                 _adt_def,
                                 _variant_index,
-                                substs,
-                                _user_substs,
+                                args,
+                                _user_args,
                                 _active_field_index
                             ) => {
-                                self.visit_substs(substs, location);
+                                self.visit_args(args, location);
                             }
                             AggregateKind::Closure(
                                 _,
-                                closure_substs
+                                closure_args
                             ) => {
-                                self.visit_substs(closure_substs, location);
+                                self.visit_args(closure_args, location);
                             }
                             AggregateKind::Generator(
                                 _,
-                                generator_substs,
+                                generator_args,
                                 _movability,
                             ) => {
-                                self.visit_substs(generator_substs, location);
+                                self.visit_args(generator_args, location);
                             }
                         }
 
@@ -933,7 +933,7 @@ macro_rules! make_mir_visitor {
             fn super_region(&mut self, _region: $(& $mutability)? ty::Region<'tcx>) {
             }
 
-            fn super_substs(&mut self, _substs: & $($mutability)? SubstsRef<'tcx>) {
+            fn super_args(&mut self, _args: & $($mutability)? GenericArgsRef<'tcx>) {
             }
 
             // Convenience methods
diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index 28e699cd269de..a8aec3096d5de 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -6,8 +6,8 @@ use crate::mir::interpret::ConstValue;
 use crate::traits;
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::{TyAndLayout, ValidityRequirement};
-use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{GenericArg, GenericArgsRef};
 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
 use rustc_hir::hir_id::{HirId, OwnerId};
 use rustc_query_system::query::{DefaultCacheSelector, SingleCacheSelector, VecCacheSelector};
@@ -286,7 +286,7 @@ impl Key for (DefId, SimplifiedType) {
     }
 }
 
-impl<'tcx> Key for SubstsRef<'tcx> {
+impl<'tcx> Key for GenericArgsRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
@@ -294,7 +294,7 @@ impl<'tcx> Key for SubstsRef<'tcx> {
     }
 }
 
-impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
+impl<'tcx> Key for (DefId, GenericArgsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
@@ -310,7 +310,7 @@ impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
     }
 }
 
-impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
+impl<'tcx> Key for (LocalDefId, DefId, GenericArgsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
@@ -487,7 +487,7 @@ impl Key for (Symbol, u32, u32) {
     }
 }
 
-impl<'tcx> Key for (DefId, Ty<'tcx>, SubstsRef<'tcx>, ty::ParamEnv<'tcx>) {
+impl<'tcx> Key for (DefId, Ty<'tcx>, GenericArgsRef<'tcx>, ty::ParamEnv<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index a059590e6ad23..45fa82ba68ad5 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -44,7 +44,6 @@ use crate::traits::{
 };
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::layout::ValidityRequirement;
-use crate::ty::subst::{GenericArg, SubstsRef};
 use crate::ty::util::AlwaysRequiresDrop;
 use crate::ty::GeneratorDiagnosticData;
 use crate::ty::TyCtxtFeed;
@@ -52,6 +51,7 @@ use crate::ty::{
     self, print::describe_as_module, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt,
     UnusedGenericParams,
 };
+use crate::ty::{GenericArg, GenericArgsRef};
 use rustc_arena::TypedArena;
 use rustc_ast as ast;
 use rustc_ast::expand::{allocator::AllocatorKind, StrippedCfgItem};
@@ -1032,7 +1032,7 @@ rustc_queries! {
     }
 
     /// Obtain all the calls into other local functions
-    query mir_inliner_callees(key: ty::InstanceDef<'tcx>) -> &'tcx [(DefId, SubstsRef<'tcx>)] {
+    query mir_inliner_callees(key: ty::InstanceDef<'tcx>) -> &'tcx [(DefId, GenericArgsRef<'tcx>)] {
         fatal_cycle
         desc { |tcx|
             "computing all local function calls in `{}`",
@@ -1537,7 +1537,7 @@ rustc_queries! {
     /// added or removed in any upstream crate. Instead use the narrower
     /// `upstream_monomorphizations_for`, `upstream_drop_glue_for`, or, even
     /// better, `Instance::upstream_monomorphization()`.
-    query upstream_monomorphizations(_: ()) -> &'tcx DefIdMap<FxHashMap<SubstsRef<'tcx>, CrateNum>> {
+    query upstream_monomorphizations(_: ()) -> &'tcx DefIdMap<FxHashMap<GenericArgsRef<'tcx>, CrateNum>> {
         arena_cache
         desc { "collecting available upstream monomorphizations" }
     }
@@ -1550,7 +1550,7 @@ rustc_queries! {
     /// You likely want to call `Instance::upstream_monomorphization()`
     /// instead of invoking this query directly.
     query upstream_monomorphizations_for(def_id: DefId)
-        -> Option<&'tcx FxHashMap<SubstsRef<'tcx>, CrateNum>>
+        -> Option<&'tcx FxHashMap<GenericArgsRef<'tcx>, CrateNum>>
     {
         desc { |tcx|
             "collecting available upstream monomorphizations for `{}`",
@@ -1560,7 +1560,7 @@ rustc_queries! {
     }
 
     /// Returns the upstream crate that exports drop-glue for the given
-    /// type (`substs` is expected to be a single-item list containing the
+    /// type (`args` is expected to be a single-item list containing the
     /// type one wants drop-glue for).
     ///
     /// This is a subset of `upstream_monomorphizations_for` in order to
@@ -1574,8 +1574,8 @@ rustc_queries! {
     /// NOTE: This query could easily be extended to also support other
     ///       common functions that have are large set of monomorphizations
     ///       (like `Clone::clone` for example).
-    query upstream_drop_glue_for(substs: SubstsRef<'tcx>) -> Option<CrateNum> {
-        desc { "available upstream drop-glue for `{:?}`", substs }
+    query upstream_drop_glue_for(args: GenericArgsRef<'tcx>) -> Option<CrateNum> {
+        desc { "available upstream drop-glue for `{:?}`", args }
     }
 
     /// Returns a list of all `extern` blocks of a crate.
@@ -2053,7 +2053,7 @@ rustc_queries! {
         desc { "normalizing `{:?}`", goal.value.value.value }
     }
 
-    query subst_and_check_impossible_predicates(key: (DefId, SubstsRef<'tcx>)) -> bool {
+    query subst_and_check_impossible_predicates(key: (DefId, GenericArgsRef<'tcx>)) -> bool {
         desc { |tcx|
             "checking impossible substituted predicates: `{}`",
             tcx.def_path_str(key.0)
@@ -2104,16 +2104,16 @@ rustc_queries! {
     }
 
     /// Attempt to resolve the given `DefId` to an `Instance`, for the
-    /// given generics args (`SubstsRef`), returning one of:
+    /// given generics args (`GenericArgsRef`), returning one of:
     ///  * `Ok(Some(instance))` on success
-    ///  * `Ok(None)` when the `SubstsRef` are still too generic,
+    ///  * `Ok(None)` when the `GenericArgsRef` are still too generic,
     ///    and therefore don't allow finding the final `Instance`
     ///  * `Err(ErrorGuaranteed)` when the `Instance` resolution process
     ///    couldn't complete due to errors elsewhere - this is distinct
     ///    from `Ok(None)` to avoid misleading diagnostics when an error
     ///    has already been/will be emitted, for the original cause
     query resolve_instance(
-        key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>
+        key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>
     ) -> Result<Option<ty::Instance<'tcx>>, ErrorGuaranteed> {
         desc { "resolving instance `{}`", ty::Instance::new(key.value.0, key.value.1) }
     }
diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs
index e9af5070e5e81..e070b05472023 100644
--- a/compiler/rustc_middle/src/thir.rs
+++ b/compiler/rustc_middle/src/thir.rs
@@ -19,8 +19,8 @@ use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::AllocId;
 use rustc_middle::mir::{self, BinOp, BorrowKind, FakeReadCause, Mutability, UnOp};
 use rustc_middle::ty::adjustment::PointerCoercion;
-use rustc_middle::ty::subst::SubstsRef;
-use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarSubsts};
+use rustc_middle::ty::GenericArgsRef;
+use rustc_middle::ty::{self, AdtDef, FnSig, List, Ty, UpvarArgs};
 use rustc_middle::ty::{CanonicalUserType, CanonicalUserTypeAnnotation};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::{sym, Span, Symbol, DUMMY_SP};
@@ -150,9 +150,9 @@ pub struct AdtExpr<'tcx> {
     pub adt_def: AdtDef<'tcx>,
     /// The variant of the ADT.
     pub variant_index: VariantIdx,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 
-    /// Optional user-given substs: for something like `let x =
+    /// Optional user-given args: for something like `let x =
     /// Bar::<T> { ... }`.
     pub user_ty: UserTy<'tcx>,
 
@@ -164,7 +164,7 @@ pub struct AdtExpr<'tcx> {
 #[derive(Clone, Debug, HashStable)]
 pub struct ClosureExpr<'tcx> {
     pub closure_id: LocalDefId,
-    pub substs: UpvarSubsts<'tcx>,
+    pub args: UpvarArgs<'tcx>,
     pub upvars: Box<[ExprId]>,
     pub movability: Option<hir::Movability>,
     pub fake_reads: Vec<(ExprId, FakeReadCause, hir::HirId)>,
@@ -418,7 +418,7 @@ pub enum ExprKind<'tcx> {
     /// An inline `const` block, e.g. `const {}`.
     ConstBlock {
         did: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     },
     /// An array literal constructed from one repeated element, e.g. `[1; 5]`.
     Repeat {
@@ -466,7 +466,7 @@ pub enum ExprKind<'tcx> {
     /// Associated constants and named constants
     NamedConst {
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         user_ty: UserTy<'tcx>,
     },
     ConstParam {
@@ -714,7 +714,7 @@ pub enum PatKind<'tcx> {
     /// multiple variants.
     Variant {
         adt_def: AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         variant_index: VariantIdx,
         subpatterns: Vec<FieldPat<'tcx>>,
     },
diff --git a/compiler/rustc_middle/src/thir/visit.rs b/compiler/rustc_middle/src/thir/visit.rs
index 14bc1ac0ce75f..55ec17423ec93 100644
--- a/compiler/rustc_middle/src/thir/visit.rs
+++ b/compiler/rustc_middle/src/thir/visit.rs
@@ -101,7 +101,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
             }
         }
         Become { value } => visitor.visit_expr(&visitor.thir()[value]),
-        ConstBlock { did: _, substs: _ } => {}
+        ConstBlock { did: _, args: _ } => {}
         Repeat { value, count: _ } => {
             visitor.visit_expr(&visitor.thir()[value]);
         }
@@ -115,7 +115,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
             ref base,
             adt_def: _,
             variant_index: _,
-            substs: _,
+            args: _,
             user_ty: _,
         }) => {
             for field in &**fields {
@@ -130,7 +130,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         }
         Closure(box ClosureExpr {
             closure_id: _,
-            substs: _,
+            args: _,
             upvars: _,
             movability: _,
             fake_reads: _,
@@ -138,7 +138,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
         Literal { lit: _, neg: _ } => {}
         NonHirLiteral { lit: _, user_ty: _ } => {}
         ZstLiteral { user_ty: _ } => {}
-        NamedConst { def_id: _, substs: _, user_ty: _ } => {}
+        NamedConst { def_id: _, args: _, user_ty: _ } => {}
         ConstParam { param: _, def_id: _ } => {}
         StaticRef { alloc_id: _, ty: _, def_id: _ } => {}
         InlineAsm(box InlineAsmExpr { ref operands, template: _, options: _, line_spans: _ }) => {
@@ -227,7 +227,7 @@ pub fn walk_pat<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, pat: &Pat<'
             name: _,
         } => visitor.visit_pat(&subpattern),
         Binding { .. } | Wild => {}
-        Variant { subpatterns, adt_def: _, substs: _, variant_index: _ } | Leaf { subpatterns } => {
+        Variant { subpatterns, adt_def: _, args: _, variant_index: _ } | Leaf { subpatterns } => {
             for subpattern in subpatterns {
                 visitor.visit_pat(&subpattern.pattern);
             }
diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index c7d2e4c22d293..b7ffed57a0be0 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -12,7 +12,7 @@ pub mod util;
 use crate::infer::canonical::Canonical;
 use crate::mir::ConstraintCategory;
 use crate::ty::abstract_const::NotConstEvaluatable;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, AdtKind, Ty, TyCtxt};
 
 use rustc_data_structures::sync::Lrc;
@@ -199,7 +199,7 @@ impl<'tcx> ObligationCause<'tcx> {
 pub struct UnifyReceiverContext<'tcx> {
     pub assoc_item: ty::AssocItem,
     pub param_env: ty::ParamEnv<'tcx>,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 #[derive(Clone, PartialEq, Eq, Lift, Default, HashStable)]
@@ -696,7 +696,7 @@ impl<'tcx, N> ImplSource<'tcx, N> {
         match self {
             ImplSource::UserDefined(i) => ImplSource::UserDefined(ImplSourceUserDefinedData {
                 impl_def_id: i.impl_def_id,
-                substs: i.substs,
+                args: i.args,
                 nested: i.nested.into_iter().map(f).collect(),
             }),
             ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct),
@@ -729,7 +729,7 @@ impl<'tcx, N> ImplSource<'tcx, N> {
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceUserDefinedData<'tcx, N> {
     pub impl_def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
     pub nested: Vec<N>,
 }
 
diff --git a/compiler/rustc_middle/src/traits/query.rs b/compiler/rustc_middle/src/traits/query.rs
index 60a38747fdf05..950a59e9695cb 100644
--- a/compiler/rustc_middle/src/traits/query.rs
+++ b/compiler/rustc_middle/src/traits/query.rs
@@ -8,7 +8,7 @@
 use crate::error::DropCheckOverflow;
 use crate::infer::canonical::{Canonical, QueryResponse};
 use crate::ty::error::TypeError;
-use crate::ty::subst::GenericArg;
+use crate::ty::GenericArg;
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_span::source_map::Span;
 
@@ -132,7 +132,7 @@ impl<'tcx> DropckOutlivesResult<'tcx> {
 pub struct DropckConstraint<'tcx> {
     /// Types that are required to be alive in order for this
     /// type to be valid for destruction.
-    pub outlives: Vec<ty::subst::GenericArg<'tcx>>,
+    pub outlives: Vec<ty::GenericArg<'tcx>>,
 
     /// Types that could not be resolved: projections and params.
     pub dtorck_types: Vec<Ty<'tcx>>,
diff --git a/compiler/rustc_middle/src/traits/specialization_graph.rs b/compiler/rustc_middle/src/traits/specialization_graph.rs
index dc2cd20356094..18a57b6181a9e 100644
--- a/compiler/rustc_middle/src/traits/specialization_graph.rs
+++ b/compiler/rustc_middle/src/traits/specialization_graph.rs
@@ -259,7 +259,9 @@ pub fn ancestors(
 
     if let Some(reported) = specialization_graph.has_errored {
         Err(reported)
-    } else if let Err(reported) = tcx.type_of(start_from_impl).subst_identity().error_reported() {
+    } else if let Err(reported) =
+        tcx.type_of(start_from_impl).instantiate_identity().error_reported()
+    {
         Err(reported)
     } else {
         Ok(Ancestors {
diff --git a/compiler/rustc_middle/src/traits/structural_impls.rs b/compiler/rustc_middle/src/traits/structural_impls.rs
index a703e3c956228..e2cd118500b65 100644
--- a/compiler/rustc_middle/src/traits/structural_impls.rs
+++ b/compiler/rustc_middle/src/traits/structural_impls.rs
@@ -26,8 +26,8 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::ImplSourceUserDefinedData<'tcx,
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "ImplSourceUserDefinedData(impl_def_id={:?}, substs={:?}, nested={:?})",
-            self.impl_def_id, self.substs, self.nested
+            "ImplSourceUserDefinedData(impl_def_id={:?}, args={:?}, nested={:?})",
+            self.impl_def_id, self.args, self.nested
         )
     }
 }
diff --git a/compiler/rustc_middle/src/ty/abstract_const.rs b/compiler/rustc_middle/src/ty/abstract_const.rs
index ffee7ba28c33e..0364a620810a0 100644
--- a/compiler/rustc_middle/src/ty/abstract_const.rs
+++ b/compiler/rustc_middle/src/ty/abstract_const.rs
@@ -55,8 +55,8 @@ impl<'tcx> TyCtxt<'tcx> {
                     ty::ConstKind::Unevaluated(uv) => match self.tcx.thir_abstract_const(uv.def) {
                         Err(e) => ty::Const::new_error(self.tcx, e, c.ty()),
                         Ok(Some(bac)) => {
-                            let substs = self.tcx.erase_regions(uv.substs);
-                            let bac = bac.subst(self.tcx, substs);
+                            let args = self.tcx.erase_regions(uv.args);
+                            let bac = bac.instantiate(self.tcx, args);
                             return bac.fold_with(self);
                         }
                         Ok(None) => c,
diff --git a/compiler/rustc_middle/src/ty/assoc.rs b/compiler/rustc_middle/src/ty/assoc.rs
index cce609c261e8d..4e746a49d847d 100644
--- a/compiler/rustc_middle/src/ty/assoc.rs
+++ b/compiler/rustc_middle/src/ty/assoc.rs
@@ -84,11 +84,15 @@ impl AssocItem {
                 // late-bound regions, and we don't want method signatures to show up
                 // `as for<'r> fn(&'r MyType)`. Pretty-printing handles late-bound
                 // regions just fine, showing `fn(&MyType)`.
-                tcx.fn_sig(self.def_id).subst_identity().skip_binder().to_string()
+                tcx.fn_sig(self.def_id).instantiate_identity().skip_binder().to_string()
             }
             ty::AssocKind::Type => format!("type {};", self.name),
             ty::AssocKind::Const => {
-                format!("const {}: {:?};", self.name, tcx.type_of(self.def_id).subst_identity())
+                format!(
+                    "const {}: {:?};",
+                    self.name,
+                    tcx.type_of(self.def_id).instantiate_identity()
+                )
             }
         }
     }
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index 6adbb44a15316..b4f4f9bef8e88 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -13,7 +13,7 @@ use crate::mir::{
     interpret::{AllocId, ConstAllocation},
 };
 use crate::traits;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, AdtDef, Ty};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::ty::TyCtxt;
@@ -254,12 +254,12 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Clause<'tcx> {
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for SubstsRef<'tcx> {
+impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArgsRef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
         let tcx = decoder.interner();
-        tcx.mk_substs_from_iter(
-            (0..len).map::<ty::subst::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
+        tcx.mk_args_from_iter(
+            (0..len).map::<ty::GenericArg<'tcx>, _>(|_| Decodable::decode(decoder)),
         )
     }
 }
diff --git a/compiler/rustc_middle/src/ty/consts.rs b/compiler/rustc_middle/src/ty/consts.rs
index 1cbfe99f87fa0..bf9f5846ed9ff 100644
--- a/compiler/rustc_middle/src/ty/consts.rs
+++ b/compiler/rustc_middle/src/ty/consts.rs
@@ -1,6 +1,6 @@
 use crate::middle::resolve_bound_vars as rbv;
 use crate::mir::interpret::{AllocId, ConstValue, LitToConstInput, Scalar};
-use crate::ty::{self, InternalSubsts, ParamEnv, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::{self, GenericArgs, ParamEnv, ParamEnvAnd, Ty, TyCtxt, TypeVisitableExt};
 use rustc_data_structures::intern::Interned;
 use rustc_error_messages::MultiSpan;
 use rustc_hir as hir;
@@ -171,7 +171,7 @@ impl<'tcx> Const<'tcx> {
                 tcx,
                 ty::UnevaluatedConst {
                     def: def.to_def_id(),
-                    substs: InternalSubsts::identity_for_item(tcx, def.to_def_id()),
+                    args: GenericArgs::identity_for_item(tcx, def.to_def_id()),
                 },
                 ty,
             ),
@@ -225,7 +225,7 @@ impl<'tcx> Const<'tcx> {
             )) => {
                 // Use the type from the param's definition, since we can resolve it,
                 // not the expected parameter type from WithOptConstParam.
-                let param_ty = tcx.type_of(def_id).subst_identity();
+                let param_ty = tcx.type_of(def_id).instantiate_identity();
                 match tcx.named_bound_var(expr.hir_id) {
                     Some(rbv::ResolvedArg::EarlyBound(_)) => {
                         // Find the name and index of the const parameter by indexing the generics of
@@ -406,14 +406,14 @@ impl<'tcx> Const<'tcx> {
             // any region variables.
 
             // HACK(eddyb) when the query key would contain inference variables,
-            // attempt using identity substs and `ParamEnv` instead, that will succeed
+            // attempt using identity args and `ParamEnv` instead, that will succeed
             // when the expression doesn't depend on any parameters.
             // FIXME(eddyb, skinny121) pass `InferCtxt` into here when it's available, so that
             // we can call `infcx.const_eval_resolve` which handles inference variables.
             let param_env_and = if (param_env, unevaluated).has_non_region_infer() {
                 tcx.param_env(unevaluated.def).and(ty::UnevaluatedConst {
                     def: unevaluated.def,
-                    substs: InternalSubsts::identity_for_item(tcx, unevaluated.def),
+                    args: GenericArgs::identity_for_item(tcx, unevaluated.def),
                 })
             } else {
                 tcx.erase_regions(param_env)
@@ -430,8 +430,8 @@ impl<'tcx> Const<'tcx> {
                 EvalMode::Typeck => {
                     match tcx.const_eval_resolve_for_typeck(param_env, unevaluated, None) {
                         // NOTE(eddyb) `val` contains no lifetimes/types/consts,
-                        // and we use the original type, so nothing from `substs`
-                        // (which may be identity substs, see above),
+                        // and we use the original type, so nothing from `args`
+                        // (which may be identity args, see above),
                         // can leak through `val` into the const we return.
                         Ok(val) => Some(Ok(EvalResult::ValTree(val?))),
                         Err(ErrorHandled::TooGeneric) => None,
@@ -441,8 +441,8 @@ impl<'tcx> Const<'tcx> {
                 EvalMode::Mir => {
                     match tcx.const_eval_resolve(param_env, unevaluated.expand(), None) {
                         // NOTE(eddyb) `val` contains no lifetimes/types/consts,
-                        // and we use the original type, so nothing from `substs`
-                        // (which may be identity substs, see above),
+                        // and we use the original type, so nothing from `args`
+                        // (which may be identity args, see above),
                         // can leak through `val` into the const we return.
                         Ok(val) => Some(Ok(EvalResult::ConstVal(val))),
                         Err(ErrorHandled::TooGeneric) => None,
diff --git a/compiler/rustc_middle/src/ty/consts/kind.rs b/compiler/rustc_middle/src/ty/consts/kind.rs
index 5f2b6d42bf86e..6c76075c214dd 100644
--- a/compiler/rustc_middle/src/ty/consts/kind.rs
+++ b/compiler/rustc_middle/src/ty/consts/kind.rs
@@ -1,7 +1,7 @@
 use super::Const;
 use crate::mir;
 use crate::ty::abstract_const::CastKind;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, List, Ty};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir::def_id::DefId;
@@ -12,7 +12,7 @@ use rustc_macros::HashStable;
 #[derive(Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub struct UnevaluatedConst<'tcx> {
     pub def: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 impl rustc_errors::IntoDiagnosticArg for UnevaluatedConst<'_> {
@@ -24,14 +24,14 @@ impl rustc_errors::IntoDiagnosticArg for UnevaluatedConst<'_> {
 impl<'tcx> UnevaluatedConst<'tcx> {
     #[inline]
     pub fn expand(self) -> mir::UnevaluatedConst<'tcx> {
-        mir::UnevaluatedConst { def: self.def, substs: self.substs, promoted: None }
+        mir::UnevaluatedConst { def: self.def, args: self.args, promoted: None }
     }
 }
 
 impl<'tcx> UnevaluatedConst<'tcx> {
     #[inline]
-    pub fn new(def: DefId, substs: SubstsRef<'tcx>) -> UnevaluatedConst<'tcx> {
-        UnevaluatedConst { def, substs }
+    pub fn new(def: DefId, args: GenericArgsRef<'tcx>) -> UnevaluatedConst<'tcx> {
+        UnevaluatedConst { def, args }
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 6990fbbb63489..8bb13edbe9501 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -30,7 +30,7 @@ use crate::ty::{
     Predicate, PredicateKind, Region, RegionKind, ReprOptions, TraitObjectVisitor, Ty, TyKind,
     TyVid, TypeAndMut, Visibility,
 };
-use crate::ty::{GenericArg, InternalSubsts, SubstsRef};
+use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use rustc_ast::{self as ast, attr};
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -84,7 +84,7 @@ use std::ops::{Bound, Deref};
 #[allow(rustc::usage_of_ty_tykind)]
 impl<'tcx> Interner for TyCtxt<'tcx> {
     type AdtDef = ty::AdtDef<'tcx>;
-    type SubstsRef = ty::SubstsRef<'tcx>;
+    type GenericArgsRef = ty::GenericArgsRef<'tcx>;
     type DefId = DefId;
     type Binder<T> = Binder<'tcx, T>;
     type Ty = Ty<'tcx>;
@@ -142,7 +142,7 @@ pub struct CtxtInterners<'tcx> {
     // they're accessed quite often.
     type_: InternedSet<'tcx, WithCachedTypeInfo<TyKind<'tcx>>>,
     const_lists: InternedSet<'tcx, List<ty::Const<'tcx>>>,
-    substs: InternedSet<'tcx, InternalSubsts<'tcx>>,
+    args: InternedSet<'tcx, GenericArgs<'tcx>>,
     type_lists: InternedSet<'tcx, List<Ty<'tcx>>>,
     canonical_var_infos: InternedSet<'tcx, List<CanonicalVarInfo<'tcx>>>,
     region: InternedSet<'tcx, RegionKind<'tcx>>,
@@ -167,7 +167,7 @@ impl<'tcx> CtxtInterners<'tcx> {
             arena,
             type_: Default::default(),
             const_lists: Default::default(),
-            substs: Default::default(),
+            args: Default::default(),
             type_lists: Default::default(),
             region: Default::default(),
             poly_existential_predicates: Default::default(),
@@ -682,7 +682,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Creates a type context and call the closure with a `TyCtxt` reference
     /// to the context. The closure enforces that the type context and any interned
-    /// value (types, substs, etc.) can only be used while `ty::tls` has a valid
+    /// value (types, args, etc.) can only be used while `ty::tls` has a valid
     /// reference to the context, to allow formatting values that need it.
     pub fn create_global_ctxt(
         s: &'tcx Session,
@@ -1083,7 +1083,7 @@ impl<'tcx> TyCtxt<'tcx> {
             _ => return None,
         }
 
-        let ret_ty = self.type_of(scope_def_id).subst_identity();
+        let ret_ty = self.type_of(scope_def_id).instantiate_identity();
         match ret_ty.kind() {
             ty::FnDef(_, _) => {
                 let sig = ret_ty.fn_sig(self);
@@ -1125,7 +1125,7 @@ impl<'tcx> TyCtxt<'tcx> {
             self,
             self.lifetimes.re_static,
             self.type_of(self.require_lang_item(LangItem::PanicLocation, None))
-                .subst(self, self.mk_substs(&[self.lifetimes.re_static.into()])),
+                .instantiate(self, self.mk_args(&[self.lifetimes.re_static.into()])),
         )
     }
 
@@ -1168,7 +1168,7 @@ impl<'tcx> TyCtxt<'tcx> {
 /// A trait implemented for all `X<'a>` types that can be safely and
 /// efficiently converted to `X<'tcx>` as long as they are part of the
 /// provided `TyCtxt<'tcx>`.
-/// This can be done, for example, for `Ty<'tcx>` or `SubstsRef<'tcx>`
+/// This can be done, for example, for `Ty<'tcx>` or `GenericArgsRef<'tcx>`
 /// by looking them up in their respective interners.
 ///
 /// However, this is still not the best implementation as it does
@@ -1234,8 +1234,8 @@ nop_list_lift! {canonical_var_infos; CanonicalVarInfo<'a> => CanonicalVarInfo<'t
 nop_list_lift! {projs; ProjectionKind => ProjectionKind}
 nop_list_lift! {bound_variable_kinds; ty::BoundVariableKind => ty::BoundVariableKind}
 
-// This is the impl for `&'a InternalSubsts<'a>`.
-nop_list_lift! {substs; GenericArg<'a> => GenericArg<'tcx>}
+// This is the impl for `&'a GenericArgs<'a>`.
+nop_list_lift! {args; GenericArg<'a> => GenericArg<'tcx>}
 
 CloneLiftImpls! {
     Constness,
@@ -1347,7 +1347,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     Foreign
                 )?;
 
-                writeln!(fmt, "InternalSubsts interner: #{}", self.0.interners.substs.len())?;
+                writeln!(fmt, "GenericArgs interner: #{}", self.0.interners.args.len())?;
                 writeln!(fmt, "Region interner: #{}", self.0.interners.region.len())?;
                 writeln!(
                     fmt,
@@ -1503,7 +1503,7 @@ macro_rules! slice_interners {
 // should be used when possible, because it's faster.
 slice_interners!(
     const_lists: pub mk_const_list(Const<'tcx>),
-    substs: pub mk_substs(GenericArg<'tcx>),
+    args: pub mk_args(GenericArg<'tcx>),
     type_lists: pub mk_type_list(Ty<'tcx>),
     canonical_var_infos: pub mk_canonical_var_infos(CanonicalVarInfo<'tcx>),
     poly_existential_predicates: intern_poly_existential_predicates(PolyExistentialPredicate<'tcx>),
@@ -1617,12 +1617,12 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline(always)]
-    pub(crate) fn check_and_mk_substs(
+    pub(crate) fn check_and_mk_args(
         self,
         _def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
-    ) -> SubstsRef<'tcx> {
-        let substs = substs.into_iter().map(Into::into);
+        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+    ) -> GenericArgsRef<'tcx> {
+        let args = args.into_iter().map(Into::into);
         #[cfg(debug_assertions)]
         {
             let generics = self.generics_of(_def_id);
@@ -1638,12 +1638,12 @@ impl<'tcx> TyCtxt<'tcx> {
             };
             assert_eq!(
                 (n, Some(n)),
-                substs.size_hint(),
+                args.size_hint(),
                 "wrong number of generic parameters for {_def_id:?}: {:?}",
-                substs.collect::<Vec<_>>(),
+                args.collect::<Vec<_>>(),
             );
         }
-        self.mk_substs_from_iter(substs)
+        self.mk_args_from_iter(args)
     }
 
     #[inline]
@@ -1801,12 +1801,12 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_type_list(xs))
     }
 
-    pub fn mk_substs_from_iter<I, T>(self, iter: I) -> T::Output
+    pub fn mk_args_from_iter<I, T>(self, iter: I) -> T::Output
     where
         I: Iterator<Item = T>,
         T: CollectAndApply<GenericArg<'tcx>, &'tcx List<GenericArg<'tcx>>>,
     {
-        T::collect_and_apply(iter, |xs| self.mk_substs(xs))
+        T::collect_and_apply(iter, |xs| self.mk_args(xs))
     }
 
     pub fn mk_canonical_var_infos_from_iter<I, T>(self, iter: I) -> T::Output
@@ -1833,21 +1833,21 @@ impl<'tcx> TyCtxt<'tcx> {
         T::collect_and_apply(iter, |xs| self.mk_fields(xs))
     }
 
-    pub fn mk_substs_trait(
+    pub fn mk_args_trait(
         self,
         self_ty: Ty<'tcx>,
         rest: impl IntoIterator<Item = GenericArg<'tcx>>,
-    ) -> SubstsRef<'tcx> {
-        self.mk_substs_from_iter(iter::once(self_ty.into()).chain(rest))
+    ) -> GenericArgsRef<'tcx> {
+        self.mk_args_from_iter(iter::once(self_ty.into()).chain(rest))
     }
 
     pub fn mk_alias_ty(
         self,
         def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> ty::AliasTy<'tcx> {
-        let substs = self.check_and_mk_substs(def_id, substs);
-        ty::AliasTy { def_id, substs, _use_mk_alias_ty_instead: () }
+        let args = self.check_and_mk_args(def_id, args);
+        ty::AliasTy { def_id, args, _use_mk_alias_ty_instead: () }
     }
 
     pub fn mk_bound_variable_kinds_from_iter<I, T>(self, iter: I) -> T::Output
diff --git a/compiler/rustc_middle/src/ty/diagnostics.rs b/compiler/rustc_middle/src/ty/diagnostics.rs
index a0b17c374e49e..905e855896e42 100644
--- a/compiler/rustc_middle/src/ty/diagnostics.rs
+++ b/compiler/rustc_middle/src/ty/diagnostics.rs
@@ -71,7 +71,7 @@ impl<'tcx> Ty<'tcx> {
     /// ADTs with no type arguments.
     pub fn is_simple_text(self) -> bool {
         match self.kind() {
-            Adt(_, substs) => substs.non_erasable_generics().next().is_none(),
+            Adt(_, args) => args.non_erasable_generics().next().is_none(),
             Ref(_, ty, _) => ty.is_simple_text(),
             _ => self.is_simple_ty(),
         }
@@ -491,7 +491,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for IsSuggestableVisitor<'tcx> {
 
             Alias(Opaque, AliasTy { def_id, .. }) => {
                 let parent = self.tcx.parent(def_id);
-                let parent_ty = self.tcx.type_of(parent).subst_identity();
+                let parent_ty = self.tcx.type_of(parent).instantiate_identity();
                 if let DefKind::TyAlias | DefKind::AssocTy = self.tcx.def_kind(parent)
                     && let Alias(Opaque, AliasTy { def_id: parent_opaque_def_id, .. }) = *parent_ty.kind()
                     && parent_opaque_def_id == def_id
@@ -558,8 +558,8 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for MakeSuggestableFolder<'tcx> {
         let t = match *t.kind() {
             Infer(InferTy::TyVar(_)) if self.infer_suggestable => t,
 
-            FnDef(def_id, substs) => {
-                Ty::new_fn_ptr(self.tcx, self.tcx.fn_sig(def_id).subst(self.tcx, substs))
+            FnDef(def_id, args) => {
+                Ty::new_fn_ptr(self.tcx, self.tcx.fn_sig(def_id).instantiate(self.tcx, args))
             }
 
             // FIXME(compiler-errors): We could replace these with infer, I guess.
@@ -575,7 +575,7 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for MakeSuggestableFolder<'tcx> {
 
             Alias(Opaque, AliasTy { def_id, .. }) => {
                 let parent = self.tcx.parent(def_id);
-                let parent_ty = self.tcx.type_of(parent).subst_identity();
+                let parent_ty = self.tcx.type_of(parent).instantiate_identity();
                 if let hir::def::DefKind::TyAlias | hir::def::DefKind::AssocTy = self.tcx.def_kind(parent)
                     && let Alias(Opaque, AliasTy { def_id: parent_opaque_def_id, .. }) = *parent_ty.kind()
                     && parent_opaque_def_id == def_id
diff --git a/compiler/rustc_middle/src/ty/fast_reject.rs b/compiler/rustc_middle/src/ty/fast_reject.rs
index 76f61d9ac9c2d..e86ff4d26aaab 100644
--- a/compiler/rustc_middle/src/ty/fast_reject.rs
+++ b/compiler/rustc_middle/src/ty/fast_reject.rs
@@ -1,6 +1,6 @@
 use crate::mir::Mutability;
-use crate::ty::subst::GenericArgKind;
-use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::GenericArgKind;
+use crate::ty::{self, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
 use rustc_hir::def_id::DefId;
 use std::fmt::Debug;
 use std::hash::Hash;
@@ -188,12 +188,12 @@ pub struct DeepRejectCtxt {
 }
 
 impl DeepRejectCtxt {
-    pub fn substs_refs_may_unify<'tcx>(
+    pub fn args_refs_may_unify<'tcx>(
         self,
-        obligation_substs: SubstsRef<'tcx>,
-        impl_substs: SubstsRef<'tcx>,
+        obligation_args: GenericArgsRef<'tcx>,
+        impl_args: GenericArgsRef<'tcx>,
     ) -> bool {
-        iter::zip(obligation_substs, impl_substs).all(|(obl, imp)| {
+        iter::zip(obligation_args, impl_args).all(|(obl, imp)| {
             match (obl.unpack(), imp.unpack()) {
                 // We don't fast reject based on regions for now.
                 (GenericArgKind::Lifetime(_), GenericArgKind::Lifetime(_)) => true,
@@ -258,9 +258,9 @@ impl DeepRejectCtxt {
                 }
                 _ => false,
             },
-            ty::Adt(obl_def, obl_substs) => match k {
-                &ty::Adt(impl_def, impl_substs) => {
-                    obl_def == impl_def && self.substs_refs_may_unify(obl_substs, impl_substs)
+            ty::Adt(obl_def, obl_args) => match k {
+                &ty::Adt(impl_def, impl_args) => {
+                    obl_def == impl_def && self.args_refs_may_unify(obl_args, impl_args)
                 }
                 _ => false,
             },
diff --git a/compiler/rustc_middle/src/ty/flags.rs b/compiler/rustc_middle/src/ty/flags.rs
index ff391794703d5..bbd4a62333098 100644
--- a/compiler/rustc_middle/src/ty/flags.rs
+++ b/compiler/rustc_middle/src/ty/flags.rs
@@ -1,5 +1,5 @@
-use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, InferConst, Ty, TypeFlags};
+use crate::ty::{GenericArg, GenericArgKind};
 use std::slice;
 
 #[derive(Debug)]
@@ -105,48 +105,48 @@ impl FlagComputation {
                 self.add_flags(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
             }
 
-            ty::Generator(_, substs, _) => {
-                let substs = substs.as_generator();
+            ty::Generator(_, args, _) => {
+                let args = args.as_generator();
                 let should_remove_further_specializable =
                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
-                self.add_substs(substs.parent_substs());
+                self.add_args(args.parent_args());
                 if should_remove_further_specializable {
                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
                 }
 
-                self.add_ty(substs.resume_ty());
-                self.add_ty(substs.return_ty());
-                self.add_ty(substs.witness());
-                self.add_ty(substs.yield_ty());
-                self.add_ty(substs.tupled_upvars_ty());
+                self.add_ty(args.resume_ty());
+                self.add_ty(args.return_ty());
+                self.add_ty(args.witness());
+                self.add_ty(args.yield_ty());
+                self.add_ty(args.tupled_upvars_ty());
             }
 
             &ty::GeneratorWitness(ts) => {
                 self.bound_computation(ts, |flags, ts| flags.add_tys(ts));
             }
 
-            ty::GeneratorWitnessMIR(_, substs) => {
+            ty::GeneratorWitnessMIR(_, args) => {
                 let should_remove_further_specializable =
                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
-                self.add_substs(substs);
+                self.add_args(args);
                 if should_remove_further_specializable {
                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
                 }
                 self.add_flags(TypeFlags::HAS_TY_GENERATOR);
             }
 
-            &ty::Closure(_, substs) => {
-                let substs = substs.as_closure();
+            &ty::Closure(_, args) => {
+                let args = args.as_closure();
                 let should_remove_further_specializable =
                     !self.flags.contains(TypeFlags::STILL_FURTHER_SPECIALIZABLE);
-                self.add_substs(substs.parent_substs());
+                self.add_args(args.parent_args());
                 if should_remove_further_specializable {
                     self.flags -= TypeFlags::STILL_FURTHER_SPECIALIZABLE;
                 }
 
-                self.add_ty(substs.sig_as_fn_ptr_ty());
-                self.add_ty(substs.kind_ty());
-                self.add_ty(substs.tupled_upvars_ty());
+                self.add_ty(args.sig_as_fn_ptr_ty());
+                self.add_ty(args.kind_ty());
+                self.add_ty(args.tupled_upvars_ty());
             }
 
             &ty::Bound(debruijn, _) => {
@@ -172,8 +172,8 @@ impl FlagComputation {
                 }
             }
 
-            &ty::Adt(_, substs) => {
-                self.add_substs(substs);
+            &ty::Adt(_, args) => {
+                self.add_args(args);
             }
 
             &ty::Alias(kind, data) => {
@@ -189,7 +189,7 @@ impl FlagComputation {
             &ty::Dynamic(obj, r, _) => {
                 for predicate in obj.iter() {
                     self.bound_computation(predicate, |computation, predicate| match predicate {
-                        ty::ExistentialPredicate::Trait(tr) => computation.add_substs(tr.substs),
+                        ty::ExistentialPredicate::Trait(tr) => computation.add_args(tr.args),
                         ty::ExistentialPredicate::Projection(p) => {
                             computation.add_existential_projection(&p);
                         }
@@ -220,8 +220,8 @@ impl FlagComputation {
                 self.add_tys(types);
             }
 
-            &ty::FnDef(_, substs) => {
-                self.add_substs(substs);
+            &ty::FnDef(_, args) => {
+                self.add_args(args);
             }
 
             &ty::FnPtr(fn_sig) => self.bound_computation(fn_sig, |computation, fn_sig| {
@@ -238,7 +238,7 @@ impl FlagComputation {
     fn add_predicate_atom(&mut self, atom: ty::PredicateKind<'_>) {
         match atom {
             ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred)) => {
-                self.add_substs(trait_pred.trait_ref.substs);
+                self.add_args(trait_pred.trait_ref.args);
             }
             ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(ty::OutlivesPredicate(
                 a,
@@ -274,11 +274,11 @@ impl FlagComputation {
                 self.add_term(term);
             }
             ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(arg)) => {
-                self.add_substs(slice::from_ref(&arg));
+                self.add_args(slice::from_ref(&arg));
             }
             ty::PredicateKind::ObjectSafe(_def_id) => {}
-            ty::PredicateKind::ClosureKind(_def_id, substs, _kind) => {
-                self.add_substs(substs);
+            ty::PredicateKind::ClosureKind(_def_id, args, _kind) => {
+                self.add_args(args);
             }
             ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(uv)) => {
                 self.add_const(uv);
@@ -317,7 +317,7 @@ impl FlagComputation {
         self.add_ty(c.ty());
         match c.kind() {
             ty::ConstKind::Unevaluated(uv) => {
-                self.add_substs(uv.substs);
+                self.add_args(uv.args);
                 self.add_flags(TypeFlags::HAS_CT_PROJECTION);
             }
             ty::ConstKind::Infer(infer) => {
@@ -365,7 +365,7 @@ impl FlagComputation {
     }
 
     fn add_existential_projection(&mut self, projection: &ty::ExistentialProjection<'_>) {
-        self.add_substs(projection.substs);
+        self.add_args(projection.args);
         match projection.term.unpack() {
             ty::TermKind::Ty(ty) => self.add_ty(ty),
             ty::TermKind::Const(ct) => self.add_const(ct),
@@ -373,11 +373,11 @@ impl FlagComputation {
     }
 
     fn add_alias_ty(&mut self, alias_ty: ty::AliasTy<'_>) {
-        self.add_substs(alias_ty.substs);
+        self.add_args(alias_ty.args);
     }
 
-    fn add_substs(&mut self, substs: &[GenericArg<'_>]) {
-        for kind in substs {
+    fn add_args(&mut self, args: &[GenericArg<'_>]) {
+        for kind in args {
             match kind.unpack() {
                 GenericArgKind::Type(ty) => self.add_ty(ty),
                 GenericArgKind::Lifetime(lt) => self.add_region(lt),
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/generic_args.rs
similarity index 79%
rename from compiler/rustc_middle/src/ty/subst.rs
rename to compiler/rustc_middle/src/ty/generic_args.rs
index e1a58b975576e..12af845649439 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -1,8 +1,8 @@
-// Type substitutions.
+// Generic arguments.
 
 use crate::ty::codec::{TyDecoder, TyEncoder};
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
-use crate::ty::sty::{ClosureSubsts, GeneratorSubsts, InlineConstSubsts};
+use crate::ty::sty::{ClosureArgs, GeneratorArgs, InlineConstArgs};
 use crate::ty::visit::{TypeVisitable, TypeVisitableExt, TypeVisitor};
 use crate::ty::{self, Lift, List, ParamConst, Ty, TyCtxt};
 
@@ -174,7 +174,7 @@ impl<'tcx> GenericArg<'tcx> {
     }
 
     /// Unpack the `GenericArg` as a type when it is known certainly to be a type.
-    /// This is true in cases where `Substs` is used in places where the kinds are known
+    /// This is true in cases where `GenericArgs` is used in places where the kinds are known
     /// to be limited (e.g. in tuples, where the only parameters are type parameters).
     pub fn expect_ty(self) -> Ty<'tcx> {
         self.as_type().unwrap_or_else(|| bug!("expected a type, but found another kind"))
@@ -241,13 +241,13 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArg<'tcx> {
     }
 }
 
-/// List of generic arguments that are gonna be used to substitute generic parameters.
-pub type InternalSubsts<'tcx> = List<GenericArg<'tcx>>;
+/// List of generic arguments that are gonna be used to replace generic parameters.
+pub type GenericArgs<'tcx> = List<GenericArg<'tcx>>;
 
-pub type SubstsRef<'tcx> = &'tcx InternalSubsts<'tcx>;
+pub type GenericArgsRef<'tcx> = &'tcx GenericArgs<'tcx>;
 
-impl<'tcx> InternalSubsts<'tcx> {
-    /// Converts substs to a type list.
+impl<'tcx> GenericArgs<'tcx> {
+    /// Converts generic args to a type list.
     ///
     /// # Panics
     ///
@@ -255,66 +255,71 @@ impl<'tcx> InternalSubsts<'tcx> {
     pub fn into_type_list(&self, tcx: TyCtxt<'tcx>) -> &'tcx List<Ty<'tcx>> {
         tcx.mk_type_list_from_iter(self.iter().map(|arg| match arg.unpack() {
             GenericArgKind::Type(ty) => ty,
-            _ => bug!("`into_type_list` called on substs with non-types"),
+            _ => bug!("`into_type_list` called on generic arg with non-types"),
         }))
     }
 
-    /// Interpret these substitutions as the substitutions of a closure type.
-    /// Closure substitutions have a particular structure controlled by the
+    /// Interpret these generic args as the args of a closure type.
+    /// Closure args have a particular structure controlled by the
     /// compiler that encodes information like the signature and closure kind;
-    /// see `ty::ClosureSubsts` struct for more comments.
-    pub fn as_closure(&'tcx self) -> ClosureSubsts<'tcx> {
-        ClosureSubsts { substs: self }
+    /// see `ty::ClosureArgs` struct for more comments.
+    pub fn as_closure(&'tcx self) -> ClosureArgs<'tcx> {
+        ClosureArgs { args: self }
     }
 
-    /// Interpret these substitutions as the substitutions of a generator type.
-    /// Generator substitutions have a particular structure controlled by the
+    /// Interpret these generic args as the args of a generator type.
+    /// Generator args have a particular structure controlled by the
     /// compiler that encodes information like the signature and generator kind;
-    /// see `ty::GeneratorSubsts` struct for more comments.
-    pub fn as_generator(&'tcx self) -> GeneratorSubsts<'tcx> {
-        GeneratorSubsts { substs: self }
+    /// see `ty::GeneratorArgs` struct for more comments.
+    pub fn as_generator(&'tcx self) -> GeneratorArgs<'tcx> {
+        GeneratorArgs { args: self }
     }
 
-    /// Interpret these substitutions as the substitutions of an inline const.
-    /// Inline const substitutions have a particular structure controlled by the
+    /// Interpret these generic args as the args of an inline const.
+    /// Inline const args have a particular structure controlled by the
     /// compiler that encodes information like the inferred type;
-    /// see `ty::InlineConstSubsts` struct for more comments.
-    pub fn as_inline_const(&'tcx self) -> InlineConstSubsts<'tcx> {
-        InlineConstSubsts { substs: self }
+    /// see `ty::InlineConstArgs` struct for more comments.
+    pub fn as_inline_const(&'tcx self) -> InlineConstArgs<'tcx> {
+        InlineConstArgs { args: self }
     }
 
-    /// Creates an `InternalSubsts` that maps each generic parameter to itself.
-    pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: impl Into<DefId>) -> SubstsRef<'tcx> {
+    /// Creates an `GenericArgs` that maps each generic parameter to itself.
+    pub fn identity_for_item(tcx: TyCtxt<'tcx>, def_id: impl Into<DefId>) -> GenericArgsRef<'tcx> {
         Self::for_item(tcx, def_id.into(), |param, _| tcx.mk_param_from_def(param))
     }
 
-    /// Creates an `InternalSubsts` for generic parameter definitions,
+    /// Creates an `GenericArgs` for generic parameter definitions,
     /// by calling closures to obtain each kind.
-    /// The closures get to observe the `InternalSubsts` as they're
+    /// The closures get to observe the `GenericArgs` as they're
     /// being built, which can be used to correctly
-    /// substitute defaults of generic parameters.
-    pub fn for_item<F>(tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> SubstsRef<'tcx>
+    /// replace defaults of generic parameters.
+    pub fn for_item<F>(tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> GenericArgsRef<'tcx>
     where
         F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
     {
         let defs = tcx.generics_of(def_id);
         let count = defs.count();
-        let mut substs = SmallVec::with_capacity(count);
-        Self::fill_item(&mut substs, tcx, defs, &mut mk_kind);
-        tcx.mk_substs(&substs)
+        let mut args = SmallVec::with_capacity(count);
+        Self::fill_item(&mut args, tcx, defs, &mut mk_kind);
+        tcx.mk_args(&args)
     }
 
-    pub fn extend_to<F>(&self, tcx: TyCtxt<'tcx>, def_id: DefId, mut mk_kind: F) -> SubstsRef<'tcx>
+    pub fn extend_to<F>(
+        &self,
+        tcx: TyCtxt<'tcx>,
+        def_id: DefId,
+        mut mk_kind: F,
+    ) -> GenericArgsRef<'tcx>
     where
         F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
     {
-        Self::for_item(tcx, def_id, |param, substs| {
-            self.get(param.index as usize).cloned().unwrap_or_else(|| mk_kind(param, substs))
+        Self::for_item(tcx, def_id, |param, args| {
+            self.get(param.index as usize).cloned().unwrap_or_else(|| mk_kind(param, args))
         })
     }
 
     pub fn fill_item<F>(
-        substs: &mut SmallVec<[GenericArg<'tcx>; 8]>,
+        args: &mut SmallVec<[GenericArg<'tcx>; 8]>,
         tcx: TyCtxt<'tcx>,
         defs: &ty::Generics,
         mk_kind: &mut F,
@@ -323,38 +328,38 @@ impl<'tcx> InternalSubsts<'tcx> {
     {
         if let Some(def_id) = defs.parent {
             let parent_defs = tcx.generics_of(def_id);
-            Self::fill_item(substs, tcx, parent_defs, mk_kind);
+            Self::fill_item(args, tcx, parent_defs, mk_kind);
         }
-        Self::fill_single(substs, defs, mk_kind)
+        Self::fill_single(args, defs, mk_kind)
     }
 
     pub fn fill_single<F>(
-        substs: &mut SmallVec<[GenericArg<'tcx>; 8]>,
+        args: &mut SmallVec<[GenericArg<'tcx>; 8]>,
         defs: &ty::Generics,
         mk_kind: &mut F,
     ) where
         F: FnMut(&ty::GenericParamDef, &[GenericArg<'tcx>]) -> GenericArg<'tcx>,
     {
-        substs.reserve(defs.params.len());
+        args.reserve(defs.params.len());
         for param in &defs.params {
-            let kind = mk_kind(param, substs);
-            assert_eq!(param.index as usize, substs.len(), "{substs:#?}, {defs:#?}");
-            substs.push(kind);
+            let kind = mk_kind(param, args);
+            assert_eq!(param.index as usize, args.len(), "{args:#?}, {defs:#?}");
+            args.push(kind);
         }
     }
 
-    // Extend an `original_substs` list to the full number of substs expected by `def_id`,
+    // Extend an `original_args` list to the full number of args expected by `def_id`,
     // filling in the missing parameters with error ty/ct or 'static regions.
     pub fn extend_with_error(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        original_substs: &[GenericArg<'tcx>],
-    ) -> SubstsRef<'tcx> {
-        ty::InternalSubsts::for_item(tcx, def_id, |def, substs| {
-            if let Some(subst) = original_substs.get(def.index as usize) {
-                *subst
+        original_args: &[GenericArg<'tcx>],
+    ) -> GenericArgsRef<'tcx> {
+        ty::GenericArgs::for_item(tcx, def_id, |def, args| {
+            if let Some(arg) = original_args.get(def.index as usize) {
+                *arg
             } else {
-                def.to_error(tcx, substs)
+                def.to_error(tcx, args)
             }
         })
     }
@@ -410,9 +415,9 @@ impl<'tcx> InternalSubsts<'tcx> {
         self.type_at(def.index as usize).into()
     }
 
-    /// Transform from substitutions for a child of `source_ancestor`
-    /// (e.g., a trait or impl) to substitutions for the same child
-    /// in a different item, with `target_substs` as the base for
+    /// Transform from generic args for a child of `source_ancestor`
+    /// (e.g., a trait or impl) to args for the same child
+    /// in a different item, with `target_args` as the base for
     /// the target impl/trait, with the source child-specific
     /// parameters (e.g., method parameters) on top of that base.
     ///
@@ -423,23 +428,23 @@ impl<'tcx> InternalSubsts<'tcx> {
     /// impl<U> X<U> for U { fn f<V>() {} }
     /// ```
     ///
-    /// * If `self` is `[Self, S, T]`: the identity substs of `f` in the trait.
+    /// * If `self` is `[Self, S, T]`: the identity args of `f` in the trait.
     /// * If `source_ancestor` is the def_id of the trait.
-    /// * If `target_substs` is `[U]`, the substs for the impl.
-    /// * Then we will return `[U, T]`, the subst for `f` in the impl that
+    /// * If `target_args` is `[U]`, the args for the impl.
+    /// * Then we will return `[U, T]`, the arg for `f` in the impl that
     ///   are needed for it to match the trait.
     pub fn rebase_onto(
         &self,
         tcx: TyCtxt<'tcx>,
         source_ancestor: DefId,
-        target_substs: SubstsRef<'tcx>,
-    ) -> SubstsRef<'tcx> {
+        target_args: GenericArgsRef<'tcx>,
+    ) -> GenericArgsRef<'tcx> {
         let defs = tcx.generics_of(source_ancestor);
-        tcx.mk_substs_from_iter(target_substs.iter().chain(self.iter().skip(defs.params.len())))
+        tcx.mk_args_from_iter(target_args.iter().chain(self.iter().skip(defs.params.len())))
     }
 
-    pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> SubstsRef<'tcx> {
-        tcx.mk_substs_from_iter(self.iter().take(generics.count()))
+    pub fn truncate_to(&self, tcx: TyCtxt<'tcx>, generics: &ty::Generics) -> GenericArgsRef<'tcx> {
+        tcx.mk_args_from_iter(self.iter().take(generics.count()))
     }
 
     pub fn host_effect_param(&'tcx self) -> Option<ty::Const<'tcx>> {
@@ -447,7 +452,7 @@ impl<'tcx> InternalSubsts<'tcx> {
     }
 }
 
-impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for SubstsRef<'tcx> {
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for GenericArgsRef<'tcx> {
     fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
         folder: &mut F,
@@ -456,16 +461,12 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for SubstsRef<'tcx> {
         // common length lists, to avoid the overhead of `SmallVec` creation.
         // The match arms are in order of frequency. The 1, 2, and 0 cases are
         // typically hit in 90--99.99% of cases. When folding doesn't change
-        // the substs, it's faster to reuse the existing substs rather than
-        // calling `mk_substs`.
+        // the args, it's faster to reuse the existing args rather than
+        // calling `mk_args`.
         match self.len() {
             1 => {
                 let param0 = self[0].try_fold_with(folder)?;
-                if param0 == self[0] {
-                    Ok(self)
-                } else {
-                    Ok(folder.interner().mk_substs(&[param0]))
-                }
+                if param0 == self[0] { Ok(self) } else { Ok(folder.interner().mk_args(&[param0])) }
             }
             2 => {
                 let param0 = self[0].try_fold_with(folder)?;
@@ -473,11 +474,11 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for SubstsRef<'tcx> {
                 if param0 == self[0] && param1 == self[1] {
                     Ok(self)
                 } else {
-                    Ok(folder.interner().mk_substs(&[param0, param1]))
+                    Ok(folder.interner().mk_args(&[param0, param1]))
                 }
             }
             0 => Ok(self),
-            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_substs(v)),
+            _ => ty::util::fold_list(self, folder, |tcx, v| tcx.mk_args(v)),
         }
     }
 }
@@ -487,7 +488,7 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for &'tcx ty::List<Ty<'tcx>> {
         self,
         folder: &mut F,
     ) -> Result<Self, F::Error> {
-        // This code is fairly hot, though not as hot as `SubstsRef`.
+        // This code is fairly hot, though not as hot as `GenericArgsRef`.
         //
         // When compiling stage 2, I get the following results:
         //
@@ -525,18 +526,18 @@ impl<'tcx, T: TypeVisitable<TyCtxt<'tcx>>> TypeVisitable<TyCtxt<'tcx>> for &'tcx
 }
 
 /// Similar to [`super::Binder`] except that it tracks early bound generics, i.e. `struct Foo<T>(T)`
-/// needs `T` substituted immediately. This type primarily exists to avoid forgetting to call
-/// `subst`.
+/// needs `T` instantiated immediately. This type primarily exists to avoid forgetting to call
+/// `instantiate`.
 ///
-/// If you don't have anything to `subst`, you may be looking for
-/// [`subst_identity`](EarlyBinder::subst_identity) or [`skip_binder`](EarlyBinder::skip_binder).
+/// If you don't have anything to `instantiate`, you may be looking for
+/// [`instantiate_identity`](EarlyBinder::instantiate_identity) or [`skip_binder`](EarlyBinder::skip_binder).
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
 #[derive(Encodable, Decodable, HashStable)]
 pub struct EarlyBinder<T> {
     value: T,
 }
 
-/// For early binders, you should first call `subst` before using any visitors.
+/// For early binders, you should first call `instantiate` before using any visitors.
 impl<'tcx, T> !TypeFoldable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
 impl<'tcx, T> !TypeVisitable<TyCtxt<'tcx>> for ty::EarlyBinder<T> {}
 
@@ -580,7 +581,7 @@ impl<T> EarlyBinder<T> {
     /// This can be used to extract data that does not depend on generic parameters
     /// (e.g., getting the `DefId` of the inner value or getting the number of
     /// arguments of an `FnSig`). Otherwise, consider using
-    /// [`subst_identity`](EarlyBinder::subst_identity).
+    /// [`instantiate_identity`](EarlyBinder::instantiate_identity).
     ///
     /// To skip the binder on `x: &EarlyBinder<T>` to obtain `&T`, leverage
     /// [`EarlyBinder::as_ref`](EarlyBinder::as_ref): `x.as_ref().skip_binder()`.
@@ -609,35 +610,31 @@ impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
 where
     I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
-    pub fn subst_iter(
-        self,
-        tcx: TyCtxt<'tcx>,
-        substs: &'s [GenericArg<'tcx>],
-    ) -> SubstIter<'s, 'tcx, I> {
-        SubstIter { it: self.value.into_iter(), tcx, substs }
+    pub fn arg_iter(self, tcx: TyCtxt<'tcx>, args: &'s [GenericArg<'tcx>]) -> ArgIter<'s, 'tcx, I> {
+        ArgIter { it: self.value.into_iter(), tcx, args }
     }
 
-    /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
+    /// Similar to [`instantiate_identity`](EarlyBinder::instantiate_identity),
     /// but on an iterator of `TypeFoldable` values.
-    pub fn subst_identity_iter(self) -> I::IntoIter {
+    pub fn instantiate_identity_iter(self) -> I::IntoIter {
         self.value.into_iter()
     }
 }
 
-pub struct SubstIter<'s, 'tcx, I: IntoIterator> {
+pub struct ArgIter<'s, 'tcx, I: IntoIterator> {
     it: I::IntoIter,
     tcx: TyCtxt<'tcx>,
-    substs: &'s [GenericArg<'tcx>],
+    args: &'s [GenericArg<'tcx>],
 }
 
-impl<'tcx, I: IntoIterator> Iterator for SubstIter<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> Iterator for ArgIter<'_, 'tcx, I>
 where
     I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     type Item = I::Item;
 
     fn next(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder { value: self.it.next()? }.subst(self.tcx, self.substs))
+        Some(EarlyBinder { value: self.it.next()? }.instantiate(self.tcx, self.args))
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -645,17 +642,17 @@ where
     }
 }
 
-impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIter<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> DoubleEndedIterator for ArgIter<'_, 'tcx, I>
 where
     I::IntoIter: DoubleEndedIterator,
     I::Item: TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
-        Some(EarlyBinder { value: self.it.next_back()? }.subst(self.tcx, self.substs))
+        Some(EarlyBinder { value: self.it.next_back()? }.instantiate(self.tcx, self.args))
     }
 }
 
-impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIter<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> ExactSizeIterator for ArgIter<'_, 'tcx, I>
 where
     I::IntoIter: ExactSizeIterator,
     I::Item: TypeFoldable<TyCtxt<'tcx>>,
@@ -667,28 +664,30 @@ where
     I::Item: Deref,
     <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
-    pub fn subst_iter_copied(
+    pub fn arg_iter_copied(
         self,
         tcx: TyCtxt<'tcx>,
-        substs: &'s [GenericArg<'tcx>],
-    ) -> SubstIterCopied<'s, 'tcx, I> {
-        SubstIterCopied { it: self.value.into_iter(), tcx, substs }
+        args: &'s [GenericArg<'tcx>],
+    ) -> ArgIterCopied<'s, 'tcx, I> {
+        ArgIterCopied { it: self.value.into_iter(), tcx, args }
     }
 
-    /// Similar to [`subst_identity`](EarlyBinder::subst_identity),
+    /// Similar to [`instantiate_identity`](EarlyBinder::instantiate_identity),
     /// but on an iterator of values that deref to a `TypeFoldable`.
-    pub fn subst_identity_iter_copied(self) -> impl Iterator<Item = <I::Item as Deref>::Target> {
+    pub fn instantiate_identity_iter_copied(
+        self,
+    ) -> impl Iterator<Item = <I::Item as Deref>::Target> {
         self.value.into_iter().map(|v| *v)
     }
 }
 
-pub struct SubstIterCopied<'a, 'tcx, I: IntoIterator> {
+pub struct ArgIterCopied<'a, 'tcx, I: IntoIterator> {
     it: I::IntoIter,
     tcx: TyCtxt<'tcx>,
-    substs: &'a [GenericArg<'tcx>],
+    args: &'a [GenericArg<'tcx>],
 }
 
-impl<'tcx, I: IntoIterator> Iterator for SubstIterCopied<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> Iterator for ArgIterCopied<'_, 'tcx, I>
 where
     I::Item: Deref,
     <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
@@ -696,7 +695,7 @@ where
     type Item = <I::Item as Deref>::Target;
 
     fn next(&mut self) -> Option<Self::Item> {
-        self.it.next().map(|value| EarlyBinder { value: *value }.subst(self.tcx, self.substs))
+        self.it.next().map(|value| EarlyBinder { value: *value }.instantiate(self.tcx, self.args))
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
@@ -704,18 +703,20 @@ where
     }
 }
 
-impl<'tcx, I: IntoIterator> DoubleEndedIterator for SubstIterCopied<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> DoubleEndedIterator for ArgIterCopied<'_, 'tcx, I>
 where
     I::IntoIter: DoubleEndedIterator,
     I::Item: Deref,
     <I::Item as Deref>::Target: Copy + TypeFoldable<TyCtxt<'tcx>>,
 {
     fn next_back(&mut self) -> Option<Self::Item> {
-        self.it.next_back().map(|value| EarlyBinder { value: *value }.subst(self.tcx, self.substs))
+        self.it
+            .next_back()
+            .map(|value| EarlyBinder { value: *value }.instantiate(self.tcx, self.args))
     }
 }
 
-impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIterCopied<'_, 'tcx, I>
+impl<'tcx, I: IntoIterator> ExactSizeIterator for ArgIterCopied<'_, 'tcx, I>
 where
     I::IntoIter: ExactSizeIterator,
     I::Item: Deref,
@@ -746,20 +747,20 @@ impl<T: Iterator> Iterator for EarlyBinderIter<T> {
 }
 
 impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> {
-    pub fn subst(self, tcx: TyCtxt<'tcx>, substs: &[GenericArg<'tcx>]) -> T {
-        let mut folder = SubstFolder { tcx, substs, binders_passed: 0 };
+    pub fn instantiate(self, tcx: TyCtxt<'tcx>, args: &[GenericArg<'tcx>]) -> T {
+        let mut folder = ArgFolder { tcx, args, binders_passed: 0 };
         self.value.fold_with(&mut folder)
     }
 
-    /// Makes the identity substitution `T0 => T0, ..., TN => TN`.
+    /// Makes the identity replacement `T0 => T0, ..., TN => TN`.
     /// Conceptually, this converts universally bound variables into placeholders
     /// when inside of a given item.
     ///
     /// For example, consider `for<T> fn foo<T>(){ .. }`:
     /// - Outside of `foo`, `T` is bound (represented by the presence of `EarlyBinder`).
     /// - Inside of the body of `foo`, we treat `T` as a placeholder by calling
-    /// `subst_identity` to discharge the `EarlyBinder`.
-    pub fn subst_identity(self) -> T {
+    /// `instantiate_identity` to discharge the `EarlyBinder`.
+    pub fn instantiate_identity(self) -> T {
         self.value
     }
 
@@ -772,15 +773,15 @@ impl<'tcx, T: TypeFoldable<TyCtxt<'tcx>>> ty::EarlyBinder<T> {
 ///////////////////////////////////////////////////////////////////////////
 // The actual substitution engine itself is a type folder.
 
-struct SubstFolder<'a, 'tcx> {
+struct ArgFolder<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    substs: &'a [GenericArg<'tcx>],
+    args: &'a [GenericArg<'tcx>],
 
     /// Number of region binders we have passed through while doing the substitution
     binders_passed: u32,
 }
 
-impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for SubstFolder<'a, 'tcx> {
+impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for ArgFolder<'a, 'tcx> {
     #[inline]
     fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx
@@ -799,12 +800,12 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for SubstFolder<'a, 'tcx> {
     fn fold_region(&mut self, r: ty::Region<'tcx>) -> ty::Region<'tcx> {
         #[cold]
         #[inline(never)]
-        fn region_param_out_of_range(data: ty::EarlyBoundRegion, substs: &[GenericArg<'_>]) -> ! {
+        fn region_param_out_of_range(data: ty::EarlyBoundRegion, args: &[GenericArg<'_>]) -> ! {
             bug!(
-                "Region parameter out of range when substituting in region {} (index={}, substs = {:?})",
+                "Region parameter out of range when substituting in region {} (index={}, args = {:?})",
                 data.name,
                 data.index,
-                substs,
+                args,
             )
         }
 
@@ -826,11 +827,11 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for SubstFolder<'a, 'tcx> {
         // the specialized routine `ty::replace_late_regions()`.
         match *r {
             ty::ReEarlyBound(data) => {
-                let rk = self.substs.get(data.index as usize).map(|k| k.unpack());
+                let rk = self.args.get(data.index as usize).map(|k| k.unpack());
                 match rk {
                     Some(GenericArgKind::Lifetime(lt)) => self.shift_region_through_binders(lt),
                     Some(other) => region_param_invalid(data, other),
-                    None => region_param_out_of_range(data, self.substs),
+                    None => region_param_out_of_range(data, self.args),
                 }
             }
             ty::ReLateBound(..)
@@ -863,10 +864,10 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for SubstFolder<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
+impl<'a, 'tcx> ArgFolder<'a, 'tcx> {
     fn ty_for_param(&self, p: ty::ParamTy, source_ty: Ty<'tcx>) -> Ty<'tcx> {
-        // Look up the type in the substitutions. It really should be in there.
-        let opt_ty = self.substs.get(p.index as usize).map(|k| k.unpack());
+        // Look up the type in the args. It really should be in there.
+        let opt_ty = self.args.get(p.index as usize).map(|k| k.unpack());
         let ty = match opt_ty {
             Some(GenericArgKind::Type(ty)) => ty,
             Some(kind) => self.type_param_expected(p, source_ty, kind),
@@ -880,12 +881,12 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
     #[inline(never)]
     fn type_param_expected(&self, p: ty::ParamTy, ty: Ty<'tcx>, kind: GenericArgKind<'tcx>) -> ! {
         bug!(
-            "expected type for `{:?}` ({:?}/{}) but found {:?} when substituting, substs={:?}",
+            "expected type for `{:?}` ({:?}/{}) but found {:?} when substituting, args={:?}",
             p,
             ty,
             p.index,
             kind,
-            self.substs,
+            self.args,
         )
     }
 
@@ -893,17 +894,17 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
     #[inline(never)]
     fn type_param_out_of_range(&self, p: ty::ParamTy, ty: Ty<'tcx>) -> ! {
         bug!(
-            "type parameter `{:?}` ({:?}/{}) out of range when substituting, substs={:?}",
+            "type parameter `{:?}` ({:?}/{}) out of range when substituting, args={:?}",
             p,
             ty,
             p.index,
-            self.substs,
+            self.args,
         )
     }
 
     fn const_for_param(&self, p: ParamConst, source_ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
-        // Look up the const in the substitutions. It really should be in there.
-        let opt_ct = self.substs.get(p.index as usize).map(|k| k.unpack());
+        // Look up the const in the args. It really should be in there.
+        let opt_ct = self.args.get(p.index as usize).map(|k| k.unpack());
         let ct = match opt_ct {
             Some(GenericArgKind::Const(ct)) => ct,
             Some(kind) => self.const_param_expected(p, source_ct, kind),
@@ -922,12 +923,12 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
         kind: GenericArgKind<'tcx>,
     ) -> ! {
         bug!(
-            "expected const for `{:?}` ({:?}/{}) but found {:?} when substituting substs={:?}",
+            "expected const for `{:?}` ({:?}/{}) but found {:?} when substituting args={:?}",
             p,
             ct,
             p.index,
             kind,
-            self.substs,
+            self.args,
         )
     }
 
@@ -935,11 +936,11 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
     #[inline(never)]
     fn const_param_out_of_range(&self, p: ty::ParamConst, ct: ty::Const<'tcx>) -> ! {
         bug!(
-            "const parameter `{:?}` ({:?}/{}) out of range when substituting substs={:?}",
+            "const parameter `{:?}` ({:?}/{}) out of range when substituting args={:?}",
             p,
             ct,
             p.index,
-            self.substs,
+            self.args,
         )
     }
 
@@ -1011,13 +1012,13 @@ impl<'a, 'tcx> SubstFolder<'a, 'tcx> {
     }
 }
 
-/// Stores the user-given substs to reach some fully qualified path
+/// Stores the user-given args to reach some fully qualified path
 /// (e.g., `<T>::Item` or `<T as Trait>::Item`).
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
-pub struct UserSubsts<'tcx> {
-    /// The substitutions for the item as given by the user.
-    pub substs: SubstsRef<'tcx>,
+pub struct UserArgs<'tcx> {
+    /// The args for the item as given by the user.
+    pub args: GenericArgsRef<'tcx>,
 
     /// The self type, in the case of a `<T>::Item` path (when applied
     /// to an inherent impl). See `UserSelfTy` below.
@@ -1037,7 +1038,7 @@ pub struct UserSubsts<'tcx> {
 /// when you then have a path like `<Foo<&'static u32>>::method`,
 /// this struct would carry the `DefId` of the impl along with the
 /// self type `Foo<u32>`. Then we can instantiate the parameters of
-/// the impl (with the substs from `UserSubsts`) and apply those to
+/// the impl (with the args from `UserArgs`) and apply those to
 /// the self type, giving `Foo<?A>`. Finally, we unify that with
 /// the self type here, which contains `?A` to be `&'static u32`
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash, TyEncodable, TyDecodable)]
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 6c7125c4cb728..338590717d052 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -1,5 +1,5 @@
 use crate::ty;
-use crate::ty::{EarlyBinder, SubstsRef};
+use crate::ty::{EarlyBinder, GenericArgsRef};
 use rustc_ast as ast;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
@@ -97,14 +97,14 @@ impl GenericParamDef {
     pub fn to_error<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,
-        preceding_substs: &[ty::GenericArg<'tcx>],
+        preceding_args: &[ty::GenericArg<'tcx>],
     ) -> ty::GenericArg<'tcx> {
         match &self.kind {
             ty::GenericParamDefKind::Lifetime => ty::Region::new_error_misc(tcx).into(),
             ty::GenericParamDefKind::Type { .. } => Ty::new_misc_error(tcx).into(),
             ty::GenericParamDefKind::Const { .. } => ty::Const::new_misc_error(
                 tcx,
-                tcx.type_of(self.def_id).subst(tcx, preceding_substs),
+                tcx.type_of(self.def_id).instantiate(tcx, preceding_args),
             )
             .into(),
         }
@@ -136,7 +136,7 @@ pub struct Generics {
     pub has_self: bool,
     pub has_late_bound_regions: Option<Span>,
 
-    // The index of the host effect when substituted. (i.e. might be index to parent substs)
+    // The index of the host effect when substituted. (i.e. might be index to parent args)
     pub host_effect_index: Option<usize>,
 }
 
@@ -278,14 +278,14 @@ impl<'tcx> Generics {
         })
     }
 
-    /// Returns the substs corresponding to the generic parameters
+    /// Returns the args corresponding to the generic parameters
     /// of this item, excluding `Self`.
     ///
     /// **This should only be used for diagnostics purposes.**
-    pub fn own_substs_no_defaults(
+    pub fn own_args_no_defaults(
         &'tcx self,
         tcx: TyCtxt<'tcx>,
-        substs: &'tcx [ty::GenericArg<'tcx>],
+        args: &'tcx [ty::GenericArg<'tcx>],
     ) -> &'tcx [ty::GenericArg<'tcx>] {
         let mut own_params = self.parent_count..self.count();
         if self.has_self && self.parent.is_none() {
@@ -304,22 +304,22 @@ impl<'tcx> Generics {
             .rev()
             .take_while(|param| {
                 param.default_value(tcx).is_some_and(|default| {
-                    default.subst(tcx, substs) == substs[param.index as usize]
+                    default.instantiate(tcx, args) == args[param.index as usize]
                 })
             })
             .count();
 
-        &substs[own_params]
+        &args[own_params]
     }
 
-    /// Returns the substs corresponding to the generic parameters of this item, excluding `Self`.
+    /// Returns the args corresponding to the generic parameters of this item, excluding `Self`.
     ///
     /// **This should only be used for diagnostics purposes.**
-    pub fn own_substs(
+    pub fn own_args(
         &'tcx self,
-        substs: &'tcx [ty::GenericArg<'tcx>],
+        args: &'tcx [ty::GenericArg<'tcx>],
     ) -> &'tcx [ty::GenericArg<'tcx>] {
-        let own = &substs[self.parent_count..][..self.params.len()];
+        let own = &args[self.parent_count..][..self.params.len()];
         if self.has_self && self.parent.is_none() { &own[1..] } else { &own }
     }
 }
@@ -335,19 +335,19 @@ impl<'tcx> GenericPredicates<'tcx> {
     pub fn instantiate(
         &self,
         tcx: TyCtxt<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> InstantiatedPredicates<'tcx> {
         let mut instantiated = InstantiatedPredicates::empty();
-        self.instantiate_into(tcx, &mut instantiated, substs);
+        self.instantiate_into(tcx, &mut instantiated, args);
         instantiated
     }
 
     pub fn instantiate_own(
         &self,
         tcx: TyCtxt<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> impl Iterator<Item = (Clause<'tcx>, Span)> + DoubleEndedIterator + ExactSizeIterator {
-        EarlyBinder::bind(self.predicates).subst_iter_copied(tcx, substs)
+        EarlyBinder::bind(self.predicates).arg_iter_copied(tcx, args)
     }
 
     #[instrument(level = "debug", skip(self, tcx))]
@@ -355,14 +355,14 @@ impl<'tcx> GenericPredicates<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         instantiated: &mut InstantiatedPredicates<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) {
         if let Some(def_id) = self.parent {
-            tcx.predicates_of(def_id).instantiate_into(tcx, instantiated, substs);
+            tcx.predicates_of(def_id).instantiate_into(tcx, instantiated, args);
         }
-        instantiated
-            .predicates
-            .extend(self.predicates.iter().map(|(p, _)| EarlyBinder::bind(*p).subst(tcx, substs)));
+        instantiated.predicates.extend(
+            self.predicates.iter().map(|(p, _)| EarlyBinder::bind(*p).instantiate(tcx, args)),
+        );
         instantiated.spans.extend(self.predicates.iter().map(|(_, sp)| *sp));
     }
 
diff --git a/compiler/rustc_middle/src/ty/impls_ty.rs b/compiler/rustc_middle/src/ty/impls_ty.rs
index 02baa395c3c2f..b03874a90e8d5 100644
--- a/compiler/rustc_middle/src/ty/impls_ty.rs
+++ b/compiler/rustc_middle/src/ty/impls_ty.rs
@@ -67,7 +67,7 @@ impl<'a> ToStableHashKey<StableHashingContext<'a>> for SimplifiedType {
     }
 }
 
-impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArg<'tcx> {
+impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::GenericArg<'tcx> {
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
         self.unpack().hash_stable(hcx, hasher);
     }
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
index 295cb14646109..f278cace99dc4 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/inhabited_predicate.rs
@@ -19,7 +19,7 @@ pub enum InhabitedPredicate<'tcx> {
     /// type has restricted visibility.
     NotInModule(DefId),
     /// Inhabited if some generic type is inhabited.
-    /// These are replaced by calling [`Self::subst`].
+    /// These are replaced by calling [`Self::instantiate`].
     GenericType(Ty<'tcx>),
     /// A AND B
     And(&'tcx [InhabitedPredicate<'tcx>; 2]),
@@ -162,14 +162,14 @@ impl<'tcx> InhabitedPredicate<'tcx> {
     }
 
     /// Replaces generic types with its corresponding predicate
-    pub fn subst(self, tcx: TyCtxt<'tcx>, substs: ty::SubstsRef<'tcx>) -> Self {
-        self.subst_opt(tcx, substs).unwrap_or(self)
+    pub fn instantiate(self, tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> Self {
+        self.instantiate_opt(tcx, args).unwrap_or(self)
     }
 
-    fn subst_opt(self, tcx: TyCtxt<'tcx>, substs: ty::SubstsRef<'tcx>) -> Option<Self> {
+    fn instantiate_opt(self, tcx: TyCtxt<'tcx>, args: ty::GenericArgsRef<'tcx>) -> Option<Self> {
         match self {
             Self::ConstIsZero(c) => {
-                let c = ty::EarlyBinder::bind(c).subst(tcx, substs);
+                let c = ty::EarlyBinder::bind(c).instantiate(tcx, args);
                 let pred = match c.try_to_target_usize(tcx) {
                     Some(0) => Self::True,
                     Some(1..) => Self::False,
@@ -178,17 +178,17 @@ impl<'tcx> InhabitedPredicate<'tcx> {
                 Some(pred)
             }
             Self::GenericType(t) => {
-                Some(ty::EarlyBinder::bind(t).subst(tcx, substs).inhabited_predicate(tcx))
+                Some(ty::EarlyBinder::bind(t).instantiate(tcx, args).inhabited_predicate(tcx))
             }
-            Self::And(&[a, b]) => match a.subst_opt(tcx, substs) {
-                None => b.subst_opt(tcx, substs).map(|b| a.and(tcx, b)),
+            Self::And(&[a, b]) => match a.instantiate_opt(tcx, args) {
+                None => b.instantiate_opt(tcx, args).map(|b| a.and(tcx, b)),
                 Some(InhabitedPredicate::False) => Some(InhabitedPredicate::False),
-                Some(a) => Some(a.and(tcx, b.subst_opt(tcx, substs).unwrap_or(b))),
+                Some(a) => Some(a.and(tcx, b.instantiate_opt(tcx, args).unwrap_or(b))),
             },
-            Self::Or(&[a, b]) => match a.subst_opt(tcx, substs) {
-                None => b.subst_opt(tcx, substs).map(|b| a.or(tcx, b)),
+            Self::Or(&[a, b]) => match a.instantiate_opt(tcx, args) {
+                None => b.instantiate_opt(tcx, args).map(|b| a.or(tcx, b)),
                 Some(InhabitedPredicate::True) => Some(InhabitedPredicate::True),
-                Some(a) => Some(a.or(tcx, b.subst_opt(tcx, substs).unwrap_or(b))),
+                Some(a) => Some(a.or(tcx, b.instantiate_opt(tcx, args).unwrap_or(b))),
             },
             _ => None,
         }
diff --git a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
index b92d84152b47d..4dac6891b3062 100644
--- a/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
+++ b/compiler/rustc_middle/src/ty/inhabitedness/mod.rs
@@ -58,7 +58,7 @@ pub(crate) fn provide(providers: &mut Providers) {
 }
 
 /// Returns an `InhabitedPredicate` that is generic over type parameters and
-/// requires calling [`InhabitedPredicate::subst`]
+/// requires calling [`InhabitedPredicate::instantiate`]
 fn inhabited_predicate_adt(tcx: TyCtxt<'_>, def_id: DefId) -> InhabitedPredicate<'_> {
     if let Some(def_id) = def_id.as_local() {
         if matches!(tcx.representability(def_id), ty::Representability::Infinite) {
@@ -87,7 +87,7 @@ impl<'tcx> VariantDef {
         InhabitedPredicate::all(
             tcx,
             self.fields.iter().map(|field| {
-                let pred = tcx.type_of(field.did).subst_identity().inhabited_predicate(tcx);
+                let pred = tcx.type_of(field.did).instantiate_identity().inhabited_predicate(tcx);
                 if adt.is_enum() {
                     return pred;
                 }
@@ -114,8 +114,8 @@ impl<'tcx> Ty<'tcx> {
             Never => InhabitedPredicate::False,
             Param(_) | Alias(ty::Projection, _) => InhabitedPredicate::GenericType(self),
             // FIXME(inherent_associated_types): Most likely we can just map to `GenericType` like above.
-            // However it's unclear if the substs passed to `InhabitedPredicate::subst` are of the correct
-            // format, i.e. don't contain parent substs. If you hit this case, please verify this beforehand.
+            // However it's unclear if the args passed to `InhabitedPredicate::instantiate` are of the correct
+            // format, i.e. don't contain parent args. If you hit this case, please verify this beforehand.
             Alias(ty::Inherent, _) => {
                 bug!("unimplemented: inhabitedness checking for inherent projections")
             }
@@ -189,7 +189,7 @@ impl<'tcx> Ty<'tcx> {
 /// N.B. this query should only be called through `Ty::inhabited_predicate`
 fn inhabited_predicate_type<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> InhabitedPredicate<'tcx> {
     match *ty.kind() {
-        Adt(adt, substs) => tcx.inhabited_predicate_adt(adt.did()).subst(tcx, substs),
+        Adt(adt, args) => tcx.inhabited_predicate_adt(adt.did()).instantiate(tcx, args),
 
         Tuple(tys) => {
             InhabitedPredicate::all(tcx, tys.iter().map(|ty| ty.inhabited_predicate(tcx)))
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs
index ae57e954ff4ef..48e88daa89073 100644
--- a/compiler/rustc_middle/src/ty/instance.rs
+++ b/compiler/rustc_middle/src/ty/instance.rs
@@ -1,7 +1,7 @@
 use crate::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use crate::ty::print::{FmtPrinter, Printer};
 use crate::ty::{self, Ty, TyCtxt, TypeFoldable, TypeSuperFoldable};
-use crate::ty::{EarlyBinder, InternalSubsts, SubstsRef, TypeVisitableExt};
+use crate::ty::{EarlyBinder, GenericArgs, GenericArgsRef, TypeVisitableExt};
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
@@ -16,13 +16,13 @@ use std::fmt;
 /// A monomorphized `InstanceDef`.
 ///
 /// Monomorphization happens on-the-fly and no monomorphized MIR is ever created. Instead, this type
-/// simply couples a potentially generic `InstanceDef` with some substs, and codegen and const eval
+/// simply couples a potentially generic `InstanceDef` with some args, and codegen and const eval
 /// will do all required substitution as they run.
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, TyEncodable, TyDecodable)]
 #[derive(HashStable, Lift, TypeFoldable, TypeVisitable)]
 pub struct Instance<'tcx> {
     pub def: InstanceDef<'tcx>,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug)]
@@ -115,7 +115,7 @@ impl<'tcx> Instance<'tcx> {
     /// lifetimes erased, allowing a `ParamEnv` to be specified for use during normalization.
     pub fn ty(&self, tcx: TyCtxt<'tcx>, param_env: ty::ParamEnv<'tcx>) -> Ty<'tcx> {
         let ty = tcx.type_of(self.def.def_id());
-        tcx.subst_and_normalize_erasing_regions(self.substs, param_env, ty)
+        tcx.subst_and_normalize_erasing_regions(self.args, param_env, ty)
     }
 
     /// Finds a crate that contains a monomorphization of this instance that
@@ -139,13 +139,13 @@ impl<'tcx> Instance<'tcx> {
         }
 
         // If this a non-generic instance, it cannot be a shared monomorphization.
-        self.substs.non_erasable_generics().next()?;
+        self.args.non_erasable_generics().next()?;
 
         match self.def {
             InstanceDef::Item(def) => tcx
                 .upstream_monomorphizations_for(def)
-                .and_then(|monos| monos.get(&self.substs).cloned()),
-            InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.substs),
+                .and_then(|monos| monos.get(&self.args).cloned()),
+            InstanceDef::DropGlue(_, Some(_)) => tcx.upstream_drop_glue_for(self.args),
             _ => None,
         }
     }
@@ -265,8 +265,8 @@ impl<'tcx> InstanceDef<'tcx> {
     }
 
     /// Returns `true` when the MIR body associated with this instance should be monomorphized
-    /// by its users (e.g. codegen or miri) by substituting the `substs` from `Instance` (see
-    /// `Instance::substs_for_mir_body`).
+    /// by its users (e.g. codegen or miri) by substituting the `args` from `Instance` (see
+    /// `Instance::args_for_mir_body`).
     ///
     /// Otherwise, returns `false` only for some kinds of shims where the construction of the MIR
     /// body should perform necessary substitutions.
@@ -294,10 +294,10 @@ fn fmt_instance(
     type_length: rustc_session::Limit,
 ) -> fmt::Result {
     ty::tls::with(|tcx| {
-        let substs = tcx.lift(instance.substs).expect("could not lift for printing");
+        let args = tcx.lift(instance.args).expect("could not lift for printing");
 
         let s = FmtPrinter::new_with_limit(tcx, Namespace::ValueNS, type_length)
-            .print_def_path(instance.def_id(), substs)?
+            .print_def_path(instance.def_id(), args)?
             .into_buffer();
         f.write_str(&s)
     })?;
@@ -333,18 +333,18 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
 }
 
 impl<'tcx> Instance<'tcx> {
-    pub fn new(def_id: DefId, substs: SubstsRef<'tcx>) -> Instance<'tcx> {
+    pub fn new(def_id: DefId, args: GenericArgsRef<'tcx>) -> Instance<'tcx> {
         assert!(
-            !substs.has_escaping_bound_vars(),
-            "substs of instance {:?} not normalized for codegen: {:?}",
+            !args.has_escaping_bound_vars(),
+            "args of instance {:?} not normalized for codegen: {:?}",
             def_id,
-            substs
+            args
         );
-        Instance { def: InstanceDef::Item(def_id), substs }
+        Instance { def: InstanceDef::Item(def_id), args }
     }
 
     pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {
-        let substs = InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
+        let args = GenericArgs::for_item(tcx, def_id, |param, _| match param.kind {
             ty::GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
             ty::GenericParamDefKind::Type { .. } => {
                 bug!("Instance::mono: {:?} has type parameters", def_id)
@@ -354,7 +354,7 @@ impl<'tcx> Instance<'tcx> {
             }
         });
 
-        Instance::new(def_id, substs)
+        Instance::new(def_id, args)
     }
 
     #[inline]
@@ -362,7 +362,7 @@ impl<'tcx> Instance<'tcx> {
         self.def.def_id()
     }
 
-    /// Resolves a `(def_id, substs)` pair to an (optional) instance -- most commonly,
+    /// Resolves a `(def_id, args)` pair to an (optional) instance -- most commonly,
     /// this is used to find the precise code that will run for a trait method invocation,
     /// if known.
     ///
@@ -390,29 +390,29 @@ impl<'tcx> Instance<'tcx> {
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
         // All regions in the result of this query are erased, so it's
         // fine to erase all of the input regions.
 
-        // HACK(eddyb) erase regions in `substs` first, so that `param_env.and(...)`
+        // HACK(eddyb) erase regions in `args` first, so that `param_env.and(...)`
         // below is more likely to ignore the bounds in scope (e.g. if the only
-        // generic parameters mentioned by `substs` were lifetime ones).
-        let substs = tcx.erase_regions(substs);
-        tcx.resolve_instance(tcx.erase_regions(param_env.and((def_id, substs))))
+        // generic parameters mentioned by `args` were lifetime ones).
+        let args = tcx.erase_regions(args);
+        tcx.resolve_instance(tcx.erase_regions(param_env.and((def_id, args))))
     }
 
     pub fn expect_resolve(
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Instance<'tcx> {
-        match ty::Instance::resolve(tcx, param_env, def_id, substs) {
+        match ty::Instance::resolve(tcx, param_env, def_id, args) {
             Ok(Some(instance)) => instance,
             instance => bug!(
                 "failed to resolve instance for {}: {instance:#?}",
-                tcx.def_path_str_with_substs(def_id, substs)
+                tcx.def_path_str_with_args(def_id, args)
             ),
         }
     }
@@ -421,12 +421,12 @@ impl<'tcx> Instance<'tcx> {
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Option<Instance<'tcx>> {
-        debug!("resolve(def_id={:?}, substs={:?})", def_id, substs);
+        debug!("resolve(def_id={:?}, args={:?})", def_id, args);
         // Use either `resolve_closure` or `resolve_for_vtable`
         assert!(!tcx.is_closure(def_id), "Called `resolve_for_fn_ptr` on closure: {:?}", def_id);
-        Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
+        Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
             match resolved.def {
                 InstanceDef::Item(def) if resolved.def.requires_caller_location(tcx) => {
                     debug!(" => fn pointer created for function with #[track_caller]");
@@ -447,18 +447,18 @@ impl<'tcx> Instance<'tcx> {
         tcx: TyCtxt<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Option<Instance<'tcx>> {
-        debug!("resolve_for_vtable(def_id={:?}, substs={:?})", def_id, substs);
-        let fn_sig = tcx.fn_sig(def_id).subst_identity();
+        debug!("resolve_for_vtable(def_id={:?}, args={:?})", def_id, args);
+        let fn_sig = tcx.fn_sig(def_id).instantiate_identity();
         let is_vtable_shim = !fn_sig.inputs().skip_binder().is_empty()
             && fn_sig.input(0).skip_binder().is_param(0)
             && tcx.generics_of(def_id).has_self;
         if is_vtable_shim {
             debug!(" => associated item with unsizeable self: Self");
-            Some(Instance { def: InstanceDef::VTableShim(def_id), substs })
+            Some(Instance { def: InstanceDef::VTableShim(def_id), args })
         } else {
-            Instance::resolve(tcx, param_env, def_id, substs).ok().flatten().map(|mut resolved| {
+            Instance::resolve(tcx, param_env, def_id, args).ok().flatten().map(|mut resolved| {
                 match resolved.def {
                     InstanceDef::Item(def) => {
                         // We need to generate a shim when we cannot guarantee that
@@ -489,12 +489,12 @@ impl<'tcx> Instance<'tcx> {
                         {
                             if tcx.is_closure(def) {
                                 debug!(" => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}",
-                                       def, def_id, substs);
+                                       def, def_id, args);
 
                                 // Create a shim for the `FnOnce/FnMut/Fn` method we are calling
                                 // - unlike functions, invoking a closure always goes through a
                                 // trait.
-                                resolved = Instance { def: InstanceDef::ReifyShim(def_id), substs };
+                                resolved = Instance { def: InstanceDef::ReifyShim(def_id), args };
                             } else {
                                 debug!(
                                     " => vtable fn pointer created for function with #[track_caller]: {:?}", def
@@ -518,28 +518,28 @@ impl<'tcx> Instance<'tcx> {
     pub fn resolve_closure(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        substs: ty::SubstsRef<'tcx>,
+        args: ty::GenericArgsRef<'tcx>,
         requested_kind: ty::ClosureKind,
     ) -> Option<Instance<'tcx>> {
-        let actual_kind = substs.as_closure().kind();
+        let actual_kind = args.as_closure().kind();
 
         match needs_fn_once_adapter_shim(actual_kind, requested_kind) {
-            Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, substs),
-            _ => Some(Instance::new(def_id, substs)),
+            Ok(true) => Instance::fn_once_adapter_instance(tcx, def_id, args),
+            _ => Some(Instance::new(def_id, args)),
         }
     }
 
     pub fn resolve_drop_in_place(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> ty::Instance<'tcx> {
         let def_id = tcx.require_lang_item(LangItem::DropInPlace, None);
-        let substs = tcx.mk_substs(&[ty.into()]);
-        Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
+        let args = tcx.mk_args(&[ty.into()]);
+        Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
     }
 
     #[instrument(level = "debug", skip(tcx), ret)]
     pub fn fn_once_adapter_instance(
         tcx: TyCtxt<'tcx>,
         closure_did: DefId,
-        substs: ty::SubstsRef<'tcx>,
+        args: ty::GenericArgsRef<'tcx>,
     ) -> Option<Instance<'tcx>> {
         let fn_once = tcx.require_lang_item(LangItem::FnOnce, None);
         let call_once = tcx
@@ -552,30 +552,30 @@ impl<'tcx> Instance<'tcx> {
             tcx.codegen_fn_attrs(closure_did).flags.contains(CodegenFnAttrFlags::TRACK_CALLER);
         let def = ty::InstanceDef::ClosureOnceShim { call_once, track_caller };
 
-        let self_ty = Ty::new_closure(tcx, closure_did, substs);
+        let self_ty = Ty::new_closure(tcx, closure_did, args);
 
-        let sig = substs.as_closure().sig();
+        let sig = args.as_closure().sig();
         let sig =
             tcx.try_normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), sig).ok()?;
         assert_eq!(sig.inputs().len(), 1);
-        let substs = tcx.mk_substs_trait(self_ty, [sig.inputs()[0].into()]);
+        let args = tcx.mk_args_trait(self_ty, [sig.inputs()[0].into()]);
 
         debug!(?self_ty, ?sig);
-        Some(Instance { def, substs })
+        Some(Instance { def, args })
     }
 
     /// Depending on the kind of `InstanceDef`, the MIR body associated with an
     /// instance is expressed in terms of the generic parameters of `self.def_id()`, and in other
     /// cases the MIR body is expressed in terms of the types found in the substitution array.
     /// In the former case, we want to substitute those generic types and replace them with the
-    /// values from the substs when monomorphizing the function body. But in the latter case, we
+    /// values from the args when monomorphizing the function body. But in the latter case, we
     /// don't want to do that substitution, since it has already been done effectively.
     ///
-    /// This function returns `Some(substs)` in the former case and `None` otherwise -- i.e., if
+    /// This function returns `Some(args)` in the former case and `None` otherwise -- i.e., if
     /// this function returns `None`, then the MIR body does not require substitution during
     /// codegen.
-    fn substs_for_mir_body(&self) -> Option<SubstsRef<'tcx>> {
-        self.def.has_polymorphic_mir_body().then_some(self.substs)
+    fn args_for_mir_body(&self) -> Option<GenericArgsRef<'tcx>> {
+        self.def.has_polymorphic_mir_body().then_some(self.args)
     }
 
     pub fn subst_mir<T>(&self, tcx: TyCtxt<'tcx>, v: EarlyBinder<&T>) -> T
@@ -583,10 +583,10 @@ impl<'tcx> Instance<'tcx> {
         T: TypeFoldable<TyCtxt<'tcx>> + Copy,
     {
         let v = v.map_bound(|v| *v);
-        if let Some(substs) = self.substs_for_mir_body() {
-            v.subst(tcx, substs)
+        if let Some(args) = self.args_for_mir_body() {
+            v.instantiate(tcx, args)
         } else {
-            v.subst_identity()
+            v.instantiate_identity()
         }
     }
 
@@ -600,8 +600,8 @@ impl<'tcx> Instance<'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
-        if let Some(substs) = self.substs_for_mir_body() {
-            tcx.subst_and_normalize_erasing_regions(substs, param_env, v)
+        if let Some(args) = self.args_for_mir_body() {
+            tcx.subst_and_normalize_erasing_regions(args, param_env, v)
         } else {
             tcx.normalize_erasing_regions(param_env, v.skip_binder())
         }
@@ -617,14 +617,14 @@ impl<'tcx> Instance<'tcx> {
     where
         T: TypeFoldable<TyCtxt<'tcx>> + Clone,
     {
-        if let Some(substs) = self.substs_for_mir_body() {
-            tcx.try_subst_and_normalize_erasing_regions(substs, param_env, v)
+        if let Some(args) = self.args_for_mir_body() {
+            tcx.try_subst_and_normalize_erasing_regions(args, param_env, v)
         } else {
             tcx.try_normalize_erasing_regions(param_env, v.skip_binder())
         }
     }
 
-    /// Returns a new `Instance` where generic parameters in `instance.substs` are replaced by
+    /// Returns a new `Instance` where generic parameters in `instance.args` are replaced by
     /// identity parameters if they are determined to be unused in `instance.def`.
     pub fn polymorphize(self, tcx: TyCtxt<'tcx>) -> Self {
         debug!("polymorphize: running polymorphization analysis");
@@ -632,18 +632,18 @@ impl<'tcx> Instance<'tcx> {
             return self;
         }
 
-        let polymorphized_substs = polymorphize(tcx, self.def, self.substs);
-        debug!("polymorphize: self={:?} polymorphized_substs={:?}", self, polymorphized_substs);
-        Self { def: self.def, substs: polymorphized_substs }
+        let polymorphized_args = polymorphize(tcx, self.def, self.args);
+        debug!("polymorphize: self={:?} polymorphized_args={:?}", self, polymorphized_args);
+        Self { def: self.def, args: polymorphized_args }
     }
 }
 
 fn polymorphize<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance: ty::InstanceDef<'tcx>,
-    substs: SubstsRef<'tcx>,
-) -> SubstsRef<'tcx> {
-    debug!("polymorphize({:?}, {:?})", instance, substs);
+    args: GenericArgsRef<'tcx>,
+) -> GenericArgsRef<'tcx> {
+    debug!("polymorphize({:?}, {:?})", instance, args);
     let unused = tcx.unused_generic_params(instance);
     debug!("polymorphize: unused={:?}", unused);
 
@@ -653,9 +653,9 @@ fn polymorphize<'tcx>(
     // multiple mono items (and eventually symbol clashes).
     let def_id = instance.def_id();
     let upvars_ty = if tcx.is_closure(def_id) {
-        Some(substs.as_closure().tupled_upvars_ty())
+        Some(args.as_closure().tupled_upvars_ty())
     } else if tcx.type_of(def_id).skip_binder().is_generator() {
-        Some(substs.as_generator().tupled_upvars_ty())
+        Some(args.as_generator().tupled_upvars_ty())
     } else {
         None
     };
@@ -674,22 +674,22 @@ fn polymorphize<'tcx>(
         fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
             debug!("fold_ty: ty={:?}", ty);
             match *ty.kind() {
-                ty::Closure(def_id, substs) => {
-                    let polymorphized_substs =
-                        polymorphize(self.tcx, ty::InstanceDef::Item(def_id), substs);
-                    if substs == polymorphized_substs {
+                ty::Closure(def_id, args) => {
+                    let polymorphized_args =
+                        polymorphize(self.tcx, ty::InstanceDef::Item(def_id), args);
+                    if args == polymorphized_args {
                         ty
                     } else {
-                        Ty::new_closure(self.tcx, def_id, polymorphized_substs)
+                        Ty::new_closure(self.tcx, def_id, polymorphized_args)
                     }
                 }
-                ty::Generator(def_id, substs, movability) => {
-                    let polymorphized_substs =
-                        polymorphize(self.tcx, ty::InstanceDef::Item(def_id), substs);
-                    if substs == polymorphized_substs {
+                ty::Generator(def_id, args, movability) => {
+                    let polymorphized_args =
+                        polymorphize(self.tcx, ty::InstanceDef::Item(def_id), args);
+                    if args == polymorphized_args {
                         ty
                     } else {
-                        Ty::new_generator(self.tcx, def_id, polymorphized_substs, movability)
+                        Ty::new_generator(self.tcx, def_id, polymorphized_args, movability)
                     }
                 }
                 _ => ty.super_fold_with(self),
@@ -697,7 +697,7 @@ fn polymorphize<'tcx>(
         }
     }
 
-    InternalSubsts::for_item(tcx, def_id, |param, _| {
+    GenericArgs::for_item(tcx, def_id, |param, _| {
         let is_unused = unused.is_unused(param.index);
         debug!("polymorphize: param={:?} is_unused={:?}", param, is_unused);
         match param.kind {
@@ -706,7 +706,7 @@ fn polymorphize<'tcx>(
                 // ..and has upvars..
                 has_upvars &&
                 // ..and this param has the same type as the tupled upvars..
-                upvars_ty == Some(substs[param.index as usize].expect_ty()) => {
+                upvars_ty == Some(args[param.index as usize].expect_ty()) => {
                     // ..then double-check that polymorphization marked it used..
                     debug_assert!(!is_unused);
                     // ..and polymorphize any closures/generators captured as upvars.
@@ -725,7 +725,7 @@ fn polymorphize<'tcx>(
                     tcx.mk_param_from_def(param),
 
             // Otherwise, use the parameter as before.
-            _ => substs[param.index as usize],
+            _ => args[param.index as usize],
         }
     })
 }
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs
index d95b05ef75408..61d95e64c9c50 100644
--- a/compiler/rustc_middle/src/ty/layout.rs
+++ b/compiler/rustc_middle/src/ty/layout.rs
@@ -374,7 +374,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                 }
             }
 
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 // Only newtypes and enums w/ nullable pointer optimization.
                 if def.is_union() || def.variants().is_empty() || def.variants().len() > 2 {
                     return Err(err);
@@ -385,7 +385,7 @@ impl<'tcx> SizeSkeleton<'tcx> {
                     let i = VariantIdx::from_usize(i);
                     let fields =
                         def.variant(i).fields.iter().map(|field| {
-                            SizeSkeleton::compute(field.ty(tcx, substs), tcx, param_env)
+                            SizeSkeleton::compute(field.ty(tcx, args), tcx, param_env)
                         });
                     let mut ptr = None;
                     for field in fields {
@@ -861,9 +861,9 @@ where
                         // offers better information than `std::ptr::metadata::VTable`,
                         // and we rely on this layout information to trigger a panic in
                         // `std::mem::uninitialized::<&dyn Trait>()`, for example.
-                        if let ty::Adt(def, substs) = metadata.kind()
+                        if let ty::Adt(def, args) = metadata.kind()
                             && Some(def.did()) == tcx.lang_items().dyn_metadata()
-                            && substs.type_at(0).is_trait()
+                            && args.type_at(0).is_trait()
                         {
                             mk_dyn_vtable()
                         } else {
@@ -885,16 +885,15 @@ where
                 ty::Str => TyMaybeWithLayout::Ty(tcx.types.u8),
 
                 // Tuples, generators and closures.
-                ty::Closure(_, ref substs) => field_ty_or_layout(
-                    TyAndLayout { ty: substs.as_closure().tupled_upvars_ty(), ..this },
+                ty::Closure(_, ref args) => field_ty_or_layout(
+                    TyAndLayout { ty: args.as_closure().tupled_upvars_ty(), ..this },
                     cx,
                     i,
                 ),
 
-                ty::Generator(def_id, ref substs, _) => match this.variants {
+                ty::Generator(def_id, ref args, _) => match this.variants {
                     Variants::Single { index } => TyMaybeWithLayout::Ty(
-                        substs
-                            .as_generator()
+                        args.as_generator()
                             .state_tys(def_id, tcx)
                             .nth(index.as_usize())
                             .unwrap()
@@ -905,18 +904,18 @@ where
                         if i == tag_field {
                             return TyMaybeWithLayout::TyAndLayout(tag_layout(tag));
                         }
-                        TyMaybeWithLayout::Ty(substs.as_generator().prefix_tys().nth(i).unwrap())
+                        TyMaybeWithLayout::Ty(args.as_generator().prefix_tys().nth(i).unwrap())
                     }
                 },
 
                 ty::Tuple(tys) => TyMaybeWithLayout::Ty(tys[i]),
 
                 // ADTs.
-                ty::Adt(def, substs) => {
+                ty::Adt(def, args) => {
                     match this.variants {
                         Variants::Single { index } => {
                             let field = &def.variant(index).fields[FieldIdx::from_usize(i)];
-                            TyMaybeWithLayout::Ty(field.ty(tcx, substs))
+                            TyMaybeWithLayout::Ty(field.ty(tcx, args))
                         }
 
                         // Discriminant field for enums (where applicable).
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index f23ea986d5594..0411890ab5139 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -28,6 +28,7 @@ use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::util::Discr;
 pub use adt::*;
 pub use assoc::*;
+pub use generic_args::*;
 pub use generics::*;
 use rustc_ast as ast;
 use rustc_ast::node_id::NodeMap;
@@ -54,7 +55,6 @@ use rustc_span::{ExpnId, ExpnKind, Span};
 use rustc_target::abi::{Align, FieldIdx, Integer, IntegerType, VariantIdx};
 pub use rustc_target::abi::{ReprFlags, ReprOptions};
 pub use rustc_type_ir::{DebugWithInfcx, InferCtxtLike, OptWithInfcx};
-pub use subst::*;
 pub use vtable::*;
 
 use std::fmt::Debug;
@@ -97,12 +97,12 @@ pub use self::rvalue_scopes::RvalueScopes;
 pub use self::sty::BoundRegionKind::*;
 pub use self::sty::{
     AliasTy, Article, Binder, BoundRegion, BoundRegionKind, BoundTy, BoundTyKind, BoundVar,
-    BoundVariableKind, CanonicalPolyFnSig, ClosureSubsts, ClosureSubstsParts, ConstKind, ConstVid,
+    BoundVariableKind, CanonicalPolyFnSig, ClosureArgs, ClosureArgsParts, ConstKind, ConstVid,
     EarlyBoundRegion, ExistentialPredicate, ExistentialProjection, ExistentialTraitRef, FnSig,
-    FreeRegion, GenSig, GeneratorSubsts, GeneratorSubstsParts, InlineConstSubsts,
-    InlineConstSubstsParts, ParamConst, ParamTy, PolyExistentialPredicate,
-    PolyExistentialProjection, PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef,
-    Region, RegionKind, RegionVid, TraitRef, TyKind, TypeAndMut, UpvarSubsts, VarianceDiagInfo,
+    FreeRegion, GenSig, GeneratorArgs, GeneratorArgsParts, InlineConstArgs, InlineConstArgsParts,
+    ParamConst, ParamTy, PolyExistentialPredicate, PolyExistentialProjection,
+    PolyExistentialTraitRef, PolyFnSig, PolyGenSig, PolyTraitRef, Region, RegionKind, RegionVid,
+    TraitRef, TyKind, TypeAndMut, UpvarArgs, VarianceDiagInfo,
 };
 pub use self::trait_def::TraitDef;
 pub use self::typeck_results::{
@@ -126,7 +126,6 @@ pub mod layout;
 pub mod normalize_erasing_regions;
 pub mod print;
 pub mod relate;
-pub mod subst;
 pub mod trait_def;
 pub mod util;
 pub mod visit;
@@ -140,6 +139,7 @@ mod consts;
 mod context;
 mod diagnostics;
 mod erase_regions;
+mod generic_args;
 mod generics;
 mod impls_ty;
 mod instance;
@@ -676,9 +676,9 @@ pub enum PredicateKind<'tcx> {
     ObjectSafe(DefId),
 
     /// No direct syntax. May be thought of as `where T: FnFoo<...>`
-    /// for some substitutions `...` and `T` being a closure type.
+    /// for some generic args `...` and `T` being a closure type.
     /// Satisfied (or refuted) once we know the closure's kind.
-    ClosureKind(DefId, SubstsRef<'tcx>, ClosureKind),
+    ClosureKind(DefId, GenericArgsRef<'tcx>, ClosureKind),
 
     /// `T1 <: T2`
     ///
@@ -813,15 +813,15 @@ impl<'tcx> Clause<'tcx> {
         // this trick achieves that).
 
         // Working through the second example:
-        // trait_ref: for<'x> T: Foo1<'^0.0>; substs: [T, '^0.0]
-        // predicate: for<'b> Self: Bar1<'a, '^0.0>; substs: [Self, 'a, '^0.0]
+        // trait_ref: for<'x> T: Foo1<'^0.0>; args: [T, '^0.0]
+        // predicate: for<'b> Self: Bar1<'a, '^0.0>; args: [Self, 'a, '^0.0]
         // We want to end up with:
         //     for<'x, 'b> T: Bar1<'^0.0, '^0.1>
         // To do this:
         // 1) We must shift all bound vars in predicate by the length
         //    of trait ref's bound vars. So, we would end up with predicate like
         //    Self: Bar1<'a, '^0.1>
-        // 2) We can then apply the trait substs to this, ending up with
+        // 2) We can then apply the trait args to this, ending up with
         //    T: Bar1<'^0.0, '^0.1>
         // 3) Finally, to create the final bound vars, we concatenate the bound
         //    vars of the trait ref with those of the predicate:
@@ -833,7 +833,7 @@ impl<'tcx> Clause<'tcx> {
         let shifted_pred =
             tcx.shift_bound_var_indices(trait_bound_vars.len(), bound_pred.skip_binder());
         // 2) Self: Bar1<'a, '^0.1> -> T: Bar1<'^0.0, '^0.1>
-        let new = EarlyBinder::bind(shifted_pred).subst(tcx, trait_ref.skip_binder().substs);
+        let new = EarlyBinder::bind(shifted_pred).instantiate(tcx, trait_ref.skip_binder().args);
         // 3) ['x] + ['b] -> ['x, 'b]
         let bound_vars =
             tcx.mk_bound_variable_kinds_from_iter(trait_bound_vars.iter().chain(pred_bound_vars));
@@ -1079,7 +1079,7 @@ impl<'tcx> Term<'tcx> {
                 _ => None,
             },
             TermKind::Const(ct) => match ct.kind() {
-                ConstKind::Unevaluated(uv) => Some(tcx.mk_alias_ty(uv.def, uv.substs)),
+                ConstKind::Unevaluated(uv) => Some(tcx.mk_alias_ty(uv.def, uv.args)),
                 _ => None,
             },
         }
@@ -1558,7 +1558,7 @@ impl<'a, 'tcx> IntoIterator for &'a InstantiatedPredicates<'tcx> {
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct OpaqueTypeKey<'tcx> {
     pub def_id: LocalDefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 #[derive(Copy, Clone, Debug, TypeFoldable, TypeVisitable, HashStable, TyEncodable, TyDecodable)]
@@ -1629,21 +1629,21 @@ impl<'tcx> OpaqueHiddenType<'tcx> {
         // typeck errors have subpar spans for opaque types, so delay error reporting until borrowck.
         ignore_errors: bool,
     ) -> Self {
-        let OpaqueTypeKey { def_id, substs } = opaque_type_key;
+        let OpaqueTypeKey { def_id, args } = opaque_type_key;
 
-        // Use substs to build up a reverse map from regions to their
+        // Use args to build up a reverse map from regions to their
         // identity mappings. This is necessary because of `impl
         // Trait` lifetimes are computed by replacing existing
         // lifetimes with 'static and remapping only those used in the
         // `impl Trait` return type, resulting in the parameters
         // shifting.
-        let id_substs = InternalSubsts::identity_for_item(tcx, def_id);
-        debug!(?id_substs);
+        let id_args = GenericArgs::identity_for_item(tcx, def_id);
+        debug!(?id_args);
 
-        // This zip may have several times the same lifetime in `substs` paired with a different
-        // lifetime from `id_substs`. Simply `collect`ing the iterator is the correct behaviour:
+        // This zip may have several times the same lifetime in `args` paired with a different
+        // lifetime from `id_args`. Simply `collect`ing the iterator is the correct behaviour:
         // it will pick the last one, which is the one we introduced in the impl-trait desugaring.
-        let map = substs.iter().zip(id_substs).collect();
+        let map = args.iter().zip(id_args).collect();
         debug!("map = {:#?}", map);
 
         // Convert the type from the function into a type valid outside
@@ -2164,10 +2164,10 @@ impl Hash for FieldDef {
 }
 
 impl<'tcx> FieldDef {
-    /// Returns the type of this field. The resulting type is not normalized. The `subst` is
+    /// Returns the type of this field. The resulting type is not normalized. The `arg` is
     /// typically obtained via the second field of [`TyKind::Adt`].
-    pub fn ty(&self, tcx: TyCtxt<'tcx>, subst: SubstsRef<'tcx>) -> Ty<'tcx> {
-        tcx.type_of(self.did).subst(tcx, subst)
+    pub fn ty(&self, tcx: TyCtxt<'tcx>, arg: GenericArgsRef<'tcx>) -> Ty<'tcx> {
+        tcx.type_of(self.did).instantiate(tcx, arg)
     }
 
     /// Computes the `Ident` of this variant by looking up the `Span`
@@ -2391,8 +2391,8 @@ impl<'tcx> TyCtxt<'tcx> {
         let impl_trait_ref2 = self.impl_trait_ref(def_id2);
         // If either trait impl references an error, they're allowed to overlap,
         // as one of them essentially doesn't exist.
-        if impl_trait_ref1.is_some_and(|tr| tr.subst_identity().references_error())
-            || impl_trait_ref2.is_some_and(|tr| tr.subst_identity().references_error())
+        if impl_trait_ref1.is_some_and(|tr| tr.instantiate_identity().references_error())
+            || impl_trait_ref2.is_some_and(|tr| tr.instantiate_identity().references_error())
         {
             return Some(ImplOverlapKind::Permitted { marker: false });
         }
diff --git a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
index a0c8d299f48ba..3c2c4483c7356 100644
--- a/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
+++ b/compiler/rustc_middle/src/ty/normalize_erasing_regions.rs
@@ -9,7 +9,7 @@
 
 use crate::traits::query::NoSolution;
 use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
-use crate::ty::{self, EarlyBinder, SubstsRef, Ty, TyCtxt, TypeVisitableExt};
+use crate::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
 
 #[derive(Debug, Copy, Clone, HashStable, TyEncodable, TyDecodable)]
 pub enum NormalizationError<'tcx> {
@@ -137,7 +137,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// use `try_subst_and_normalize_erasing_regions` instead.
     pub fn subst_and_normalize_erasing_regions<T>(
         self,
-        param_substs: SubstsRef<'tcx>,
+        param_args: GenericArgsRef<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         value: EarlyBinder<T>,
     ) -> T
@@ -146,12 +146,12 @@ impl<'tcx> TyCtxt<'tcx> {
     {
         debug!(
             "subst_and_normalize_erasing_regions(\
-             param_substs={:?}, \
+             param_args={:?}, \
              value={:?}, \
              param_env={:?})",
-            param_substs, value, param_env,
+            param_args, value, param_env,
         );
-        let substituted = value.subst(self, param_substs);
+        let substituted = value.instantiate(self, param_args);
         self.normalize_erasing_regions(param_env, substituted)
     }
 
@@ -161,7 +161,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// not assume that normalization succeeds.
     pub fn try_subst_and_normalize_erasing_regions<T>(
         self,
-        param_substs: SubstsRef<'tcx>,
+        param_args: GenericArgsRef<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         value: EarlyBinder<T>,
     ) -> Result<T, NormalizationError<'tcx>>
@@ -170,12 +170,12 @@ impl<'tcx> TyCtxt<'tcx> {
     {
         debug!(
             "subst_and_normalize_erasing_regions(\
-             param_substs={:?}, \
+             param_args={:?}, \
              value={:?}, \
              param_env={:?})",
-            param_substs, value, param_env,
+            param_args, value, param_env,
         );
-        let substituted = value.subst(self, param_substs);
+        let substituted = value.instantiate(self, param_args);
         self.try_normalize_erasing_regions(param_env, substituted)
     }
 }
diff --git a/compiler/rustc_middle/src/ty/opaque_types.rs b/compiler/rustc_middle/src/ty/opaque_types.rs
index b10921eff082f..7ae8be2dab398 100644
--- a/compiler/rustc_middle/src/ty/opaque_types.rs
+++ b/compiler/rustc_middle/src/ty/opaque_types.rs
@@ -1,7 +1,7 @@
 use crate::error::ConstNotUsedTraitAlias;
 use crate::ty::fold::{TypeFolder, TypeSuperFoldable};
-use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, Ty, TyCtxt, TypeFoldable};
+use crate::ty::{GenericArg, GenericArgKind};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
@@ -49,11 +49,11 @@ impl<'tcx> ReverseMapper<'tcx> {
         kind.fold_with(self)
     }
 
-    fn fold_closure_substs(
+    fn fold_closure_args(
         &mut self,
         def_id: DefId,
-        substs: ty::SubstsRef<'tcx>,
-    ) -> ty::SubstsRef<'tcx> {
+        args: ty::GenericArgsRef<'tcx>,
+    ) -> ty::GenericArgsRef<'tcx> {
         // I am a horrible monster and I pray for death. When
         // we encounter a closure here, it is always a closure
         // from within the function that we are currently
@@ -79,7 +79,7 @@ impl<'tcx> ReverseMapper<'tcx> {
         // during codegen.
 
         let generics = self.tcx.generics_of(def_id);
-        self.tcx.mk_substs_from_iter(substs.iter().enumerate().map(|(index, kind)| {
+        self.tcx.mk_args_from_iter(args.iter().enumerate().map(|(index, kind)| {
             if index < generics.parent_count {
                 // Accommodate missing regions in the parent kinds...
                 self.fold_kind_no_missing_regions_error(kind)
@@ -148,19 +148,19 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for ReverseMapper<'tcx> {
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
         match *ty.kind() {
-            ty::Closure(def_id, substs) => {
-                let substs = self.fold_closure_substs(def_id, substs);
-                Ty::new_closure(self.tcx, def_id, substs)
+            ty::Closure(def_id, args) => {
+                let args = self.fold_closure_args(def_id, args);
+                Ty::new_closure(self.tcx, def_id, args)
             }
 
-            ty::Generator(def_id, substs, movability) => {
-                let substs = self.fold_closure_substs(def_id, substs);
-                Ty::new_generator(self.tcx, def_id, substs, movability)
+            ty::Generator(def_id, args, movability) => {
+                let args = self.fold_closure_args(def_id, args);
+                Ty::new_generator(self.tcx, def_id, args, movability)
             }
 
-            ty::GeneratorWitnessMIR(def_id, substs) => {
-                let substs = self.fold_closure_substs(def_id, substs);
-                Ty::new_generator_witness_mir(self.tcx, def_id, substs)
+            ty::GeneratorWitnessMIR(def_id, args) => {
+                let args = self.fold_closure_args(def_id, args);
+                Ty::new_generator_witness_mir(self.tcx, def_id, args)
             }
 
             ty::Param(param) => {
diff --git a/compiler/rustc_middle/src/ty/print/mod.rs b/compiler/rustc_middle/src/ty/print/mod.rs
index 2de0a3f75dcf6..83a75d0c6b987 100644
--- a/compiler/rustc_middle/src/ty/print/mod.rs
+++ b/compiler/rustc_middle/src/ty/print/mod.rs
@@ -42,19 +42,19 @@ pub trait Printer<'tcx>: Sized {
     fn print_def_path(
         self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
-        self.default_print_def_path(def_id, substs)
+        self.default_print_def_path(def_id, args)
     }
 
     fn print_impl_path(
         self,
         impl_def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
         self_ty: Ty<'tcx>,
         trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<Self::Path, Self::Error> {
-        self.default_print_impl_path(impl_def_id, substs, self_ty, trait_ref)
+        self.default_print_impl_path(impl_def_id, args, self_ty, trait_ref)
     }
 
     fn print_region(self, region: ty::Region<'tcx>) -> Result<Self::Region, Self::Error>;
@@ -102,7 +102,7 @@ pub trait Printer<'tcx>: Sized {
     fn default_print_def_path(
         self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
         let key = self.tcx().def_key(def_id);
         debug!(?key);
@@ -117,25 +117,28 @@ pub trait Printer<'tcx>: Sized {
                 let generics = self.tcx().generics_of(def_id);
                 let self_ty = self.tcx().type_of(def_id);
                 let impl_trait_ref = self.tcx().impl_trait_ref(def_id);
-                let (self_ty, impl_trait_ref) = if substs.len() >= generics.count() {
+                let (self_ty, impl_trait_ref) = if args.len() >= generics.count() {
                     (
-                        self_ty.subst(self.tcx(), substs),
-                        impl_trait_ref.map(|i| i.subst(self.tcx(), substs)),
+                        self_ty.instantiate(self.tcx(), args),
+                        impl_trait_ref.map(|i| i.instantiate(self.tcx(), args)),
                     )
                 } else {
-                    (self_ty.subst_identity(), impl_trait_ref.map(|i| i.subst_identity()))
+                    (
+                        self_ty.instantiate_identity(),
+                        impl_trait_ref.map(|i| i.instantiate_identity()),
+                    )
                 };
-                self.print_impl_path(def_id, substs, self_ty, impl_trait_ref)
+                self.print_impl_path(def_id, args, self_ty, impl_trait_ref)
             }
 
             _ => {
                 let parent_def_id = DefId { index: key.parent.unwrap(), ..def_id };
 
-                let mut parent_substs = substs;
+                let mut parent_args = args;
                 let mut trait_qualify_parent = false;
-                if !substs.is_empty() {
+                if !args.is_empty() {
                     let generics = self.tcx().generics_of(def_id);
-                    parent_substs = &substs[..generics.parent_count.min(substs.len())];
+                    parent_args = &args[..generics.parent_count.min(args.len())];
 
                     match key.disambiguated_data.data {
                         // Closures' own generics are only captures, don't print them.
@@ -148,10 +151,10 @@ pub trait Printer<'tcx>: Sized {
                         // If we have any generic arguments to print, we do that
                         // on top of the same path, but without its own generics.
                         _ => {
-                            if !generics.params.is_empty() && substs.len() >= generics.count() {
-                                let args = generics.own_substs_no_defaults(self.tcx(), substs);
+                            if !generics.params.is_empty() && args.len() >= generics.count() {
+                                let args = generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
-                                    |cx| cx.print_def_path(def_id, parent_substs),
+                                    |cx| cx.print_def_path(def_id, parent_args),
                                     args,
                                 );
                             }
@@ -162,7 +165,7 @@ pub trait Printer<'tcx>: Sized {
                     // logic, instead of doing it when printing the child.
                     trait_qualify_parent = generics.has_self
                         && generics.parent == Some(parent_def_id)
-                        && parent_substs.len() == generics.parent_count
+                        && parent_args.len() == generics.parent_count
                         && self.tcx().generics_of(parent_def_id).parent_count == 0;
                 }
 
@@ -172,11 +175,11 @@ pub trait Printer<'tcx>: Sized {
                             let trait_ref = ty::TraitRef::new(
                                 cx.tcx(),
                                 parent_def_id,
-                                parent_substs.iter().copied(),
+                                parent_args.iter().copied(),
                             );
                             cx.path_qualified(trait_ref.self_ty(), Some(trait_ref))
                         } else {
-                            cx.print_def_path(parent_def_id, parent_substs)
+                            cx.print_def_path(parent_def_id, parent_args)
                         }
                     },
                     &key.disambiguated_data,
@@ -188,7 +191,7 @@ pub trait Printer<'tcx>: Sized {
     fn default_print_impl_path(
         self,
         impl_def_id: DefId,
-        _substs: &'tcx [GenericArg<'tcx>],
+        _args: &'tcx [GenericArg<'tcx>],
         self_ty: Ty<'tcx>,
         impl_trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<Self::Path, Self::Error> {
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 96cf36eb99614..3591acdea565d 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -224,9 +224,9 @@ pub trait PrettyPrinter<'tcx>:
     fn print_value_path(
         self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
-        self.print_def_path(def_id, substs)
+        self.print_def_path(def_id, args)
     }
 
     fn in_binder<T>(self, value: &ty::Binder<'tcx, T>) -> Result<Self, Self::Error>
@@ -679,12 +679,12 @@ pub trait PrettyPrinter<'tcx>:
                 }
                 p!(")")
             }
-            ty::FnDef(def_id, substs) => {
+            ty::FnDef(def_id, args) => {
                 if with_no_queries() {
-                    p!(print_def_path(def_id, substs));
+                    p!(print_def_path(def_id, args));
                 } else {
-                    let sig = self.tcx().fn_sig(def_id).subst(self.tcx(), substs);
-                    p!(print(sig), " {{", print_value_path(def_id, substs), "}}");
+                    let sig = self.tcx().fn_sig(def_id).instantiate(self.tcx(), args);
+                    p!(print(sig), " {{", print_value_path(def_id, args), "}}");
                 }
             }
             ty::FnPtr(ref bare_fn) => p!(print(bare_fn)),
@@ -715,8 +715,8 @@ pub trait PrettyPrinter<'tcx>:
                     false => p!(write("{s}")),
                 },
             },
-            ty::Adt(def, substs) => {
-                p!(print_def_path(def.did(), substs));
+            ty::Adt(def, args) => {
+                p!(print_def_path(def.did(), args));
             }
             ty::Dynamic(data, r, repr) => {
                 let print_r = self.should_print_region(r);
@@ -739,7 +739,7 @@ pub trait PrettyPrinter<'tcx>:
                 if !(self.should_print_verbose() || with_no_queries())
                     && self.tcx().is_impl_trait_in_trait(data.def_id)
                 {
-                    return self.pretty_print_opaque_impl_type(data.def_id, data.substs);
+                    return self.pretty_print_opaque_impl_type(data.def_id, data.args);
                 } else {
                     p!(print(data))
                 }
@@ -751,7 +751,7 @@ pub trait PrettyPrinter<'tcx>:
                     false => p!(write("{name}")),
                 },
             },
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
                 // We use verbose printing in 'NO_QUERIES' mode, to
                 // avoid needing to call `predicates_of`. This should
                 // only affect certain debug messages (e.g. messages printed
@@ -759,7 +759,7 @@ pub trait PrettyPrinter<'tcx>:
                 // and should have no effect on any compiler output.
                 if self.should_print_verbose() {
                     // FIXME(eddyb) print this with `print_def_path`.
-                    p!(write("Opaque({:?}, {:?})", def_id, substs));
+                    p!(write("Opaque({:?}, {:?})", def_id, args));
                     return Ok(self);
                 }
 
@@ -769,17 +769,17 @@ pub trait PrettyPrinter<'tcx>:
                         // NOTE: I know we should check for NO_QUERIES here, but it's alright.
                         // `type_of` on a type alias or assoc type should never cause a cycle.
                         if let ty::Alias(ty::Opaque, ty::AliasTy { def_id: d, .. }) =
-                            *self.tcx().type_of(parent).subst_identity().kind()
+                            *self.tcx().type_of(parent).instantiate_identity().kind()
                         {
                             if d == def_id {
                                 // If the type alias directly starts with the `impl` of the
                                 // opaque type we're printing, then skip the `::{opaque#1}`.
-                                p!(print_def_path(parent, substs));
+                                p!(print_def_path(parent, args));
                                 return Ok(self);
                             }
                         }
                         // Complex opaque type, e.g. `type Foo = (i32, impl Debug);`
-                        p!(print_def_path(def_id, substs));
+                        p!(print_def_path(def_id, args));
                         return Ok(self);
                     }
                     _ => {
@@ -787,13 +787,13 @@ pub trait PrettyPrinter<'tcx>:
                             p!(print_def_path(def_id, &[]));
                             return Ok(self);
                         } else {
-                            return self.pretty_print_opaque_impl_type(def_id, substs);
+                            return self.pretty_print_opaque_impl_type(def_id, args);
                         }
                     }
                 }
             }
             ty::Str => p!("str"),
-            ty::Generator(did, substs, movability) => {
+            ty::Generator(did, args, movability) => {
                 p!(write("["));
                 let generator_kind = self.tcx().generator_kind(did).unwrap();
                 let should_print_movability =
@@ -818,20 +818,20 @@ pub trait PrettyPrinter<'tcx>:
                             self.tcx().sess.source_map().span_to_embeddable_string(span)
                         ));
                     } else {
-                        p!(write("@"), print_def_path(did, substs));
+                        p!(write("@"), print_def_path(did, args));
                     }
                 } else {
-                    p!(print_def_path(did, substs));
+                    p!(print_def_path(did, args));
                     p!(" upvar_tys=(");
-                    if !substs.as_generator().is_valid() {
+                    if !args.as_generator().is_valid() {
                         p!("unavailable");
                     } else {
-                        self = self.comma_sep(substs.as_generator().upvar_tys())?;
+                        self = self.comma_sep(args.as_generator().upvar_tys())?;
                     }
                     p!(")");
 
-                    if substs.as_generator().is_valid() {
-                        p!(" ", print(substs.as_generator().witness()));
+                    if args.as_generator().is_valid() {
+                        p!(" ", print(args.as_generator().witness()));
                     }
                 }
 
@@ -840,7 +840,7 @@ pub trait PrettyPrinter<'tcx>:
             ty::GeneratorWitness(types) => {
                 p!(in_binder(&types));
             }
-            ty::GeneratorWitnessMIR(did, substs) => {
+            ty::GeneratorWitnessMIR(did, args) => {
                 p!(write("["));
                 if !self.tcx().sess.verbose() {
                     p!("generator witness");
@@ -854,22 +854,22 @@ pub trait PrettyPrinter<'tcx>:
                             self.tcx().sess.source_map().span_to_embeddable_string(span)
                         ));
                     } else {
-                        p!(write("@"), print_def_path(did, substs));
+                        p!(write("@"), print_def_path(did, args));
                     }
                 } else {
-                    p!(print_def_path(did, substs));
+                    p!(print_def_path(did, args));
                 }
 
                 p!("]")
             }
-            ty::Closure(did, substs) => {
+            ty::Closure(did, args) => {
                 p!(write("["));
                 if !self.should_print_verbose() {
                     p!(write("closure"));
                     // FIXME(eddyb) should use `def_span`.
                     if let Some(did) = did.as_local() {
                         if self.tcx().sess.opts.unstable_opts.span_free_formats {
-                            p!("@", print_def_path(did.to_def_id(), substs));
+                            p!("@", print_def_path(did.to_def_id(), args));
                         } else {
                             let span = self.tcx().def_span(did);
                             let preference = if FORCE_TRIMMED_PATH.with(|flag| flag.get()) {
@@ -885,21 +885,21 @@ pub trait PrettyPrinter<'tcx>:
                             ));
                         }
                     } else {
-                        p!(write("@"), print_def_path(did, substs));
+                        p!(write("@"), print_def_path(did, args));
                     }
                 } else {
-                    p!(print_def_path(did, substs));
-                    if !substs.as_closure().is_valid() {
-                        p!(" closure_substs=(unavailable)");
-                        p!(write(" substs={:?}", substs));
+                    p!(print_def_path(did, args));
+                    if !args.as_closure().is_valid() {
+                        p!(" closure_args=(unavailable)");
+                        p!(write(" args={:?}", args));
                     } else {
-                        p!(" closure_kind_ty=", print(substs.as_closure().kind_ty()));
+                        p!(" closure_kind_ty=", print(args.as_closure().kind_ty()));
                         p!(
                             " closure_sig_as_fn_ptr_ty=",
-                            print(substs.as_closure().sig_as_fn_ptr_ty())
+                            print(args.as_closure().sig_as_fn_ptr_ty())
                         );
                         p!(" upvar_tys=(");
-                        self = self.comma_sep(substs.as_closure().upvar_tys())?;
+                        self = self.comma_sep(args.as_closure().upvar_tys())?;
                         p!(")");
                     }
                 }
@@ -915,7 +915,7 @@ pub trait PrettyPrinter<'tcx>:
     fn pretty_print_opaque_impl_type(
         mut self,
         def_id: DefId,
-        substs: &'tcx ty::List<ty::GenericArg<'tcx>>,
+        args: &'tcx ty::List<ty::GenericArg<'tcx>>,
     ) -> Result<Self::Type, Self::Error> {
         let tcx = self.tcx();
 
@@ -928,7 +928,7 @@ pub trait PrettyPrinter<'tcx>:
         let mut is_sized = false;
         let mut lifetimes = SmallVec::<[ty::Region<'tcx>; 1]>::new();
 
-        for (predicate, _) in bounds.subst_iter_copied(tcx, substs) {
+        for (predicate, _) in bounds.arg_iter_copied(tcx, args) {
             let bound_predicate = predicate.kind();
 
             match bound_predicate.skip_binder() {
@@ -978,9 +978,9 @@ pub trait PrettyPrinter<'tcx>:
                 define_scoped_cx!(cx);
                 // Get the (single) generic ty (the args) of this FnOnce trait ref.
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
+                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
 
-                match (entry.return_ty, args[0].expect_ty()) {
+                match (entry.return_ty, own_args[0].expect_ty()) {
                     // We can only print `impl Fn() -> ()` if we have a tuple of args and we recorded
                     // a return type.
                     (Some(return_ty), arg_tys) if matches!(arg_tys.kind(), ty::Tuple(_)) => {
@@ -1044,12 +1044,12 @@ pub trait PrettyPrinter<'tcx>:
                 p!(print(trait_ref.print_only_trait_name()));
 
                 let generics = tcx.generics_of(trait_ref.def_id);
-                let args = generics.own_substs_no_defaults(tcx, trait_ref.substs);
+                let own_args = generics.own_args_no_defaults(tcx, trait_ref.args);
 
-                if !args.is_empty() || !assoc_items.is_empty() {
+                if !own_args.is_empty() || !assoc_items.is_empty() {
                     let mut first = true;
 
-                    for ty in args {
+                    for ty in own_args {
                         if first {
                             p!("<");
                             first = false;
@@ -1068,8 +1068,8 @@ pub trait PrettyPrinter<'tcx>:
                             && assoc.trait_container(tcx) == tcx.lang_items().gen_trait()
                             && assoc.name == rustc_span::sym::Return
                         {
-                            if let ty::Generator(_, substs, _) = substs.type_at(0).kind() {
-                                let return_ty = substs.as_generator().return_ty();
+                            if let ty::Generator(_, args, _) = args.type_at(0).kind() {
+                                let return_ty = args.as_generator().return_ty();
                                 if !return_ty.is_ty_var() {
                                     return_ty.into()
                                 } else {
@@ -1182,7 +1182,7 @@ pub trait PrettyPrinter<'tcx>:
                     &def_key.disambiguated_data,
                 )
             },
-            &alias_ty.substs[1..],
+            &alias_ty.args[1..],
         )
     }
 
@@ -1211,7 +1211,7 @@ pub trait PrettyPrinter<'tcx>:
                 // Special-case `Fn(...) -> ...` and re-sugar it.
                 let fn_trait_kind = cx.tcx().fn_trait_kind_from_def_id(principal.def_id);
                 if !cx.should_print_verbose() && fn_trait_kind.is_some() {
-                    if let ty::Tuple(tys) = principal.substs.type_at(0).kind() {
+                    if let ty::Tuple(tys) = principal.args.type_at(0).kind() {
                         let mut projections = predicates.projection_bounds();
                         if let (Some(proj), None) = (projections.next(), projections.next()) {
                             p!(pretty_fn_sig(
@@ -1234,7 +1234,7 @@ pub trait PrettyPrinter<'tcx>:
                     let args = cx
                         .tcx()
                         .generics_of(principal.def_id)
-                        .own_substs_no_defaults(cx.tcx(), principal.substs);
+                        .own_args_no_defaults(cx.tcx(), principal.args);
 
                     let mut projections = predicates.projection_bounds();
 
@@ -1341,10 +1341,10 @@ pub trait PrettyPrinter<'tcx>:
         }
 
         match ct.kind() {
-            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs }) => {
+            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args }) => {
                 match self.tcx().def_kind(def) {
                     DefKind::Const | DefKind::AssocConst => {
-                        p!(print_value_path(def, substs))
+                        p!(print_value_path(def, args))
                     }
                     DefKind::AnonConst => {
                         if def.is_local()
@@ -1449,7 +1449,7 @@ pub trait PrettyPrinter<'tcx>:
                     self.tcx().try_get_global_alloc(alloc_id)
                 {
                     self = self.typed_value(
-                        |this| this.print_value_path(instance.def_id(), instance.substs),
+                        |this| this.print_value_path(instance.def_id(), instance.args),
                         |this| this.print_type(ty),
                         " as ",
                     )?;
@@ -1619,11 +1619,11 @@ pub trait PrettyPrinter<'tcx>:
                             ": ",
                         )?;
                     }
-                    ty::Adt(def, substs) => {
+                    ty::Adt(def, args) => {
                         let variant_idx =
                             contents.variant.expect("destructed const of adt without variant idx");
                         let variant_def = &def.variant(variant_idx);
-                        p!(print_value_path(variant_def.def_id, substs));
+                        p!(print_value_path(variant_def.def_id, args));
                         match variant_def.ctor_kind() {
                             Some(CtorKind::Const) => {}
                             Some(CtorKind::Fn) => {
@@ -1673,7 +1673,7 @@ pub trait PrettyPrinter<'tcx>:
 
     fn pretty_closure_as_impl(
         mut self,
-        closure: ty::ClosureSubsts<'tcx>,
+        closure: ty::ClosureArgs<'tcx>,
     ) -> Result<Self::Const, Self::Error> {
         let sig = closure.sig();
         let kind = closure.kind_ty().to_opt_closure_kind().unwrap_or(ty::ClosureKind::Fn);
@@ -1798,29 +1798,29 @@ impl<'t> TyCtxt<'t> {
     /// Returns a string identifying this `DefId`. This string is
     /// suitable for user output.
     pub fn def_path_str(self, def_id: impl IntoQueryParam<DefId>) -> String {
-        self.def_path_str_with_substs(def_id, &[])
+        self.def_path_str_with_args(def_id, &[])
     }
 
-    pub fn def_path_str_with_substs(
+    pub fn def_path_str_with_args(
         self,
         def_id: impl IntoQueryParam<DefId>,
-        substs: &'t [GenericArg<'t>],
+        args: &'t [GenericArg<'t>],
     ) -> String {
         let def_id = def_id.into_query_param();
         let ns = guess_def_namespace(self, def_id);
         debug!("def_path_str: def_id={:?}, ns={:?}", def_id, ns);
-        FmtPrinter::new(self, ns).print_def_path(def_id, substs).unwrap().into_buffer()
+        FmtPrinter::new(self, ns).print_def_path(def_id, args).unwrap().into_buffer()
     }
 
-    pub fn value_path_str_with_substs(
+    pub fn value_path_str_with_args(
         self,
         def_id: impl IntoQueryParam<DefId>,
-        substs: &'t [GenericArg<'t>],
+        args: &'t [GenericArg<'t>],
     ) -> String {
         let def_id = def_id.into_query_param();
         let ns = guess_def_namespace(self, def_id);
         debug!("value_path_str: def_id={:?}, ns={:?}", def_id, ns);
-        FmtPrinter::new(self, ns).print_value_path(def_id, substs).unwrap().into_buffer()
+        FmtPrinter::new(self, ns).print_value_path(def_id, args).unwrap().into_buffer()
     }
 }
 
@@ -1847,11 +1847,11 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
     fn print_def_path(
         mut self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
         define_scoped_cx!(self);
 
-        if substs.is_empty() {
+        if args.is_empty() {
             match self.try_print_trimmed_def_path(def_id)? {
                 (cx, true) => return Ok(cx),
                 (cx, false) => self = cx,
@@ -1900,7 +1900,7 @@ impl<'tcx> Printer<'tcx> for FmtPrinter<'_, 'tcx> {
             }
         }
 
-        self.default_print_def_path(def_id, substs)
+        self.default_print_def_path(def_id, args)
     }
 
     fn print_region(self, region: ty::Region<'tcx>) -> Result<Self::Region, Self::Error> {
@@ -2044,10 +2044,10 @@ impl<'tcx> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx> {
     fn print_value_path(
         mut self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
         let was_in_value = std::mem::replace(&mut self.in_value, true);
-        self = self.print_def_path(def_id, substs)?;
+        self = self.print_def_path(def_id, args)?;
         self.in_value = was_in_value;
 
         Ok(self)
@@ -2695,7 +2695,7 @@ impl<'tcx> ty::PolyTraitPredicate<'tcx> {
 
 #[derive(Debug, Copy, Clone, Lift)]
 pub struct PrintClosureAsImpl<'tcx> {
-    pub closure: ty::ClosureSubsts<'tcx>,
+    pub closure: ty::ClosureArgs<'tcx>,
 }
 
 forward_display_to_print! {
@@ -2771,7 +2771,7 @@ define_print_and_forward_display! {
     }
 
     TraitRefPrintOnlyTraitPath<'tcx> {
-        p!(print_def_path(self.0.def_id, self.0.substs));
+        p!(print_def_path(self.0.def_id, self.0.args));
     }
 
     TraitRefPrintOnlyTraitName<'tcx> {
@@ -2842,7 +2842,7 @@ define_print_and_forward_display! {
         if let DefKind::Impl { of_trait: false } = cx.tcx().def_kind(cx.tcx().parent(self.def_id)) {
             p!(pretty_print_inherent_projection(self))
         } else {
-            p!(print_def_path(self.def_id, self.substs));
+            p!(print_def_path(self.def_id, self.args));
         }
     }
 
@@ -2891,7 +2891,7 @@ define_print_and_forward_display! {
             ty::PredicateKind::ObjectSafe(trait_def_id) => {
                 p!("the trait `", print_def_path(trait_def_id, &[]), "` is object-safe")
             }
-            ty::PredicateKind::ClosureKind(closure_def_id, _closure_substs, kind) => p!(
+            ty::PredicateKind::ClosureKind(closure_def_id, _closure_args, kind) => p!(
                 "the closure `",
                 print_value_path(closure_def_id, &[]),
                 write("` implements the trait `{}`", kind)
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 54dedf31d9fb7..bf9adabdab1c4 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -6,7 +6,7 @@
 
 use crate::ty::error::{ExpectedFound, TypeError};
 use crate::ty::{self, Expr, ImplSubject, Term, TermKind, Ty, TyCtxt, TypeFoldable};
-use crate::ty::{GenericArg, GenericArgKind, SubstsRef};
+use crate::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_target::spec::abi;
@@ -43,23 +43,23 @@ pub trait TypeRelation<'tcx>: Sized {
         Relate::relate(self, a, b)
     }
 
-    /// Relate the two substitutions for the given item. The default
+    /// Relate the two args for the given item. The default
     /// is to look up the variance for the item and proceed
     /// accordingly.
-    fn relate_item_substs(
+    fn relate_item_args(
         &mut self,
         item_def_id: DefId,
-        a_subst: SubstsRef<'tcx>,
-        b_subst: SubstsRef<'tcx>,
-    ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
+        a_arg: GenericArgsRef<'tcx>,
+        b_arg: GenericArgsRef<'tcx>,
+    ) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
         debug!(
-            "relate_item_substs(item_def_id={:?}, a_subst={:?}, b_subst={:?})",
-            item_def_id, a_subst, b_subst
+            "relate_item_args(item_def_id={:?}, a_arg={:?}, b_arg={:?})",
+            item_def_id, a_arg, b_arg
         );
 
         let tcx = self.tcx();
         let opt_variances = tcx.variances_of(item_def_id);
-        relate_substs_with_variances(self, item_def_id, opt_variances, a_subst, b_subst, true)
+        relate_args_with_variances(self, item_def_id, opt_variances, a_arg, b_arg, true)
     }
 
     /// Switch variance for the purpose of relating `a` and `b`.
@@ -134,31 +134,32 @@ pub fn relate_type_and_mut<'tcx, R: TypeRelation<'tcx>>(
 }
 
 #[inline]
-pub fn relate_substs<'tcx, R: TypeRelation<'tcx>>(
+pub fn relate_args<'tcx, R: TypeRelation<'tcx>>(
     relation: &mut R,
-    a_subst: SubstsRef<'tcx>,
-    b_subst: SubstsRef<'tcx>,
-) -> RelateResult<'tcx, SubstsRef<'tcx>> {
-    relation.tcx().mk_substs_from_iter(iter::zip(a_subst, b_subst).map(|(a, b)| {
+    a_arg: GenericArgsRef<'tcx>,
+    b_arg: GenericArgsRef<'tcx>,
+) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
+    relation.tcx().mk_args_from_iter(iter::zip(a_arg, b_arg).map(|(a, b)| {
         relation.relate_with_variance(ty::Invariant, ty::VarianceDiagInfo::default(), a, b)
     }))
 }
 
-pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>(
+pub fn relate_args_with_variances<'tcx, R: TypeRelation<'tcx>>(
     relation: &mut R,
     ty_def_id: DefId,
     variances: &[ty::Variance],
-    a_subst: SubstsRef<'tcx>,
-    b_subst: SubstsRef<'tcx>,
+    a_arg: GenericArgsRef<'tcx>,
+    b_arg: GenericArgsRef<'tcx>,
     fetch_ty_for_diag: bool,
-) -> RelateResult<'tcx, SubstsRef<'tcx>> {
+) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
     let tcx = relation.tcx();
 
     let mut cached_ty = None;
-    let params = iter::zip(a_subst, b_subst).enumerate().map(|(i, (a, b))| {
+    let params = iter::zip(a_arg, b_arg).enumerate().map(|(i, (a, b))| {
         let variance = variances[i];
         let variance_info = if variance == ty::Invariant && fetch_ty_for_diag {
-            let ty = *cached_ty.get_or_insert_with(|| tcx.type_of(ty_def_id).subst(tcx, a_subst));
+            let ty =
+                *cached_ty.get_or_insert_with(|| tcx.type_of(ty_def_id).instantiate(tcx, a_arg));
             ty::VarianceDiagInfo::Invariant { ty, param_index: i.try_into().unwrap() }
         } else {
             ty::VarianceDiagInfo::default()
@@ -166,7 +167,7 @@ pub fn relate_substs_with_variances<'tcx, R: TypeRelation<'tcx>>(
         relation.relate_with_variance(variance, variance_info, a, b)
     });
 
-    tcx.mk_substs_from_iter(params)
+    tcx.mk_args_from_iter(params)
 }
 
 impl<'tcx> Relate<'tcx> for ty::FnSig<'tcx> {
@@ -272,8 +273,8 @@ impl<'tcx> Relate<'tcx> for ty::AliasTy<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::ProjectionMismatched(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let substs = relation.relate(a.substs, b.substs)?;
-            Ok(relation.tcx().mk_alias_ty(a.def_id, substs))
+            let args = relation.relate(a.args, b.args)?;
+            Ok(relation.tcx().mk_alias_ty(a.def_id, args))
         }
     }
 }
@@ -293,13 +294,13 @@ impl<'tcx> Relate<'tcx> for ty::ExistentialProjection<'tcx> {
                 a.term,
                 b.term,
             )?;
-            let substs = relation.relate_with_variance(
+            let args = relation.relate_with_variance(
                 ty::Invariant,
                 ty::VarianceDiagInfo::default(),
-                a.substs,
-                b.substs,
+                a.args,
+                b.args,
             )?;
-            Ok(ty::ExistentialProjection { def_id: a.def_id, substs, term })
+            Ok(ty::ExistentialProjection { def_id: a.def_id, args, term })
         }
     }
 }
@@ -314,8 +315,8 @@ impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let substs = relate_substs(relation, a.substs, b.substs)?;
-            Ok(ty::TraitRef::new(relation.tcx(), a.def_id, substs))
+            let args = relate_args(relation, a.args, b.args)?;
+            Ok(ty::TraitRef::new(relation.tcx(), a.def_id, args))
         }
     }
 }
@@ -330,8 +331,8 @@ impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> {
         if a.def_id != b.def_id {
             Err(TypeError::Traits(expected_found(relation, a.def_id, b.def_id)))
         } else {
-            let substs = relate_substs(relation, a.substs, b.substs)?;
-            Ok(ty::ExistentialTraitRef { def_id: a.def_id, substs })
+            let args = relate_args(relation, a.args, b.args)?;
+            Ok(ty::ExistentialTraitRef { def_id: a.def_id, args })
         }
     }
 }
@@ -426,9 +427,9 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
 
         (ty::Placeholder(p1), ty::Placeholder(p2)) if p1 == p2 => Ok(a),
 
-        (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs)) if a_def == b_def => {
-            let substs = relation.relate_item_substs(a_def.did(), a_substs, b_substs)?;
-            Ok(Ty::new_adt(tcx, a_def, substs))
+        (&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args)) if a_def == b_def => {
+            let args = relation.relate_item_args(a_def.did(), a_args, b_args)?;
+            Ok(Ty::new_adt(tcx, a_def, args))
         }
 
         (&ty::Foreign(a_id), &ty::Foreign(b_id)) if a_id == b_id => Ok(Ty::new_foreign(tcx, a_id)),
@@ -442,14 +443,14 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(Ty::new_dynamic(tcx, relation.relate(a_obj, b_obj)?, region_bound, a_repr))
         }
 
-        (&ty::Generator(a_id, a_substs, movability), &ty::Generator(b_id, b_substs, _))
+        (&ty::Generator(a_id, a_args, movability), &ty::Generator(b_id, b_args, _))
             if a_id == b_id =>
         {
             // All Generator types with the same id represent
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
-            let substs = relation.relate(a_substs, b_substs)?;
-            Ok(Ty::new_generator(tcx, a_id, substs, movability))
+            let args = relation.relate(a_args, b_args)?;
+            Ok(Ty::new_generator(tcx, a_id, args, movability))
         }
 
         (&ty::GeneratorWitness(a_types), &ty::GeneratorWitness(b_types)) => {
@@ -462,22 +463,22 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(Ty::new_generator_witness(tcx, types))
         }
 
-        (&ty::GeneratorWitnessMIR(a_id, a_substs), &ty::GeneratorWitnessMIR(b_id, b_substs))
+        (&ty::GeneratorWitnessMIR(a_id, a_args), &ty::GeneratorWitnessMIR(b_id, b_args))
             if a_id == b_id =>
         {
             // All GeneratorWitness types with the same id represent
             // the (anonymous) type of the same generator expression. So
             // all of their regions should be equated.
-            let substs = relation.relate(a_substs, b_substs)?;
-            Ok(Ty::new_generator_witness_mir(tcx, a_id, substs))
+            let args = relation.relate(a_args, b_args)?;
+            Ok(Ty::new_generator_witness_mir(tcx, a_id, args))
         }
 
-        (&ty::Closure(a_id, a_substs), &ty::Closure(b_id, b_substs)) if a_id == b_id => {
+        (&ty::Closure(a_id, a_args), &ty::Closure(b_id, b_args)) if a_id == b_id => {
             // All Closure types with the same id represent
             // the (anonymous) type of the same closure expression. So
             // all of their regions should be equated.
-            let substs = relation.relate(a_substs, b_substs)?;
-            Ok(Ty::new_closure(tcx, a_id, &substs))
+            let args = relation.relate(a_args, b_args)?;
+            Ok(Ty::new_closure(tcx, a_id, &args))
         }
 
         (&ty::RawPtr(a_mt), &ty::RawPtr(b_mt)) => {
@@ -535,11 +536,9 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             }
         }
 
-        (&ty::FnDef(a_def_id, a_substs), &ty::FnDef(b_def_id, b_substs))
-            if a_def_id == b_def_id =>
-        {
-            let substs = relation.relate_item_substs(a_def_id, a_substs, b_substs)?;
-            Ok(Ty::new_fn_def(tcx, a_def_id, substs))
+        (&ty::FnDef(a_def_id, a_args), &ty::FnDef(b_def_id, b_args)) if a_def_id == b_def_id => {
+            let args = relation.relate_item_args(a_def_id, a_args, b_args)?;
+            Ok(Ty::new_fn_def(tcx, a_def_id, args))
         }
 
         (&ty::FnPtr(a_fty), &ty::FnPtr(b_fty)) => {
@@ -547,22 +546,22 @@ pub fn structurally_relate_tys<'tcx, R: TypeRelation<'tcx>>(
             Ok(Ty::new_fn_ptr(tcx, fty))
         }
 
-        // The substs of opaque types may not all be invariant, so we have
+        // The args of opaque types may not all be invariant, so we have
         // to treat them separately from other aliases.
         (
-            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, substs: a_substs, .. }),
-            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, substs: b_substs, .. }),
+            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: a_def_id, args: a_args, .. }),
+            &ty::Alias(ty::Opaque, ty::AliasTy { def_id: b_def_id, args: b_args, .. }),
         ) if a_def_id == b_def_id => {
             let opt_variances = tcx.variances_of(a_def_id);
-            let substs = relate_substs_with_variances(
+            let args = relate_args_with_variances(
                 relation,
                 a_def_id,
                 opt_variances,
-                a_substs,
-                b_substs,
+                a_args,
+                b_args,
                 false, // do not fetch `type_of(a_def_id)`, as it will cause a cycle
             )?;
-            Ok(Ty::new_opaque(tcx, a_def_id, substs))
+            Ok(Ty::new_opaque(tcx, a_def_id, args))
         }
 
         // Alias tend to mostly already be handled downstream due to normalization.
@@ -618,15 +617,15 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
         // be stabilized.
         (ty::ConstKind::Unevaluated(au), ty::ConstKind::Unevaluated(bu)) if au.def == bu.def => {
             assert_eq!(a.ty(), b.ty());
-            let substs = relation.relate_with_variance(
+            let args = relation.relate_with_variance(
                 ty::Variance::Invariant,
                 ty::VarianceDiagInfo::default(),
-                au.substs,
-                bu.substs,
+                au.args,
+                bu.args,
             )?;
             return Ok(ty::Const::new_unevaluated(
                 tcx,
-                ty::UnevaluatedConst { def: au.def, substs },
+                ty::UnevaluatedConst { def: au.def, args },
                 a.ty(),
             ));
         }
@@ -640,7 +639,7 @@ pub fn structurally_relate_consts<'tcx, R: TypeRelation<'tcx>>(
             // FIXME(generic_const_exprs): relating the `ty()`s is a little weird since it is supposed to
             // ICE If they mismatch. Unfortunately `ConstKind::Expr` is a little special and can be thought
             // of as being generic over the argument types, however this is implicit so these types don't get
-            // related when we relate the substs of the item this const arg is for.
+            // related when we relate the args of the item this const arg is for.
             let expr = match (ae, be) {
                 (Expr::Binop(a_op, al, ar), Expr::Binop(b_op, bl, br)) if a_op == b_op => {
                     r.relate(al.ty(), bl.ty())?;
@@ -714,35 +713,35 @@ impl<'tcx> Relate<'tcx> for &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> {
     }
 }
 
-impl<'tcx> Relate<'tcx> for ty::ClosureSubsts<'tcx> {
+impl<'tcx> Relate<'tcx> for ty::ClosureArgs<'tcx> {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
-        a: ty::ClosureSubsts<'tcx>,
-        b: ty::ClosureSubsts<'tcx>,
-    ) -> RelateResult<'tcx, ty::ClosureSubsts<'tcx>> {
-        let substs = relate_substs(relation, a.substs, b.substs)?;
-        Ok(ty::ClosureSubsts { substs })
+        a: ty::ClosureArgs<'tcx>,
+        b: ty::ClosureArgs<'tcx>,
+    ) -> RelateResult<'tcx, ty::ClosureArgs<'tcx>> {
+        let args = relate_args(relation, a.args, b.args)?;
+        Ok(ty::ClosureArgs { args })
     }
 }
 
-impl<'tcx> Relate<'tcx> for ty::GeneratorSubsts<'tcx> {
+impl<'tcx> Relate<'tcx> for ty::GeneratorArgs<'tcx> {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
-        a: ty::GeneratorSubsts<'tcx>,
-        b: ty::GeneratorSubsts<'tcx>,
-    ) -> RelateResult<'tcx, ty::GeneratorSubsts<'tcx>> {
-        let substs = relate_substs(relation, a.substs, b.substs)?;
-        Ok(ty::GeneratorSubsts { substs })
+        a: ty::GeneratorArgs<'tcx>,
+        b: ty::GeneratorArgs<'tcx>,
+    ) -> RelateResult<'tcx, ty::GeneratorArgs<'tcx>> {
+        let args = relate_args(relation, a.args, b.args)?;
+        Ok(ty::GeneratorArgs { args })
     }
 }
 
-impl<'tcx> Relate<'tcx> for SubstsRef<'tcx> {
+impl<'tcx> Relate<'tcx> for GenericArgsRef<'tcx> {
     fn relate<R: TypeRelation<'tcx>>(
         relation: &mut R,
-        a: SubstsRef<'tcx>,
-        b: SubstsRef<'tcx>,
-    ) -> RelateResult<'tcx, SubstsRef<'tcx>> {
-        relate_substs(relation, a, b)
+        a: GenericArgsRef<'tcx>,
+        b: GenericArgsRef<'tcx>,
+    ) -> RelateResult<'tcx, GenericArgsRef<'tcx>> {
+        relate_args(relation, a, b)
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index c82ce9112fcbb..9d380a58d9fa3 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -222,8 +222,8 @@ impl<'tcx> fmt::Debug for ty::PredicateKind<'tcx> {
             ty::PredicateKind::ObjectSafe(trait_def_id) => {
                 write!(f, "ObjectSafe({:?})", trait_def_id)
             }
-            ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
-                write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_substs, kind)
+            ty::PredicateKind::ClosureKind(closure_def_id, closure_args, kind) => {
+                write!(f, "ClosureKind({:?}, {:?}, {:?})", closure_def_id, closure_args, kind)
             }
             ty::PredicateKind::ConstEquate(c1, c2) => write!(f, "ConstEquate({:?}, {:?})", c1, c2),
             ty::PredicateKind::Ambiguous => write!(f, "Ambiguous"),
@@ -245,7 +245,7 @@ impl<'tcx> DebugWithInfcx<TyCtxt<'tcx>> for AliasTy<'tcx> {
         f: &mut core::fmt::Formatter<'_>,
     ) -> core::fmt::Result {
         f.debug_struct("AliasTy")
-            .field("substs", &this.map(|data| data.substs))
+            .field("args", &this.map(|data| data.args))
             .field("def_id", &this.data.def_id)
             .finish()
     }
@@ -322,7 +322,7 @@ impl<'tcx> DebugWithInfcx<TyCtxt<'tcx>> for ty::UnevaluatedConst<'tcx> {
     ) -> core::fmt::Result {
         f.debug_struct("UnevaluatedConst")
             .field("def", &this.data.def)
-            .field("substs", &this.wrap(this.data.substs))
+            .field("args", &this.wrap(this.data.args))
             .finish()
     }
 }
@@ -695,26 +695,26 @@ impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for Ty<'tcx> {
             ty::RawPtr(tm) => ty::RawPtr(tm.try_fold_with(folder)?),
             ty::Array(typ, sz) => ty::Array(typ.try_fold_with(folder)?, sz.try_fold_with(folder)?),
             ty::Slice(typ) => ty::Slice(typ.try_fold_with(folder)?),
-            ty::Adt(tid, substs) => ty::Adt(tid, substs.try_fold_with(folder)?),
+            ty::Adt(tid, args) => ty::Adt(tid, args.try_fold_with(folder)?),
             ty::Dynamic(trait_ty, region, representation) => ty::Dynamic(
                 trait_ty.try_fold_with(folder)?,
                 region.try_fold_with(folder)?,
                 representation,
             ),
             ty::Tuple(ts) => ty::Tuple(ts.try_fold_with(folder)?),
-            ty::FnDef(def_id, substs) => ty::FnDef(def_id, substs.try_fold_with(folder)?),
+            ty::FnDef(def_id, args) => ty::FnDef(def_id, args.try_fold_with(folder)?),
             ty::FnPtr(f) => ty::FnPtr(f.try_fold_with(folder)?),
             ty::Ref(r, ty, mutbl) => {
                 ty::Ref(r.try_fold_with(folder)?, ty.try_fold_with(folder)?, mutbl)
             }
-            ty::Generator(did, substs, movability) => {
-                ty::Generator(did, substs.try_fold_with(folder)?, movability)
+            ty::Generator(did, args, movability) => {
+                ty::Generator(did, args.try_fold_with(folder)?, movability)
             }
             ty::GeneratorWitness(types) => ty::GeneratorWitness(types.try_fold_with(folder)?),
-            ty::GeneratorWitnessMIR(did, substs) => {
-                ty::GeneratorWitnessMIR(did, substs.try_fold_with(folder)?)
+            ty::GeneratorWitnessMIR(did, args) => {
+                ty::GeneratorWitnessMIR(did, args.try_fold_with(folder)?)
             }
-            ty::Closure(did, substs) => ty::Closure(did, substs.try_fold_with(folder)?),
+            ty::Closure(did, args) => ty::Closure(did, args.try_fold_with(folder)?),
             ty::Alias(kind, data) => ty::Alias(kind, data.try_fold_with(folder)?),
 
             ty::Bool
@@ -748,22 +748,22 @@ impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for Ty<'tcx> {
                 sz.visit_with(visitor)
             }
             ty::Slice(typ) => typ.visit_with(visitor),
-            ty::Adt(_, substs) => substs.visit_with(visitor),
+            ty::Adt(_, args) => args.visit_with(visitor),
             ty::Dynamic(ref trait_ty, ref reg, _) => {
                 trait_ty.visit_with(visitor)?;
                 reg.visit_with(visitor)
             }
             ty::Tuple(ts) => ts.visit_with(visitor),
-            ty::FnDef(_, substs) => substs.visit_with(visitor),
+            ty::FnDef(_, args) => args.visit_with(visitor),
             ty::FnPtr(ref f) => f.visit_with(visitor),
             ty::Ref(r, ty, _) => {
                 r.visit_with(visitor)?;
                 ty.visit_with(visitor)
             }
-            ty::Generator(_did, ref substs, _) => substs.visit_with(visitor),
+            ty::Generator(_did, ref args, _) => args.visit_with(visitor),
             ty::GeneratorWitness(ref types) => types.visit_with(visitor),
-            ty::GeneratorWitnessMIR(_did, ref substs) => substs.visit_with(visitor),
-            ty::Closure(_did, ref substs) => substs.visit_with(visitor),
+            ty::GeneratorWitnessMIR(_did, ref args) => args.visit_with(visitor),
+            ty::Closure(_did, ref args) => args.visit_with(visitor),
             ty::Alias(_, ref data) => data.visit_with(visitor),
 
             ty::Bool
@@ -943,7 +943,7 @@ impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::UnevaluatedConst<'tcx> {
         &self,
         visitor: &mut V,
     ) -> ControlFlow<V::BreakTy> {
-        self.substs.visit_with(visitor)
+        self.args.visit_with(visitor)
     }
 }
 
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 9f4515b95e738..66d8a79de4228 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -3,13 +3,13 @@
 #![allow(rustc::usage_of_ty_tykind)]
 
 use crate::infer::canonical::Canonical;
-use crate::ty::subst::{GenericArg, InternalSubsts, SubstsRef};
 use crate::ty::visit::ValidateBoundVars;
 use crate::ty::InferTy::*;
 use crate::ty::{
     self, AdtDef, Discr, Term, Ty, TyCtxt, TypeFlags, TypeSuperVisitable, TypeVisitable,
     TypeVisitableExt, TypeVisitor,
 };
+use crate::ty::{GenericArg, GenericArgs, GenericArgsRef};
 use crate::ty::{List, ParamEnv};
 use hir::def::DefKind;
 use polonius_engine::Atom;
@@ -218,7 +218,7 @@ impl<'tcx> Article for TyKind<'tcx> {
 ///
 /// ## Generators
 ///
-/// Generators are handled similarly in `GeneratorSubsts`. The set of
+/// Generators are handled similarly in `GeneratorArgs`. The set of
 /// type parameters is similar, but `CK` and `CS` are replaced by the
 /// following type parameters:
 ///
@@ -231,33 +231,30 @@ impl<'tcx> Article for TyKind<'tcx> {
 ///   completion of the generator.
 /// * `GW`: The "generator witness".
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TypeFoldable, TypeVisitable, Lift)]
-pub struct ClosureSubsts<'tcx> {
+pub struct ClosureArgs<'tcx> {
     /// Lifetime and type parameters from the enclosing function,
     /// concatenated with a tuple containing the types of the upvars.
     ///
     /// These are separated out because codegen wants to pass them around
     /// when monomorphizing.
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 /// Struct returned by `split()`.
-pub struct ClosureSubstsParts<'tcx, T> {
-    pub parent_substs: &'tcx [GenericArg<'tcx>],
+pub struct ClosureArgsParts<'tcx, T> {
+    pub parent_args: &'tcx [GenericArg<'tcx>],
     pub closure_kind_ty: T,
     pub closure_sig_as_fn_ptr_ty: T,
     pub tupled_upvars_ty: T,
 }
 
-impl<'tcx> ClosureSubsts<'tcx> {
-    /// Construct `ClosureSubsts` from `ClosureSubstsParts`, containing `Substs`
+impl<'tcx> ClosureArgs<'tcx> {
+    /// Construct `ClosureArgs` from `ClosureArgsParts`, containing `Args`
     /// for the closure parent, alongside additional closure-specific components.
-    pub fn new(
-        tcx: TyCtxt<'tcx>,
-        parts: ClosureSubstsParts<'tcx, Ty<'tcx>>,
-    ) -> ClosureSubsts<'tcx> {
-        ClosureSubsts {
-            substs: tcx.mk_substs_from_iter(
-                parts.parent_substs.iter().copied().chain(
+    pub fn new(tcx: TyCtxt<'tcx>, parts: ClosureArgsParts<'tcx, Ty<'tcx>>) -> ClosureArgs<'tcx> {
+        ClosureArgs {
+            args: tcx.mk_args_from_iter(
+                parts.parent_args.iter().copied().chain(
                     [parts.closure_kind_ty, parts.closure_sig_as_fn_ptr_ty, parts.tupled_upvars_ty]
                         .iter()
                         .map(|&ty| ty.into()),
@@ -266,38 +263,34 @@ impl<'tcx> ClosureSubsts<'tcx> {
         }
     }
 
-    /// Divides the closure substs into their respective components.
-    /// The ordering assumed here must match that used by `ClosureSubsts::new` above.
-    fn split(self) -> ClosureSubstsParts<'tcx, GenericArg<'tcx>> {
-        match self.substs[..] {
-            [
-                ref parent_substs @ ..,
-                closure_kind_ty,
-                closure_sig_as_fn_ptr_ty,
-                tupled_upvars_ty,
-            ] => ClosureSubstsParts {
-                parent_substs,
-                closure_kind_ty,
-                closure_sig_as_fn_ptr_ty,
-                tupled_upvars_ty,
-            },
-            _ => bug!("closure substs missing synthetics"),
+    /// Divides the closure args into their respective components.
+    /// The ordering assumed here must match that used by `ClosureArgs::new` above.
+    fn split(self) -> ClosureArgsParts<'tcx, GenericArg<'tcx>> {
+        match self.args[..] {
+            [ref parent_args @ .., closure_kind_ty, closure_sig_as_fn_ptr_ty, tupled_upvars_ty] => {
+                ClosureArgsParts {
+                    parent_args,
+                    closure_kind_ty,
+                    closure_sig_as_fn_ptr_ty,
+                    tupled_upvars_ty,
+                }
+            }
+            _ => bug!("closure args missing synthetics"),
         }
     }
 
     /// Returns `true` only if enough of the synthetic types are known to
-    /// allow using all of the methods on `ClosureSubsts` without panicking.
+    /// allow using all of the methods on `ClosureArgs` without panicking.
     ///
     /// Used primarily by `ty::print::pretty` to be able to handle closure
     /// types that haven't had their synthetic types substituted in.
     pub fn is_valid(self) -> bool {
-        self.substs.len() >= 3
-            && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
+        self.args.len() >= 3 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
     }
 
     /// Returns the substitutions of the closure's parent.
-    pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
-        self.split().parent_substs
+    pub fn parent_args(self) -> &'tcx [GenericArg<'tcx>] {
+        self.split().parent_args
     }
 
     /// Returns an iterator over the list of types of captured paths by the closure.
@@ -323,7 +316,7 @@ impl<'tcx> ClosureSubsts<'tcx> {
 
     /// Returns the closure kind for this closure; may return a type
     /// variable during inference. To get the closure kind during
-    /// inference, use `infcx.closure_kind(substs)`.
+    /// inference, use `infcx.closure_kind(args)`.
     pub fn kind_ty(self) -> Ty<'tcx> {
         self.split().closure_kind_ty.expect_ty()
     }
@@ -331,7 +324,7 @@ impl<'tcx> ClosureSubsts<'tcx> {
     /// Returns the `fn` pointer type representing the closure signature for this
     /// closure.
     // FIXME(eddyb) this should be unnecessary, as the shallowly resolved
-    // type is known at the time of the creation of `ClosureSubsts`,
+    // type is known at the time of the creation of `ClosureArgs`,
     // see `rustc_hir_analysis::check::closure`.
     pub fn sig_as_fn_ptr_ty(self) -> Ty<'tcx> {
         self.split().closure_sig_as_fn_ptr_ty.expect_ty()
@@ -360,14 +353,14 @@ impl<'tcx> ClosureSubsts<'tcx> {
     }
 }
 
-/// Similar to `ClosureSubsts`; see the above documentation for more.
+/// Similar to `ClosureArgs`; see the above documentation for more.
 #[derive(Copy, Clone, PartialEq, Eq, Debug, TypeFoldable, TypeVisitable, Lift)]
-pub struct GeneratorSubsts<'tcx> {
-    pub substs: SubstsRef<'tcx>,
+pub struct GeneratorArgs<'tcx> {
+    pub args: GenericArgsRef<'tcx>,
 }
 
-pub struct GeneratorSubstsParts<'tcx, T> {
-    pub parent_substs: &'tcx [GenericArg<'tcx>],
+pub struct GeneratorArgsParts<'tcx, T> {
+    pub parent_args: &'tcx [GenericArg<'tcx>],
     pub resume_ty: T,
     pub yield_ty: T,
     pub return_ty: T,
@@ -375,16 +368,16 @@ pub struct GeneratorSubstsParts<'tcx, T> {
     pub tupled_upvars_ty: T,
 }
 
-impl<'tcx> GeneratorSubsts<'tcx> {
-    /// Construct `GeneratorSubsts` from `GeneratorSubstsParts`, containing `Substs`
+impl<'tcx> GeneratorArgs<'tcx> {
+    /// Construct `GeneratorArgs` from `GeneratorArgsParts`, containing `Args`
     /// for the generator parent, alongside additional generator-specific components.
     pub fn new(
         tcx: TyCtxt<'tcx>,
-        parts: GeneratorSubstsParts<'tcx, Ty<'tcx>>,
-    ) -> GeneratorSubsts<'tcx> {
-        GeneratorSubsts {
-            substs: tcx.mk_substs_from_iter(
-                parts.parent_substs.iter().copied().chain(
+        parts: GeneratorArgsParts<'tcx, Ty<'tcx>>,
+    ) -> GeneratorArgs<'tcx> {
+        GeneratorArgs {
+            args: tcx.mk_args_from_iter(
+                parts.parent_args.iter().copied().chain(
                     [
                         parts.resume_ty,
                         parts.yield_ty,
@@ -399,13 +392,13 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         }
     }
 
-    /// Divides the generator substs into their respective components.
-    /// The ordering assumed here must match that used by `GeneratorSubsts::new` above.
-    fn split(self) -> GeneratorSubstsParts<'tcx, GenericArg<'tcx>> {
-        match self.substs[..] {
-            [ref parent_substs @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
-                GeneratorSubstsParts {
-                    parent_substs,
+    /// Divides the generator args into their respective components.
+    /// The ordering assumed here must match that used by `GeneratorArgs::new` above.
+    fn split(self) -> GeneratorArgsParts<'tcx, GenericArg<'tcx>> {
+        match self.args[..] {
+            [ref parent_args @ .., resume_ty, yield_ty, return_ty, witness, tupled_upvars_ty] => {
+                GeneratorArgsParts {
+                    parent_args,
                     resume_ty,
                     yield_ty,
                     return_ty,
@@ -413,23 +406,22 @@ impl<'tcx> GeneratorSubsts<'tcx> {
                     tupled_upvars_ty,
                 }
             }
-            _ => bug!("generator substs missing synthetics"),
+            _ => bug!("generator args missing synthetics"),
         }
     }
 
     /// Returns `true` only if enough of the synthetic types are known to
-    /// allow using all of the methods on `GeneratorSubsts` without panicking.
+    /// allow using all of the methods on `GeneratorArgs` without panicking.
     ///
     /// Used primarily by `ty::print::pretty` to be able to handle generator
     /// types that haven't had their synthetic types substituted in.
     pub fn is_valid(self) -> bool {
-        self.substs.len() >= 5
-            && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
+        self.args.len() >= 5 && matches!(self.split().tupled_upvars_ty.expect_ty().kind(), Tuple(_))
     }
 
     /// Returns the substitutions of the generator's parent.
-    pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
-        self.split().parent_substs
+    pub fn parent_args(self) -> &'tcx [GenericArg<'tcx>] {
+        self.split().parent_args
     }
 
     /// This describes the types that can be contained in a generator.
@@ -498,7 +490,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
     }
 }
 
-impl<'tcx> GeneratorSubsts<'tcx> {
+impl<'tcx> GeneratorArgs<'tcx> {
     /// Generator has not been resumed yet.
     pub const UNRESUMED: usize = 0;
     /// Generator has returned or is completed.
@@ -577,7 +569,7 @@ impl<'tcx> GeneratorSubsts<'tcx> {
         let layout = tcx.generator_layout(def_id).unwrap();
         layout.variant_fields.iter().map(move |variant| {
             variant.iter().map(move |field| {
-                ty::EarlyBinder::bind(layout.field_tys[*field].ty).subst(tcx, self.substs)
+                ty::EarlyBinder::bind(layout.field_tys[*field].ty).instantiate(tcx, self.args)
             })
         })
     }
@@ -591,20 +583,20 @@ impl<'tcx> GeneratorSubsts<'tcx> {
 }
 
 #[derive(Debug, Copy, Clone, HashStable)]
-pub enum UpvarSubsts<'tcx> {
-    Closure(SubstsRef<'tcx>),
-    Generator(SubstsRef<'tcx>),
+pub enum UpvarArgs<'tcx> {
+    Closure(GenericArgsRef<'tcx>),
+    Generator(GenericArgsRef<'tcx>),
 }
 
-impl<'tcx> UpvarSubsts<'tcx> {
+impl<'tcx> UpvarArgs<'tcx> {
     /// Returns an iterator over the list of types of captured paths by the closure/generator.
     /// In case there was a type error in figuring out the types of the captured path, an
     /// empty iterator is returned.
     #[inline]
     pub fn upvar_tys(self) -> impl Iterator<Item = Ty<'tcx>> + 'tcx {
         let tupled_tys = match self {
-            UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
-            UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
+            UpvarArgs::Closure(args) => args.as_closure().tupled_upvars_ty(),
+            UpvarArgs::Generator(args) => args.as_generator().tupled_upvars_ty(),
         };
 
         match tupled_tys.kind() {
@@ -620,8 +612,8 @@ impl<'tcx> UpvarSubsts<'tcx> {
     #[inline]
     pub fn tupled_upvars_ty(self) -> Ty<'tcx> {
         match self {
-            UpvarSubsts::Closure(substs) => substs.as_closure().tupled_upvars_ty(),
-            UpvarSubsts::Generator(substs) => substs.as_generator().tupled_upvars_ty(),
+            UpvarArgs::Closure(args) => args.as_closure().tupled_upvars_ty(),
+            UpvarArgs::Generator(args) => args.as_generator().tupled_upvars_ty(),
         }
     }
 }
@@ -638,46 +630,46 @@ impl<'tcx> UpvarSubsts<'tcx> {
 ///
 /// When the inline const is instantiated, `R` is substituted as the actual inferred
 /// type of the constant. The reason that `R` is represented as an extra type parameter
-/// is the same reason that [`ClosureSubsts`] have `CS` and `U` as type parameters:
+/// is the same reason that [`ClosureArgs`] have `CS` and `U` as type parameters:
 /// inline const can reference lifetimes that are internal to the creating function.
 #[derive(Copy, Clone, Debug)]
-pub struct InlineConstSubsts<'tcx> {
+pub struct InlineConstArgs<'tcx> {
     /// Generic parameters from the enclosing item,
     /// concatenated with the inferred type of the constant.
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 /// Struct returned by `split()`.
-pub struct InlineConstSubstsParts<'tcx, T> {
-    pub parent_substs: &'tcx [GenericArg<'tcx>],
+pub struct InlineConstArgsParts<'tcx, T> {
+    pub parent_args: &'tcx [GenericArg<'tcx>],
     pub ty: T,
 }
 
-impl<'tcx> InlineConstSubsts<'tcx> {
-    /// Construct `InlineConstSubsts` from `InlineConstSubstsParts`.
+impl<'tcx> InlineConstArgs<'tcx> {
+    /// Construct `InlineConstArgs` from `InlineConstArgsParts`.
     pub fn new(
         tcx: TyCtxt<'tcx>,
-        parts: InlineConstSubstsParts<'tcx, Ty<'tcx>>,
-    ) -> InlineConstSubsts<'tcx> {
-        InlineConstSubsts {
-            substs: tcx.mk_substs_from_iter(
-                parts.parent_substs.iter().copied().chain(std::iter::once(parts.ty.into())),
+        parts: InlineConstArgsParts<'tcx, Ty<'tcx>>,
+    ) -> InlineConstArgs<'tcx> {
+        InlineConstArgs {
+            args: tcx.mk_args_from_iter(
+                parts.parent_args.iter().copied().chain(std::iter::once(parts.ty.into())),
             ),
         }
     }
 
-    /// Divides the inline const substs into their respective components.
-    /// The ordering assumed here must match that used by `InlineConstSubsts::new` above.
-    fn split(self) -> InlineConstSubstsParts<'tcx, GenericArg<'tcx>> {
-        match self.substs[..] {
-            [ref parent_substs @ .., ty] => InlineConstSubstsParts { parent_substs, ty },
-            _ => bug!("inline const substs missing synthetics"),
+    /// Divides the inline const args into their respective components.
+    /// The ordering assumed here must match that used by `InlineConstArgs::new` above.
+    fn split(self) -> InlineConstArgsParts<'tcx, GenericArg<'tcx>> {
+        match self.args[..] {
+            [ref parent_args @ .., ty] => InlineConstArgsParts { parent_args, ty },
+            _ => bug!("inline const args missing synthetics"),
         }
     }
 
     /// Returns the substitutions of the inline const's parent.
-    pub fn parent_substs(self) -> &'tcx [GenericArg<'tcx>] {
-        self.split().parent_substs
+    pub fn parent_args(self) -> &'tcx [GenericArg<'tcx>] {
+        self.split().parent_args
     }
 
     /// Returns the type of this inline const.
@@ -748,10 +740,9 @@ impl<'tcx> PolyExistentialPredicate<'tcx> {
                     ty::TraitRef::new(tcx, did, [self_ty])
                 } else {
                     // If this is an ill-formed auto trait, then synthesize
-                    // new error substs for the missing generics.
-                    let err_substs =
-                        ty::InternalSubsts::extend_with_error(tcx, did, &[self_ty.into()]);
-                    ty::TraitRef::new(tcx, did, err_substs)
+                    // new error args for the missing generics.
+                    let err_args = ty::GenericArgs::extend_with_error(tcx, did, &[self_ty.into()]);
+                    ty::TraitRef::new(tcx, did, err_args)
                 };
                 self.rebind(trait_ref).without_const().to_predicate(tcx)
             }
@@ -827,7 +818,7 @@ impl<'tcx> List<ty::PolyExistentialPredicate<'tcx>> {
 /// T: Foo<U>
 /// ```
 /// This would be represented by a trait-reference where the `DefId` is the
-/// `DefId` for the trait `Foo` and the substs define `T` as parameter 0,
+/// `DefId` for the trait `Foo` and the args define `T` as parameter 0,
 /// and `U` as parameter 1.
 ///
 /// Trait references also appear in object types like `Foo<U>`, but in
@@ -836,7 +827,7 @@ impl<'tcx> List<ty::PolyExistentialPredicate<'tcx>> {
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct TraitRef<'tcx> {
     pub def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
     /// This field exists to prevent the creation of `TraitRef` without
     /// calling [`TraitRef::new`].
     pub(super) _use_trait_ref_new_instead: (),
@@ -846,42 +837,42 @@ impl<'tcx> TraitRef<'tcx> {
     pub fn new(
         tcx: TyCtxt<'tcx>,
         trait_def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Self {
-        let substs = tcx.check_and_mk_substs(trait_def_id, substs);
-        Self { def_id: trait_def_id, substs, _use_trait_ref_new_instead: () }
+        let args = tcx.check_and_mk_args(trait_def_id, args);
+        Self { def_id: trait_def_id, args, _use_trait_ref_new_instead: () }
     }
 
     pub fn from_lang_item(
         tcx: TyCtxt<'tcx>,
         trait_lang_item: LangItem,
         span: Span,
-        substs: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
+        args: impl IntoIterator<Item: Into<ty::GenericArg<'tcx>>>,
     ) -> Self {
         let trait_def_id = tcx.require_lang_item(trait_lang_item, Some(span));
-        Self::new(tcx, trait_def_id, substs)
+        Self::new(tcx, trait_def_id, args)
     }
 
     pub fn from_method(
         tcx: TyCtxt<'tcx>,
         trait_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> ty::TraitRef<'tcx> {
         let defs = tcx.generics_of(trait_id);
-        ty::TraitRef::new(tcx, trait_id, tcx.mk_substs(&substs[..defs.params.len()]))
+        ty::TraitRef::new(tcx, trait_id, tcx.mk_args(&args[..defs.params.len()]))
     }
 
     /// Returns a `TraitRef` of the form `P0: Foo<P1..Pn>` where `Pi`
     /// are the parameters defined on trait.
     pub fn identity(tcx: TyCtxt<'tcx>, def_id: DefId) -> TraitRef<'tcx> {
-        ty::TraitRef::new(tcx, def_id, InternalSubsts::identity_for_item(tcx, def_id))
+        ty::TraitRef::new(tcx, def_id, GenericArgs::identity_for_item(tcx, def_id))
     }
 
     pub fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
         ty::TraitRef::new(
             tcx,
             self.def_id,
-            [self_ty.into()].into_iter().chain(self.substs.iter().skip(1)),
+            [self_ty.into()].into_iter().chain(self.args.iter().skip(1)),
         )
     }
 
@@ -899,7 +890,7 @@ impl<'tcx> TraitRef<'tcx> {
 
     #[inline]
     pub fn self_ty(&self) -> Ty<'tcx> {
-        self.substs.type_at(0)
+        self.args.type_at(0)
     }
 }
 
@@ -932,7 +923,7 @@ impl<'tcx> IntoDiagnosticArg for TraitRef<'tcx> {
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct ExistentialTraitRef<'tcx> {
     pub def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 }
 
 impl<'tcx> ExistentialTraitRef<'tcx> {
@@ -941,11 +932,11 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
         trait_ref: ty::TraitRef<'tcx>,
     ) -> ty::ExistentialTraitRef<'tcx> {
         // Assert there is a Self.
-        trait_ref.substs.type_at(0);
+        trait_ref.args.type_at(0);
 
         ty::ExistentialTraitRef {
             def_id: trait_ref.def_id,
-            substs: tcx.mk_substs(&trait_ref.substs[1..]),
+            args: tcx.mk_args(&trait_ref.args[1..]),
         }
     }
 
@@ -957,7 +948,7 @@ impl<'tcx> ExistentialTraitRef<'tcx> {
         // otherwise the escaping vars would be captured by the binder
         // debug_assert!(!self_ty.has_escaping_bound_vars());
 
-        ty::TraitRef::new(tcx, self.def_id, [self_ty.into()].into_iter().chain(self.substs.iter()))
+        ty::TraitRef::new(tcx, self.def_id, [self_ty.into()].into_iter().chain(self.args.iter()))
     }
 }
 
@@ -1226,7 +1217,7 @@ pub struct AliasTy<'tcx> {
     ///
     /// For RPIT the substitutions are for the generics of the function,
     /// while for TAIT it is used for the generic parameters of the alias.
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
 
     /// The `DefId` of the `TraitItem` or `ImplItem` for the associated type `N` depending on whether
     /// this is a projection or an inherent projection or the `DefId` of the `OpaqueType` item if
@@ -1264,11 +1255,11 @@ impl<'tcx> AliasTy<'tcx> {
 /// The following methods work only with associated type projections.
 impl<'tcx> AliasTy<'tcx> {
     pub fn self_ty(self) -> Ty<'tcx> {
-        self.substs.type_at(0)
+        self.args.type_at(0)
     }
 
     pub fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self {
-        tcx.mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.substs.iter().skip(1)))
+        tcx.mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.args.iter().skip(1)))
     }
 }
 
@@ -1281,10 +1272,10 @@ impl<'tcx> AliasTy<'tcx> {
         }
     }
 
-    /// Extracts the underlying trait reference and own substs from this projection.
+    /// Extracts the underlying trait reference and own args from this projection.
     /// For example, if this is a projection of `<T as StreamingIterator>::Item<'a>`,
-    /// then this function would return a `T: StreamingIterator` trait reference and `['a]` as the own substs
-    pub fn trait_ref_and_own_substs(
+    /// then this function would return a `T: StreamingIterator` trait reference and `['a]` as the own args
+    pub fn trait_ref_and_own_args(
         self,
         tcx: TyCtxt<'tcx>,
     ) -> (ty::TraitRef<'tcx>, &'tcx [ty::GenericArg<'tcx>]) {
@@ -1292,8 +1283,8 @@ impl<'tcx> AliasTy<'tcx> {
         let trait_def_id = self.trait_def_id(tcx);
         let trait_generics = tcx.generics_of(trait_def_id);
         (
-            ty::TraitRef::new(tcx, trait_def_id, self.substs.truncate_to(tcx, trait_generics)),
-            &self.substs[trait_generics.count()..],
+            ty::TraitRef::new(tcx, trait_def_id, self.args.truncate_to(tcx, trait_generics)),
+            &self.args[trait_generics.count()..],
         )
     }
 
@@ -1301,18 +1292,18 @@ impl<'tcx> AliasTy<'tcx> {
     /// For example, if this is a projection of `<T as Iterator>::Item`,
     /// then this function would return a `T: Iterator` trait reference.
     ///
-    /// WARNING: This will drop the substs for generic associated types
-    /// consider calling [Self::trait_ref_and_own_substs] to get those
+    /// WARNING: This will drop the args for generic associated types
+    /// consider calling [Self::trait_ref_and_own_args] to get those
     /// as well.
     pub fn trait_ref(self, tcx: TyCtxt<'tcx>) -> ty::TraitRef<'tcx> {
         let def_id = self.trait_def_id(tcx);
-        ty::TraitRef::new(tcx, def_id, self.substs.truncate_to(tcx, tcx.generics_of(def_id)))
+        ty::TraitRef::new(tcx, def_id, self.args.truncate_to(tcx, tcx.generics_of(def_id)))
     }
 }
 
 /// The following methods work only with inherent associated type projections.
 impl<'tcx> AliasTy<'tcx> {
-    /// Transform the substitutions to have the given `impl` substs as the base and the GAT substs on top of that.
+    /// Transform the substitutions to have the given `impl` args as the base and the GAT args on top of that.
     ///
     /// Does the following transformation:
     ///
@@ -1322,14 +1313,14 @@ impl<'tcx> AliasTy<'tcx> {
     ///     I_i impl subst
     ///     P_j GAT subst
     /// ```
-    pub fn rebase_substs_onto_impl(
+    pub fn rebase_args_onto_impl(
         self,
-        impl_substs: ty::SubstsRef<'tcx>,
+        impl_args: ty::GenericArgsRef<'tcx>,
         tcx: TyCtxt<'tcx>,
-    ) -> ty::SubstsRef<'tcx> {
+    ) -> ty::GenericArgsRef<'tcx> {
         debug_assert_eq!(self.kind(tcx), ty::Inherent);
 
-        tcx.mk_substs_from_iter(impl_substs.into_iter().chain(self.substs.into_iter().skip(1)))
+        tcx.mk_args_from_iter(impl_args.into_iter().chain(self.args.into_iter().skip(1)))
     }
 }
 
@@ -1649,7 +1640,7 @@ impl From<BoundVar> for BoundTy {
 #[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct ExistentialProjection<'tcx> {
     pub def_id: DefId,
-    pub substs: SubstsRef<'tcx>,
+    pub args: GenericArgsRef<'tcx>,
     pub term: Term<'tcx>,
 }
 
@@ -1663,8 +1654,8 @@ impl<'tcx> ExistentialProjection<'tcx> {
     pub fn trait_ref(&self, tcx: TyCtxt<'tcx>) -> ty::ExistentialTraitRef<'tcx> {
         let def_id = tcx.parent(self.def_id);
         let subst_count = tcx.generics_of(def_id).count() - 1;
-        let substs = tcx.mk_substs(&self.substs[..subst_count]);
-        ty::ExistentialTraitRef { def_id, substs }
+        let args = tcx.mk_args(&self.args[..subst_count]);
+        ty::ExistentialTraitRef { def_id, args }
     }
 
     pub fn with_self_ty(
@@ -1677,7 +1668,7 @@ impl<'tcx> ExistentialProjection<'tcx> {
 
         ty::ProjectionPredicate {
             projection_ty: tcx
-                .mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.substs)),
+                .mk_alias_ty(self.def_id, [self_ty.into()].into_iter().chain(self.args)),
             term: self.term,
         }
     }
@@ -1687,11 +1678,11 @@ impl<'tcx> ExistentialProjection<'tcx> {
         projection_predicate: ty::ProjectionPredicate<'tcx>,
     ) -> Self {
         // Assert there is a Self.
-        projection_predicate.projection_ty.substs.type_at(0);
+        projection_predicate.projection_ty.args.type_at(0);
 
         Self {
             def_id: projection_predicate.projection_ty.def_id,
-            substs: tcx.mk_substs(&projection_predicate.projection_ty.substs[1..]),
+            args: tcx.mk_args(&projection_predicate.projection_ty.args[1..]),
             term: projection_predicate.term,
         }
     }
@@ -1979,8 +1970,8 @@ impl<'tcx> Ty<'tcx> {
     }
 
     #[inline]
-    pub fn new_opaque(tcx: TyCtxt<'tcx>, def_id: DefId, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        Ty::new_alias(tcx, ty::Opaque, tcx.mk_alias_ty(def_id, substs))
+    pub fn new_opaque(tcx: TyCtxt<'tcx>, def_id: DefId, args: GenericArgsRef<'tcx>) -> Ty<'tcx> {
+        Ty::new_alias(tcx, ty::Opaque, tcx.mk_alias_ty(def_id, args))
     }
 
     /// Constructs a `TyKind::Error` type with current `ErrorGuaranteed`
@@ -2072,8 +2063,8 @@ impl<'tcx> Ty<'tcx> {
     }
 
     #[inline]
-    pub fn new_adt(tcx: TyCtxt<'tcx>, def: AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> Ty<'tcx> {
-        Ty::new(tcx, Adt(def, substs))
+    pub fn new_adt(tcx: TyCtxt<'tcx>, def: AdtDef<'tcx>, args: GenericArgsRef<'tcx>) -> Ty<'tcx> {
+        Ty::new(tcx, Adt(def, args))
     }
 
     #[inline]
@@ -2117,10 +2108,10 @@ impl<'tcx> Ty<'tcx> {
     pub fn new_fn_def(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
-        let substs = tcx.check_and_mk_substs(def_id, substs);
-        Ty::new(tcx, FnDef(def_id, substs))
+        let args = tcx.check_and_mk_args(def_id, args);
+        Ty::new(tcx, FnDef(def_id, args))
     }
 
     #[inline]
@@ -2142,38 +2133,38 @@ impl<'tcx> Ty<'tcx> {
     pub fn new_projection(
         tcx: TyCtxt<'tcx>,
         item_def_id: DefId,
-        substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+        args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
     ) -> Ty<'tcx> {
-        Ty::new_alias(tcx, ty::Projection, tcx.mk_alias_ty(item_def_id, substs))
+        Ty::new_alias(tcx, ty::Projection, tcx.mk_alias_ty(item_def_id, args))
     }
 
     #[inline]
     pub fn new_closure(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        closure_substs: SubstsRef<'tcx>,
+        closure_args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
         debug_assert_eq!(
-            closure_substs.len(),
+            closure_args.len(),
             tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 3,
             "closure constructed with incorrect substitutions"
         );
-        Ty::new(tcx, Closure(def_id, closure_substs))
+        Ty::new(tcx, Closure(def_id, closure_args))
     }
 
     #[inline]
     pub fn new_generator(
         tcx: TyCtxt<'tcx>,
         def_id: DefId,
-        generator_substs: SubstsRef<'tcx>,
+        generator_args: GenericArgsRef<'tcx>,
         movability: hir::Movability,
     ) -> Ty<'tcx> {
         debug_assert_eq!(
-            generator_substs.len(),
+            generator_args.len(),
             tcx.generics_of(tcx.typeck_root_def_id(def_id)).count() + 5,
             "generator constructed with incorrect number of substitutions"
         );
-        Ty::new(tcx, Generator(def_id, generator_substs, movability))
+        Ty::new(tcx, Generator(def_id, generator_args, movability))
     }
 
     #[inline]
@@ -2188,9 +2179,9 @@ impl<'tcx> Ty<'tcx> {
     pub fn new_generator_witness_mir(
         tcx: TyCtxt<'tcx>,
         id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Ty<'tcx> {
-        Ty::new(tcx, GeneratorWitnessMIR(id, substs))
+        Ty::new(tcx, GeneratorWitnessMIR(id, args))
     }
 
     // misc
@@ -2214,19 +2205,18 @@ impl<'tcx> Ty<'tcx> {
 
     fn new_generic_adt(tcx: TyCtxt<'tcx>, wrapper_def_id: DefId, ty_param: Ty<'tcx>) -> Ty<'tcx> {
         let adt_def = tcx.adt_def(wrapper_def_id);
-        let substs =
-            InternalSubsts::for_item(tcx, wrapper_def_id, |param, substs| match param.kind {
-                GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => bug!(),
-                GenericParamDefKind::Type { has_default, .. } => {
-                    if param.index == 0 {
-                        ty_param.into()
-                    } else {
-                        assert!(has_default);
-                        tcx.type_of(param.def_id).subst(tcx, substs).into()
-                    }
+        let args = GenericArgs::for_item(tcx, wrapper_def_id, |param, args| match param.kind {
+            GenericParamDefKind::Lifetime | GenericParamDefKind::Const { .. } => bug!(),
+            GenericParamDefKind::Type { has_default, .. } => {
+                if param.index == 0 {
+                    ty_param.into()
+                } else {
+                    assert!(has_default);
+                    tcx.type_of(param.def_id).instantiate(tcx, args).into()
                 }
-            });
-        Ty::new(tcx, Adt(adt_def, substs))
+            }
+        });
+        Ty::new(tcx, Adt(adt_def, args))
     }
 
     #[inline]
@@ -2257,8 +2247,8 @@ impl<'tcx> Ty<'tcx> {
     pub fn new_task_context(tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         let context_did = tcx.require_lang_item(LangItem::Context, None);
         let context_adt_ref = tcx.adt_def(context_did);
-        let context_substs = tcx.mk_substs(&[tcx.lifetimes.re_erased.into()]);
-        let context_ty = Ty::new_adt(tcx, context_adt_ref, context_substs);
+        let context_args = tcx.mk_args(&[tcx.lifetimes.re_erased.into()]);
+        let context_ty = Ty::new_adt(tcx, context_adt_ref, context_args);
         Ty::new_mut_ref(tcx, tcx.lifetimes.re_erased, context_ty)
     }
 }
@@ -2382,10 +2372,10 @@ impl<'tcx> Ty<'tcx> {
 
     pub fn simd_size_and_type(self, tcx: TyCtxt<'tcx>) -> (u64, Ty<'tcx>) {
         match self.kind() {
-            Adt(def, substs) => {
+            Adt(def, args) => {
                 assert!(def.repr().simd(), "`simd_size_and_type` called on non-SIMD type");
                 let variant = def.non_enum_variant();
-                let f0_ty = variant.fields[FieldIdx::from_u32(0)].ty(tcx, substs);
+                let f0_ty = variant.fields[FieldIdx::from_u32(0)].ty(tcx, args);
 
                 match f0_ty.kind() {
                     // If the first field is an array, we assume it is the only field and its
@@ -2446,7 +2436,7 @@ impl<'tcx> Ty<'tcx> {
     /// Panics if called on any type other than `Box<T>`.
     pub fn boxed_ty(self) -> Ty<'tcx> {
         match self.kind() {
-            Adt(def, substs) if def.is_box() => substs.type_at(0),
+            Adt(def, args) if def.is_box() => args.type_at(0),
             _ => bug!("`boxed_ty` is called on non-box type {:?}", self),
         }
     }
@@ -2610,14 +2600,14 @@ impl<'tcx> Ty<'tcx> {
 
     pub fn fn_sig(self, tcx: TyCtxt<'tcx>) -> PolyFnSig<'tcx> {
         match self.kind() {
-            FnDef(def_id, substs) => tcx.fn_sig(*def_id).subst(tcx, substs),
+            FnDef(def_id, args) => tcx.fn_sig(*def_id).instantiate(tcx, args),
             FnPtr(f) => *f,
             Error(_) => {
                 // ignore errors (#54954)
                 ty::Binder::dummy(FnSig::fake())
             }
             Closure(..) => bug!(
-                "to get the signature of a closure, use `substs.as_closure().sig()` not `fn_sig()`",
+                "to get the signature of a closure, use `args.as_closure().sig()` not `fn_sig()`",
             ),
             _ => bug!("Ty::fn_sig() called on non-fn type: {:?}", self),
         }
@@ -2651,7 +2641,7 @@ impl<'tcx> Ty<'tcx> {
     #[inline]
     pub fn tuple_fields(self) -> &'tcx List<Ty<'tcx>> {
         match self.kind() {
-            Tuple(substs) => substs,
+            Tuple(args) => args,
             _ => bug!("tuple_fields called on non-tuple"),
         }
     }
@@ -2663,8 +2653,8 @@ impl<'tcx> Ty<'tcx> {
     pub fn variant_range(self, tcx: TyCtxt<'tcx>) -> Option<Range<VariantIdx>> {
         match self.kind() {
             TyKind::Adt(adt, _) => Some(adt.variant_range()),
-            TyKind::Generator(def_id, substs, _) => {
-                Some(substs.as_generator().variant_range(*def_id, tcx))
+            TyKind::Generator(def_id, args, _) => {
+                Some(args.as_generator().variant_range(*def_id, tcx))
             }
             _ => None,
         }
@@ -2689,8 +2679,8 @@ impl<'tcx> Ty<'tcx> {
             TyKind::Adt(adt, _) if adt.is_enum() => {
                 Some(adt.discriminant_for_variant(tcx, variant_index))
             }
-            TyKind::Generator(def_id, substs, _) => {
-                Some(substs.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
+            TyKind::Generator(def_id, args, _) => {
+                Some(args.as_generator().discriminant_for_variant(*def_id, tcx, variant_index))
             }
             _ => None,
         }
@@ -2700,13 +2690,13 @@ impl<'tcx> Ty<'tcx> {
     pub fn discriminant_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
         match self.kind() {
             ty::Adt(adt, _) if adt.is_enum() => adt.repr().discr_type().to_ty(tcx),
-            ty::Generator(_, substs, _) => substs.as_generator().discr_ty(tcx),
+            ty::Generator(_, args, _) => args.as_generator().discr_ty(tcx),
 
             ty::Param(_) | ty::Alias(..) | ty::Infer(ty::TyVar(_)) => {
                 let assoc_items = tcx.associated_item_def_ids(
                     tcx.require_lang_item(hir::LangItem::DiscriminantKind, None),
                 );
-                Ty::new_projection(tcx, assoc_items[0], tcx.mk_substs(&[self.into()]))
+                Ty::new_projection(tcx, assoc_items[0], tcx.mk_args(&[self.into()]))
             }
 
             ty::Bool
@@ -2779,7 +2769,7 @@ impl<'tcx> Ty<'tcx> {
             ty::Str | ty::Slice(_) => (tcx.types.usize, false),
             ty::Dynamic(..) => {
                 let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
-                (tcx.type_of(dyn_metadata).subst(tcx, &[tail.into()]), false)
+                (tcx.type_of(dyn_metadata).instantiate(tcx, &[tail.into()]), false)
             },
 
             // type parameters only have unit metadata if they're sized, so return true
@@ -2796,7 +2786,7 @@ impl<'tcx> Ty<'tcx> {
     }
 
     /// When we create a closure, we record its kind (i.e., what trait
-    /// it implements) into its `ClosureSubsts` using a type
+    /// it implements) into its `ClosureArgs` using a type
     /// parameter. This is kind of a phantom type, except that the
     /// most convenient thing for us to are the integral types. This
     /// function converts such a special type into the closure
@@ -2859,7 +2849,7 @@ impl<'tcx> Ty<'tcx> {
 
             ty::Tuple(tys) => tys.iter().all(|ty| ty.is_trivially_sized(tcx)),
 
-            ty::Adt(def, _substs) => def.sized_constraint(tcx).skip_binder().is_empty(),
+            ty::Adt(def, _args) => def.sized_constraint(tcx).skip_binder().is_empty(),
 
             ty::Alias(..) | ty::Param(_) | ty::Placeholder(..) => false,
 
diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs
index 98c70e330f1cc..6e55e7915c92d 100644
--- a/compiler/rustc_middle/src/ty/trait_def.rs
+++ b/compiler/rustc_middle/src/ty/trait_def.rs
@@ -236,7 +236,7 @@ pub(super) fn trait_impls_of_provider(tcx: TyCtxt<'_>, trait_id: DefId) -> Trait
     for &impl_def_id in tcx.hir().trait_impls(trait_id) {
         let impl_def_id = impl_def_id.to_def_id();
 
-        let impl_self_ty = tcx.type_of(impl_def_id).subst_identity();
+        let impl_self_ty = tcx.type_of(impl_def_id).instantiate_identity();
         if impl_self_ty.references_error() {
             continue;
         }
diff --git a/compiler/rustc_middle/src/ty/typeck_results.rs b/compiler/rustc_middle/src/ty/typeck_results.rs
index 9c25c01b05676..327cd0a5d7b31 100644
--- a/compiler/rustc_middle/src/ty/typeck_results.rs
+++ b/compiler/rustc_middle/src/ty/typeck_results.rs
@@ -4,7 +4,7 @@ use crate::{
     traits::ObligationCause,
     ty::{
         self, tls, BindingMode, BoundVar, CanonicalPolyFnSig, ClosureSizeProfileData,
-        GenericArgKind, InternalSubsts, SubstsRef, Ty, UserSubsts,
+        GenericArgKind, GenericArgs, GenericArgsRef, Ty, UserArgs,
     },
 };
 use rustc_data_structures::{
@@ -53,7 +53,7 @@ pub struct TypeckResults<'tcx> {
     /// of this node. This only applies to nodes that refer to entities
     /// parameterized by type parameters, such as generic fns, types, or
     /// other items.
-    node_substs: ItemLocalMap<SubstsRef<'tcx>>,
+    node_args: ItemLocalMap<GenericArgsRef<'tcx>>,
 
     /// This will either store the canonicalized types provided by the user
     /// or the substitutions that the user explicitly gave (if any) attached
@@ -264,7 +264,7 @@ impl<'tcx> TypeckResults<'tcx> {
             user_provided_types: Default::default(),
             user_provided_sigs: Default::default(),
             node_types: Default::default(),
-            node_substs: Default::default(),
+            node_args: Default::default(),
             adjustments: Default::default(),
             pat_binding_modes: Default::default(),
             pat_adjustments: Default::default(),
@@ -384,18 +384,18 @@ impl<'tcx> TypeckResults<'tcx> {
         self.node_types.get(&id.local_id).cloned()
     }
 
-    pub fn node_substs_mut(&mut self) -> LocalTableInContextMut<'_, SubstsRef<'tcx>> {
-        LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.node_substs }
+    pub fn node_args_mut(&mut self) -> LocalTableInContextMut<'_, GenericArgsRef<'tcx>> {
+        LocalTableInContextMut { hir_owner: self.hir_owner, data: &mut self.node_args }
     }
 
-    pub fn node_substs(&self, id: hir::HirId) -> SubstsRef<'tcx> {
+    pub fn node_args(&self, id: hir::HirId) -> GenericArgsRef<'tcx> {
         validate_hir_id_for_typeck_results(self.hir_owner, id);
-        self.node_substs.get(&id.local_id).cloned().unwrap_or_else(|| InternalSubsts::empty())
+        self.node_args.get(&id.local_id).cloned().unwrap_or_else(|| GenericArgs::empty())
     }
 
-    pub fn node_substs_opt(&self, id: hir::HirId) -> Option<SubstsRef<'tcx>> {
+    pub fn node_args_opt(&self, id: hir::HirId) -> Option<GenericArgsRef<'tcx>> {
         validate_hir_id_for_typeck_results(self.hir_owner, id);
-        self.node_substs.get(&id.local_id).cloned()
+        self.node_args.get(&id.local_id).cloned()
     }
 
     /// Returns the type of a pattern as a monotype. Like [`expr_ty`], this function
@@ -670,12 +670,12 @@ impl<'tcx> CanonicalUserType<'tcx> {
     pub fn is_identity(&self) -> bool {
         match self.value {
             UserType::Ty(_) => false,
-            UserType::TypeOf(_, user_substs) => {
-                if user_substs.user_self_ty.is_some() {
+            UserType::TypeOf(_, user_args) => {
+                if user_args.user_self_ty.is_some() {
                     return false;
                 }
 
-                iter::zip(user_substs.substs, BoundVar::new(0)..).all(|(kind, cvar)| {
+                iter::zip(user_args.args, BoundVar::new(0)..).all(|(kind, cvar)| {
                     match kind.unpack() {
                         GenericArgKind::Type(ty) => match ty.kind() {
                             ty::Bound(debruijn, b) => {
@@ -720,5 +720,5 @@ pub enum UserType<'tcx> {
 
     /// The canonical type is the result of `type_of(def_id)` with the
     /// given substitutions applied.
-    TypeOf(DefId, UserSubsts<'tcx>),
+    TypeOf(DefId, UserArgs<'tcx>),
 }
diff --git a/compiler/rustc_middle/src/ty/util.rs b/compiler/rustc_middle/src/ty/util.rs
index 8a83214edc738..b4852ab888157 100644
--- a/compiler/rustc_middle/src/ty/util.rs
+++ b/compiler/rustc_middle/src/ty/util.rs
@@ -7,7 +7,7 @@ use crate::ty::{
     self, FallibleTypeFolder, ToPredicate, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
     TypeVisitableExt,
 };
-use crate::ty::{GenericArgKind, SubstsRef};
+use crate::ty::{GenericArgKind, GenericArgsRef};
 use rustc_apfloat::Float as _;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_data_structures::stable_hasher::{Hash128, HashStable, StableHasher};
@@ -226,14 +226,14 @@ impl<'tcx> TyCtxt<'tcx> {
                 return Ty::new_error(self, reported);
             }
             match *ty.kind() {
-                ty::Adt(def, substs) => {
+                ty::Adt(def, args) => {
                     if !def.is_struct() {
                         break;
                     }
                     match def.non_enum_variant().tail_opt() {
                         Some(field) => {
                             f();
-                            ty = field.ty(self, substs);
+                            ty = field.ty(self, args);
                         }
                         None => break,
                     }
@@ -301,12 +301,12 @@ impl<'tcx> TyCtxt<'tcx> {
         let (mut a, mut b) = (source, target);
         loop {
             match (&a.kind(), &b.kind()) {
-                (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
+                (&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args))
                     if a_def == b_def && a_def.is_struct() =>
                 {
                     if let Some(f) = a_def.non_enum_variant().tail_opt() {
-                        a = f.ty(self, a_substs);
-                        b = f.ty(self, b_substs);
+                        a = f.ty(self, a_args);
+                        b = f.ty(self, b_args);
                     } else {
                         break;
                     }
@@ -349,7 +349,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let drop_trait = self.lang_items().drop_trait()?;
         self.ensure().coherent_trait(drop_trait);
 
-        let ty = self.type_of(adt_did).subst_identity();
+        let ty = self.type_of(adt_did).instantiate_identity();
         let mut dtor_candidate = None;
         self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
             if validate(self, impl_did).is_err() {
@@ -384,7 +384,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Note that this returns only the constraints for the
     /// destructor of `def` itself. For the destructors of the
     /// contents, you need `adt_dtorck_constraint`.
-    pub fn destructor_constraints(self, def: ty::AdtDef<'tcx>) -> Vec<ty::subst::GenericArg<'tcx>> {
+    pub fn destructor_constraints(self, def: ty::AdtDef<'tcx>) -> Vec<ty::GenericArg<'tcx>> {
         let dtor = match def.destructor(self) {
             None => {
                 debug!("destructor_constraints({:?}) - no dtor", def.did());
@@ -401,7 +401,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // must be live.
 
         // We need to return the list of parameters from the ADTs
-        // generics/substs that correspond to impure parameters on the
+        // generics/args that correspond to impure parameters on the
         // impl's generics. This is a bit ugly, but conceptually simple:
         //
         // Suppose our ADT looks like the following
@@ -413,21 +413,21 @@ impl<'tcx> TyCtxt<'tcx> {
         //     impl<#[may_dangle] P0, P1, P2> Drop for S<P1, P2, P0>
         //
         // We want to return the parameters (X, Y). For that, we match
-        // up the item-substs <X, Y, Z> with the substs on the impl ADT,
-        // <P1, P2, P0>, and then look up which of the impl substs refer to
+        // up the item-args <X, Y, Z> with the args on the impl ADT,
+        // <P1, P2, P0>, and then look up which of the impl args refer to
         // parameters marked as pure.
 
-        let impl_substs = match *self.type_of(impl_def_id).subst_identity().kind() {
-            ty::Adt(def_, substs) if def_ == def => substs,
+        let impl_args = match *self.type_of(impl_def_id).instantiate_identity().kind() {
+            ty::Adt(def_, args) if def_ == def => args,
             _ => bug!(),
         };
 
-        let item_substs = match *self.type_of(def.did()).subst_identity().kind() {
-            ty::Adt(def_, substs) if def_ == def => substs,
+        let item_args = match *self.type_of(def.did()).instantiate_identity().kind() {
+            ty::Adt(def_, args) if def_ == def => args,
             _ => bug!(),
         };
 
-        let result = iter::zip(item_substs, impl_substs)
+        let result = iter::zip(item_args, impl_args)
             .filter(|&(_, k)| {
                 match k.unpack() {
                     GenericArgKind::Lifetime(region) => match region.kind() {
@@ -460,12 +460,12 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Checks whether each generic argument is simply a unique generic parameter.
     pub fn uses_unique_generic_params(
         self,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         ignore_regions: CheckRegions,
     ) -> Result<(), NotUniqueParam<'tcx>> {
         let mut seen = GrowableBitSet::default();
         let mut seen_late = FxHashSet::default();
-        for arg in substs {
+        for arg in args {
             match arg.unpack() {
                 GenericArgKind::Lifetime(lt) => match (ignore_regions, lt.kind()) {
                     (CheckRegions::Bound, ty::ReLateBound(di, reg)) => {
@@ -511,10 +511,10 @@ impl<'tcx> TyCtxt<'tcx> {
     /// for better caching.
     pub fn uses_unique_placeholders_ignoring_regions(
         self,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Result<(), NotUniqueParam<'tcx>> {
         let mut seen = GrowableBitSet::default();
-        for arg in substs {
+        for arg in args {
             match arg.unpack() {
                 // Ignore regions, since we can't resolve those in a canonicalized
                 // query in the trait solver.
@@ -595,7 +595,7 @@ impl<'tcx> TyCtxt<'tcx> {
         def_id
     }
 
-    /// Given the `DefId` and substs a closure, creates the type of
+    /// Given the `DefId` and args a closure, creates the type of
     /// `self` argument that the closure expects. For example, for a
     /// `Fn` closure, this would return a reference type `&T` where
     /// `T = closure_ty`.
@@ -608,11 +608,11 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn closure_env_ty(
         self,
         closure_def_id: DefId,
-        closure_substs: SubstsRef<'tcx>,
+        closure_args: GenericArgsRef<'tcx>,
         env_region: ty::Region<'tcx>,
     ) -> Option<Ty<'tcx>> {
-        let closure_ty = Ty::new_closure(self, closure_def_id, closure_substs);
-        let closure_kind_ty = closure_substs.as_closure().kind_ty();
+        let closure_ty = Ty::new_closure(self, closure_def_id, closure_args);
+        let closure_kind_ty = closure_args.as_closure().kind_ty();
         let closure_kind = closure_kind_ty.to_opt_closure_kind()?;
         let env_ty = match closure_kind {
             ty::ClosureKind::Fn => Ty::new_imm_ref(self, env_region, closure_ty),
@@ -655,7 +655,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Returns the type a reference to the thread local takes in MIR.
     pub fn thread_local_ptr_ty(self, def_id: DefId) -> Ty<'tcx> {
-        let static_ty = self.type_of(def_id).subst_identity();
+        let static_ty = self.type_of(def_id).instantiate_identity();
         if self.is_mutable_static(def_id) {
             Ty::new_mut_ptr(self, static_ty)
         } else if self.is_foreign_item(def_id) {
@@ -671,7 +671,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // Make sure that any constants in the static's type are evaluated.
         let static_ty = self.normalize_erasing_regions(
             ty::ParamEnv::empty(),
-            self.type_of(def_id).subst_identity(),
+            self.type_of(def_id).instantiate_identity(),
         );
 
         // Make sure that accesses to unsafe statics end up using raw pointers.
@@ -720,7 +720,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn try_expand_impl_trait_type(
         self,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Result<Ty<'tcx>, Ty<'tcx>> {
         let mut visitor = OpaqueTypeExpander {
             seen_opaque_tys: FxHashSet::default(),
@@ -733,7 +733,7 @@ impl<'tcx> TyCtxt<'tcx> {
             tcx: self,
         };
 
-        let expanded_type = visitor.expand_opaque_ty(def_id, substs).unwrap();
+        let expanded_type = visitor.expand_opaque_ty(def_id, args).unwrap();
         if visitor.found_recursion { Err(expanded_type) } else { Ok(expanded_type) }
     }
 
@@ -800,7 +800,7 @@ struct OpaqueTypeExpander<'tcx> {
     seen_opaque_tys: FxHashSet<DefId>,
     // Cache of all expansions we've seen so far. This is a critical
     // optimization for some large types produced by async fn trees.
-    expanded_cache: FxHashMap<(DefId, SubstsRef<'tcx>), Ty<'tcx>>,
+    expanded_cache: FxHashMap<(DefId, GenericArgsRef<'tcx>), Ty<'tcx>>,
     primary_def_id: Option<DefId>,
     found_recursion: bool,
     found_any_recursion: bool,
@@ -813,19 +813,19 @@ struct OpaqueTypeExpander<'tcx> {
 }
 
 impl<'tcx> OpaqueTypeExpander<'tcx> {
-    fn expand_opaque_ty(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
+    fn expand_opaque_ty(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> Option<Ty<'tcx>> {
         if self.found_any_recursion {
             return None;
         }
-        let substs = substs.fold_with(self);
+        let args = args.fold_with(self);
         if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
-            let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
+            let expanded_ty = match self.expanded_cache.get(&(def_id, args)) {
                 Some(expanded_ty) => *expanded_ty,
                 None => {
                     let generic_ty = self.tcx.type_of(def_id);
-                    let concrete_ty = generic_ty.subst(self.tcx, substs);
+                    let concrete_ty = generic_ty.instantiate(self.tcx, args);
                     let expanded_ty = self.fold_ty(concrete_ty);
-                    self.expanded_cache.insert((def_id, substs), expanded_ty);
+                    self.expanded_cache.insert((def_id, args), expanded_ty);
                     expanded_ty
                 }
             };
@@ -842,21 +842,21 @@ impl<'tcx> OpaqueTypeExpander<'tcx> {
         }
     }
 
-    fn expand_generator(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) -> Option<Ty<'tcx>> {
+    fn expand_generator(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) -> Option<Ty<'tcx>> {
         if self.found_any_recursion {
             return None;
         }
-        let substs = substs.fold_with(self);
+        let args = args.fold_with(self);
         if !self.check_recursion || self.seen_opaque_tys.insert(def_id) {
-            let expanded_ty = match self.expanded_cache.get(&(def_id, substs)) {
+            let expanded_ty = match self.expanded_cache.get(&(def_id, args)) {
                 Some(expanded_ty) => *expanded_ty,
                 None => {
                     for bty in self.tcx.generator_hidden_types(def_id) {
-                        let hidden_ty = bty.subst(self.tcx, substs);
+                        let hidden_ty = bty.instantiate(self.tcx, args);
                         self.fold_ty(hidden_ty);
                     }
-                    let expanded_ty = Ty::new_generator_witness_mir(self.tcx, def_id, substs);
-                    self.expanded_cache.insert((def_id, substs), expanded_ty);
+                    let expanded_ty = Ty::new_generator_witness_mir(self.tcx, def_id, args);
+                    self.expanded_cache.insert((def_id, args), expanded_ty);
                     expanded_ty
                 }
             };
@@ -880,16 +880,16 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for OpaqueTypeExpander<'tcx> {
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) = *t.kind() {
-            self.expand_opaque_ty(def_id, substs).unwrap_or(t)
+        let mut t = if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) = *t.kind() {
+            self.expand_opaque_ty(def_id, args).unwrap_or(t)
         } else if t.has_opaque_types() || t.has_generators() {
             t.super_fold_with(self)
         } else {
             t
         };
         if self.expand_generators {
-            if let ty::GeneratorWitnessMIR(def_id, substs) = *t.kind() {
-                t = self.expand_generator(def_id, substs).unwrap_or(t);
+            if let ty::GeneratorWitnessMIR(def_id, args) = *t.kind() {
+                t = self.expand_generator(def_id, args).unwrap_or(t);
             }
         }
         t
diff --git a/compiler/rustc_middle/src/ty/walk.rs b/compiler/rustc_middle/src/ty/walk.rs
index 04a635a68034d..7c3d9ed390a22 100644
--- a/compiler/rustc_middle/src/ty/walk.rs
+++ b/compiler/rustc_middle/src/ty/walk.rs
@@ -1,8 +1,8 @@
 //! An iterator over the type substructure.
 //! WARNING: this does not keep track of the region depth.
 
-use crate::ty::subst::{GenericArg, GenericArgKind};
 use crate::ty::{self, Ty};
+use crate::ty::{GenericArg, GenericArgKind};
 use rustc_data_structures::sso::SsoHashSet;
 use smallvec::SmallVec;
 
@@ -166,33 +166,33 @@ fn push_inner<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent: GenericArg<'tcx>)
                 stack.push(lt.into());
             }
             ty::Alias(_, data) => {
-                stack.extend(data.substs.iter().rev());
+                stack.extend(data.args.iter().rev());
             }
             ty::Dynamic(obj, lt, _) => {
                 stack.push(lt.into());
                 stack.extend(obj.iter().rev().flat_map(|predicate| {
-                    let (substs, opt_ty) = match predicate.skip_binder() {
-                        ty::ExistentialPredicate::Trait(tr) => (tr.substs, None),
-                        ty::ExistentialPredicate::Projection(p) => (p.substs, Some(p.term)),
+                    let (args, opt_ty) = match predicate.skip_binder() {
+                        ty::ExistentialPredicate::Trait(tr) => (tr.args, None),
+                        ty::ExistentialPredicate::Projection(p) => (p.args, Some(p.term)),
                         ty::ExistentialPredicate::AutoTrait(_) =>
                         // Empty iterator
                         {
-                            (ty::InternalSubsts::empty(), None)
+                            (ty::GenericArgs::empty(), None)
                         }
                     };
 
-                    substs.iter().rev().chain(opt_ty.map(|term| match term.unpack() {
+                    args.iter().rev().chain(opt_ty.map(|term| match term.unpack() {
                         ty::TermKind::Ty(ty) => ty.into(),
                         ty::TermKind::Const(ct) => ct.into(),
                     }))
                 }));
             }
-            ty::Adt(_, substs)
-            | ty::Closure(_, substs)
-            | ty::Generator(_, substs, _)
-            | ty::GeneratorWitnessMIR(_, substs)
-            | ty::FnDef(_, substs) => {
-                stack.extend(substs.iter().rev());
+            ty::Adt(_, args)
+            | ty::Closure(_, args)
+            | ty::Generator(_, args, _)
+            | ty::GeneratorWitnessMIR(_, args)
+            | ty::FnDef(_, args) => {
+                stack.extend(args.iter().rev());
             }
             ty::Tuple(ts) => stack.extend(ts.iter().rev().map(GenericArg::from)),
             ty::GeneratorWitness(ts) => {
@@ -233,7 +233,7 @@ fn push_inner<'tcx>(stack: &mut TypeWalkerStack<'tcx>, parent: GenericArg<'tcx>)
                 },
 
                 ty::ConstKind::Unevaluated(ct) => {
-                    stack.extend(ct.substs.iter().rev());
+                    stack.extend(ct.args.iter().rev());
                 }
             }
         }
diff --git a/compiler/rustc_middle/src/util/call_kind.rs b/compiler/rustc_middle/src/util/call_kind.rs
index 98d55ea6d4025..4e2a2c6ae0acc 100644
--- a/compiler/rustc_middle/src/util/call_kind.rs
+++ b/compiler/rustc_middle/src/util/call_kind.rs
@@ -2,7 +2,7 @@
 //! as well as errors when attempting to call a non-const function in a const
 //! context.
 
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{AssocItemContainer, Instance, ParamEnv, Ty, TyCtxt};
 use rustc_hir::def_id::DefId;
 use rustc_hir::{lang_items, LangItem};
@@ -43,7 +43,7 @@ pub enum CallKind<'tcx> {
         self_arg: Option<Ident>,
         desugaring: Option<(CallDesugaringKind, Ty<'tcx>)>,
         method_did: DefId,
-        method_substs: SubstsRef<'tcx>,
+        method_args: GenericArgsRef<'tcx>,
     },
     /// A call to `Fn(..)::call(..)`, desugared from `my_closure(a, b, c)`
     FnCall { fn_trait_id: DefId, self_ty: Ty<'tcx> },
@@ -63,7 +63,7 @@ pub fn call_kind<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ParamEnv<'tcx>,
     method_did: DefId,
-    method_substs: SubstsRef<'tcx>,
+    method_args: GenericArgsRef<'tcx>,
     fn_call_span: Span,
     from_hir_call: bool,
     self_arg: Option<Ident>,
@@ -92,19 +92,19 @@ pub fn call_kind<'tcx>(
     // an FnOnce call, an operator (e.g. `<<`), or a
     // deref coercion.
     let kind = if let Some(trait_id) = fn_call {
-        Some(CallKind::FnCall { fn_trait_id: trait_id, self_ty: method_substs.type_at(0) })
+        Some(CallKind::FnCall { fn_trait_id: trait_id, self_ty: method_args.type_at(0) })
     } else if let Some(trait_id) = operator {
-        Some(CallKind::Operator { self_arg, trait_id, self_ty: method_substs.type_at(0) })
+        Some(CallKind::Operator { self_arg, trait_id, self_ty: method_args.type_at(0) })
     } else if is_deref {
         let deref_target = tcx.get_diagnostic_item(sym::deref_target).and_then(|deref_target| {
-            Instance::resolve(tcx, param_env, deref_target, method_substs).transpose()
+            Instance::resolve(tcx, param_env, deref_target, method_args).transpose()
         });
         if let Some(Ok(instance)) = deref_target {
             let deref_target_ty = instance.ty(tcx, param_env);
             Some(CallKind::DerefCoercion {
                 deref_target: tcx.def_span(instance.def_id()),
                 deref_target_ty,
-                self_ty: method_substs.type_at(0),
+                self_ty: method_args.type_at(0),
             })
         } else {
             None
@@ -119,24 +119,24 @@ pub fn call_kind<'tcx>(
         let desugaring = if Some(method_did) == tcx.lang_items().into_iter_fn()
             && fn_call_span.desugaring_kind() == Some(DesugaringKind::ForLoop)
         {
-            Some((CallDesugaringKind::ForLoopIntoIter, method_substs.type_at(0)))
+            Some((CallDesugaringKind::ForLoopIntoIter, method_args.type_at(0)))
         } else if fn_call_span.desugaring_kind() == Some(DesugaringKind::QuestionMark) {
             if Some(method_did) == tcx.lang_items().branch_fn() {
-                Some((CallDesugaringKind::QuestionBranch, method_substs.type_at(0)))
+                Some((CallDesugaringKind::QuestionBranch, method_args.type_at(0)))
             } else if Some(method_did) == tcx.lang_items().from_residual_fn() {
-                Some((CallDesugaringKind::QuestionFromResidual, method_substs.type_at(0)))
+                Some((CallDesugaringKind::QuestionFromResidual, method_args.type_at(0)))
             } else {
                 None
             }
         } else if Some(method_did) == tcx.lang_items().from_output_fn()
             && fn_call_span.desugaring_kind() == Some(DesugaringKind::TryBlock)
         {
-            Some((CallDesugaringKind::TryBlockFromOutput, method_substs.type_at(0)))
+            Some((CallDesugaringKind::TryBlockFromOutput, method_args.type_at(0)))
         } else if fn_call_span.is_desugaring(DesugaringKind::Await) {
-            Some((CallDesugaringKind::Await, method_substs.type_at(0)))
+            Some((CallDesugaringKind::Await, method_args.type_at(0)))
         } else {
             None
         };
-        CallKind::Normal { self_arg, desugaring, method_did, method_substs }
+        CallKind::Normal { self_arg, desugaring, method_did, method_args }
     })
 }
diff --git a/compiler/rustc_middle/src/util/find_self_call.rs b/compiler/rustc_middle/src/util/find_self_call.rs
index 0eab0adf07e48..1b845334c49b5 100644
--- a/compiler/rustc_middle/src/util/find_self_call.rs
+++ b/compiler/rustc_middle/src/util/find_self_call.rs
@@ -1,5 +1,5 @@
 use crate::mir::*;
-use crate::ty::subst::SubstsRef;
+use crate::ty::GenericArgsRef;
 use crate::ty::{self, TyCtxt};
 use rustc_span::def_id::DefId;
 
@@ -11,21 +11,21 @@ pub fn find_self_call<'tcx>(
     body: &Body<'tcx>,
     local: Local,
     block: BasicBlock,
-) -> Option<(DefId, SubstsRef<'tcx>)> {
+) -> Option<(DefId, GenericArgsRef<'tcx>)> {
     debug!("find_self_call(local={:?}): terminator={:?}", local, &body[block].terminator);
     if let Some(Terminator { kind: TerminatorKind::Call { func, args, .. }, .. }) =
         &body[block].terminator
     {
         debug!("find_self_call: func={:?}", func);
         if let Operand::Constant(box Constant { literal, .. }) = func {
-            if let ty::FnDef(def_id, substs) = *literal.ty().kind() {
+            if let ty::FnDef(def_id, fn_args) = *literal.ty().kind() {
                 if let Some(ty::AssocItem { fn_has_self_parameter: true, .. }) =
                     tcx.opt_associated_item(def_id)
                 {
-                    debug!("find_self_call: args={:?}", args);
+                    debug!("find_self_call: args={:?}", fn_args);
                     if let [Operand::Move(self_place) | Operand::Copy(self_place), ..] = **args {
                         if self_place.as_local() == Some(local) {
-                            return Some((def_id, substs));
+                            return Some((def_id, fn_args));
                         }
                     }
                 }
diff --git a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
index 8a84175990043..295cddb1e15b4 100644
--- a/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
+++ b/compiler/rustc_mir_build/src/build/custom/parse/instruction.rs
@@ -192,12 +192,12 @@ impl<'tcx, 'body> ParseCtxt<'tcx, 'body> {
                     fields.iter().map(|e| self.parse_operand(*e)).collect::<Result<_, _>>()?
                 ))
             },
-            ExprKind::Adt(box AdtExpr{ adt_def, variant_index, substs, fields, .. }) => {
+            ExprKind::Adt(box AdtExpr{ adt_def, variant_index, args, fields, .. }) => {
                 let is_union = adt_def.is_union();
                 let active_field_index = is_union.then(|| fields[0].name);
 
                 Ok(Rvalue::Aggregate(
-                    Box::new(AggregateKind::Adt(adt_def.did(), *variant_index, substs, None, active_field_index)),
+                    Box::new(AggregateKind::Adt(adt_def.did(), *variant_index, args, None, active_field_index)),
                     fields.iter().map(|f| self.parse_operand(f.expr)).collect::<Result<_, _>>()?
                 ))
             },
diff --git a/compiler/rustc_mir_build/src/build/expr/as_constant.rs b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
index 3fe751ae0a5e3..aaa37446e24d3 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_constant.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_constant.rs
@@ -75,10 +75,10 @@ pub fn as_constant_inner<'tcx>(
 
             Constant { span, user_ty, literal }
         }
-        ExprKind::NamedConst { def_id, substs, ref user_ty } => {
+        ExprKind::NamedConst { def_id, args, ref user_ty } => {
             let user_ty = user_ty.as_ref().and_then(push_cuta);
 
-            let uneval = mir::UnevaluatedConst::new(def_id, substs);
+            let uneval = mir::UnevaluatedConst::new(def_id, args);
             let literal = ConstantKind::Unevaluated(uneval, ty);
 
             Constant { user_ty, span, literal }
@@ -89,8 +89,8 @@ pub fn as_constant_inner<'tcx>(
 
             Constant { user_ty: None, span, literal }
         }
-        ExprKind::ConstBlock { did: def_id, substs } => {
-            let uneval = mir::UnevaluatedConst::new(def_id, substs);
+        ExprKind::ConstBlock { did: def_id, args } => {
+            let uneval = mir::UnevaluatedConst::new(def_id, args);
             let literal = ConstantKind::Unevaluated(uneval, ty);
 
             Constant { user_ty: None, span, literal }
diff --git a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
index 32ffb990be61f..7817c3d0d8090 100644
--- a/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
+++ b/compiler/rustc_mir_build/src/build/expr/as_rvalue.rs
@@ -16,7 +16,7 @@ use rustc_middle::mir::*;
 use rustc_middle::thir::*;
 use rustc_middle::ty::cast::{mir_cast_kind, CastTy};
 use rustc_middle::ty::layout::IntegerExt;
-use rustc_middle::ty::{self, Ty, UpvarSubsts};
+use rustc_middle::ty::{self, Ty, UpvarArgs};
 use rustc_span::Span;
 
 impl<'a, 'tcx> Builder<'a, 'tcx> {
@@ -382,7 +382,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             }
             ExprKind::Closure(box ClosureExpr {
                 closure_id,
-                substs,
+                args,
                 ref upvars,
                 movability,
                 ref fake_reads,
@@ -470,19 +470,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     })
                     .collect();
 
-                let result = match substs {
-                    UpvarSubsts::Generator(substs) => {
+                let result = match args {
+                    UpvarArgs::Generator(args) => {
                         // We implicitly set the discriminant to 0. See
                         // librustc_mir/transform/deaggregator.rs for details.
                         let movability = movability.unwrap();
-                        Box::new(AggregateKind::Generator(
-                            closure_id.to_def_id(),
-                            substs,
-                            movability,
-                        ))
+                        Box::new(AggregateKind::Generator(closure_id.to_def_id(), args, movability))
                     }
-                    UpvarSubsts::Closure(substs) => {
-                        Box::new(AggregateKind::Closure(closure_id.to_def_id(), substs))
+                    UpvarArgs::Closure(args) => {
+                        Box::new(AggregateKind::Closure(closure_id.to_def_id(), args))
                     }
                 };
                 block.and(Rvalue::Aggregate(result, operands))
diff --git a/compiler/rustc_mir_build/src/build/expr/into.rs b/compiler/rustc_mir_build/src/build/expr/into.rs
index e30fdcbbe185b..c750727903fdc 100644
--- a/compiler/rustc_mir_build/src/build/expr/into.rs
+++ b/compiler/rustc_mir_build/src/build/expr/into.rs
@@ -317,7 +317,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             ExprKind::Adt(box AdtExpr {
                 adt_def,
                 variant_index,
-                substs,
+                args,
                 ref user_ty,
                 ref fields,
                 ref base,
@@ -382,7 +382,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let adt = Box::new(AggregateKind::Adt(
                     adt_def.did(),
                     variant_index,
-                    substs,
+                    args,
                     user_ty,
                     active_field_index,
                 ));
diff --git a/compiler/rustc_mir_build/src/build/matches/mod.rs b/compiler/rustc_mir_build/src/build/matches/mod.rs
index 34e0e572a1bef..6f14891cb7865 100644
--- a/compiler/rustc_mir_build/src/build/matches/mod.rs
+++ b/compiler/rustc_mir_build/src/build/matches/mod.rs
@@ -806,7 +806,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
             }
 
-            PatKind::Variant { adt_def, substs: _, variant_index, ref subpatterns } => {
+            PatKind::Variant { adt_def, args: _, variant_index, ref subpatterns } => {
                 for subpattern in subpatterns {
                     let subpattern_user_ty =
                         pattern_user_ty.clone().variant(adt_def, variant_index, subpattern.field);
diff --git a/compiler/rustc_mir_build/src/build/matches/simplify.rs b/compiler/rustc_mir_build/src/build/matches/simplify.rs
index f6b1955fdec4d..17ac1f4e0cea6 100644
--- a/compiler/rustc_mir_build/src/build/matches/simplify.rs
+++ b/compiler/rustc_mir_build/src/build/matches/simplify.rs
@@ -259,13 +259,13 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 }
             }
 
-            PatKind::Variant { adt_def, substs, variant_index, ref subpatterns } => {
+            PatKind::Variant { adt_def, args, variant_index, ref subpatterns } => {
                 let irrefutable = adt_def.variants().iter_enumerated().all(|(i, v)| {
                     i == variant_index || {
                         self.tcx.features().exhaustive_patterns
                             && !v
                                 .inhabited_predicate(self.tcx, adt_def)
-                                .subst(self.tcx, substs)
+                                .instantiate(self.tcx, args)
                                 .apply_ignore_module(self.tcx, self.param_env)
                     }
                 }) && (adt_def.did().is_local()
diff --git a/compiler/rustc_mir_build/src/build/matches/test.rs b/compiler/rustc_mir_build/src/build/matches/test.rs
index 9ac5f00ee461b..275878a39195b 100644
--- a/compiler/rustc_mir_build/src/build/matches/test.rs
+++ b/compiler/rustc_mir_build/src/build/matches/test.rs
@@ -30,7 +30,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
     /// It is a bug to call this with a not-fully-simplified pattern.
     pub(super) fn test<'pat>(&mut self, match_pair: &MatchPair<'pat, 'tcx>) -> Test<'tcx> {
         match match_pair.pattern.kind {
-            PatKind::Variant { adt_def, substs: _, variant_index: _, subpatterns: _ } => Test {
+            PatKind::Variant { adt_def, args: _, variant_index: _, subpatterns: _ } => Test {
                 span: match_pair.pattern.span,
                 kind: TestKind::Switch {
                     adt_def,
@@ -867,7 +867,7 @@ fn trait_method<'tcx>(
     tcx: TyCtxt<'tcx>,
     trait_def_id: DefId,
     method_name: Symbol,
-    substs: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item: Into<GenericArg<'tcx>>>,
 ) -> ConstantKind<'tcx> {
     // The unhygienic comparison here is acceptable because this is only
     // used on known traits.
@@ -877,7 +877,7 @@ fn trait_method<'tcx>(
         .find(|item| item.kind == ty::AssocKind::Fn)
         .expect("trait method not found");
 
-    let method_ty = Ty::new_fn_def(tcx, item.def_id, substs);
+    let method_ty = Ty::new_fn_def(tcx, item.def_id, args);
 
     ConstantKind::zero_sized(method_ty)
 }
diff --git a/compiler/rustc_mir_build/src/build/mod.rs b/compiler/rustc_mir_build/src/build/mod.rs
index a91ced4a211a3..17295fe1d344a 100644
--- a/compiler/rustc_mir_build/src/build/mod.rs
+++ b/compiler/rustc_mir_build/src/build/mod.rs
@@ -482,7 +482,7 @@ fn construct_fn<'tcx>(
     let (yield_ty, return_ty) = if generator_kind.is_some() {
         let gen_ty = arguments[thir::UPVAR_ENV_PARAM].ty;
         let gen_sig = match gen_ty.kind() {
-            ty::Generator(_, gen_substs, ..) => gen_substs.as_generator().sig(),
+            ty::Generator(_, gen_args, ..) => gen_args.as_generator().sig(),
             _ => {
                 span_bug!(span, "generator w/o generator type: {:?}", gen_ty)
             }
@@ -627,11 +627,9 @@ fn construct_error(tcx: TyCtxt<'_>, def: LocalDefId, err: ErrorGuaranteed) -> Bo
     let num_params = match body_owner_kind {
         hir::BodyOwnerKind::Fn => tcx.fn_sig(def).skip_binder().inputs().skip_binder().len(),
         hir::BodyOwnerKind::Closure => {
-            let ty = tcx.type_of(def).subst_identity();
+            let ty = tcx.type_of(def).instantiate_identity();
             match ty.kind() {
-                ty::Closure(_, substs) => {
-                    1 + substs.as_closure().sig().inputs().skip_binder().len()
-                }
+                ty::Closure(_, args) => 1 + args.as_closure().sig().inputs().skip_binder().len(),
                 ty::Generator(..) => 2,
                 _ => bug!("expected closure or generator, found {ty:?}"),
             }
@@ -778,9 +776,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             closure_ty = *ty;
         }
 
-        let upvar_substs = match closure_ty.kind() {
-            ty::Closure(_, substs) => ty::UpvarSubsts::Closure(substs),
-            ty::Generator(_, substs, _) => ty::UpvarSubsts::Generator(substs),
+        let upvar_args = match closure_ty.kind() {
+            ty::Closure(_, args) => ty::UpvarArgs::Closure(args),
+            ty::Generator(_, args, _) => ty::UpvarArgs::Generator(args),
             _ => return,
         };
 
@@ -789,7 +787,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // with the closure's DefId. Here, we run through that vec of UpvarIds for
         // the given closure and use the necessary information to create upvar
         // debuginfo and to fill `self.upvars`.
-        let capture_tys = upvar_substs.upvar_tys();
+        let capture_tys = upvar_args.upvar_tys();
 
         let tcx = self.tcx;
         self.upvars = tcx
diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs
index 6e9df1c2daa63..8b4ff9bb86830 100644
--- a/compiler/rustc_mir_build/src/check_unsafety.rs
+++ b/compiler/rustc_mir_build/src/check_unsafety.rs
@@ -383,7 +383,7 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             ExprKind::Adt(box AdtExpr {
                 adt_def,
                 variant_index: _,
-                substs: _,
+                args: _,
                 user_ty: _,
                 fields: _,
                 base: _,
@@ -393,14 +393,14 @@ impl<'a, 'tcx> Visitor<'a, 'tcx> for UnsafetyVisitor<'a, 'tcx> {
             },
             ExprKind::Closure(box ClosureExpr {
                 closure_id,
-                substs: _,
+                args: _,
                 upvars: _,
                 movability: _,
                 fake_reads: _,
             }) => {
                 self.visit_inner_body(closure_id);
             }
-            ExprKind::ConstBlock { did, substs: _ } => {
+            ExprKind::ConstBlock { did, args: _ } => {
                 let def_id = did.expect_local();
                 self.visit_inner_body(def_id);
             }
diff --git a/compiler/rustc_mir_build/src/lints.rs b/compiler/rustc_mir_build/src/lints.rs
index 8e41957af0eba..3f0cc69ec595a 100644
--- a/compiler/rustc_mir_build/src/lints.rs
+++ b/compiler/rustc_mir_build/src/lints.rs
@@ -4,8 +4,8 @@ use rustc_data_structures::graph::iterate::{
 };
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::{self, BasicBlock, BasicBlocks, Body, Operand, TerminatorKind};
-use rustc_middle::ty::subst::{GenericArg, InternalSubsts};
 use rustc_middle::ty::{self, Instance, TyCtxt};
+use rustc_middle::ty::{GenericArg, GenericArgs};
 use rustc_session::lint::builtin::UNCONDITIONAL_RECURSION;
 use rustc_span::Span;
 use std::ops::ControlFlow;
@@ -14,16 +14,16 @@ pub(crate) fn check<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
     let def_id = body.source.def_id().expect_local();
 
     if let DefKind::Fn | DefKind::AssocFn = tcx.def_kind(def_id) {
-        // If this is trait/impl method, extract the trait's substs.
-        let trait_substs = match tcx.trait_of_item(def_id.to_def_id()) {
+        // If this is trait/impl method, extract the trait's args.
+        let trait_args = match tcx.trait_of_item(def_id.to_def_id()) {
             Some(trait_def_id) => {
-                let trait_substs_count = tcx.generics_of(trait_def_id).count();
-                &InternalSubsts::identity_for_item(tcx, def_id)[..trait_substs_count]
+                let trait_args_count = tcx.generics_of(trait_def_id).count();
+                &GenericArgs::identity_for_item(tcx, def_id)[..trait_args_count]
             }
             _ => &[],
         };
 
-        let mut vis = Search { tcx, body, reachable_recursive_calls: vec![], trait_substs };
+        let mut vis = Search { tcx, body, reachable_recursive_calls: vec![], trait_args };
         if let Some(NonRecursive) =
             TriColorDepthFirstSearch::new(&body.basic_blocks).run_from_start(&mut vis)
         {
@@ -51,7 +51,7 @@ struct NonRecursive;
 struct Search<'mir, 'tcx> {
     tcx: TyCtxt<'tcx>,
     body: &'mir Body<'tcx>,
-    trait_substs: &'tcx [GenericArg<'tcx>],
+    trait_args: &'tcx [GenericArg<'tcx>],
 
     reachable_recursive_calls: Vec<Span>,
 }
@@ -59,7 +59,7 @@ struct Search<'mir, 'tcx> {
 impl<'mir, 'tcx> Search<'mir, 'tcx> {
     /// Returns `true` if `func` refers to the function we are searching in.
     fn is_recursive_call(&self, func: &Operand<'tcx>, args: &[Operand<'tcx>]) -> bool {
-        let Search { tcx, body, trait_substs, .. } = *self;
+        let Search { tcx, body, trait_args, .. } = *self;
         // Resolving function type to a specific instance that is being called is expensive. To
         // avoid the cost we check the number of arguments first, which is sufficient to reject
         // most of calls as non-recursive.
@@ -70,23 +70,23 @@ impl<'mir, 'tcx> Search<'mir, 'tcx> {
         let param_env = tcx.param_env(caller);
 
         let func_ty = func.ty(body, tcx);
-        if let ty::FnDef(callee, substs) = *func_ty.kind() {
-            let normalized_substs = tcx.normalize_erasing_regions(param_env, substs);
-            let (callee, call_substs) = if let Ok(Some(instance)) =
-                Instance::resolve(tcx, param_env, callee, normalized_substs)
+        if let ty::FnDef(callee, args) = *func_ty.kind() {
+            let normalized_args = tcx.normalize_erasing_regions(param_env, args);
+            let (callee, call_args) = if let Ok(Some(instance)) =
+                Instance::resolve(tcx, param_env, callee, normalized_args)
             {
-                (instance.def_id(), instance.substs)
+                (instance.def_id(), instance.args)
             } else {
-                (callee, normalized_substs)
+                (callee, normalized_args)
             };
 
             // FIXME(#57965): Make this work across function boundaries
 
-            // If this is a trait fn, the substs on the trait have to match, or we might be
+            // If this is a trait fn, the args on the trait have to match, or we might be
             // calling into an entirely different method (for example, a call from the default
             // method in the trait to `<A as Trait<B>>::method`, where `A` and/or `B` are
             // specific types).
-            return callee == caller && &call_substs[..trait_substs.len()] == trait_substs;
+            return callee == caller && &call_args[..trait_args.len()] == trait_args;
         }
 
         false
diff --git a/compiler/rustc_mir_build/src/thir/cx/expr.rs b/compiler/rustc_mir_build/src/thir/cx/expr.rs
index accc02b5987a3..711a9126c04a3 100644
--- a/compiler/rustc_mir_build/src/thir/cx/expr.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/expr.rs
@@ -15,9 +15,9 @@ use rustc_middle::thir::*;
 use rustc_middle::ty::adjustment::{
     Adjust, Adjustment, AutoBorrow, AutoBorrowMutability, PointerCoercion,
 };
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{
-    self, AdtKind, InlineConstSubsts, InlineConstSubstsParts, ScalarInt, Ty, UpvarSubsts, UserType,
+    self, AdtKind, InlineConstArgs, InlineConstArgsParts, ScalarInt, Ty, UpvarArgs, UserType,
 };
 use rustc_span::{sym, Span};
 use rustc_target::abi::{FieldIdx, FIRST_VARIANT};
@@ -210,7 +210,7 @@ impl<'tcx> Cx<'tcx> {
 
             let res = self.typeck_results().qpath_res(qpath, source.hir_id);
             let ty = self.typeck_results().node_type(source.hir_id);
-            let ty::Adt(adt_def, substs) = ty.kind() else {
+            let ty::Adt(adt_def, args) = ty.kind() else {
                 return ExprKind::Cast { source: self.mirror_expr(source) };
             };
 
@@ -242,7 +242,7 @@ impl<'tcx> Cx<'tcx> {
                 // in case we are offsetting from a computed discriminant
                 // and not the beginning of discriminants (which is always `0`)
                 Some(did) => {
-                    let kind = ExprKind::NamedConst { def_id: did, substs, user_ty: None };
+                    let kind = ExprKind::NamedConst { def_id: did, args, user_ty: None };
                     let lhs =
                         self.thir.exprs.push(Expr { temp_lifetime, ty: discr_ty, span, kind });
                     let bin = ExprKind::Binary { op: BinOp::Add, lhs, rhs: offset };
@@ -372,7 +372,7 @@ impl<'tcx> Cx<'tcx> {
                         None
                     };
                     if let Some((adt_def, index)) = adt_data {
-                        let substs = self.typeck_results().node_substs(fun.hir_id);
+                        let node_args = self.typeck_results().node_args(fun.hir_id);
                         let user_provided_types = self.typeck_results().user_provided_types();
                         let user_ty =
                             user_provided_types.get(fun.hir_id).copied().map(|mut u_ty| {
@@ -393,7 +393,7 @@ impl<'tcx> Cx<'tcx> {
                             .collect();
                         ExprKind::Adt(Box::new(AdtExpr {
                             adt_def,
-                            substs,
+                            args: node_args,
                             variant_index: index,
                             fields: field_refs,
                             user_ty,
@@ -511,7 +511,7 @@ impl<'tcx> Cx<'tcx> {
             }
 
             hir::ExprKind::Struct(ref qpath, ref fields, ref base) => match expr_ty.kind() {
-                ty::Adt(adt, substs) => match adt.adt_kind() {
+                ty::Adt(adt, args) => match adt.adt_kind() {
                     AdtKind::Struct | AdtKind::Union => {
                         let user_provided_types = self.typeck_results().user_provided_types();
                         let user_ty = user_provided_types.get(expr.hir_id).copied().map(Box::new);
@@ -519,7 +519,7 @@ impl<'tcx> Cx<'tcx> {
                         ExprKind::Adt(Box::new(AdtExpr {
                             adt_def: *adt,
                             variant_index: FIRST_VARIANT,
-                            substs,
+                            args,
                             user_ty,
                             fields: self.field_refs(fields),
                             base: base.map(|base| FruInfo {
@@ -546,7 +546,7 @@ impl<'tcx> Cx<'tcx> {
                                 ExprKind::Adt(Box::new(AdtExpr {
                                     adt_def: *adt,
                                     variant_index: index,
-                                    substs,
+                                    args,
                                     user_ty,
                                     fields: self.field_refs(fields),
                                     base: None,
@@ -565,10 +565,10 @@ impl<'tcx> Cx<'tcx> {
 
             hir::ExprKind::Closure { .. } => {
                 let closure_ty = self.typeck_results().expr_ty(expr);
-                let (def_id, substs, movability) = match *closure_ty.kind() {
-                    ty::Closure(def_id, substs) => (def_id, UpvarSubsts::Closure(substs), None),
-                    ty::Generator(def_id, substs, movability) => {
-                        (def_id, UpvarSubsts::Generator(substs), Some(movability))
+                let (def_id, args, movability) = match *closure_ty.kind() {
+                    ty::Closure(def_id, args) => (def_id, UpvarArgs::Closure(args), None),
+                    ty::Generator(def_id, args, movability) => {
+                        (def_id, UpvarArgs::Generator(args), Some(movability))
                     }
                     _ => {
                         span_bug!(expr.span, "closure expr w/o closure type: {:?}", closure_ty);
@@ -580,7 +580,7 @@ impl<'tcx> Cx<'tcx> {
                     .tcx
                     .closure_captures(def_id)
                     .iter()
-                    .zip(substs.upvar_tys())
+                    .zip(args.upvar_tys())
                     .map(|(captured_place, ty)| {
                         let upvars = self.capture_upvar(expr, captured_place, ty);
                         self.thir.exprs.push(upvars)
@@ -601,7 +601,7 @@ impl<'tcx> Cx<'tcx> {
 
                 ExprKind::Closure(Box::new(ClosureExpr {
                     closure_id: def_id,
-                    substs,
+                    args,
                     upvars,
                     movability,
                     fake_reads,
@@ -684,13 +684,11 @@ impl<'tcx> Cx<'tcx> {
                 let ty = self.typeck_results().node_type(anon_const.hir_id);
                 let did = anon_const.def_id.to_def_id();
                 let typeck_root_def_id = tcx.typeck_root_def_id(did);
-                let parent_substs =
-                    tcx.erase_regions(InternalSubsts::identity_for_item(tcx, typeck_root_def_id));
-                let substs =
-                    InlineConstSubsts::new(tcx, InlineConstSubstsParts { parent_substs, ty })
-                        .substs;
+                let parent_args =
+                    tcx.erase_regions(GenericArgs::identity_for_item(tcx, typeck_root_def_id));
+                let args = InlineConstArgs::new(tcx, InlineConstArgsParts { parent_args, ty }).args;
 
-                ExprKind::ConstBlock { did, substs }
+                ExprKind::ConstBlock { did, args }
             }
             // Now comes the rote stuff:
             hir::ExprKind::Repeat(ref v, _) => {
@@ -809,12 +807,12 @@ impl<'tcx> Cx<'tcx> {
         Expr { temp_lifetime, ty: expr_ty, span: expr.span, kind }
     }
 
-    fn user_substs_applied_to_res(
+    fn user_args_applied_to_res(
         &mut self,
         hir_id: hir::HirId,
         res: Res,
     ) -> Option<Box<ty::CanonicalUserType<'tcx>>> {
-        debug!("user_substs_applied_to_res: res={:?}", res);
+        debug!("user_args_applied_to_res: res={:?}", res);
         let user_provided_type = match res {
             // A reference to something callable -- e.g., a fn, method, or
             // a tuple-struct or tuple-variant. This has the type of a
@@ -832,15 +830,15 @@ impl<'tcx> Cx<'tcx> {
             // this variant -- but with the substitutions given by the
             // user.
             Res::Def(DefKind::Ctor(_, CtorKind::Const), _) => {
-                self.user_substs_applied_to_ty_of_hir_id(hir_id).map(Box::new)
+                self.user_args_applied_to_ty_of_hir_id(hir_id).map(Box::new)
             }
 
             // `Self` is used in expression as a tuple struct constructor or a unit struct constructor
-            Res::SelfCtor(_) => self.user_substs_applied_to_ty_of_hir_id(hir_id).map(Box::new),
+            Res::SelfCtor(_) => self.user_args_applied_to_ty_of_hir_id(hir_id).map(Box::new),
 
-            _ => bug!("user_substs_applied_to_res: unexpected res {:?} at {:?}", res, hir_id),
+            _ => bug!("user_args_applied_to_res: unexpected res {:?} at {:?}", res, hir_id),
         };
-        debug!("user_substs_applied_to_res: user_provided_type={:?}", user_provided_type);
+        debug!("user_args_applied_to_res: user_provided_type={:?}", user_provided_type);
         user_provided_type
     }
 
@@ -859,13 +857,13 @@ impl<'tcx> Cx<'tcx> {
                     self.typeck_results().type_dependent_def(expr.hir_id).unwrap_or_else(|| {
                         span_bug!(expr.span, "no type-dependent def for method callee")
                     });
-                let user_ty = self.user_substs_applied_to_res(expr.hir_id, Res::Def(kind, def_id));
+                let user_ty = self.user_args_applied_to_res(expr.hir_id, Res::Def(kind, def_id));
                 debug!("method_callee: user_ty={:?}", user_ty);
                 (
                     Ty::new_fn_def(
                         self.tcx(),
                         def_id,
-                        self.typeck_results().node_substs(expr.hir_id),
+                        self.typeck_results().node_args(expr.hir_id),
                     ),
                     user_ty,
                 )
@@ -892,14 +890,14 @@ impl<'tcx> Cx<'tcx> {
     }
 
     fn convert_path_expr(&mut self, expr: &'tcx hir::Expr<'tcx>, res: Res) -> ExprKind<'tcx> {
-        let substs = self.typeck_results().node_substs(expr.hir_id);
+        let args = self.typeck_results().node_args(expr.hir_id);
         match res {
             // A regular function, constructor function or a constant.
             Res::Def(DefKind::Fn, _)
             | Res::Def(DefKind::AssocFn, _)
             | Res::Def(DefKind::Ctor(_, CtorKind::Fn), _)
             | Res::SelfCtor(_) => {
-                let user_ty = self.user_substs_applied_to_res(expr.hir_id, res);
+                let user_ty = self.user_args_applied_to_res(expr.hir_id, res);
                 ExprKind::ZstLiteral { user_ty }
             }
 
@@ -914,8 +912,8 @@ impl<'tcx> Cx<'tcx> {
             }
 
             Res::Def(DefKind::Const, def_id) | Res::Def(DefKind::AssocConst, def_id) => {
-                let user_ty = self.user_substs_applied_to_res(expr.hir_id, res);
-                ExprKind::NamedConst { def_id, substs, user_ty }
+                let user_ty = self.user_args_applied_to_res(expr.hir_id, res);
+                ExprKind::NamedConst { def_id, args, user_ty }
             }
 
             Res::Def(DefKind::Ctor(_, CtorKind::Const), def_id) => {
@@ -926,10 +924,10 @@ impl<'tcx> Cx<'tcx> {
                 match ty.kind() {
                     // A unit struct/variant which is used as a value.
                     // We return a completely different ExprKind here to account for this special case.
-                    ty::Adt(adt_def, substs) => ExprKind::Adt(Box::new(AdtExpr {
+                    ty::Adt(adt_def, args) => ExprKind::Adt(Box::new(AdtExpr {
                         adt_def: *adt_def,
                         variant_index: adt_def.variant_index_with_ctor_id(def_id),
-                        substs,
+                        args,
                         user_ty,
                         fields: Box::new([]),
                         base: None,
diff --git a/compiler/rustc_mir_build/src/thir/cx/mod.rs b/compiler/rustc_mir_build/src/thir/cx/mod.rs
index e09e22af761e5..d98cc76adfbd7 100644
--- a/compiler/rustc_mir_build/src/thir/cx/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/cx/mod.rs
@@ -122,7 +122,7 @@ impl<'tcx> Cx<'tcx> {
             DefKind::Closure => {
                 let closure_ty = self.typeck_results.node_type(owner_id);
 
-                let ty::Closure(closure_def_id, closure_substs) = *closure_ty.kind() else {
+                let ty::Closure(closure_def_id, closure_args) = *closure_ty.kind() else {
                     bug!("closure expr does not have closure type: {:?}", closure_ty);
                 };
 
@@ -134,7 +134,7 @@ impl<'tcx> Cx<'tcx> {
                 };
                 let env_region = ty::Region::new_late_bound(self.tcx, ty::INNERMOST, br);
                 let closure_env_ty =
-                    self.tcx.closure_env_ty(closure_def_id, closure_substs, env_region).unwrap();
+                    self.tcx.closure_env_ty(closure_def_id, closure_args, env_region).unwrap();
                 let liberated_closure_env_ty = self.tcx.erase_late_bound_regions(
                     ty::Binder::bind_with_vars(closure_env_ty, bound_vars),
                 );
@@ -186,7 +186,7 @@ impl<'tcx> Cx<'tcx> {
 
                 self.tcx
                     .type_of(va_list_did)
-                    .subst(self.tcx, &[self.tcx.lifetimes.re_erased.into()])
+                    .instantiate(self.tcx, &[self.tcx.lifetimes.re_erased.into()])
             } else {
                 fn_sig.inputs()[index]
             };
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
index 0eaaa411415f5..38c866c50a2ff 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs
@@ -501,12 +501,12 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
         let witness_1_is_privately_uninhabited =
             if cx.tcx.features().exhaustive_patterns
                 && let Some(witness_1) = witnesses.get(0)
-                && let ty::Adt(adt, substs) = witness_1.ty().kind()
+                && let ty::Adt(adt, args) = witness_1.ty().kind()
                 && adt.is_enum()
                 && let Constructor::Variant(variant_index) = witness_1.ctor()
             {
                 let variant = adt.variant(*variant_index);
-                let inhabited = variant.inhabited_predicate(cx.tcx, *adt).subst(cx.tcx, substs);
+                let inhabited = variant.inhabited_predicate(cx.tcx, *adt).instantiate(cx.tcx, args);
                 assert!(inhabited.apply(cx.tcx, cx.param_env, cx.module));
                 !inhabited.apply_ignore_module(cx.tcx, cx.param_env)
             } else {
diff --git a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
index 050b01294b465..251c6b4b6daf3 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/const_to_pat.rs
@@ -332,20 +332,20 @@ impl<'tcx> ConstToPat<'tcx> {
                 tcx.sess.emit_err(err);
                 PatKind::Wild
             }
-            ty::Adt(adt_def, substs) if adt_def.is_enum() => {
+            ty::Adt(adt_def, args) if adt_def.is_enum() => {
                 let (&variant_index, fields) = cv.unwrap_branch().split_first().unwrap();
                 let variant_index =
                     VariantIdx::from_u32(variant_index.unwrap_leaf().try_to_u32().ok().unwrap());
                 PatKind::Variant {
                     adt_def: *adt_def,
-                    substs,
+                    args,
                     variant_index,
                     subpatterns: self.field_pats(
                         fields.iter().copied().zip(
                             adt_def.variants()[variant_index]
                                 .fields
                                 .iter()
-                                .map(|field| field.ty(self.tcx(), substs)),
+                                .map(|field| field.ty(self.tcx(), args)),
                         ),
                     )?,
                 }
@@ -354,9 +354,9 @@ impl<'tcx> ConstToPat<'tcx> {
                 subpatterns: self
                     .field_pats(cv.unwrap_branch().iter().copied().zip(fields.iter()))?,
             },
-            ty::Adt(def, substs) => PatKind::Leaf {
+            ty::Adt(def, args) => PatKind::Leaf {
                 subpatterns: self.field_pats(cv.unwrap_branch().iter().copied().zip(
-                    def.non_enum_variant().fields.iter().map(|field| field.ty(self.tcx(), substs)),
+                    def.non_enum_variant().fields.iter().map(|field| field.ty(self.tcx(), args)),
                 ))?,
             },
             ty::Slice(elem_ty) => PatKind::Slice {
diff --git a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
index 9df6d2f43ad57..4228597cdc957 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/deconstruct_pat.rs
@@ -922,7 +922,7 @@ impl<'tcx> SplitWildcard<'tcx> {
                 let kind = if cx.is_uninhabited(*sub_ty) { FixedLen(0) } else { VarLen(0, 0) };
                 smallvec![Slice(Slice::new(None, kind))]
             }
-            ty::Adt(def, substs) if def.is_enum() => {
+            ty::Adt(def, args) if def.is_enum() => {
                 // If the enum is declared as `#[non_exhaustive]`, we treat it as if it had an
                 // additional "unknown" constructor.
                 // There is no point in enumerating all possible variants, because the user can't
@@ -950,21 +950,19 @@ impl<'tcx> SplitWildcard<'tcx> {
                 let is_secretly_empty =
                     def.variants().is_empty() && !is_exhaustive_pat_feature && !pcx.is_top_level;
 
-                let mut ctors: SmallVec<[_; 1]> = def
-                    .variants()
-                    .iter_enumerated()
-                    .filter(|(_, v)| {
-                        // If `exhaustive_patterns` is enabled, we exclude variants known to be
-                        // uninhabited.
-                        !is_exhaustive_pat_feature
-                            || v.inhabited_predicate(cx.tcx, *def).subst(cx.tcx, substs).apply(
-                                cx.tcx,
-                                cx.param_env,
-                                cx.module,
-                            )
-                    })
-                    .map(|(idx, _)| Variant(idx))
-                    .collect();
+                let mut ctors: SmallVec<[_; 1]> =
+                    def.variants()
+                        .iter_enumerated()
+                        .filter(|(_, v)| {
+                            // If `exhaustive_patterns` is enabled, we exclude variants known to be
+                            // uninhabited.
+                            !is_exhaustive_pat_feature
+                                || v.inhabited_predicate(cx.tcx, *def)
+                                    .instantiate(cx.tcx, args)
+                                    .apply(cx.tcx, cx.param_env, cx.module)
+                        })
+                        .map(|(idx, _)| Variant(idx))
+                        .collect();
 
                 if is_secretly_empty || is_declared_nonexhaustive {
                     ctors.push(NonExhaustive);
@@ -1156,12 +1154,12 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
         ty: Ty<'tcx>,
         variant: &'a VariantDef,
     ) -> impl Iterator<Item = (FieldIdx, Ty<'tcx>)> + Captures<'a> + Captures<'p> {
-        let ty::Adt(adt, substs) = ty.kind() else { bug!() };
+        let ty::Adt(adt, args) = ty.kind() else { bug!() };
         // Whether we must not match the fields of this variant exhaustively.
         let is_non_exhaustive = variant.is_field_list_non_exhaustive() && !adt.did().is_local();
 
         variant.fields.iter().enumerate().filter_map(move |(i, field)| {
-            let ty = field.ty(cx.tcx, substs);
+            let ty = field.ty(cx.tcx, args);
             // `field.ty()` doesn't normalize after substituting.
             let ty = cx.tcx.normalize_erasing_regions(cx.param_env, ty);
             let is_visible = adt.is_enum() || field.vis.is_accessible_from(cx.module, cx.tcx);
@@ -1183,11 +1181,11 @@ impl<'p, 'tcx> Fields<'p, 'tcx> {
             Single | Variant(_) => match pcx.ty.kind() {
                 ty::Tuple(fs) => Fields::wildcards_from_tys(pcx.cx, fs.iter(), pcx.span),
                 ty::Ref(_, rty, _) => Fields::wildcards_from_tys(pcx.cx, once(*rty), pcx.span),
-                ty::Adt(adt, substs) => {
+                ty::Adt(adt, args) => {
                     if adt.is_box() {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
                         // patterns. If we're here we can assume this is a box pattern.
-                        Fields::wildcards_from_tys(pcx.cx, once(substs.type_at(0)), pcx.span)
+                        Fields::wildcards_from_tys(pcx.cx, once(args.type_at(0)), pcx.span)
                     } else {
                         let variant = &adt.variant(constructor.variant_index_for_adt(*adt));
                         let tys = Fields::list_variant_nonhidden_fields(pcx.cx, pcx.ty, variant)
@@ -1294,7 +1292,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         }
                         fields = Fields::from_iter(cx, wilds);
                     }
-                    ty::Adt(adt, substs) if adt.is_box() => {
+                    ty::Adt(adt, args) if adt.is_box() => {
                         // The only legal patterns of type `Box` (outside `std`) are `_` and box
                         // patterns. If we're here we can assume this is a box pattern.
                         // FIXME(Nadrieril): A `Box` can in theory be matched either with `Box(_,
@@ -1311,7 +1309,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         let pat = if let Some(pat) = pattern {
                             mkpat(&pat.pattern)
                         } else {
-                            DeconstructedPat::wildcard(substs.type_at(0), pat.span)
+                            DeconstructedPat::wildcard(args.type_at(0), pat.span)
                         };
                         ctor = Single;
                         fields = Fields::singleton(cx, pat);
@@ -1437,7 +1435,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                     // the pattern is a box pattern.
                     PatKind::Deref { subpattern: subpatterns.next().unwrap() }
                 }
-                ty::Adt(adt_def, substs) => {
+                ty::Adt(adt_def, args) => {
                     let variant_index = self.ctor.variant_index_for_adt(*adt_def);
                     let variant = &adt_def.variant(variant_index);
                     let subpatterns = Fields::list_variant_nonhidden_fields(cx, self.ty, variant)
@@ -1446,7 +1444,7 @@ impl<'p, 'tcx> DeconstructedPat<'p, 'tcx> {
                         .collect();
 
                     if adt_def.is_enum() {
-                        PatKind::Variant { adt_def: *adt_def, substs, variant_index, subpatterns }
+                        PatKind::Variant { adt_def: *adt_def, args, variant_index, subpatterns }
                     } else {
                         PatKind::Leaf { subpatterns }
                     }
diff --git a/compiler/rustc_mir_build/src/thir/pattern/mod.rs b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
index 600995927842d..3c3cbbf36148d 100644
--- a/compiler/rustc_mir_build/src/thir/pattern/mod.rs
+++ b/compiler/rustc_mir_build/src/thir/pattern/mod.rs
@@ -23,10 +23,10 @@ use rustc_middle::mir::interpret::{
 use rustc_middle::mir::{self, ConstantKind, UserTypeProjection};
 use rustc_middle::mir::{BorrowKind, Mutability};
 use rustc_middle::thir::{Ascription, BindingMode, FieldPat, LocalVarId, Pat, PatKind, PatRange};
-use rustc_middle::ty::subst::{GenericArg, SubstsRef};
 use rustc_middle::ty::CanonicalUserTypeAnnotation;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, AdtDef, Region, Ty, TyCtxt, UserType};
+use rustc_middle::ty::{GenericArg, GenericArgsRef};
 use rustc_span::{Span, Symbol};
 use rustc_target::abi::FieldIdx;
 
@@ -416,8 +416,8 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                 let enum_id = self.tcx.parent(variant_id);
                 let adt_def = self.tcx.adt_def(enum_id);
                 if adt_def.is_enum() {
-                    let substs = match ty.kind() {
-                        ty::Adt(_, substs) | ty::FnDef(_, substs) => substs,
+                    let args = match ty.kind() {
+                        ty::Adt(_, args) | ty::FnDef(_, args) => args,
                         ty::Error(_) => {
                             // Avoid ICE (#50585)
                             return PatKind::Wild;
@@ -426,7 +426,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
                     };
                     PatKind::Variant {
                         adt_def,
-                        substs,
+                        args,
                         variant_index: adt_def.variant_index_with_id(variant_id),
                         subpatterns,
                     }
@@ -460,7 +460,7 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
             }
         };
 
-        if let Some(user_ty) = self.user_substs_applied_to_ty_of_hir_id(hir_id) {
+        if let Some(user_ty) = self.user_args_applied_to_ty_of_hir_id(hir_id) {
             debug!("lower_variant_or_leaf: kind={:?} user_ty={:?} span={:?}", kind, user_ty, span);
             let annotation = CanonicalUserTypeAnnotation {
                 user_ty: Box::new(user_ty),
@@ -496,13 +496,13 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         // Use `Reveal::All` here because patterns are always monomorphic even if their function
         // isn't.
         let param_env_reveal_all = self.param_env.with_reveal_all_normalized(self.tcx);
-        // N.B. There is no guarantee that substs collected in typeck results are fully normalized,
+        // N.B. There is no guarantee that args collected in typeck results are fully normalized,
         // so they need to be normalized in order to pass to `Instance::resolve`, which will ICE
         // if given unnormalized types.
-        let substs = self
+        let args = self
             .tcx
-            .normalize_erasing_regions(param_env_reveal_all, self.typeck_results.node_substs(id));
-        let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, substs) {
+            .normalize_erasing_regions(param_env_reveal_all, self.typeck_results.node_args(id));
+        let instance = match ty::Instance::resolve(self.tcx, param_env_reveal_all, def_id, args) {
             Ok(Some(i)) => i,
             Ok(None) => {
                 // It should be assoc consts if there's no error but we cannot resolve it.
@@ -617,16 +617,14 @@ impl<'a, 'tcx> PatCtxt<'a, 'tcx> {
         }
 
         let typeck_root_def_id = tcx.typeck_root_def_id(def_id.to_def_id());
-        let parent_substs =
-            tcx.erase_regions(ty::InternalSubsts::identity_for_item(tcx, typeck_root_def_id));
-        let substs =
-            ty::InlineConstSubsts::new(tcx, ty::InlineConstSubstsParts { parent_substs, ty })
-                .substs;
+        let parent_args =
+            tcx.erase_regions(ty::GenericArgs::identity_for_item(tcx, typeck_root_def_id));
+        let args = ty::InlineConstArgs::new(tcx, ty::InlineConstArgsParts { parent_args, ty }).args;
 
-        let uneval = mir::UnevaluatedConst { def: def_id.to_def_id(), substs, promoted: None };
-        debug_assert!(!substs.has_free_regions());
+        let uneval = mir::UnevaluatedConst { def: def_id.to_def_id(), args, promoted: None };
+        debug_assert!(!args.has_free_regions());
 
-        let ct = ty::UnevaluatedConst { def: def_id.to_def_id(), substs: substs };
+        let ct = ty::UnevaluatedConst { def: def_id.to_def_id(), args: args };
         // First try using a valtree in order to destructure the constant into a pattern.
         if let Ok(Some(valtree)) =
             self.tcx.const_eval_resolve_for_typeck(self.param_env, ct, Some(span))
@@ -754,7 +752,7 @@ macro_rules! ClonePatternFoldableImpls {
 ClonePatternFoldableImpls! { <'tcx>
     Span, FieldIdx, Mutability, Symbol, LocalVarId, usize,
     Region<'tcx>, Ty<'tcx>, BindingMode, AdtDef<'tcx>,
-    SubstsRef<'tcx>, &'tcx GenericArg<'tcx>, UserType<'tcx>,
+    GenericArgsRef<'tcx>, &'tcx GenericArg<'tcx>, UserType<'tcx>,
     UserTypeProjection, CanonicalUserTypeAnnotation<'tcx>
 }
 
@@ -804,10 +802,10 @@ impl<'tcx> PatternFoldable<'tcx> for PatKind<'tcx> {
                     is_primary,
                 }
             }
-            PatKind::Variant { adt_def, substs, variant_index, ref subpatterns } => {
+            PatKind::Variant { adt_def, args, variant_index, ref subpatterns } => {
                 PatKind::Variant {
                     adt_def: adt_def.fold_with(folder),
-                    substs: substs.fold_with(folder),
+                    args: args.fold_with(folder),
                     variant_index,
                     subpatterns: subpatterns.fold_with(folder),
                 }
diff --git a/compiler/rustc_mir_build/src/thir/print.rs b/compiler/rustc_mir_build/src/thir/print.rs
index 8d7c624a80560..903dbeeadfa26 100644
--- a/compiler/rustc_mir_build/src/thir/print.rs
+++ b/compiler/rustc_mir_build/src/thir/print.rs
@@ -427,10 +427,10 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
                 self.print_expr(*value, depth_lvl + 2);
                 print_indented!(self, "}", depth_lvl);
             }
-            ConstBlock { did, substs } => {
+            ConstBlock { did, args } => {
                 print_indented!(self, "ConstBlock {", depth_lvl);
                 print_indented!(self, format!("did: {:?}", did), depth_lvl + 1);
-                print_indented!(self, format!("substs: {:?}", substs), depth_lvl + 1);
+                print_indented!(self, format!("args: {:?}", args), depth_lvl + 1);
                 print_indented!(self, "}", depth_lvl);
             }
             Repeat { value, count } => {
@@ -499,11 +499,11 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
             ZstLiteral { user_ty } => {
                 print_indented!(self, format!("ZstLiteral(user_ty: {:?})", user_ty), depth_lvl);
             }
-            NamedConst { def_id, substs, user_ty } => {
+            NamedConst { def_id, args, user_ty } => {
                 print_indented!(self, "NamedConst {", depth_lvl);
                 print_indented!(self, format!("def_id: {:?}", def_id), depth_lvl + 1);
                 print_indented!(self, format!("user_ty: {:?}", user_ty), depth_lvl + 1);
-                print_indented!(self, format!("substs: {:?}", substs), depth_lvl + 1);
+                print_indented!(self, format!("args: {:?}", args), depth_lvl + 1);
                 print_indented!(self, "}", depth_lvl);
             }
             ConstParam { param, def_id } => {
@@ -560,7 +560,7 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
             format!("variant_index: {:?}", adt_expr.variant_index),
             depth_lvl + 1
         );
-        print_indented!(self, format!("substs: {:?}", adt_expr.substs), depth_lvl + 1);
+        print_indented!(self, format!("args: {:?}", adt_expr.args), depth_lvl + 1);
         print_indented!(self, format!("user_ty: {:?}", adt_expr.user_ty), depth_lvl + 1);
 
         for (i, field_expr) in adt_expr.fields.iter().enumerate() {
@@ -662,11 +662,11 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
 
                 print_indented!(self, "}", depth_lvl + 1);
             }
-            PatKind::Variant { adt_def, substs, variant_index, subpatterns } => {
+            PatKind::Variant { adt_def, args, variant_index, subpatterns } => {
                 print_indented!(self, "Variant {", depth_lvl + 1);
                 print_indented!(self, "adt_def: ", depth_lvl + 2);
                 self.print_adt_def(*adt_def, depth_lvl + 3);
-                print_indented!(self, format!("substs: {:?}", substs), depth_lvl + 2);
+                print_indented!(self, format!("args: {:?}", args), depth_lvl + 2);
                 print_indented!(self, format!("variant_index: {:?}", variant_index), depth_lvl + 2);
 
                 if subpatterns.len() > 0 {
@@ -784,11 +784,11 @@ impl<'a, 'tcx> ThirPrinter<'a, 'tcx> {
     }
 
     fn print_closure_expr(&mut self, expr: &ClosureExpr<'tcx>, depth_lvl: usize) {
-        let ClosureExpr { closure_id, substs, upvars, movability, fake_reads } = expr;
+        let ClosureExpr { closure_id, args, upvars, movability, fake_reads } = expr;
 
         print_indented!(self, "ClosureExpr {", depth_lvl);
         print_indented!(self, format!("closure_id: {:?}", closure_id), depth_lvl + 1);
-        print_indented!(self, format!("substs: {:?}", substs), depth_lvl + 1);
+        print_indented!(self, format!("args: {:?}", args), depth_lvl + 1);
 
         if upvars.len() > 0 {
             print_indented!(self, "upvars: [", depth_lvl + 1);
diff --git a/compiler/rustc_mir_build/src/thir/util.rs b/compiler/rustc_mir_build/src/thir/util.rs
index c58ed1ac0b891..9106b4d33fcd1 100644
--- a/compiler/rustc_mir_build/src/thir/util.rs
+++ b/compiler/rustc_mir_build/src/thir/util.rs
@@ -9,7 +9,7 @@ pub(crate) trait UserAnnotatedTyHelpers<'tcx> {
     /// Looks up the type associated with this hir-id and applies the
     /// user-given substitutions; the hir-id must map to a suitable
     /// type.
-    fn user_substs_applied_to_ty_of_hir_id(
+    fn user_args_applied_to_ty_of_hir_id(
         &self,
         hir_id: hir::HirId,
     ) -> Option<CanonicalUserType<'tcx>> {
diff --git a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
index 0540a5e943b4f..1d7d905c937d4 100644
--- a/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
+++ b/compiler/rustc_mir_dataflow/src/elaborate_drops.rs
@@ -4,8 +4,8 @@ use rustc_index::Idx;
 use rustc_middle::mir::patch::MirPatch;
 use rustc_middle::mir::*;
 use rustc_middle::traits::Reveal;
-use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::util::IntTypeExt;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 use std::{fmt, iter};
@@ -263,7 +263,7 @@ where
         base_place: Place<'tcx>,
         variant_path: D::Path,
         variant: &'tcx ty::VariantDef,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Vec<(Place<'tcx>, Option<D::Path>)> {
         variant
             .fields
@@ -276,7 +276,7 @@ where
 
                 assert_eq!(self.elaborator.param_env().reveal(), Reveal::All);
                 let field_ty =
-                    tcx.normalize_erasing_regions(self.elaborator.param_env(), f.ty(tcx, substs));
+                    tcx.normalize_erasing_regions(self.elaborator.param_env(), f.ty(tcx, args));
 
                 (tcx.mk_place_field(base_place, field, field_ty), subpath)
             })
@@ -414,16 +414,16 @@ where
     fn open_drop_for_box_contents(
         &mut self,
         adt: ty::AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         succ: BasicBlock,
         unwind: Unwind,
     ) -> BasicBlock {
         // drop glue is sent straight to codegen
         // box cannot be directly dereferenced
-        let unique_ty = adt.non_enum_variant().fields[FieldIdx::new(0)].ty(self.tcx(), substs);
+        let unique_ty = adt.non_enum_variant().fields[FieldIdx::new(0)].ty(self.tcx(), args);
         let unique_variant = unique_ty.ty_adt_def().unwrap().non_enum_variant();
-        let nonnull_ty = unique_variant.fields[FieldIdx::from_u32(0)].ty(self.tcx(), substs);
-        let ptr_ty = Ty::new_imm_ptr(self.tcx(), substs[0].expect_ty());
+        let nonnull_ty = unique_variant.fields[FieldIdx::from_u32(0)].ty(self.tcx(), args);
+        let ptr_ty = Ty::new_imm_ptr(self.tcx(), args[0].expect_ty());
 
         let unique_place = self.tcx().mk_place_field(self.place, FieldIdx::new(0), unique_ty);
         let nonnull_place = self.tcx().mk_place_field(unique_place, FieldIdx::new(0), nonnull_ty);
@@ -436,7 +436,11 @@ where
     }
 
     #[instrument(level = "debug", ret)]
-    fn open_drop_for_adt(&mut self, adt: ty::AdtDef<'tcx>, substs: SubstsRef<'tcx>) -> BasicBlock {
+    fn open_drop_for_adt(
+        &mut self,
+        adt: ty::AdtDef<'tcx>,
+        args: GenericArgsRef<'tcx>,
+    ) -> BasicBlock {
         if adt.variants().is_empty() {
             return self.elaborator.patch().new_block(BasicBlockData {
                 statements: vec![],
@@ -453,7 +457,7 @@ where
         let contents_drop = if skip_contents {
             (self.succ, self.unwind)
         } else {
-            self.open_drop_for_adt_contents(adt, substs)
+            self.open_drop_for_adt_contents(adt, args)
         };
 
         if adt.is_box() {
@@ -463,7 +467,7 @@ where
                 .1
                 .map(|unwind| self.destructor_call_block((unwind, Unwind::InCleanup)));
 
-            self.open_drop_for_box_contents(adt, substs, succ, unwind)
+            self.open_drop_for_box_contents(adt, args, succ, unwind)
         } else if adt.has_dtor(self.tcx()) {
             self.destructor_call_block(contents_drop)
         } else {
@@ -474,7 +478,7 @@ where
     fn open_drop_for_adt_contents(
         &mut self,
         adt: ty::AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> (BasicBlock, Unwind) {
         let (succ, unwind) = self.drop_ladder_bottom();
         if !adt.is_enum() {
@@ -482,18 +486,18 @@ where
                 self.place,
                 self.path,
                 &adt.variant(FIRST_VARIANT),
-                substs,
+                args,
             );
             self.drop_ladder(fields, succ, unwind)
         } else {
-            self.open_drop_for_multivariant(adt, substs, succ, unwind)
+            self.open_drop_for_multivariant(adt, args, succ, unwind)
         }
     }
 
     fn open_drop_for_multivariant(
         &mut self,
         adt: ty::AdtDef<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         succ: BasicBlock,
         unwind: Unwind,
     ) -> (BasicBlock, Unwind) {
@@ -515,7 +519,7 @@ where
                     self.place,
                     ProjectionElem::Downcast(Some(variant.name), variant_index),
                 );
-                let fields = self.move_paths_for_fields(base_place, variant_path, &variant, substs);
+                let fields = self.move_paths_for_fields(base_place, variant_path, &variant, args);
                 values.push(discr.val);
                 if let Unwind::To(unwind) = unwind {
                     // We can't use the half-ladder from the original
@@ -550,7 +554,7 @@ where
                 let have_field_with_drop_glue = variant
                     .fields
                     .iter()
-                    .any(|field| field.ty(tcx, substs).needs_drop(tcx, param_env));
+                    .any(|field| field.ty(tcx, args).needs_drop(tcx, param_env));
                 if have_field_with_drop_glue {
                     have_otherwise_with_drop_glue = true;
                 }
@@ -856,8 +860,8 @@ where
     fn open_drop(&mut self) -> BasicBlock {
         let ty = self.place_ty(self.place);
         match ty.kind() {
-            ty::Closure(_, substs) => {
-                let tys: Vec<_> = substs.as_closure().upvar_tys().collect();
+            ty::Closure(_, args) => {
+                let tys: Vec<_> = args.as_closure().upvar_tys().collect();
                 self.open_drop_for_tuple(&tys)
             }
             // Note that `elaborate_drops` only drops the upvars of a generator,
@@ -866,12 +870,12 @@ where
             // This should only happen for the self argument on the resume function.
             // It effectively only contains upvars until the generator transformation runs.
             // See librustc_body/transform/generator.rs for more details.
-            ty::Generator(_, substs, _) => {
-                let tys: Vec<_> = substs.as_generator().upvar_tys().collect();
+            ty::Generator(_, args, _) => {
+                let tys: Vec<_> = args.as_generator().upvar_tys().collect();
                 self.open_drop_for_tuple(&tys)
             }
             ty::Tuple(fields) => self.open_drop_for_tuple(fields),
-            ty::Adt(def, substs) => self.open_drop_for_adt(*def, substs),
+            ty::Adt(def, args) => self.open_drop_for_adt(*def, args),
             ty::Dynamic(..) => self.complete_drop(self.succ, self.unwind),
             ty::Array(ety, size) => {
                 let size = size.try_eval_target_usize(self.tcx(), self.elaborator.param_env());
diff --git a/compiler/rustc_mir_dataflow/src/rustc_peek.rs b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
index 156231c3ae161..775c522b476f6 100644
--- a/compiler/rustc_mir_dataflow/src/rustc_peek.rs
+++ b/compiler/rustc_mir_dataflow/src/rustc_peek.rs
@@ -190,14 +190,14 @@ impl PeekCall {
         if let mir::TerminatorKind::Call { func: Operand::Constant(func), args, .. } =
             &terminator.kind
         {
-            if let ty::FnDef(def_id, substs) = *func.literal.ty().kind() {
+            if let ty::FnDef(def_id, fn_args) = *func.literal.ty().kind() {
                 let name = tcx.item_name(def_id);
                 if !tcx.is_intrinsic(def_id) || name != sym::rustc_peek {
                     return None;
                 }
 
-                assert_eq!(args.len(), 1);
-                let kind = PeekCallKind::from_arg_ty(substs.type_at(0));
+                assert_eq!(fn_args.len(), 1);
+                let kind = PeekCallKind::from_arg_ty(fn_args.type_at(0));
                 let arg = match &args[0] {
                     Operand::Copy(place) | Operand::Move(place) => {
                         if let Some(local) = place.as_local() {
diff --git a/compiler/rustc_mir_dataflow/src/value_analysis.rs b/compiler/rustc_mir_dataflow/src/value_analysis.rs
index 5693e5a4a712a..fd6b1dc5c0761 100644
--- a/compiler/rustc_mir_dataflow/src/value_analysis.rs
+++ b/compiler/rustc_mir_dataflow/src/value_analysis.rs
@@ -999,14 +999,14 @@ pub fn iter_fields<'tcx>(
                 f(None, field.into(), ty);
             }
         }
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             if def.is_union() {
                 return;
             }
             for (v_index, v_def) in def.variants().iter_enumerated() {
                 let variant = if def.is_struct() { None } else { Some(v_index) };
                 for (f_index, f_def) in v_def.fields.iter().enumerate() {
-                    let field_ty = f_def.ty(tcx, substs);
+                    let field_ty = f_def.ty(tcx, args);
                     let field_ty = tcx
                         .try_normalize_erasing_regions(param_env, field_ty)
                         .unwrap_or_else(|_| tcx.erase_regions(field_ty));
@@ -1014,8 +1014,8 @@ pub fn iter_fields<'tcx>(
                 }
             }
         }
-        ty::Closure(_, substs) => {
-            iter_fields(substs.as_closure().tupled_upvars_ty(), tcx, param_env, f);
+        ty::Closure(_, args) => {
+            iter_fields(args.as_closure().tupled_upvars_ty(), tcx, param_env, f);
         }
         _ => (),
     }
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index f3ac679f97b21..6437a227d47c9 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -14,7 +14,7 @@ use rustc_middle::mir::visit::{
 };
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::{def_id::DefId, Span, DUMMY_SP};
 use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout};
@@ -87,7 +87,7 @@ impl<'tcx> MirPass<'tcx> for ConstProp {
             return;
         }
 
-        let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator();
+        let is_generator = tcx.type_of(def_id.to_def_id()).instantiate_identity().is_generator();
         // FIXME(welseywiser) const prop doesn't work on generators because of query cycles
         // computing their layout.
         if is_generator {
@@ -338,7 +338,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         tcx: TyCtxt<'tcx>,
     ) -> ConstPropagator<'mir, 'tcx> {
         let def_id = body.source.def_id();
-        let substs = &InternalSubsts::identity_for_item(tcx, def_id);
+        let args = &GenericArgs::identity_for_item(tcx, def_id);
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
 
         let can_const_prop = CanConstProp::check(tcx, param_env, body);
@@ -350,7 +350,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret_layout = ecx
-            .layout_of(body.bound_return_ty().subst(tcx, substs))
+            .layout_of(body.bound_return_ty().instantiate(tcx, args))
             .ok()
             // Don't bother allocating memory for large values.
             // I don't know how return types can seem to be unsized but this happens in the
@@ -366,7 +366,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             .into();
 
         ecx.push_stack_frame(
-            Instance::new(def_id, substs),
+            Instance::new(def_id, args),
             dummy_body,
             &ret,
             StackPopCleanup::Root { cleanup: false },
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index 759650fe4db3a..01b945afda636 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -16,7 +16,7 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{
     self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt,
 };
@@ -55,7 +55,7 @@ impl<'tcx> MirLint<'tcx> for ConstProp {
             return;
         }
 
-        let is_generator = tcx.type_of(def_id.to_def_id()).subst_identity().is_generator();
+        let is_generator = tcx.type_of(def_id.to_def_id()).instantiate_identity().is_generator();
         // FIXME(welseywiser) const prop doesn't work on generators because of query cycles
         // computing their layout.
         if is_generator {
@@ -171,7 +171,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         tcx: TyCtxt<'tcx>,
     ) -> ConstPropagator<'mir, 'tcx> {
         let def_id = body.source.def_id();
-        let substs = &InternalSubsts::identity_for_item(tcx, def_id);
+        let args = &GenericArgs::identity_for_item(tcx, def_id);
         let param_env = tcx.param_env_reveal_all_normalized(def_id);
 
         let can_const_prop = CanConstProp::check(tcx, param_env, body);
@@ -183,7 +183,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         );
 
         let ret_layout = ecx
-            .layout_of(body.bound_return_ty().subst(tcx, substs))
+            .layout_of(body.bound_return_ty().instantiate(tcx, args))
             .ok()
             // Don't bother allocating memory for large values.
             // I don't know how return types can seem to be unsized but this happens in the
@@ -199,7 +199,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
             .into();
 
         ecx.push_stack_frame(
-            Instance::new(def_id, substs),
+            Instance::new(def_id, args),
             dummy_body,
             &ret,
             StackPopCleanup::Root { cleanup: false },
diff --git a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
index a133c9d4782c8..60ca3dfb2dab5 100644
--- a/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
+++ b/compiler/rustc_mir_transform/src/deduce_param_attrs.rs
@@ -166,7 +166,7 @@ pub fn deduced_param_attrs<'tcx>(
 
     // Codegen won't use this information for anything if all the function parameters are passed
     // directly. Detect that and bail, for compilation speed.
-    let fn_ty = tcx.type_of(def_id).subst_identity();
+    let fn_ty = tcx.type_of(def_id).instantiate_identity();
     if matches!(fn_ty.kind(), ty::FnDef(..)) {
         if fn_ty
             .fn_sig(tcx)
diff --git a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
index cc0d7d51b60fe..e51f771e00dbe 100644
--- a/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
+++ b/compiler/rustc_mir_transform/src/elaborate_box_derefs.rs
@@ -18,9 +18,9 @@ pub fn build_ptr_tys<'tcx>(
     unique_did: DefId,
     nonnull_did: DefId,
 ) -> (Ty<'tcx>, Ty<'tcx>, Ty<'tcx>) {
-    let substs = tcx.mk_substs(&[pointee.into()]);
-    let unique_ty = tcx.type_of(unique_did).subst(tcx, substs);
-    let nonnull_ty = tcx.type_of(nonnull_did).subst(tcx, substs);
+    let args = tcx.mk_args(&[pointee.into()]);
+    let unique_ty = tcx.type_of(unique_did).instantiate(tcx, args);
+    let nonnull_ty = tcx.type_of(nonnull_did).instantiate(tcx, args);
     let ptr_ty = Ty::new_imm_ptr(tcx, pointee);
 
     (unique_ty, nonnull_ty, ptr_ty)
@@ -95,7 +95,8 @@ impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
             let unique_did =
                 tcx.adt_def(def_id).non_enum_variant().fields[FieldIdx::from_u32(0)].did;
 
-            let Some(nonnull_def) = tcx.type_of(unique_did).subst_identity().ty_adt_def() else {
+            let Some(nonnull_def) = tcx.type_of(unique_did).instantiate_identity().ty_adt_def()
+            else {
                 span_bug!(tcx.def_span(unique_did), "expected Box to contain Unique")
             };
 
diff --git a/compiler/rustc_mir_transform/src/function_item_references.rs b/compiler/rustc_mir_transform/src/function_item_references.rs
index 0b41e57be3b3a..fdf6ab33c82f7 100644
--- a/compiler/rustc_mir_transform/src/function_item_references.rs
+++ b/compiler/rustc_mir_transform/src/function_item_references.rs
@@ -2,7 +2,7 @@ use itertools::Itertools;
 use rustc_hir::def_id::DefId;
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
-use rustc_middle::ty::{self, EarlyBinder, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt};
 use rustc_session::lint::builtin::FUNCTION_ITEM_REFERENCES;
 use rustc_span::{symbol::sym, Span};
 use rustc_target::spec::abi::Abi;
@@ -40,20 +40,19 @@ impl<'tcx> Visitor<'tcx> for FunctionItemRefChecker<'_, 'tcx> {
         {
             let source_info = *self.body.source_info(location);
             let func_ty = func.ty(self.body, self.tcx);
-            if let ty::FnDef(def_id, substs_ref) = *func_ty.kind() {
+            if let ty::FnDef(def_id, args_ref) = *func_ty.kind() {
                 // Handle calls to `transmute`
                 if self.tcx.is_diagnostic_item(sym::transmute, def_id) {
                     let arg_ty = args[0].ty(self.body, self.tcx);
                     for inner_ty in arg_ty.walk().filter_map(|arg| arg.as_type()) {
-                        if let Some((fn_id, fn_substs)) =
-                            FunctionItemRefChecker::is_fn_ref(inner_ty)
+                        if let Some((fn_id, fn_args)) = FunctionItemRefChecker::is_fn_ref(inner_ty)
                         {
                             let span = self.nth_arg_span(&args, 0);
-                            self.emit_lint(fn_id, fn_substs, source_info, span);
+                            self.emit_lint(fn_id, fn_args, source_info, span);
                         }
                     }
                 } else {
-                    self.check_bound_args(def_id, substs_ref, &args, source_info);
+                    self.check_bound_args(def_id, args_ref, &args, source_info);
                 }
             }
         }
@@ -63,11 +62,11 @@ impl<'tcx> Visitor<'tcx> for FunctionItemRefChecker<'_, 'tcx> {
 
 impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     /// Emits a lint for function reference arguments bound by `fmt::Pointer` in calls to the
-    /// function defined by `def_id` with the substitutions `substs_ref`.
+    /// function defined by `def_id` with the substitutions `args_ref`.
     fn check_bound_args(
         &self,
         def_id: DefId,
-        substs_ref: SubstsRef<'tcx>,
+        args_ref: GenericArgsRef<'tcx>,
         args: &[Operand<'tcx>],
         source_info: SourceInfo,
     ) {
@@ -76,15 +75,17 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
         for bound in bounds {
             if let Some(bound_ty) = self.is_pointer_trait(bound) {
                 // Get the argument types as they appear in the function signature.
-                let arg_defs = self.tcx.fn_sig(def_id).subst_identity().skip_binder().inputs();
+                let arg_defs =
+                    self.tcx.fn_sig(def_id).instantiate_identity().skip_binder().inputs();
                 for (arg_num, arg_def) in arg_defs.iter().enumerate() {
                     // For all types reachable from the argument type in the fn sig
                     for inner_ty in arg_def.walk().filter_map(|arg| arg.as_type()) {
                         // If the inner type matches the type bound by `Pointer`
                         if inner_ty == bound_ty {
                             // Do a substitution using the parameters from the callsite
-                            let subst_ty = EarlyBinder::bind(inner_ty).subst(self.tcx, substs_ref);
-                            if let Some((fn_id, fn_substs)) =
+                            let subst_ty =
+                                EarlyBinder::bind(inner_ty).instantiate(self.tcx, args_ref);
+                            if let Some((fn_id, fn_args)) =
                                 FunctionItemRefChecker::is_fn_ref(subst_ty)
                             {
                                 let mut span = self.nth_arg_span(args, arg_num);
@@ -94,7 +95,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
                                     let callsite_ctxt = span.source_callsite().ctxt();
                                     span = span.with_ctxt(callsite_ctxt);
                                 }
-                                self.emit_lint(fn_id, fn_substs, source_info, span);
+                                self.emit_lint(fn_id, fn_args, source_info, span);
                             }
                         }
                     }
@@ -115,8 +116,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     }
 
     /// If a type is a reference or raw pointer to the anonymous type of a function definition,
-    /// returns that function's `DefId` and `SubstsRef`.
-    fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, SubstsRef<'tcx>)> {
+    /// returns that function's `DefId` and `GenericArgsRef`.
+    fn is_fn_ref(ty: Ty<'tcx>) -> Option<(DefId, GenericArgsRef<'tcx>)> {
         let referent_ty = match ty.kind() {
             ty::Ref(_, referent_ty, _) => Some(referent_ty),
             ty::RawPtr(ty_and_mut) => Some(&ty_and_mut.ty),
@@ -124,8 +125,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
         };
         referent_ty
             .map(|ref_ty| {
-                if let ty::FnDef(def_id, substs_ref) = *ref_ty.kind() {
-                    Some((def_id, substs_ref))
+                if let ty::FnDef(def_id, args_ref) = *ref_ty.kind() {
+                    Some((def_id, args_ref))
                 } else {
                     None
                 }
@@ -145,7 +146,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
     fn emit_lint(
         &self,
         fn_id: DefId,
-        fn_substs: SubstsRef<'tcx>,
+        fn_args: GenericArgsRef<'tcx>,
         source_info: SourceInfo,
         span: Span,
     ) {
@@ -155,7 +156,7 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
             .assert_crate_local()
             .lint_root;
         // FIXME: use existing printing routines to print the function signature
-        let fn_sig = self.tcx.fn_sig(fn_id).subst(self.tcx, fn_substs);
+        let fn_sig = self.tcx.fn_sig(fn_id).instantiate(self.tcx, fn_args);
         let unsafety = fn_sig.unsafety().prefix_str();
         let abi = match fn_sig.abi() {
             Abi::Rust => String::from(""),
@@ -167,8 +168,8 @@ impl<'tcx> FunctionItemRefChecker<'_, 'tcx> {
             }
         };
         let ident = self.tcx.item_name(fn_id).to_ident_string();
-        let ty_params = fn_substs.types().map(|ty| format!("{}", ty));
-        let const_params = fn_substs.consts().map(|c| format!("{}", c));
+        let ty_params = fn_args.types().map(|ty| format!("{}", ty));
+        let const_params = fn_args.consts().map(|c| format!("{}", c));
         let params = ty_params.chain(const_params).join(", ");
         let num_args = fn_sig.inputs().map_bound(|inputs| inputs.len()).skip_binder();
         let variadic = if fn_sig.c_variadic() { ", ..." } else { "" };
diff --git a/compiler/rustc_mir_transform/src/generator.rs b/compiler/rustc_mir_transform/src/generator.rs
index 1154086d9b014..eaeaff69cf391 100644
--- a/compiler/rustc_mir_transform/src/generator.rs
+++ b/compiler/rustc_mir_transform/src/generator.rs
@@ -65,7 +65,7 @@ use rustc_middle::mir::dump_mir;
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
 use rustc_middle::mir::*;
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt};
-use rustc_middle::ty::{GeneratorSubsts, SubstsRef};
+use rustc_middle::ty::{GeneratorArgs, GenericArgsRef};
 use rustc_mir_dataflow::impls::{
     MaybeBorrowedLocals, MaybeLiveLocals, MaybeRequiresStorage, MaybeStorageLive,
 };
@@ -194,11 +194,11 @@ fn replace_base<'tcx>(place: &mut Place<'tcx>, new_base: Place<'tcx>, tcx: TyCtx
 const SELF_ARG: Local = Local::from_u32(1);
 
 /// Generator has not been resumed yet.
-const UNRESUMED: usize = GeneratorSubsts::UNRESUMED;
+const UNRESUMED: usize = GeneratorArgs::UNRESUMED;
 /// Generator has returned / is completed.
-const RETURNED: usize = GeneratorSubsts::RETURNED;
+const RETURNED: usize = GeneratorArgs::RETURNED;
 /// Generator has panicked and is poisoned.
-const POISONED: usize = GeneratorSubsts::POISONED;
+const POISONED: usize = GeneratorArgs::POISONED;
 
 /// Number of variants to reserve in generator state. Corresponds to
 /// `UNRESUMED` (beginning of a generator) and `RETURNED`/`POISONED`
@@ -223,7 +223,7 @@ struct TransformVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
     is_async_kind: bool,
     state_adt_ref: AdtDef<'tcx>,
-    state_substs: SubstsRef<'tcx>,
+    state_args: GenericArgsRef<'tcx>,
 
     // The type of the discriminant in the generator struct
     discr_ty: Ty<'tcx>,
@@ -265,7 +265,7 @@ impl<'tcx> TransformVisitor<'tcx> {
             (false, true) => 1,  // Poll::Pending
         });
 
-        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_substs, None, None);
+        let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
 
         // `Poll::Pending`
         if self.is_async_kind && idx == VariantIdx::new(1) {
@@ -431,8 +431,8 @@ fn make_generator_state_argument_pinned<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body
 
     let pin_did = tcx.require_lang_item(LangItem::Pin, Some(body.span));
     let pin_adt_ref = tcx.adt_def(pin_did);
-    let substs = tcx.mk_substs(&[ref_gen_ty.into()]);
-    let pin_ref_gen_ty = Ty::new_adt(tcx, pin_adt_ref, substs);
+    let args = tcx.mk_args(&[ref_gen_ty.into()]);
+    let pin_ref_gen_ty = Ty::new_adt(tcx, pin_adt_ref, args);
 
     // Replace the by ref generator argument
     body.local_decls.raw[1].ty = pin_ref_gen_ty;
@@ -1431,7 +1431,7 @@ pub(crate) fn mir_generator_witnesses<'tcx>(
     // The first argument is the generator type passed by value
     let gen_ty = body.local_decls[ty::CAPTURE_STRUCT_LOCAL].ty;
 
-    // Get the interior types and substs which typeck computed
+    // Get the interior types and args which typeck computed
     let movable = match *gen_ty.kind() {
         ty::Generator(_, _, movability) => movability == hir::Movability::Movable,
         ty::Error(_) => return None,
@@ -1465,14 +1465,14 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         // The first argument is the generator type passed by value
         let gen_ty = body.local_decls.raw[1].ty;
 
-        // Get the discriminant type and substs which typeck computed
+        // Get the discriminant type and args which typeck computed
         let (discr_ty, upvars, interior, movable) = match *gen_ty.kind() {
-            ty::Generator(_, substs, movability) => {
-                let substs = substs.as_generator();
+            ty::Generator(_, args, movability) => {
+                let args = args.as_generator();
                 (
-                    substs.discr_ty(tcx),
-                    substs.upvar_tys().collect::<Vec<_>>(),
-                    substs.witness(),
+                    args.discr_ty(tcx),
+                    args.upvar_tys().collect::<Vec<_>>(),
+                    args.witness(),
                     movability == hir::Movability::Movable,
                 )
             }
@@ -1483,20 +1483,20 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         };
 
         let is_async_kind = matches!(body.generator_kind(), Some(GeneratorKind::Async(_)));
-        let (state_adt_ref, state_substs) = if is_async_kind {
+        let (state_adt_ref, state_args) = if is_async_kind {
             // Compute Poll<return_ty>
             let poll_did = tcx.require_lang_item(LangItem::Poll, None);
             let poll_adt_ref = tcx.adt_def(poll_did);
-            let poll_substs = tcx.mk_substs(&[body.return_ty().into()]);
-            (poll_adt_ref, poll_substs)
+            let poll_args = tcx.mk_args(&[body.return_ty().into()]);
+            (poll_adt_ref, poll_args)
         } else {
             // Compute GeneratorState<yield_ty, return_ty>
             let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
             let state_adt_ref = tcx.adt_def(state_did);
-            let state_substs = tcx.mk_substs(&[yield_ty.into(), body.return_ty().into()]);
-            (state_adt_ref, state_substs)
+            let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
+            (state_adt_ref, state_args)
         };
-        let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_substs);
+        let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args);
 
         // We rename RETURN_PLACE which has type mir.return_ty to new_ret_local
         // RETURN_PLACE then is a fresh unused local with type ret_ty.
@@ -1570,7 +1570,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
             tcx,
             is_async_kind,
             state_adt_ref,
-            state_substs,
+            state_args,
             remap,
             storage_liveness,
             always_live_locals,
diff --git a/compiler/rustc_mir_transform/src/inline.rs b/compiler/rustc_mir_transform/src/inline.rs
index 240beabfc1a98..7860cf7624796 100644
--- a/compiler/rustc_mir_transform/src/inline.rs
+++ b/compiler/rustc_mir_transform/src/inline.rs
@@ -105,7 +105,7 @@ struct Inliner<'tcx> {
     /// Caller codegen attributes.
     codegen_fn_attrs: &'tcx CodegenFnAttrs,
     /// Stack of inlined instances.
-    /// We only check the `DefId` and not the substs because we want to
+    /// We only check the `DefId` and not the args because we want to
     /// avoid inlining cases of polymorphic recursion.
     /// The number of `DefId`s is finite, so checking history is enough
     /// to ensure that we do not loop endlessly while inlining.
@@ -329,11 +329,11 @@ impl<'tcx> Inliner<'tcx> {
         let terminator = bb_data.terminator();
         if let TerminatorKind::Call { ref func, target, fn_span, .. } = terminator.kind {
             let func_ty = func.ty(caller_body, self.tcx);
-            if let ty::FnDef(def_id, substs) = *func_ty.kind() {
-                // To resolve an instance its substs have to be fully normalized.
-                let substs = self.tcx.try_normalize_erasing_regions(self.param_env, substs).ok()?;
+            if let ty::FnDef(def_id, args) = *func_ty.kind() {
+                // To resolve an instance its args have to be fully normalized.
+                let args = self.tcx.try_normalize_erasing_regions(self.param_env, args).ok()?;
                 let callee =
-                    Instance::resolve(self.tcx, self.param_env, def_id, substs).ok().flatten()?;
+                    Instance::resolve(self.tcx, self.param_env, def_id, args).ok().flatten()?;
 
                 if let InstanceDef::Virtual(..) | InstanceDef::Intrinsic(_) = callee.def {
                     return None;
@@ -343,7 +343,7 @@ impl<'tcx> Inliner<'tcx> {
                     return None;
                 }
 
-                let fn_sig = self.tcx.fn_sig(def_id).subst(self.tcx, substs);
+                let fn_sig = self.tcx.fn_sig(def_id).instantiate(self.tcx, args);
                 let source_info = SourceInfo { span: fn_span, ..terminator.source_info };
 
                 return Some(CallSite { callee, fn_sig, block: bb, target, source_info });
@@ -368,7 +368,7 @@ impl<'tcx> Inliner<'tcx> {
         // inlining. This is to ensure that the final crate doesn't have MIR that
         // reference unexported symbols
         if callsite.callee.def_id().is_local() {
-            let is_generic = callsite.callee.substs.non_erasable_generics().next().is_some();
+            let is_generic = callsite.callee.args.non_erasable_generics().next().is_some();
             if !is_generic && !callee_attrs.requests_inline() {
                 return Err("not exported");
             }
@@ -855,8 +855,8 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
             };
 
             let kind = match parent_ty.ty.kind() {
-                &ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                    self.tcx.type_of(def_id).subst(self.tcx, substs).kind()
+                &ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                    self.tcx.type_of(def_id).instantiate(self.tcx, args).kind()
                 }
                 kind => kind,
             };
@@ -869,23 +869,23 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
                     };
                     check_equal(self, *f_ty);
                 }
-                ty::Adt(adt_def, substs) => {
+                ty::Adt(adt_def, args) => {
                     let var = parent_ty.variant_index.unwrap_or(FIRST_VARIANT);
                     let Some(field) = adt_def.variant(var).fields.get(f) else {
                         self.validation = Err("malformed MIR");
                         return;
                     };
-                    check_equal(self, field.ty(self.tcx, substs));
+                    check_equal(self, field.ty(self.tcx, args));
                 }
-                ty::Closure(_, substs) => {
-                    let substs = substs.as_closure();
-                    let Some(f_ty) = substs.upvar_tys().nth(f.as_usize()) else {
+                ty::Closure(_, args) => {
+                    let args = args.as_closure();
+                    let Some(f_ty) = args.upvar_tys().nth(f.as_usize()) else {
                         self.validation = Err("malformed MIR");
                         return;
                     };
                     check_equal(self, f_ty);
                 }
-                &ty::Generator(def_id, substs, _) => {
+                &ty::Generator(def_id, args, _) => {
                     let f_ty = if let Some(var) = parent_ty.variant_index {
                         let gen_body = if def_id == self.callee_body.source.def_id() {
                             self.callee_body
@@ -910,7 +910,7 @@ impl<'tcx> Visitor<'tcx> for CostChecker<'_, 'tcx> {
 
                         f_ty.ty
                     } else {
-                        let Some(f_ty) = substs.as_generator().prefix_tys().nth(f.index()) else {
+                        let Some(f_ty) = args.as_generator().prefix_tys().nth(f.index()) else {
                             self.validation = Err("malformed MIR");
                             return;
                         };
@@ -1130,10 +1130,10 @@ fn try_instance_mir<'tcx>(
 ) -> Result<&'tcx Body<'tcx>, &'static str> {
     match instance {
         ty::InstanceDef::DropGlue(_, Some(ty)) => match ty.kind() {
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 let fields = def.all_fields();
                 for field in fields {
-                    let field_ty = field.ty(tcx, substs);
+                    let field_ty = field.ty(tcx, args);
                     if field_ty.has_param() && field_ty.has_projections() {
                         return Err("cannot build drop shim for polymorphic type");
                     }
diff --git a/compiler/rustc_mir_transform/src/inline/cycle.rs b/compiler/rustc_mir_transform/src/inline/cycle.rs
index 8a10445f8377e..822634129fc2b 100644
--- a/compiler/rustc_mir_transform/src/inline/cycle.rs
+++ b/compiler/rustc_mir_transform/src/inline/cycle.rs
@@ -3,7 +3,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::mir::TerminatorKind;
 use rustc_middle::ty::TypeVisitableExt;
-use rustc_middle::ty::{self, subst::SubstsRef, InstanceDef, TyCtxt};
+use rustc_middle::ty::{self, GenericArgsRef, InstanceDef, TyCtxt};
 use rustc_session::Limit;
 
 // FIXME: check whether it is cheaper to precompute the entire call graph instead of invoking
@@ -43,16 +43,16 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
         recursion_limit: Limit,
     ) -> bool {
         trace!(%caller);
-        for &(callee, substs) in tcx.mir_inliner_callees(caller.def) {
-            let Ok(substs) = caller.try_subst_mir_and_normalize_erasing_regions(
+        for &(callee, args) in tcx.mir_inliner_callees(caller.def) {
+            let Ok(args) = caller.try_subst_mir_and_normalize_erasing_regions(
                 tcx,
                 param_env,
-                ty::EarlyBinder::bind(substs),
+                ty::EarlyBinder::bind(args),
             ) else {
-                trace!(?caller, ?param_env, ?substs, "cannot normalize, skipping");
+                trace!(?caller, ?param_env, ?args, "cannot normalize, skipping");
                 continue;
             };
-            let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, substs) else {
+            let Ok(Some(callee)) = ty::Instance::resolve(tcx, param_env, callee, args) else {
                 trace!(?callee, "cannot resolve, skipping");
                 continue;
             };
@@ -147,7 +147,7 @@ pub(crate) fn mir_callgraph_reachable<'tcx>(
 pub(crate) fn mir_inliner_callees<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance: ty::InstanceDef<'tcx>,
-) -> &'tcx [(DefId, SubstsRef<'tcx>)] {
+) -> &'tcx [(DefId, GenericArgsRef<'tcx>)] {
     let steal;
     let guard;
     let body = match (instance, instance.def_id().as_local()) {
@@ -165,7 +165,7 @@ pub(crate) fn mir_inliner_callees<'tcx>(
         if let TerminatorKind::Call { func, .. } = &terminator.kind {
             let ty = func.ty(&body.local_decls, tcx);
             let call = match ty.kind() {
-                ty::FnDef(def_id, substs) => (*def_id, *substs),
+                ty::FnDef(def_id, args) => (*def_id, *args),
                 _ => continue,
             };
             calls.insert(call);
diff --git a/compiler/rustc_mir_transform/src/instsimplify.rs b/compiler/rustc_mir_transform/src/instsimplify.rs
index a6af2eabda1f8..a430f8da35cf8 100644
--- a/compiler/rustc_mir_transform/src/instsimplify.rs
+++ b/compiler/rustc_mir_transform/src/instsimplify.rs
@@ -5,7 +5,7 @@ use crate::MirPass;
 use rustc_hir::Mutability;
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::ValidityRequirement;
-use rustc_middle::ty::{self, ParamEnv, SubstsRef, Ty, TyCtxt};
+use rustc_middle::ty::{self, GenericArgsRef, ParamEnv, Ty, TyCtxt};
 use rustc_span::symbol::Symbol;
 use rustc_target::abi::FieldIdx;
 
@@ -163,14 +163,14 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
                 }
 
                 // Transmuting a transparent struct/union to a field's type is a projection
-                if let ty::Adt(adt_def, substs) = operand_ty.kind()
+                if let ty::Adt(adt_def, args) = operand_ty.kind()
                     && adt_def.repr().transparent()
                     && (adt_def.is_struct() || adt_def.is_union())
                     && let Some(place) = operand.place()
                 {
                     let variant = adt_def.non_enum_variant();
                     for (i, field) in variant.fields.iter().enumerate() {
-                        let field_ty = field.ty(self.tcx, substs);
+                        let field_ty = field.ty(self.tcx, args);
                         if field_ty == *cast_ty {
                             let place = place.project_deeper(&[ProjectionElem::Field(FieldIdx::from_usize(i), *cast_ty)], self.tcx);
                             let operand = if operand.is_move() { Operand::Move(place) } else { Operand::Copy(place) };
@@ -201,10 +201,10 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         let Some(destination_block) = *target else { return };
 
         // Only bother looking more if it's easy to know what we're calling
-        let Some((fn_def_id, fn_substs)) = func.const_fn_def() else { return };
+        let Some((fn_def_id, fn_args)) = func.const_fn_def() else { return };
 
         // Clone needs one subst, so we can cheaply rule out other stuff
-        if fn_substs.len() != 1 {
+        if fn_args.len() != 1 {
             return;
         }
 
@@ -226,7 +226,7 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
         if !self.tcx.consider_optimizing(|| {
             format!(
                 "InstSimplify - Call: {:?} SourceInfo: {:?}",
-                (fn_def_id, fn_substs),
+                (fn_def_id, fn_args),
                 terminator.source_info
             )
         }) {
@@ -259,14 +259,14 @@ impl<'tcx> InstSimplifyContext<'tcx, '_> {
             return;
         };
         let func_ty = func.ty(self.local_decls, self.tcx);
-        let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(self.tcx, func_ty) else {
+        let Some((intrinsic_name, args)) = resolve_rust_intrinsic(self.tcx, func_ty) else {
             return;
         };
         // The intrinsics we are interested in have one generic parameter
-        if substs.is_empty() {
+        if args.is_empty() {
             return;
         }
-        let ty = substs.type_at(0);
+        let ty = args.type_at(0);
 
         let known_is_valid = intrinsic_assert_panics(self.tcx, self.param_env, ty, intrinsic_name);
         match known_is_valid {
@@ -297,10 +297,10 @@ fn intrinsic_assert_panics<'tcx>(
 fn resolve_rust_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     func_ty: Ty<'tcx>,
-) -> Option<(Symbol, SubstsRef<'tcx>)> {
-    if let ty::FnDef(def_id, substs) = *func_ty.kind() {
+) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
+    if let ty::FnDef(def_id, args) = *func_ty.kind() {
         if tcx.is_intrinsic(def_id) {
-            return Some((tcx.item_name(def_id), substs));
+            return Some((tcx.item_name(def_id), args));
         }
     }
     None
diff --git a/compiler/rustc_mir_transform/src/large_enums.rs b/compiler/rustc_mir_transform/src/large_enums.rs
index 8ed4706e17239..19108dabdf417 100644
--- a/compiler/rustc_mir_transform/src/large_enums.rs
+++ b/compiler/rustc_mir_transform/src/large_enums.rs
@@ -48,7 +48,7 @@ impl EnumSizeOpt {
         alloc_cache: &mut FxHashMap<Ty<'tcx>, AllocId>,
     ) -> Option<(AdtDef<'tcx>, usize, AllocId)> {
         let adt_def = match ty.kind() {
-            ty::Adt(adt_def, _substs) if adt_def.is_enum() => adt_def,
+            ty::Adt(adt_def, _args) if adt_def.is_enum() => adt_def,
             _ => return None,
         };
         let layout = tcx.layout_of(param_env.and(ty)).ok()?;
diff --git a/compiler/rustc_mir_transform/src/lower_intrinsics.rs b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
index eccc59f923d18..d1ecfe9f8512d 100644
--- a/compiler/rustc_mir_transform/src/lower_intrinsics.rs
+++ b/compiler/rustc_mir_transform/src/lower_intrinsics.rs
@@ -2,7 +2,7 @@
 
 use crate::{errors, MirPass};
 use rustc_middle::mir::*;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::Span;
@@ -19,7 +19,8 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                 &mut terminator.kind
             {
                 let func_ty = func.ty(local_decls, tcx);
-                let Some((intrinsic_name, substs)) = resolve_rust_intrinsic(tcx, func_ty) else {
+                let Some((intrinsic_name, generic_args)) = resolve_rust_intrinsic(tcx, func_ty)
+                else {
                     continue;
                 };
                 match intrinsic_name {
@@ -149,7 +150,7 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
                     }
                     sym::size_of | sym::min_align_of => {
                         if let Some(target) = *target {
-                            let tp_ty = substs.type_at(0);
+                            let tp_ty = generic_args.type_at(0);
                             let null_op = match intrinsic_name {
                                 sym::size_of => NullOp::SizeOf,
                                 sym::min_align_of => NullOp::AlignOf,
@@ -317,10 +318,10 @@ impl<'tcx> MirPass<'tcx> for LowerIntrinsics {
 fn resolve_rust_intrinsic<'tcx>(
     tcx: TyCtxt<'tcx>,
     func_ty: Ty<'tcx>,
-) -> Option<(Symbol, SubstsRef<'tcx>)> {
-    if let ty::FnDef(def_id, substs) = *func_ty.kind() {
+) -> Option<(Symbol, GenericArgsRef<'tcx>)> {
+    if let ty::FnDef(def_id, args) = *func_ty.kind() {
         if tcx.is_intrinsic(def_id) {
-            return Some((tcx.item_name(def_id), substs));
+            return Some((tcx.item_name(def_id), args));
         }
     }
     None
diff --git a/compiler/rustc_mir_transform/src/remove_uninit_drops.rs b/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
index d46690cc8b975..6f9edd07d7361 100644
--- a/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
+++ b/compiler/rustc_mir_transform/src/remove_uninit_drops.rs
@@ -1,6 +1,6 @@
 use rustc_index::bit_set::ChunkedBitSet;
 use rustc_middle::mir::{Body, TerminatorKind};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, ParamEnv, Ty, TyCtxt, VariantDef};
 use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
 use rustc_mir_dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
@@ -98,7 +98,7 @@ fn is_needs_drop_and_init<'tcx>(
     // This pass is only needed for const-checking, so it doesn't handle as many cases as
     // `DropCtxt::open_drop`, since they aren't relevant in a const-context.
     match ty.kind() {
-        ty::Adt(adt, substs) => {
+        ty::Adt(adt, args) => {
             let dont_elaborate = adt.is_union() || adt.is_manually_drop() || adt.has_dtor(tcx);
             if dont_elaborate {
                 return true;
@@ -118,7 +118,7 @@ fn is_needs_drop_and_init<'tcx>(
                     let downcast =
                         move_path_children_matching(move_data, mpi, |x| x.is_downcast_to(vid));
                     let Some(dc_mpi) = downcast else {
-                        return variant_needs_drop(tcx, param_env, substs, variant);
+                        return variant_needs_drop(tcx, param_env, args, variant);
                     };
 
                     dc_mpi
@@ -130,7 +130,7 @@ fn is_needs_drop_and_init<'tcx>(
                     .fields
                     .iter()
                     .enumerate()
-                    .map(|(f, field)| (FieldIdx::from_usize(f), field.ty(tcx, substs), mpi))
+                    .map(|(f, field)| (FieldIdx::from_usize(f), field.ty(tcx, args), mpi))
                     .any(field_needs_drop_and_init)
             })
         }
@@ -148,11 +148,11 @@ fn is_needs_drop_and_init<'tcx>(
 fn variant_needs_drop<'tcx>(
     tcx: TyCtxt<'tcx>,
     param_env: ParamEnv<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     variant: &VariantDef,
 ) -> bool {
     variant.fields.iter().any(|field| {
-        let f_ty = field.ty(tcx, substs);
+        let f_ty = field.ty(tcx, args);
         f_ty.needs_drop(tcx, param_env)
     })
 }
diff --git a/compiler/rustc_mir_transform/src/remove_zsts.rs b/compiler/rustc_mir_transform/src/remove_zsts.rs
index 1f37f03cff1ca..1ba9ad8753751 100644
--- a/compiler/rustc_mir_transform/src/remove_zsts.rs
+++ b/compiler/rustc_mir_transform/src/remove_zsts.rs
@@ -15,7 +15,7 @@ impl<'tcx> MirPass<'tcx> for RemoveZsts {
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         // Avoid query cycles (generators require optimized MIR for layout).
-        if tcx.type_of(body.source.def_id()).subst_identity().is_generator() {
+        if tcx.type_of(body.source.def_id()).instantiate_identity().is_generator() {
             return;
         }
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
diff --git a/compiler/rustc_mir_transform/src/shim.rs b/compiler/rustc_mir_transform/src/shim.rs
index b176db3c9e0fd..5e8ba4f544c97 100644
--- a/compiler/rustc_mir_transform/src/shim.rs
+++ b/compiler/rustc_mir_transform/src/shim.rs
@@ -3,8 +3,8 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::lang_items::LangItem;
 use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::InternalSubsts;
-use rustc_middle::ty::{self, EarlyBinder, GeneratorSubsts, Ty, TyCtxt};
+use rustc_middle::ty::GenericArgs;
+use rustc_middle::ty::{self, EarlyBinder, GeneratorArgs, Ty, TyCtxt};
 use rustc_target::abi::{FieldIdx, VariantIdx, FIRST_VARIANT};
 
 use rustc_index::{Idx, IndexVec};
@@ -69,9 +69,9 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
         ty::InstanceDef::DropGlue(def_id, ty) => {
             // FIXME(#91576): Drop shims for generators aren't subject to the MIR passes at the end
             // of this function. Is this intentional?
-            if let Some(ty::Generator(gen_def_id, substs, _)) = ty.map(Ty::kind) {
+            if let Some(ty::Generator(gen_def_id, args, _)) = ty.map(Ty::kind) {
                 let body = tcx.optimized_mir(*gen_def_id).generator_drop().unwrap();
-                let body = EarlyBinder::bind(body.clone()).subst(tcx, substs);
+                let body = EarlyBinder::bind(body.clone()).instantiate(tcx, args);
                 debug!("make_shim({:?}) = {:?}", instance, body);
                 return body;
             }
@@ -160,12 +160,12 @@ fn build_drop_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, ty: Option<Ty<'tcx>>)
 
     assert!(!matches!(ty, Some(ty) if ty.is_generator()));
 
-    let substs = if let Some(ty) = ty {
-        tcx.mk_substs(&[ty.into()])
+    let args = if let Some(ty) = ty {
+        tcx.mk_args(&[ty.into()])
     } else {
-        InternalSubsts::identity_for_item(tcx, def_id)
+        GenericArgs::identity_for_item(tcx, def_id)
     };
-    let sig = tcx.fn_sig(def_id).subst(tcx, substs);
+    let sig = tcx.fn_sig(def_id).instantiate(tcx, args);
     let sig = tcx.erase_late_bound_regions(sig);
     let span = tcx.def_span(def_id);
 
@@ -377,12 +377,10 @@ fn build_clone_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -
 
     match self_ty.kind() {
         _ if is_copy => builder.copy_shim(),
-        ty::Closure(_, substs) => {
-            builder.tuple_like_shim(dest, src, substs.as_closure().upvar_tys())
-        }
+        ty::Closure(_, args) => builder.tuple_like_shim(dest, src, args.as_closure().upvar_tys()),
         ty::Tuple(..) => builder.tuple_like_shim(dest, src, self_ty.tuple_fields()),
-        ty::Generator(gen_def_id, substs, hir::Movability::Movable) => {
-            builder.generator_shim(dest, src, *gen_def_id, substs.as_generator())
+        ty::Generator(gen_def_id, args, hir::Movability::Movable) => {
+            builder.generator_shim(dest, src, *gen_def_id, args.as_generator())
         }
         _ => bug!("clone shim for `{:?}` which is not `Copy` and is not an aggregate", self_ty),
     };
@@ -404,7 +402,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         // we must subst the self_ty because it's
         // otherwise going to be TySelf and we can't index
         // or access fields of a Place of type TySelf.
-        let sig = tcx.fn_sig(def_id).subst(tcx, &[self_ty.into()]);
+        let sig = tcx.fn_sig(def_id).instantiate(tcx, &[self_ty.into()]);
         let sig = tcx.erase_late_bound_regions(sig);
         let span = tcx.def_span(def_id);
 
@@ -587,17 +585,17 @@ impl<'tcx> CloneShimBuilder<'tcx> {
         dest: Place<'tcx>,
         src: Place<'tcx>,
         gen_def_id: DefId,
-        substs: GeneratorSubsts<'tcx>,
+        args: GeneratorArgs<'tcx>,
     ) {
         self.block(vec![], TerminatorKind::Goto { target: self.block_index_offset(3) }, false);
         let unwind = self.block(vec![], TerminatorKind::Resume, true);
         // This will get overwritten with a switch once we know the target blocks
         let switch = self.block(vec![], TerminatorKind::Unreachable, false);
-        let unwind = self.clone_fields(dest, src, switch, unwind, substs.upvar_tys());
+        let unwind = self.clone_fields(dest, src, switch, unwind, args.upvar_tys());
         let target = self.block(vec![], TerminatorKind::Return, false);
         let unreachable = self.block(vec![], TerminatorKind::Unreachable, false);
-        let mut cases = Vec::with_capacity(substs.state_tys(gen_def_id, self.tcx).count());
-        for (index, state_tys) in substs.state_tys(gen_def_id, self.tcx).enumerate() {
+        let mut cases = Vec::with_capacity(args.state_tys(gen_def_id, self.tcx).count());
+        for (index, state_tys) in args.state_tys(gen_def_id, self.tcx).enumerate() {
             let variant_index = VariantIdx::new(index);
             let dest = self.tcx.mk_place_downcast_unnamed(dest, variant_index);
             let src = self.tcx.mk_place_downcast_unnamed(src, variant_index);
@@ -613,7 +611,7 @@ impl<'tcx> CloneShimBuilder<'tcx> {
             cases.push((index as u128, start_block));
             let _final_cleanup_block = self.clone_fields(dest, src, target, unwind, state_tys);
         }
-        let discr_ty = substs.discr_ty(self.tcx);
+        let discr_ty = args.discr_ty(self.tcx);
         let temp = self.make_place(Mutability::Mut, discr_ty);
         let rvalue = Rvalue::Discriminant(src);
         let statement = self.make_statement(StatementKind::Assign(Box::new((temp, rvalue))));
@@ -642,7 +640,7 @@ fn build_call_shim<'tcx>(
     // `FnPtrShim` contains the fn pointer type that a call shim is being built for - this is used
     // to substitute into the signature of the shim. It is not necessary for users of this
     // MIR body to perform further substitutions (see `InstanceDef::has_polymorphic_mir_body`).
-    let (sig_substs, untuple_args) = if let ty::InstanceDef::FnPtrShim(_, ty) = instance {
+    let (sig_args, untuple_args) = if let ty::InstanceDef::FnPtrShim(_, ty) = instance {
         let sig = tcx.erase_late_bound_regions(ty.fn_sig(tcx));
 
         let untuple_args = sig.inputs();
@@ -659,11 +657,11 @@ fn build_call_shim<'tcx>(
     let sig = tcx.fn_sig(def_id);
     let sig = sig.map_bound(|sig| tcx.erase_late_bound_regions(sig));
 
-    assert_eq!(sig_substs.is_some(), !instance.has_polymorphic_mir_body());
-    let mut sig = if let Some(sig_substs) = sig_substs {
-        sig.subst(tcx, &sig_substs)
+    assert_eq!(sig_args.is_some(), !instance.has_polymorphic_mir_body());
+    let mut sig = if let Some(sig_args) = sig_args {
+        sig.instantiate(tcx, &sig_args)
     } else {
-        sig.subst_identity()
+        sig.instantiate_identity()
     };
 
     if let CallKind::Indirect(fnty) = call_kind {
@@ -751,7 +749,7 @@ fn build_call_shim<'tcx>(
 
         // `FnDef` call with optional receiver.
         CallKind::Direct(def_id) => {
-            let ty = tcx.type_of(def_id).subst_identity();
+            let ty = tcx.type_of(def_id).instantiate_identity();
             (
                 Operand::Constant(Box::new(Constant {
                     span,
@@ -868,12 +866,12 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
     // Normalize the sig.
     let sig = tcx
         .fn_sig(ctor_id)
-        .subst_identity()
+        .instantiate_identity()
         .no_bound_vars()
         .expect("LBR in ADT constructor signature");
     let sig = tcx.normalize_erasing_regions(param_env, sig);
 
-    let ty::Adt(adt_def, substs) = sig.output().kind() else {
+    let ty::Adt(adt_def, args) = sig.output().kind() else {
         bug!("unexpected type for ADT ctor {:?}", sig.output());
     };
 
@@ -896,7 +894,7 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
     // return;
     debug!("build_ctor: variant_index={:?}", variant_index);
 
-    let kind = AggregateKind::Adt(adt_def.did(), variant_index, substs, None, None);
+    let kind = AggregateKind::Adt(adt_def.did(), variant_index, args, None, None);
     let variant = adt_def.variant(variant_index);
     let statement = Statement {
         kind: StatementKind::Assign(Box::new((
@@ -941,7 +939,7 @@ pub fn build_adt_ctor(tcx: TyCtxt<'_>, ctor_id: DefId) -> Body<'_> {
 fn build_fn_ptr_addr_shim<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Body<'tcx> {
     assert!(matches!(self_ty.kind(), ty::FnPtr(..)), "expected fn ptr, found {self_ty}");
     let span = tcx.def_span(def_id);
-    let Some(sig) = tcx.fn_sig(def_id).subst(tcx, &[self_ty.into()]).no_bound_vars() else {
+    let Some(sig) = tcx.fn_sig(def_id).instantiate(tcx, &[self_ty.into()]).no_bound_vars() else {
         span_bug!(span, "FnPtr::addr with bound vars for `{self_ty}`");
     };
     let locals = local_decls_for_sig(&sig, span);
diff --git a/compiler/rustc_mir_transform/src/sroa.rs b/compiler/rustc_mir_transform/src/sroa.rs
index c8fa7fc4b2a8a..e66ae8ff8845f 100644
--- a/compiler/rustc_mir_transform/src/sroa.rs
+++ b/compiler/rustc_mir_transform/src/sroa.rs
@@ -20,7 +20,7 @@ impl<'tcx> MirPass<'tcx> for ScalarReplacementOfAggregates {
         debug!(def_id = ?body.source.def_id());
 
         // Avoid query cycles (generators require optimized MIR for layout).
-        if tcx.type_of(body.source.def_id()).subst_identity().is_generator() {
+        if tcx.type_of(body.source.def_id()).instantiate_identity().is_generator() {
             return;
         }
 
@@ -64,7 +64,7 @@ fn escaping_locals<'tcx>(
         if ty.is_union() || ty.is_enum() {
             return true;
         }
-        if let ty::Adt(def, _substs) = ty.kind() {
+        if let ty::Adt(def, _args) = ty.kind() {
             if def.repr().flags.contains(ReprFlags::IS_SIMD) {
                 // Exclude #[repr(simd)] types so that they are not de-optimized into an array
                 return true;
diff --git a/compiler/rustc_monomorphize/src/collector.rs b/compiler/rustc_monomorphize/src/collector.rs
index 242269e9d1aa4..5b678d4ba78b4 100644
--- a/compiler/rustc_monomorphize/src/collector.rs
+++ b/compiler/rustc_monomorphize/src/collector.rs
@@ -178,11 +178,11 @@ use rustc_middle::mir::{self, Local, Location};
 use rustc_middle::query::TyCtxtAt;
 use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCoercion};
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
 use rustc_middle::ty::{
     self, GenericParamDefKind, Instance, InstanceDef, Ty, TyCtxt, TypeFoldable, TypeVisitableExt,
     VtblEntry,
 };
+use rustc_middle::ty::{GenericArgKind, GenericArgs};
 use rustc_middle::{middle::codegen_fn_attrs::CodegenFnAttrFlags, mir::visit::TyContext};
 use rustc_session::config::EntryFnType;
 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
@@ -393,7 +393,7 @@ fn collect_items_rec<'tcx>(
                     starting_item.span,
                     MonoItem::Fn(Instance {
                         def: InstanceDef::ThreadLocalShim(def_id),
-                        substs: InternalSubsts::empty(),
+                        args: GenericArgs::empty(),
                     }),
                 ));
             }
@@ -555,7 +555,7 @@ fn check_recursion_limit<'tcx>(
 
 fn check_type_length_limit<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) {
     let type_length = instance
-        .substs
+        .args
         .iter()
         .flat_map(|arg| arg.walk())
         .filter(|arg| match arg.unpack() {
@@ -659,11 +659,11 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirUsedCollector<'a, 'tcx> {
                 let source_ty = operand.ty(self.body, self.tcx);
                 let source_ty = self.monomorphize(source_ty);
                 match *source_ty.kind() {
-                    ty::Closure(def_id, substs) => {
+                    ty::Closure(def_id, args) => {
                         let instance = Instance::resolve_closure(
                             self.tcx,
                             def_id,
-                            substs,
+                            args,
                             ty::ClosureKind::FnOnce,
                         )
                         .expect("failed to normalize and resolve closure during codegen");
@@ -875,12 +875,11 @@ fn visit_fn_use<'tcx>(
     source: Span,
     output: &mut MonoItems<'tcx>,
 ) {
-    if let ty::FnDef(def_id, substs) = *ty.kind() {
+    if let ty::FnDef(def_id, args) = *ty.kind() {
         let instance = if is_direct_call {
-            ty::Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
+            ty::Instance::expect_resolve(tcx, ty::ParamEnv::reveal_all(), def_id, args)
         } else {
-            match ty::Instance::resolve_for_fn_ptr(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
-            {
+            match ty::Instance::resolve_for_fn_ptr(tcx, ty::ParamEnv::reveal_all(), def_id, args) {
                 Some(instance) => instance,
                 _ => bug!("failed to resolve instance for {ty}"),
             }
@@ -1043,7 +1042,7 @@ fn find_vtable_types_for_unsizing<'tcx>(
         // T as dyn* Trait
         (_, &ty::Dynamic(_, _, ty::DynStar)) => ptr_vtable(source_ty, target_ty),
 
-        (&ty::Adt(source_adt_def, source_substs), &ty::Adt(target_adt_def, target_substs)) => {
+        (&ty::Adt(source_adt_def, source_args), &ty::Adt(target_adt_def, target_args)) => {
             assert_eq!(source_adt_def, target_adt_def);
 
             let CustomCoerceUnsized::Struct(coerce_index) =
@@ -1059,8 +1058,8 @@ fn find_vtable_types_for_unsizing<'tcx>(
 
             find_vtable_types_for_unsizing(
                 tcx,
-                source_fields[coerce_index].ty(*tcx, source_substs),
-                target_fields[coerce_index].ty(*tcx, target_substs),
+                source_fields[coerce_index].ty(*tcx, source_args),
+                target_fields[coerce_index].ty(*tcx, target_args),
             )
         }
         _ => bug!(
@@ -1245,7 +1244,7 @@ impl<'v> RootCollector<'_, 'v> {
             self.tcx,
             ty::ParamEnv::reveal_all(),
             start_def_id,
-            self.tcx.mk_substs(&[main_ret_ty.into()]),
+            self.tcx.mk_args(&[main_ret_ty.into()]),
         )
         .unwrap()
         .unwrap();
@@ -1292,8 +1291,8 @@ fn create_mono_items_for_default_impls<'tcx>(
             )
         }
     };
-    let impl_substs = InternalSubsts::for_item(tcx, item.owner_id.to_def_id(), only_region_params);
-    let trait_ref = trait_ref.subst(tcx, impl_substs);
+    let impl_args = GenericArgs::for_item(tcx, item.owner_id.to_def_id(), only_region_params);
+    let trait_ref = trait_ref.instantiate(tcx, impl_args);
 
     // Unlike 'lazy' monomorphization that begins by collecting items transitively
     // called by `main` or other global items, when eagerly monomorphizing impl
@@ -1304,7 +1303,7 @@ fn create_mono_items_for_default_impls<'tcx>(
     // consider higher-ranked predicates such as `for<'a> &'a mut [u8]: Copy` to
     // be trivially false. We must now check that the impl has no impossible-to-satisfy
     // predicates.
-    if tcx.subst_and_check_impossible_predicates((item.owner_id.to_def_id(), impl_substs)) {
+    if tcx.subst_and_check_impossible_predicates((item.owner_id.to_def_id(), impl_args)) {
         return;
     }
 
@@ -1322,8 +1321,8 @@ fn create_mono_items_for_default_impls<'tcx>(
 
         // As mentioned above, the method is legal to eagerly instantiate if it
         // only has lifetime substitutions. This is validated by
-        let substs = trait_ref.substs.extend_to(tcx, method.def_id, only_region_params);
-        let instance = ty::Instance::expect_resolve(tcx, param_env, method.def_id, substs);
+        let args = trait_ref.args.extend_to(tcx, method.def_id, only_region_params);
+        let instance = ty::Instance::expect_resolve(tcx, param_env, method.def_id, args);
 
         let mono_item = create_fn_mono_item(tcx, instance, DUMMY_SP);
         if mono_item.node.is_instantiable(tcx) && should_codegen_locally(tcx, &instance) {
diff --git a/compiler/rustc_monomorphize/src/partitioning.rs b/compiler/rustc_monomorphize/src/partitioning.rs
index da76cf2236c70..391666554bb65 100644
--- a/compiler/rustc_monomorphize/src/partitioning.rs
+++ b/compiler/rustc_monomorphize/src/partitioning.rs
@@ -572,7 +572,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
             // DefId, we use the location of the impl after all.
 
             if tcx.trait_of_item(def_id).is_some() {
-                let self_ty = instance.substs.type_at(0);
+                let self_ty = instance.args.type_at(0);
                 // This is a default implementation of a trait method.
                 return characteristic_def_id_of_type(self_ty).or(Some(def_id));
             }
@@ -592,7 +592,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
                 if !tcx.sess.opts.unstable_opts.polymorphize || !instance.has_param() {
                     // This is a method within an impl, find out what the self-type is:
                     let impl_self_ty = tcx.subst_and_normalize_erasing_regions(
-                        instance.substs,
+                        instance.args,
                         ty::ParamEnv::reveal_all(),
                         tcx.type_of(impl_def_id),
                     );
@@ -745,7 +745,7 @@ fn mono_item_visibility<'tcx>(
         return Visibility::Hidden;
     }
 
-    let is_generic = instance.substs.non_erasable_generics().next().is_some();
+    let is_generic = instance.args.non_erasable_generics().next().is_some();
 
     // Upstream `DefId` instances get different handling than local ones.
     let Some(def_id) = def_id.as_local() else {
diff --git a/compiler/rustc_monomorphize/src/polymorphize.rs b/compiler/rustc_monomorphize/src/polymorphize.rs
index aa2ce65e4cc03..d31bf2072b1bf 100644
--- a/compiler/rustc_monomorphize/src/polymorphize.rs
+++ b/compiler/rustc_monomorphize/src/polymorphize.rs
@@ -14,9 +14,8 @@ use rustc_middle::mir::{
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{
     self,
-    subst::SubstsRef,
     visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor},
-    Const, Ty, TyCtxt, UnusedGenericParams,
+    Const, GenericArgsRef, Ty, TyCtxt, UnusedGenericParams,
 };
 use rustc_span::symbol::sym;
 use std::ops::ControlFlow;
@@ -229,12 +228,12 @@ struct MarkUsedGenericParams<'a, 'tcx> {
 impl<'a, 'tcx> MarkUsedGenericParams<'a, 'tcx> {
     /// Invoke `unused_generic_params` on a body contained within the current item (e.g.
     /// a closure, generator or constant).
-    #[instrument(level = "debug", skip(self, def_id, substs))]
-    fn visit_child_body(&mut self, def_id: DefId, substs: SubstsRef<'tcx>) {
+    #[instrument(level = "debug", skip(self, def_id, args))]
+    fn visit_child_body(&mut self, def_id: DefId, args: GenericArgsRef<'tcx>) {
         let instance = ty::InstanceDef::Item(def_id);
         let unused = self.tcx.unused_generic_params(instance);
         debug!(?self.unused_parameters, ?unused);
-        for (i, arg) in substs.iter().enumerate() {
+        for (i, arg) in args.iter().enumerate() {
             let i = i.try_into().unwrap();
             if unused.is_used(i) {
                 arg.visit_with(self);
@@ -252,9 +251,9 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkUsedGenericParams<'a, 'tcx> {
             if matches!(def_kind, DefKind::Closure | DefKind::Generator) {
                 // Skip visiting the closure/generator that is currently being processed. This only
                 // happens because the first argument to the closure is a reference to itself and
-                // that will call `visit_substs`, resulting in each generic parameter captured being
+                // that will call `visit_args`, resulting in each generic parameter captured being
                 // considered used by default.
-                debug!("skipping closure substs");
+                debug!("skipping closure args");
                 return;
             }
         }
@@ -267,12 +266,12 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkUsedGenericParams<'a, 'tcx> {
             ConstantKind::Ty(c) => {
                 c.visit_with(self);
             }
-            ConstantKind::Unevaluated(mir::UnevaluatedConst { def, substs: _, promoted }, ty) => {
+            ConstantKind::Unevaluated(mir::UnevaluatedConst { def, args: _, promoted }, ty) => {
                 // Avoid considering `T` unused when constants are of the form:
                 //   `<Self as Foo<T>>::foo::promoted[p]`
                 if let Some(p) = promoted {
                     if self.def_id == def && !self.tcx.generics_of(def).has_self {
-                        // If there is a promoted, don't look at the substs - since it will always contain
+                        // If there is a promoted, don't look at the args - since it will always contain
                         // the generic parameters, instead, traverse the promoted MIR.
                         let promoted = self.tcx.promoted_mir(def);
                         self.visit_body(&promoted[p]);
@@ -303,10 +302,10 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for MarkUsedGenericParams<'a, 'tcx> {
                 self.unused_parameters.mark_used(param.index);
                 ControlFlow::Continue(())
             }
-            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs })
+            ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args })
                 if matches!(self.tcx.def_kind(def), DefKind::AnonConst) =>
             {
-                self.visit_child_body(def, substs);
+                self.visit_child_body(def, args);
                 ControlFlow::Continue(())
             }
             _ => c.super_visit_with(self),
@@ -320,7 +319,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for MarkUsedGenericParams<'a, 'tcx> {
         }
 
         match *ty.kind() {
-            ty::Closure(def_id, substs) | ty::Generator(def_id, substs, ..) => {
+            ty::Closure(def_id, args) | ty::Generator(def_id, args, ..) => {
                 debug!(?def_id);
                 // Avoid cycle errors with generators.
                 if def_id == self.def_id {
@@ -329,7 +328,7 @@ impl<'a, 'tcx> TypeVisitor<TyCtxt<'tcx>> for MarkUsedGenericParams<'a, 'tcx> {
 
                 // Consider any generic parameters used by any closures/generators as used in the
                 // parent.
-                self.visit_child_body(def_id, substs);
+                self.visit_child_body(def_id, args);
                 ControlFlow::Continue(())
             }
             ty::Param(param) => {
diff --git a/compiler/rustc_monomorphize/src/util.rs b/compiler/rustc_monomorphize/src/util.rs
index f6a80b0431fc3..a3433d3d13dba 100644
--- a/compiler/rustc_monomorphize/src/util.rs
+++ b/compiler/rustc_monomorphize/src/util.rs
@@ -27,12 +27,12 @@ pub(crate) fn dump_closure_profile<'tcx>(tcx: TyCtxt<'tcx>, closure_instance: In
             typeck_results.closure_size_eval[&closure_def_id];
 
         let before_feature_tys = tcx.subst_and_normalize_erasing_regions(
-            closure_instance.substs,
+            closure_instance.args,
             param_env,
             ty::EarlyBinder::bind(before_feature_tys),
         );
         let after_feature_tys = tcx.subst_and_normalize_erasing_regions(
-            closure_instance.substs,
+            closure_instance.args,
             param_env,
             ty::EarlyBinder::bind(after_feature_tys),
         );
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index c93d65b02f9fb..ee14ffa6da8c1 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -2120,10 +2120,10 @@ impl CheckAttrVisitor<'_> {
         let ocx = ObligationCtxt::new(&infcx);
 
         let span = tcx.def_span(def_id);
-        let fresh_substs = infcx.fresh_substs_for_item(span, def_id.to_def_id());
+        let fresh_args = infcx.fresh_args_for_item(span, def_id.to_def_id());
         let sig = tcx.liberate_late_bound_regions(
             def_id.to_def_id(),
-            tcx.fn_sig(def_id).subst(tcx, fresh_substs),
+            tcx.fn_sig(def_id).instantiate(tcx, fresh_args),
         );
 
         let mut cause = ObligationCause::misc(span, def_id);
diff --git a/compiler/rustc_passes/src/dead.rs b/compiler/rustc_passes/src/dead.rs
index d5ac1cd9ce335..8cab487dd84e9 100644
--- a/compiler/rustc_passes/src/dead.rs
+++ b/compiler/rustc_passes/src/dead.rs
@@ -304,7 +304,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
             if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of)
                 && self.tcx.has_attr(trait_of, sym::rustc_trivial_field_reads)
             {
-                let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap().subst_identity();
+                let trait_ref = self.tcx.impl_trait_ref(impl_of).unwrap().instantiate_identity();
                 if let ty::Adt(adt_def, _) = trait_ref.self_ty().kind()
                     && let Some(adt_def_id) = adt_def.did().as_local()
                 {
@@ -353,7 +353,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
                     //// This is done to handle the case where, for example, the static
                     //// method of a private type is used, but the type itself is never
                     //// called directly.
-                    let self_ty = self.tcx.type_of(item).subst_identity();
+                    let self_ty = self.tcx.type_of(item).instantiate_identity();
                     match *self_ty.kind() {
                         ty::Adt(def, _) => self.check_def_id(def.did()),
                         ty::Foreign(did) => self.check_def_id(did),
@@ -707,7 +707,7 @@ impl<'tcx> DeadVisitor<'tcx> {
         if self.live_symbols.contains(&field.did.expect_local()) {
             return ShouldWarnAboutField::No;
         }
-        let field_type = self.tcx.type_of(field.did).subst_identity();
+        let field_type = self.tcx.type_of(field.did).instantiate_identity();
         if field_type.is_phantom_data() {
             return ShouldWarnAboutField::No;
         }
diff --git a/compiler/rustc_passes/src/layout_test.rs b/compiler/rustc_passes/src/layout_test.rs
index 098107f8f234d..794dbda3688c3 100644
--- a/compiler/rustc_passes/src/layout_test.rs
+++ b/compiler/rustc_passes/src/layout_test.rs
@@ -29,7 +29,7 @@ pub fn test_layout(tcx: TyCtxt<'_>) {
 fn dump_layout_of(tcx: TyCtxt<'_>, item_def_id: LocalDefId, attr: &Attribute) {
     let tcx = tcx;
     let param_env = tcx.param_env(item_def_id);
-    let ty = tcx.type_of(item_def_id).subst_identity();
+    let ty = tcx.type_of(item_def_id).instantiate_identity();
     match tcx.layout_of(param_env.and(ty)) {
         Ok(ty_layout) => {
             // Check out the `#[rustc_layout(..)]` attribute to tell what to dump.
diff --git a/compiler/rustc_passes/src/liveness.rs b/compiler/rustc_passes/src/liveness.rs
index 3ebba7056e99b..89c6704e4169a 100644
--- a/compiler/rustc_passes/src/liveness.rs
+++ b/compiler/rustc_passes/src/liveness.rs
@@ -747,7 +747,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
         let ty = self.typeck_results.node_type(hir_id);
         match ty.kind() {
-            ty::Closure(_def_id, substs) => match substs.as_closure().kind() {
+            ty::Closure(_def_id, args) => match args.as_closure().kind() {
                 ty::ClosureKind::Fn => {}
                 ty::ClosureKind::FnMut => {}
                 ty::ClosureKind::FnOnce => return succ,
diff --git a/compiler/rustc_privacy/src/lib.rs b/compiler/rustc_privacy/src/lib.rs
index fe23506b878dc..e2827252509db 100644
--- a/compiler/rustc_privacy/src/lib.rs
+++ b/compiler/rustc_privacy/src/lib.rs
@@ -28,7 +28,7 @@ use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::privacy::{EffectiveVisibilities, EffectiveVisibility, Level};
 use rustc_middle::query::Providers;
 use rustc_middle::span_bug;
-use rustc_middle::ty::subst::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, Const, GenericParamDefKind};
 use rustc_middle::ty::{TraitRef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use rustc_session::lint;
@@ -129,19 +129,19 @@ where
     V: DefIdVisitor<'tcx> + ?Sized,
 {
     fn visit_trait(&mut self, trait_ref: TraitRef<'tcx>) -> ControlFlow<V::BreakTy> {
-        let TraitRef { def_id, substs, .. } = trait_ref;
+        let TraitRef { def_id, args, .. } = trait_ref;
         self.def_id_visitor.visit_def_id(def_id, "trait", &trait_ref.print_only_trait_path())?;
-        if V::SHALLOW { ControlFlow::Continue(()) } else { substs.visit_with(self) }
+        if V::SHALLOW { ControlFlow::Continue(()) } else { args.visit_with(self) }
     }
 
     fn visit_projection_ty(&mut self, projection: ty::AliasTy<'tcx>) -> ControlFlow<V::BreakTy> {
         let tcx = self.def_id_visitor.tcx();
-        let (trait_ref, assoc_substs) = projection.trait_ref_and_own_substs(tcx);
+        let (trait_ref, assoc_args) = projection.trait_ref_and_own_args(tcx);
         self.visit_trait(trait_ref)?;
         if V::SHALLOW {
             ControlFlow::Continue(())
         } else {
-            assoc_substs.iter().try_for_each(|subst| subst.visit_with(self))
+            assoc_args.iter().try_for_each(|subst| subst.visit_with(self))
         }
     }
 
@@ -178,7 +178,7 @@ where
 
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<V::BreakTy> {
         let tcx = self.def_id_visitor.tcx();
-        // InternalSubsts are not visited here because they are visited below
+        // GenericArgs are not visited here because they are visited below
         // in `super_visit_with`.
         match *ty.kind() {
             ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), ..)
@@ -194,16 +194,16 @@ where
                 // Something like `fn() -> Priv {my_func}` is considered a private type even if
                 // `my_func` is public, so we need to visit signatures.
                 if let ty::FnDef(..) = ty.kind() {
-                    // FIXME: this should probably use `substs` from `FnDef`
-                    tcx.fn_sig(def_id).subst_identity().visit_with(self)?;
+                    // FIXME: this should probably use `args` from `FnDef`
+                    tcx.fn_sig(def_id).instantiate_identity().visit_with(self)?;
                 }
-                // Inherent static methods don't have self type in substs.
+                // Inherent static methods don't have self type in args.
                 // Something like `fn() {my_method}` type of the method
                 // `impl Pub<Priv> { pub fn my_method() {} }` is considered a private type,
                 // so we need to visit the self type additionally.
                 if let Some(assoc_item) = tcx.opt_associated_item(def_id) {
                     if let Some(impl_def_id) = assoc_item.impl_container(tcx) {
-                        tcx.type_of(impl_def_id).subst_identity().visit_with(self)?;
+                        tcx.type_of(impl_def_id).instantiate_identity().visit_with(self)?;
                     }
                 }
             }
@@ -219,7 +219,7 @@ where
                     // free type aliases, but this isn't done yet.
                     return ControlFlow::Continue(());
                 }
-                // This will also visit substs if necessary, so we don't need to recurse.
+                // This will also visit args if necessary, so we don't need to recurse.
                 return self.visit_projection_ty(proj);
             }
             ty::Alias(ty::Inherent, data) => {
@@ -238,11 +238,11 @@ where
                     &LazyDefPathStr { def_id: data.def_id, tcx },
                 )?;
 
-                // This will also visit substs if necessary, so we don't need to recurse.
+                // This will also visit args if necessary, so we don't need to recurse.
                 return if V::SHALLOW {
                     ControlFlow::Continue(())
                 } else {
-                    data.substs.iter().try_for_each(|subst| subst.visit_with(self))
+                    data.args.iter().try_for_each(|subst| subst.visit_with(self))
                 };
             }
             ty::Dynamic(predicates, ..) => {
@@ -253,10 +253,10 @@ where
                         ty::ExistentialPredicate::Trait(trait_ref) => trait_ref,
                         ty::ExistentialPredicate::Projection(proj) => proj.trait_ref(tcx),
                         ty::ExistentialPredicate::AutoTrait(def_id) => {
-                            ty::ExistentialTraitRef { def_id, substs: InternalSubsts::empty() }
+                            ty::ExistentialTraitRef { def_id, args: GenericArgs::empty() }
                         }
                     };
-                    let ty::ExistentialTraitRef { def_id, substs: _ } = trait_ref;
+                    let ty::ExistentialTraitRef { def_id, args: _ } = trait_ref;
                     self.def_id_visitor.visit_def_id(def_id, "trait", &trait_ref)?;
                 }
             }
@@ -357,9 +357,9 @@ trait VisibilityLike: Sized {
         effective_visibilities: &EffectiveVisibilities,
     ) -> Self {
         let mut find = FindMin::<_, SHALLOW> { tcx, effective_visibilities, min: Self::MAX };
-        find.visit(tcx.type_of(def_id).subst_identity());
+        find.visit(tcx.type_of(def_id).instantiate_identity());
         if let Some(trait_ref) = tcx.impl_trait_ref(def_id) {
-            find.visit_trait(trait_ref.subst_identity());
+            find.visit_trait(trait_ref.instantiate_identity());
         }
         find.min
     }
@@ -727,7 +727,7 @@ impl<'tcx> Visitor<'tcx> for EmbargoVisitor<'tcx> {
                 // Type inference is very smart sometimes. It can make an impl reachable even some
                 // components of its type or trait are unreachable. E.g. methods of
                 // `impl ReachableTrait<UnreachableTy> for ReachableTy<UnreachableTy> { ... }`
-                // can be usable from other crates (#57264). So we skip substs when calculating
+                // can be usable from other crates (#57264). So we skip args when calculating
                 // reachability and consider an impl reachable if its "shallow" type and trait are
                 // reachable.
                 //
@@ -823,13 +823,15 @@ impl ReachEverythingInTheInterfaceVisitor<'_, '_> {
                 GenericParamDefKind::Lifetime => {}
                 GenericParamDefKind::Type { has_default, .. } => {
                     if has_default {
-                        self.visit(self.ev.tcx.type_of(param.def_id).subst_identity());
+                        self.visit(self.ev.tcx.type_of(param.def_id).instantiate_identity());
                     }
                 }
                 GenericParamDefKind::Const { has_default } => {
-                    self.visit(self.ev.tcx.type_of(param.def_id).subst_identity());
+                    self.visit(self.ev.tcx.type_of(param.def_id).instantiate_identity());
                     if has_default {
-                        self.visit(self.ev.tcx.const_param_default(param.def_id).subst_identity());
+                        self.visit(
+                            self.ev.tcx.const_param_default(param.def_id).instantiate_identity(),
+                        );
                     }
                 }
             }
@@ -843,13 +845,13 @@ impl ReachEverythingInTheInterfaceVisitor<'_, '_> {
     }
 
     fn ty(&mut self) -> &mut Self {
-        self.visit(self.ev.tcx.type_of(self.item_def_id).subst_identity());
+        self.visit(self.ev.tcx.type_of(self.item_def_id).instantiate_identity());
         self
     }
 
     fn trait_ref(&mut self) -> &mut Self {
         if let Some(trait_ref) = self.ev.tcx.impl_trait_ref(self.item_def_id) {
-            self.visit_trait(trait_ref.subst_identity());
+            self.visit_trait(trait_ref.instantiate_identity());
         }
         self
     }
@@ -1124,7 +1126,7 @@ impl<'tcx> TypePrivacyVisitor<'tcx> {
         let typeck_results = self.typeck_results();
         let result: ControlFlow<()> = try {
             self.visit(typeck_results.node_type(id))?;
-            self.visit(typeck_results.node_substs(id))?;
+            self.visit(typeck_results.node_args(id))?;
             if let Some(adjustments) = typeck_results.adjustments().get(id) {
                 adjustments.iter().try_for_each(|adjustment| self.visit(adjustment.target))?;
             }
@@ -1259,7 +1261,7 @@ impl<'tcx> Visitor<'tcx> for TypePrivacyVisitor<'tcx> {
                 // Method calls have to be checked specially.
                 self.span = segment.ident.span;
                 if let Some(def_id) = self.typeck_results().type_dependent_def_id(expr.hir_id) {
-                    if self.visit(self.tcx.type_of(def_id).subst_identity()).is_break() {
+                    if self.visit(self.tcx.type_of(def_id).instantiate_identity()).is_break() {
                         return;
                     }
                 } else {
@@ -1736,12 +1738,12 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
                 GenericParamDefKind::Lifetime => {}
                 GenericParamDefKind::Type { has_default, .. } => {
                     if has_default {
-                        self.visit(self.tcx.type_of(param.def_id).subst_identity());
+                        self.visit(self.tcx.type_of(param.def_id).instantiate_identity());
                     }
                 }
                 // FIXME(generic_const_exprs): May want to look inside const here
                 GenericParamDefKind::Const { .. } => {
-                    self.visit(self.tcx.type_of(param.def_id).subst_identity());
+                    self.visit(self.tcx.type_of(param.def_id).instantiate_identity());
                 }
             }
         }
@@ -1768,7 +1770,7 @@ impl SearchInterfaceForPrivateItemsVisitor<'_> {
 
     fn ty(&mut self) -> &mut Self {
         self.in_primary_interface = true;
-        self.visit(self.tcx.type_of(self.item_def_id).subst_identity());
+        self.visit(self.tcx.type_of(self.item_def_id).instantiate_identity());
         self
     }
 
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
index f36b01c1a1f1f..846a1ffe09b17 100644
--- a/compiler/rustc_resolve/src/late.rs
+++ b/compiler/rustc_resolve/src/late.rs
@@ -1361,7 +1361,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
 
     fn visit_generic_params(&mut self, params: &'ast [GenericParam], add_self_upper: bool) {
         // For type parameter defaults, we have to ban access
-        // to following type parameters, as the InternalSubsts can only
+        // to following type parameters, as the GenericArgs can only
         // provide previous type parameters as they're built. We
         // put all the parameters on the ban list and then remove
         // them one by one as they are processed and become available.
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index d655276a991b8..4fc440ef94702 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1280,7 +1280,7 @@ symbols! {
         rustc_dummy,
         rustc_dump_env_program_clauses,
         rustc_dump_program_clauses,
-        rustc_dump_user_substs,
+        rustc_dump_user_args,
         rustc_dump_vtable,
         rustc_effective_visibility,
         rustc_error,
diff --git a/compiler/rustc_symbol_mangling/src/legacy.rs b/compiler/rustc_symbol_mangling/src/legacy.rs
index ec7032cd3bf54..3a33568084c41 100644
--- a/compiler/rustc_symbol_mangling/src/legacy.rs
+++ b/compiler/rustc_symbol_mangling/src/legacy.rs
@@ -2,8 +2,8 @@ use rustc_data_structures::stable_hasher::{Hash64, HashStable, StableHasher};
 use rustc_hir::def_id::CrateNum;
 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
 use rustc_middle::ty::print::{PrettyPrinter, Print, Printer};
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{GenericArg, GenericArgKind};
 use rustc_middle::util::common::record_time;
 
 use std::fmt::{self, Write};
@@ -26,7 +26,7 @@ pub(super) fn mangle<'tcx>(
         let key = tcx.def_key(ty_def_id);
         match key.disambiguated_data.data {
             DefPathData::TypeNs(_) | DefPathData::ValueNs(_) => {
-                instance_ty = tcx.type_of(ty_def_id).subst_identity();
+                instance_ty = tcx.type_of(ty_def_id).instantiate_identity();
                 debug!(?instance_ty);
                 break;
             }
@@ -58,7 +58,7 @@ pub(super) fn mangle<'tcx>(
             def_id,
             if let ty::InstanceDef::DropGlue(_, _) = instance.def {
                 // Add the name of the dropped type to the symbol name
-                &*instance.substs
+                &*instance.args
             } else {
                 &[]
             },
@@ -95,8 +95,8 @@ fn get_symbol_hash<'tcx>(
     instantiating_crate: Option<CrateNum>,
 ) -> Hash64 {
     let def_id = instance.def_id();
-    let substs = instance.substs;
-    debug!("get_symbol_hash(def_id={:?}, parameters={:?})", def_id, substs);
+    let args = instance.args;
+    debug!("get_symbol_hash(def_id={:?}, parameters={:?})", def_id, args);
 
     tcx.with_stable_hashing_context(|mut hcx| {
         let mut hasher = StableHasher::new();
@@ -122,7 +122,7 @@ fn get_symbol_hash<'tcx>(
                 }
 
                 // also include any type parameters (for generic items)
-                substs.hash_stable(hcx, &mut hasher);
+                args.hash_stable(hcx, &mut hasher);
 
                 if let Some(instantiating_crate) = instantiating_crate {
                     tcx.def_path_hash(instantiating_crate.as_def_id())
@@ -219,10 +219,10 @@ impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
         match *ty.kind() {
             // Print all nominal types as paths (unlike `pretty_print_type`).
-            ty::FnDef(def_id, substs)
-            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
-            | ty::Closure(def_id, substs)
-            | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),
+            ty::FnDef(def_id, args)
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
+            | ty::Closure(def_id, args)
+            | ty::Generator(def_id, args, _) => self.print_def_path(def_id, args),
 
             // The `pretty_print_type` formatting of array size depends on
             // -Zverbose flag, so we cannot reuse it here.
diff --git a/compiler/rustc_symbol_mangling/src/lib.rs b/compiler/rustc_symbol_mangling/src/lib.rs
index 692542da78ea2..22fd1f09f3a3c 100644
--- a/compiler/rustc_symbol_mangling/src/lib.rs
+++ b/compiler/rustc_symbol_mangling/src/lib.rs
@@ -108,7 +108,7 @@ use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::mir::mono::{InstantiationMode, MonoItem};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Instance, TyCtxt};
 use rustc_session::config::SymbolManglingVersion;
 
@@ -144,7 +144,7 @@ fn symbol_name_provider<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> ty
         // This closure determines the instantiating crate for instances that
         // need an instantiating-crate-suffix for their symbol name, in order
         // to differentiate between local copies.
-        if is_generic(instance.substs) {
+        if is_generic(instance.args) {
             // For generics we might find re-usable upstream instances. If there
             // is one, we rely on the symbol being instantiated locally.
             instance.upstream_monomorphization(tcx).unwrap_or(LOCAL_CRATE)
@@ -174,9 +174,9 @@ fn compute_symbol_name<'tcx>(
     compute_instantiating_crate: impl FnOnce() -> CrateNum,
 ) -> String {
     let def_id = instance.def_id();
-    let substs = instance.substs;
+    let args = instance.args;
 
-    debug!("symbol_name(def_id={:?}, substs={:?})", def_id, substs);
+    debug!("symbol_name(def_id={:?}, args={:?})", def_id, args);
 
     if let Some(def_id) = def_id.as_local() {
         if tcx.proc_macro_decls_static(()) == Some(def_id) {
@@ -246,7 +246,7 @@ fn compute_symbol_name<'tcx>(
     // the ID of the instantiating crate. This avoids symbol conflicts
     // in case the same instances is emitted in two crates of the same
     // project.
-    let avoid_cross_crate_conflicts = is_generic(substs) || is_globally_shared_function;
+    let avoid_cross_crate_conflicts = is_generic(args) || is_globally_shared_function;
 
     let instantiating_crate = avoid_cross_crate_conflicts.then(compute_instantiating_crate);
 
@@ -278,6 +278,6 @@ fn compute_symbol_name<'tcx>(
     symbol
 }
 
-fn is_generic(substs: SubstsRef<'_>) -> bool {
-    substs.non_erasable_generics().next().is_some()
+fn is_generic(args: GenericArgsRef<'_>) -> bool {
+    args.non_erasable_generics().next().is_some()
 }
diff --git a/compiler/rustc_symbol_mangling/src/test.rs b/compiler/rustc_symbol_mangling/src/test.rs
index 985b2210745f4..eddfd0df318e2 100644
--- a/compiler/rustc_symbol_mangling/src/test.rs
+++ b/compiler/rustc_symbol_mangling/src/test.rs
@@ -7,7 +7,7 @@
 use crate::errors::{Kind, TestOutput};
 use rustc_hir::def_id::LocalDefId;
 use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{subst::InternalSubsts, Instance, TyCtxt};
+use rustc_middle::ty::{GenericArgs, Instance, TyCtxt};
 use rustc_span::symbol::{sym, Symbol};
 
 const SYMBOL_NAME: Symbol = sym::rustc_symbol_name;
@@ -57,7 +57,7 @@ impl SymbolNamesTest<'_> {
             let def_id = def_id.to_def_id();
             let instance = Instance::new(
                 def_id,
-                tcx.erase_regions(InternalSubsts::identity_for_item(tcx, def_id)),
+                tcx.erase_regions(GenericArgs::identity_for_item(tcx, def_id)),
             );
             let mangled = tcx.symbol_name(instance);
             tcx.sess.emit_err(TestOutput {
diff --git a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
index 3b46275ec415f..4a938ff938a07 100644
--- a/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
+++ b/compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs
@@ -11,11 +11,11 @@ use core::fmt::Display;
 use rustc_data_structures::base_n;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
 use rustc_middle::ty::{
     self, Const, ExistentialPredicate, FloatTy, FnSig, Instance, IntTy, List, Region, RegionKind,
     TermKind, Ty, TyCtxt, UintTy,
 };
+use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_span::def_id::DefId;
 use rustc_span::sym;
 use rustc_target::abi::call::{Conv, FnAbi};
@@ -212,12 +212,12 @@ fn encode_predicate<'tcx>(
         ty::ExistentialPredicate::Trait(trait_ref) => {
             let name = encode_ty_name(tcx, trait_ref.def_id);
             let _ = write!(s, "u{}{}", name.len(), &name);
-            s.push_str(&encode_substs(tcx, trait_ref.substs, dict, options));
+            s.push_str(&encode_args(tcx, trait_ref.args, dict, options));
         }
         ty::ExistentialPredicate::Projection(projection) => {
             let name = encode_ty_name(tcx, projection.def_id);
             let _ = write!(s, "u{}{}", name.len(), &name);
-            s.push_str(&encode_substs(tcx, projection.substs, dict, options));
+            s.push_str(&encode_args(tcx, projection.args, dict, options));
             match projection.term.unpack() {
                 TermKind::Ty(ty) => s.push_str(&encode_ty(tcx, ty, dict, options)),
                 TermKind::Const(c) => s.push_str(&encode_const(tcx, c, dict, options)),
@@ -286,21 +286,21 @@ fn encode_region<'tcx>(
     s
 }
 
-/// Encodes substs using the Itanium C++ ABI with vendor extended type qualifiers and types for Rust
+/// Encodes args using the Itanium C++ ABI with vendor extended type qualifiers and types for Rust
 /// types that are not used at the FFI boundary.
-fn encode_substs<'tcx>(
+fn encode_args<'tcx>(
     tcx: TyCtxt<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     dict: &mut FxHashMap<DictKey<'tcx>, usize>,
     options: EncodeTyOptions,
 ) -> String {
     // [I<subst1..substN>E] as part of vendor extended type
     let mut s = String::new();
-    let substs: Vec<GenericArg<'_>> = substs.iter().collect();
-    if !substs.is_empty() {
+    let args: Vec<GenericArg<'_>> = args.iter().collect();
+    if !args.is_empty() {
         s.push('I');
-        for subst in substs {
-            match subst.unpack() {
+        for arg in args {
+            match arg.unpack() {
                 GenericArgKind::Lifetime(region) => {
                     s.push_str(&encode_region(tcx, region, dict, options));
                 }
@@ -524,7 +524,7 @@ fn encode_ty<'tcx>(
         }
 
         // User-defined types
-        ty::Adt(adt_def, substs) => {
+        ty::Adt(adt_def, args) => {
             let mut s = String::new();
             let def_id = adt_def.did();
             if let Some(cfi_encoding) = tcx.get_attr(def_id, sym::cfi_encoding) {
@@ -570,7 +570,7 @@ fn encode_ty<'tcx>(
                 // <subst>, as vendor extended type.
                 let name = encode_ty_name(tcx, def_id);
                 let _ = write!(s, "u{}{}", name.len(), &name);
-                s.push_str(&encode_substs(tcx, substs, dict, options));
+                s.push_str(&encode_args(tcx, args, dict, options));
                 compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             }
             typeid.push_str(&s);
@@ -608,27 +608,27 @@ fn encode_ty<'tcx>(
         }
 
         // Function types
-        ty::FnDef(def_id, substs) | ty::Closure(def_id, substs) => {
+        ty::FnDef(def_id, args) | ty::Closure(def_id, args) => {
             // u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>,
             // as vendor extended type.
             let mut s = String::new();
             let name = encode_ty_name(tcx, *def_id);
             let _ = write!(s, "u{}{}", name.len(), &name);
-            s.push_str(&encode_substs(tcx, substs, dict, options));
+            s.push_str(&encode_args(tcx, args, dict, options));
             compress(dict, DictKey::Ty(ty, TyQ::None), &mut s);
             typeid.push_str(&s);
         }
 
-        ty::Generator(def_id, substs, ..) => {
+        ty::Generator(def_id, args, ..) => {
             // u<length><name>[I<element-type1..element-typeN>E], where <element-type> is <subst>,
             // as vendor extended type.
             let mut s = String::new();
             let name = encode_ty_name(tcx, *def_id);
             let _ = write!(s, "u{}{}", name.len(), &name);
-            // Encode parent substs only
-            s.push_str(&encode_substs(
+            // Encode parent args only
+            s.push_str(&encode_args(
                 tcx,
-                tcx.mk_substs(substs.as_generator().parent_substs()),
+                tcx.mk_args(args.as_generator().parent_args()),
                 dict,
                 options,
             ));
@@ -732,18 +732,18 @@ fn transform_predicates<'tcx>(
     tcx.mk_poly_existential_predicates(&predicates)
 }
 
-/// Transforms substs for being encoded and used in the substitution dictionary.
-fn transform_substs<'tcx>(
+/// Transforms args for being encoded and used in the substitution dictionary.
+fn transform_args<'tcx>(
     tcx: TyCtxt<'tcx>,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
     options: TransformTyOptions,
-) -> SubstsRef<'tcx> {
-    let substs = substs.iter().map(|subst| match subst.unpack() {
+) -> GenericArgsRef<'tcx> {
+    let args = args.iter().map(|arg| match arg.unpack() {
         GenericArgKind::Type(ty) if ty.is_c_void(tcx) => Ty::new_unit(tcx).into(),
         GenericArgKind::Type(ty) => transform_ty(tcx, ty, options).into(),
-        _ => subst,
+        _ => arg,
     });
-    tcx.mk_substs_from_iter(substs)
+    tcx.mk_args_from_iter(args)
 }
 
 // Transforms a ty:Ty for being encoded and used in the substitution dictionary. It transforms all
@@ -825,7 +825,7 @@ fn transform_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, options: TransformTyOptio
             ty = Ty::new_slice(tcx, transform_ty(tcx, *ty0, options));
         }
 
-        ty::Adt(adt_def, substs) => {
+        ty::Adt(adt_def, args) => {
             if ty.is_c_void(tcx) {
                 ty = Ty::new_unit(tcx);
             } else if options.contains(TransformTyOptions::GENERALIZE_REPR_C) && adt_def.repr().c()
@@ -840,13 +840,13 @@ fn transform_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, options: TransformTyOptio
                 let variant = adt_def.non_enum_variant();
                 let param_env = tcx.param_env(variant.def_id);
                 let field = variant.fields.iter().find(|field| {
-                    let ty = tcx.type_of(field.did).subst_identity();
+                    let ty = tcx.type_of(field.did).instantiate_identity();
                     let is_zst =
                         tcx.layout_of(param_env.and(ty)).is_ok_and(|layout| layout.is_zst());
                     !is_zst
                 });
                 if let Some(field) = field {
-                    let ty0 = tcx.type_of(field.did).subst(tcx, substs);
+                    let ty0 = tcx.type_of(field.did).instantiate(tcx, args);
                     // Generalize any repr(transparent) user-defined type that is either a pointer
                     // or reference, and either references itself or any other type that contains or
                     // references itself, to avoid a reference cycle.
@@ -864,25 +864,20 @@ fn transform_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, options: TransformTyOptio
                     ty = Ty::new_unit(tcx);
                 }
             } else {
-                ty = Ty::new_adt(tcx, *adt_def, transform_substs(tcx, substs, options));
+                ty = Ty::new_adt(tcx, *adt_def, transform_args(tcx, args, options));
             }
         }
 
-        ty::FnDef(def_id, substs) => {
-            ty = Ty::new_fn_def(tcx, *def_id, transform_substs(tcx, substs, options));
+        ty::FnDef(def_id, args) => {
+            ty = Ty::new_fn_def(tcx, *def_id, transform_args(tcx, args, options));
         }
 
-        ty::Closure(def_id, substs) => {
-            ty = Ty::new_closure(tcx, *def_id, transform_substs(tcx, substs, options));
+        ty::Closure(def_id, args) => {
+            ty = Ty::new_closure(tcx, *def_id, transform_args(tcx, args, options));
         }
 
-        ty::Generator(def_id, substs, movability) => {
-            ty = Ty::new_generator(
-                tcx,
-                *def_id,
-                transform_substs(tcx, substs, options),
-                *movability,
-            );
+        ty::Generator(def_id, args, movability) => {
+            ty = Ty::new_generator(tcx, *def_id, transform_args(tcx, args, options), *movability);
         }
 
         ty::Ref(region, ty0, ..) => {
diff --git a/compiler/rustc_symbol_mangling/src/v0.rs b/compiler/rustc_symbol_mangling/src/v0.rs
index 5e5cc6e4e4abc..1846fda7c6340 100644
--- a/compiler/rustc_symbol_mangling/src/v0.rs
+++ b/compiler/rustc_symbol_mangling/src/v0.rs
@@ -27,7 +27,7 @@ pub(super) fn mangle<'tcx>(
 ) -> String {
     let def_id = instance.def_id();
     // FIXME(eddyb) this should ideally not be needed.
-    let substs = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.substs);
+    let args = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.args);
 
     let prefix = "_R";
     let mut cx = &mut SymbolMangler {
@@ -50,9 +50,9 @@ pub(super) fn mangle<'tcx>(
     };
 
     cx = if let Some(shim_kind) = shim_kind {
-        cx.path_append_ns(|cx| cx.print_def_path(def_id, substs), 'S', 0, shim_kind).unwrap()
+        cx.path_append_ns(|cx| cx.print_def_path(def_id, args), 'S', 0, shim_kind).unwrap()
     } else {
-        cx.print_def_path(def_id, substs).unwrap()
+        cx.print_def_path(def_id, args).unwrap()
     };
     if let Some(instantiating_crate) = instantiating_crate {
         cx = cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
@@ -245,19 +245,19 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
     fn print_def_path(
         mut self,
         def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
     ) -> Result<Self::Path, Self::Error> {
-        if let Some(&i) = self.paths.get(&(def_id, substs)) {
+        if let Some(&i) = self.paths.get(&(def_id, args)) {
             return self.print_backref(i);
         }
         let start = self.out.len();
 
-        self = self.default_print_def_path(def_id, substs)?;
+        self = self.default_print_def_path(def_id, args)?;
 
         // Only cache paths that do not refer to an enclosing
         // binder (which would change depending on context).
-        if !substs.iter().any(|k| k.has_escaping_bound_vars()) {
-            self.paths.insert((def_id, substs), start);
+        if !args.iter().any(|k| k.has_escaping_bound_vars()) {
+            self.paths.insert((def_id, args), start);
         }
         Ok(self)
     }
@@ -265,7 +265,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
     fn print_impl_path(
         mut self,
         impl_def_id: DefId,
-        substs: &'tcx [GenericArg<'tcx>],
+        args: &'tcx [GenericArg<'tcx>],
         mut self_ty: Ty<'tcx>,
         mut impl_trait_ref: Option<ty::TraitRef<'tcx>>,
     ) -> Result<Self::Path, Self::Error> {
@@ -273,8 +273,8 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
         let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
 
         let mut param_env = self.tcx.param_env_reveal_all_normalized(impl_def_id);
-        if !substs.is_empty() {
-            param_env = EarlyBinder::bind(param_env).subst(self.tcx, substs);
+        if !args.is_empty() {
+            param_env = EarlyBinder::bind(param_env).instantiate(self.tcx, args);
         }
 
         match &mut impl_trait_ref {
@@ -295,7 +295,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
 
         // Encode impl generic params if the substitutions contain parameters (implying
         // polymorphization is enabled) and this isn't an inherent impl.
-        if impl_trait_ref.is_some() && substs.iter().any(|a| a.has_non_region_param()) {
+        if impl_trait_ref.is_some() && args.iter().any(|a| a.has_non_region_param()) {
             self = self.path_generic_args(
                 |this| {
                     this.path_append_ns(
@@ -305,7 +305,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                         "",
                     )
                 },
-                substs,
+                args,
             )?;
         } else {
             self.push_disambiguator(key.disambiguated_data.disambiguator as u64);
@@ -315,7 +315,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
         self = self_ty.print(self)?;
 
         if let Some(trait_ref) = impl_trait_ref {
-            self = self.print_def_path(trait_ref.def_id, trait_ref.substs)?;
+            self = self.print_def_path(trait_ref.def_id, trait_ref.args)?;
         }
 
         Ok(self)
@@ -431,12 +431,12 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
             }
 
             // Mangle all nominal types as paths.
-            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
-            | ty::FnDef(def_id, substs)
-            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. })
-            | ty::Closure(def_id, substs)
-            | ty::Generator(def_id, substs, _) => {
-                self = self.print_def_path(def_id, substs)?;
+            ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), args)
+            | ty::FnDef(def_id, args)
+            | ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. })
+            | ty::Closure(def_id, args)
+            | ty::Generator(def_id, args, _) => {
+                self = self.print_def_path(def_id, args)?;
             }
             ty::Foreign(def_id) => {
                 self = self.print_def_path(def_id, &[])?;
@@ -537,7 +537,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                         // Use a type that can't appear in defaults of type parameters.
                         let dummy_self = Ty::new_fresh(cx.tcx, 0);
                         let trait_ref = trait_ref.with_self_ty(cx.tcx, dummy_self);
-                        cx = cx.print_def_path(trait_ref.def_id, trait_ref.substs)?;
+                        cx = cx.print_def_path(trait_ref.def_id, trait_ref.args)?;
                     }
                     ty::ExistentialPredicate::Projection(projection) => {
                         let name = cx.tcx.associated_item(projection.def_id).name;
@@ -679,13 +679,13 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
                         self.push("T");
                         self = print_field_list(self)?;
                     }
-                    ty::Adt(def, substs) => {
+                    ty::Adt(def, args) => {
                         let variant_idx =
                             contents.variant.expect("destructed const of adt without variant idx");
                         let variant_def = &def.variant(variant_idx);
 
                         self.push("V");
-                        self = self.print_def_path(variant_def.def_id, substs)?;
+                        self = self.print_def_path(variant_def.def_id, args)?;
 
                         match variant_def.ctor_kind() {
                             Some(CtorKind::Const) => {
@@ -750,7 +750,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
 
         self.push("Y");
         self = self_ty.print(self)?;
-        self.print_def_path(trait_ref.def_id, trait_ref.substs)
+        self.print_def_path(trait_ref.def_id, trait_ref.args)
     }
 
     fn path_append_impl(
diff --git a/compiler/rustc_trait_selection/src/solve/alias_relate.rs b/compiler/rustc_trait_selection/src/solve/alias_relate.rs
index 422a6ee3442f4..73362d823065a 100644
--- a/compiler/rustc_trait_selection/src/solve/alias_relate.rs
+++ b/compiler/rustc_trait_selection/src/solve/alias_relate.rs
@@ -65,7 +65,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                     direction,
                     Invert::Yes,
                 ));
-                // Relate via substs
+                // Relate via args
                 let subst_relate_response = self
                     .assemble_subst_relate_candidate(param_env, alias_lhs, alias_rhs, direction);
                 candidates.extend(subst_relate_response);
@@ -153,7 +153,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         alias_rhs: ty::AliasTy<'tcx>,
         direction: ty::AliasRelationDirection,
     ) -> QueryResult<'tcx> {
-        self.probe_candidate("substs relate").enter(|ecx| {
+        self.probe_candidate("args relate").enter(|ecx| {
             match direction {
                 ty::AliasRelationDirection::Equate => {
                     ecx.eq(param_env, alias_lhs, alias_rhs)?;
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
index a93845d33318c..1e79899889551 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/mod.rs
@@ -542,7 +542,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             ty::Alias(ty::Projection | ty::Opaque, alias_ty) => alias_ty,
         };
 
-        for assumption in self.tcx().item_bounds(alias_ty.def_id).subst(self.tcx(), alias_ty.substs)
+        for assumption in
+            self.tcx().item_bounds(alias_ty.def_id).instantiate(self.tcx(), alias_ty.args)
         {
             match G::consider_alias_bound_candidate(self, goal, assumption) {
                 Ok(result) => {
diff --git a/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs b/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
index 3bb8cad15ab40..3a1302e46baf4 100644
--- a/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
+++ b/compiler/rustc_trait_selection/src/solve/assembly/structural_traits.rs
@@ -51,36 +51,36 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_auto_trait<'tcx>(
             Ok(tys.iter().collect())
         }
 
-        ty::Closure(_, ref substs) => Ok(vec![substs.as_closure().tupled_upvars_ty()]),
+        ty::Closure(_, ref args) => Ok(vec![args.as_closure().tupled_upvars_ty()]),
 
-        ty::Generator(_, ref substs, _) => {
-            let generator_substs = substs.as_generator();
-            Ok(vec![generator_substs.tupled_upvars_ty(), generator_substs.witness()])
+        ty::Generator(_, ref args, _) => {
+            let generator_args = args.as_generator();
+            Ok(vec![generator_args.tupled_upvars_ty(), generator_args.witness()])
         }
 
         ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()),
 
-        ty::GeneratorWitnessMIR(def_id, substs) => Ok(ecx
+        ty::GeneratorWitnessMIR(def_id, args) => Ok(ecx
             .tcx()
             .generator_hidden_types(def_id)
             .map(|bty| {
                 ecx.instantiate_binder_with_placeholders(replace_erased_lifetimes_with_bound_vars(
                     tcx,
-                    bty.subst(tcx, substs),
+                    bty.instantiate(tcx, args),
                 ))
             })
             .collect()),
 
         // For `PhantomData<T>`, we pass `T`.
-        ty::Adt(def, substs) if def.is_phantom_data() => Ok(vec![substs.type_at(0)]),
+        ty::Adt(def, args) if def.is_phantom_data() => Ok(vec![args.type_at(0)]),
 
-        ty::Adt(def, substs) => Ok(def.all_fields().map(|f| f.ty(tcx, substs)).collect()),
+        ty::Adt(def, args) => Ok(def.all_fields().map(|f| f.ty(tcx, args)).collect()),
 
-        ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+        ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
             // We can resolve the `impl Trait` to its concrete type,
             // which enforces a DAG between the functions requiring
             // the auto trait bounds in question.
-            Ok(vec![tcx.type_of(def_id).subst(tcx, substs)])
+            Ok(vec![tcx.type_of(def_id).instantiate(tcx, args)])
         }
     }
 }
@@ -146,9 +146,9 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<'tcx>(
 
         ty::Tuple(tys) => Ok(tys.to_vec()),
 
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             let sized_crit = def.sized_constraint(ecx.tcx());
-            Ok(sized_crit.subst_iter_copied(ecx.tcx(), substs).collect())
+            Ok(sized_crit.arg_iter_copied(ecx.tcx(), args).collect())
         }
     }
 }
@@ -192,11 +192,11 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
 
         ty::Tuple(tys) => Ok(tys.to_vec()),
 
-        ty::Closure(_, substs) => Ok(vec![substs.as_closure().tupled_upvars_ty()]),
+        ty::Closure(_, args) => Ok(vec![args.as_closure().tupled_upvars_ty()]),
 
-        ty::Generator(_, substs, Movability::Movable) => {
+        ty::Generator(_, args, Movability::Movable) => {
             if ecx.tcx().features().generator_clone {
-                let generator = substs.as_generator();
+                let generator = args.as_generator();
                 Ok(vec![generator.tupled_upvars_ty(), generator.witness()])
             } else {
                 Err(NoSolution)
@@ -205,13 +205,13 @@ pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<'tcx>(
 
         ty::GeneratorWitness(types) => Ok(ecx.instantiate_binder_with_placeholders(types).to_vec()),
 
-        ty::GeneratorWitnessMIR(def_id, substs) => Ok(ecx
+        ty::GeneratorWitnessMIR(def_id, args) => Ok(ecx
             .tcx()
             .generator_hidden_types(def_id)
             .map(|bty| {
                 ecx.instantiate_binder_with_placeholders(replace_erased_lifetimes_with_bound_vars(
                     ecx.tcx(),
-                    bty.subst(ecx.tcx(), substs),
+                    bty.instantiate(ecx.tcx(), args),
                 ))
             })
             .collect()),
@@ -226,13 +226,13 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
 ) -> Result<Option<ty::Binder<'tcx, (Ty<'tcx>, Ty<'tcx>)>>, NoSolution> {
     match *self_ty.kind() {
         // keep this in sync with assemble_fn_pointer_candidates until the old solver is removed.
-        ty::FnDef(def_id, substs) => {
+        ty::FnDef(def_id, args) => {
             let sig = tcx.fn_sig(def_id);
             if sig.skip_binder().is_fn_trait_compatible()
                 && tcx.codegen_fn_attrs(def_id).target_features.is_empty()
             {
                 Ok(Some(
-                    sig.subst(tcx, substs)
+                    sig.instantiate(tcx, args)
                         .map_bound(|sig| (Ty::new_tup(tcx, sig.inputs()), sig.output())),
                 ))
             } else {
@@ -247,9 +247,9 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
                 Err(NoSolution)
             }
         }
-        ty::Closure(_, substs) => {
-            let closure_substs = substs.as_closure();
-            match closure_substs.kind_ty().to_opt_closure_kind() {
+        ty::Closure(_, args) => {
+            let closure_args = args.as_closure();
+            match closure_args.kind_ty().to_opt_closure_kind() {
                 // If the closure's kind doesn't extend the goal kind,
                 // then the closure doesn't implement the trait.
                 Some(closure_kind) => {
@@ -265,7 +265,7 @@ pub(in crate::solve) fn extract_tupled_inputs_and_output_from_callable<'tcx>(
                     }
                 }
             }
-            Ok(Some(closure_substs.sig().map_bound(|sig| (sig.inputs()[0], sig.output()))))
+            Ok(Some(closure_args.sig().map_bound(|sig| (sig.inputs()[0], sig.output()))))
         }
         ty::Bool
         | ty::Char
@@ -347,13 +347,13 @@ pub(in crate::solve) fn predicates_for_object_candidate<'tcx>(
     let tcx = ecx.tcx();
     let mut requirements = vec![];
     requirements.extend(
-        tcx.super_predicates_of(trait_ref.def_id).instantiate(tcx, trait_ref.substs).predicates,
+        tcx.super_predicates_of(trait_ref.def_id).instantiate(tcx, trait_ref.args).predicates,
     );
     for item in tcx.associated_items(trait_ref.def_id).in_definition_order() {
         // FIXME(associated_const_equality): Also add associated consts to
         // the requirements here.
         if item.kind == ty::AssocKind::Type {
-            requirements.extend(tcx.item_bounds(item.def_id).subst_iter(tcx, trait_ref.substs));
+            requirements.extend(tcx.item_bounds(item.def_id).arg_iter(tcx, trait_ref.args));
         }
     }
 
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
index 7b41e9754741d..6e0aa08c307bd 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
@@ -431,11 +431,8 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
                 ty::PredicateKind::Coerce(predicate) => {
                     self.compute_coerce_goal(Goal { param_env, predicate })
                 }
-                ty::PredicateKind::ClosureKind(def_id, substs, kind) => self
-                    .compute_closure_kind_goal(Goal {
-                        param_env,
-                        predicate: (def_id, substs, kind),
-                    }),
+                ty::PredicateKind::ClosureKind(def_id, args, kind) => self
+                    .compute_closure_kind_goal(Goal { param_env, predicate: (def_id, args, kind) }),
                 ty::PredicateKind::ObjectSafe(trait_def_id) => {
                     self.compute_object_safe_goal(trait_def_id)
                 }
@@ -775,24 +772,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         self.infcx.resolve_vars_if_possible(value)
     }
 
-    pub(super) fn fresh_substs_for_item(&self, def_id: DefId) -> ty::SubstsRef<'tcx> {
-        self.infcx.fresh_substs_for_item(DUMMY_SP, def_id)
+    pub(super) fn fresh_args_for_item(&self, def_id: DefId) -> ty::GenericArgsRef<'tcx> {
+        self.infcx.fresh_args_for_item(DUMMY_SP, def_id)
     }
 
-    pub(super) fn translate_substs(
+    pub(super) fn translate_args(
         &self,
         param_env: ty::ParamEnv<'tcx>,
         source_impl: DefId,
-        source_substs: ty::SubstsRef<'tcx>,
+        source_args: ty::GenericArgsRef<'tcx>,
         target_node: specialization_graph::Node,
-    ) -> ty::SubstsRef<'tcx> {
-        crate::traits::translate_substs(
-            self.infcx,
-            param_env,
-            source_impl,
-            source_substs,
-            target_node,
-        )
+    ) -> ty::GenericArgsRef<'tcx> {
+        crate::traits::translate_args(self.infcx, param_env, source_impl, source_args, target_node)
     }
 
     pub(super) fn register_ty_outlives(&self, ty: Ty<'tcx>, lt: ty::Region<'tcx>) {
@@ -864,14 +855,14 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     pub(super) fn add_item_bounds_for_hidden_type(
         &mut self,
         opaque_def_id: DefId,
-        opaque_substs: ty::SubstsRef<'tcx>,
+        opaque_args: ty::GenericArgsRef<'tcx>,
         param_env: ty::ParamEnv<'tcx>,
         hidden_ty: Ty<'tcx>,
     ) {
         let mut obligations = Vec::new();
         self.infcx.add_item_bounds_for_hidden_type(
             opaque_def_id,
-            opaque_substs,
+            opaque_args,
             ObligationCause::dummy(),
             param_env,
             hidden_ty,
@@ -897,13 +888,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 continue;
             }
             values.extend(self.probe_candidate("opaque type storage").enter(|ecx| {
-                for (a, b) in std::iter::zip(candidate_key.substs, key.substs) {
+                for (a, b) in std::iter::zip(candidate_key.args, key.args) {
                     ecx.eq(param_env, a, b)?;
                 }
                 ecx.eq(param_env, candidate_ty, ty)?;
                 ecx.add_item_bounds_for_hidden_type(
                     candidate_key.def_id.to_def_id(),
-                    candidate_key.substs,
+                    candidate_key.args,
                     param_env,
                     candidate_ty,
                 );
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
index 637d458882c16..9f58e66d04e8d 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/canonical.rs
@@ -111,7 +111,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
     ) -> CanonicalResponse<'tcx> {
         let unconstrained_response = Response {
             var_values: CanonicalVarValues {
-                var_values: self.tcx().mk_substs_from_iter(self.var_values.var_values.iter().map(
+                var_values: self.tcx().mk_args_from_iter(self.var_values.var_values.iter().map(
                     |arg| -> ty::GenericArg<'tcx> {
                         match arg.unpack() {
                             GenericArgKind::Lifetime(_) => self.next_region_infer().into(),
@@ -250,7 +250,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             }
         }
 
-        let var_values = self.tcx().mk_substs_from_iter(response.variables.iter().enumerate().map(
+        let var_values = self.tcx().mk_args_from_iter(response.variables.iter().enumerate().map(
             |(index, info)| {
                 if info.universe() != ty::UniverseIndex::ROOT {
                     // A variable from inside a binder of the query. While ideally these shouldn't
diff --git a/compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs b/compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
index 141369b03370b..8af9d0901645b 100644
--- a/compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
+++ b/compiler/rustc_trait_selection/src/solve/eval_ctxt/select.rs
@@ -202,8 +202,9 @@ fn rematch_impl<'tcx>(
     impl_def_id: DefId,
     mut nested: Vec<PredicateObligation<'tcx>>,
 ) -> SelectionResult<'tcx, Selection<'tcx>> {
-    let substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
-    let impl_trait_ref = infcx.tcx.impl_trait_ref(impl_def_id).unwrap().subst(infcx.tcx, substs);
+    let args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
+    let impl_trait_ref =
+        infcx.tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(infcx.tcx, args);
 
     nested.extend(
         infcx
@@ -214,12 +215,12 @@ fn rematch_impl<'tcx>(
     );
 
     nested.extend(
-        infcx.tcx.predicates_of(impl_def_id).instantiate(infcx.tcx, substs).into_iter().map(
+        infcx.tcx.predicates_of(impl_def_id).instantiate(infcx.tcx, args).into_iter().map(
             |(pred, _)| Obligation::new(infcx.tcx, ObligationCause::dummy(), goal.param_env, pred),
         ),
     );
 
-    Ok(Some(ImplSource::UserDefined(ImplSourceUserDefinedData { impl_def_id, substs, nested })))
+    Ok(Some(ImplSource::UserDefined(ImplSourceUserDefinedData { impl_def_id, args, nested })))
 }
 
 fn rematch_object<'tcx>(
@@ -231,21 +232,20 @@ fn rematch_object<'tcx>(
     let ty::Dynamic(data, _, source_kind) = *self_ty.kind() else { bug!() };
     let source_trait_ref = data.principal().unwrap().with_self_ty(infcx.tcx, self_ty);
 
-    let (is_upcasting, target_trait_ref_unnormalized) = if Some(goal.predicate.def_id())
-        == infcx.tcx.lang_items().unsize_trait()
-    {
-        assert_eq!(source_kind, ty::Dyn, "cannot upcast dyn*");
-        if let ty::Dynamic(data, _, ty::Dyn) = goal.predicate.trait_ref.substs.type_at(1).kind() {
-            // FIXME: We also need to ensure that the source lifetime outlives the
-            // target lifetime. This doesn't matter for codegen, though, and only
-            // *really* matters if the goal's certainty is ambiguous.
-            (true, data.principal().unwrap().with_self_ty(infcx.tcx, self_ty))
+    let (is_upcasting, target_trait_ref_unnormalized) =
+        if Some(goal.predicate.def_id()) == infcx.tcx.lang_items().unsize_trait() {
+            assert_eq!(source_kind, ty::Dyn, "cannot upcast dyn*");
+            if let ty::Dynamic(data, _, ty::Dyn) = goal.predicate.trait_ref.args.type_at(1).kind() {
+                // FIXME: We also need to ensure that the source lifetime outlives the
+                // target lifetime. This doesn't matter for codegen, though, and only
+                // *really* matters if the goal's certainty is ambiguous.
+                (true, data.principal().unwrap().with_self_ty(infcx.tcx, self_ty))
+            } else {
+                bug!()
+            }
         } else {
-            bug!()
-        }
-    } else {
-        (false, ty::Binder::dummy(goal.predicate.trait_ref))
-    };
+            (false, ty::Binder::dummy(goal.predicate.trait_ref))
+        };
 
     let mut target_trait_ref = None;
     for candidate_trait_ref in supertraits(infcx.tcx, source_trait_ref) {
@@ -323,7 +323,7 @@ fn rematch_unsize<'tcx>(
 ) -> SelectionResult<'tcx, Selection<'tcx>> {
     let tcx = infcx.tcx;
     let a_ty = goal.predicate.self_ty();
-    let b_ty = goal.predicate.trait_ref.substs.type_at(1);
+    let b_ty = goal.predicate.trait_ref.args.type_at(1);
 
     match (a_ty.kind(), b_ty.kind()) {
         (_, &ty::Dynamic(data, region, ty::Dyn)) => {
@@ -364,7 +364,7 @@ fn rematch_unsize<'tcx>(
             );
         }
         // Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>`
-        (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
+        (&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args))
             if a_def.is_struct() && a_def.did() == b_def.did() =>
         {
             let unsizing_params = tcx.unsizing_params_for_adt(a_def.did());
@@ -382,17 +382,19 @@ fn rematch_unsize<'tcx>(
                 .expect("expected unsized ADT to have a tail field");
             let tail_field_ty = tcx.type_of(tail_field.did);
 
-            let a_tail_ty = tail_field_ty.subst(tcx, a_substs);
-            let b_tail_ty = tail_field_ty.subst(tcx, b_substs);
+            let a_tail_ty = tail_field_ty.instantiate(tcx, a_args);
+            let b_tail_ty = tail_field_ty.instantiate(tcx, b_args);
 
             // Substitute just the unsizing params from B into A. The type after
             // this substitution must be equal to B. This is so we don't unsize
             // unrelated type parameters.
-            let new_a_substs =
-                tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| {
-                    if unsizing_params.contains(i as u32) { b_substs[i] } else { a }
-                }));
-            let unsized_a_ty = Ty::new_adt(tcx, a_def, new_a_substs);
+            let new_a_args = tcx.mk_args_from_iter(
+                a_args
+                    .iter()
+                    .enumerate()
+                    .map(|(i, a)| if unsizing_params.contains(i as u32) { b_args[i] } else { a }),
+            );
+            let unsized_a_ty = Ty::new_adt(tcx, a_def, new_a_args);
 
             nested.extend(
                 infcx
diff --git a/compiler/rustc_trait_selection/src/solve/mod.rs b/compiler/rustc_trait_selection/src/solve/mod.rs
index 9dfb793d0a490..94b8af966bf1e 100644
--- a/compiler/rustc_trait_selection/src/solve/mod.rs
+++ b/compiler/rustc_trait_selection/src/solve/mod.rs
@@ -123,10 +123,10 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
     #[instrument(level = "debug", skip(self))]
     fn compute_closure_kind_goal(
         &mut self,
-        goal: Goal<'tcx, (DefId, ty::SubstsRef<'tcx>, ty::ClosureKind)>,
+        goal: Goal<'tcx, (DefId, ty::GenericArgsRef<'tcx>, ty::ClosureKind)>,
     ) -> QueryResult<'tcx> {
-        let (_, substs, expected_kind) = goal.predicate;
-        let found_kind = substs.as_closure().kind_ty().to_opt_closure_kind();
+        let (_, args, expected_kind) = goal.predicate;
+        let found_kind = args.as_closure().kind_ty().to_opt_closure_kind();
 
         let Some(found_kind) = found_kind else {
             return self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
diff --git a/compiler/rustc_trait_selection/src/solve/normalize.rs b/compiler/rustc_trait_selection/src/solve/normalize.rs
index c388850d831e2..ed60071c2cd0a 100644
--- a/compiler/rustc_trait_selection/src/solve/normalize.rs
+++ b/compiler/rustc_trait_selection/src/solve/normalize.rs
@@ -117,7 +117,7 @@ impl<'tcx> NormalizationFolder<'_, 'tcx> {
             self.at.cause.clone(),
             self.at.param_env,
             ty::Binder::dummy(ty::ProjectionPredicate {
-                projection_ty: tcx.mk_alias_ty(uv.def, uv.substs),
+                projection_ty: tcx.mk_alias_ty(uv.def, uv.args),
                 term: new_infer_ct.into(),
             }),
         );
diff --git a/compiler/rustc_trait_selection/src/solve/opaques.rs b/compiler/rustc_trait_selection/src/solve/opaques.rs
index 16194f5ad69c0..2e537d1c358aa 100644
--- a/compiler/rustc_trait_selection/src/solve/opaques.rs
+++ b/compiler/rustc_trait_selection/src/solve/opaques.rs
@@ -26,8 +26,8 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 if !self.can_define_opaque_ty(opaque_ty_def_id) {
                     return Err(NoSolution);
                 }
-                // FIXME: This may have issues when the substs contain aliases...
-                match self.tcx().uses_unique_placeholders_ignoring_regions(opaque_ty.substs) {
+                // FIXME: This may have issues when the args contain aliases...
+                match self.tcx().uses_unique_placeholders_ignoring_regions(opaque_ty.args) {
                     Err(NotUniqueParam::NotParam(param)) if param.is_non_region_infer() => {
                         return self.evaluate_added_goals_and_make_canonical_response(
                             Certainty::AMBIGUOUS,
@@ -40,7 +40,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 }
                 // Prefer opaques registered already.
                 let opaque_type_key =
-                    ty::OpaqueTypeKey { def_id: opaque_ty_def_id, substs: opaque_ty.substs };
+                    ty::OpaqueTypeKey { def_id: opaque_ty_def_id, args: opaque_ty.args };
                 let matches =
                     self.unify_existing_opaque_tys(goal.param_env, opaque_type_key, expected);
                 if !matches.is_empty() {
@@ -54,7 +54,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 self.insert_hidden_type(opaque_type_key, goal.param_env, expected)?;
                 self.add_item_bounds_for_hidden_type(
                     opaque_ty.def_id,
-                    opaque_ty.substs,
+                    opaque_ty.args,
                     goal.param_env,
                     expected,
                 );
@@ -65,7 +65,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
                 // e.g. assigning `impl Copy := NotCopy`
                 self.add_item_bounds_for_hidden_type(
                     opaque_ty.def_id,
-                    opaque_ty.substs,
+                    opaque_ty.args,
                     goal.param_env,
                     expected,
                 );
@@ -73,7 +73,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             }
             (Reveal::All, _) => {
                 // FIXME: Add an assertion that opaque type storage is empty.
-                let actual = tcx.type_of(opaque_ty.def_id).subst(tcx, opaque_ty.substs);
+                let actual = tcx.type_of(opaque_ty.def_id).instantiate(tcx, opaque_ty.args);
                 self.eq(goal.param_env, expected, actual)?;
                 self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
             }
diff --git a/compiler/rustc_trait_selection/src/solve/project_goals.rs b/compiler/rustc_trait_selection/src/solve/project_goals.rs
index 9b701ca202384..564451a31ede4 100644
--- a/compiler/rustc_trait_selection/src/solve/project_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/project_goals.rs
@@ -72,7 +72,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             goal.param_env,
             ty::UnevaluatedConst::new(
                 goal.predicate.projection_ty.def_id,
-                goal.predicate.projection_ty.substs,
+                goal.predicate.projection_ty.args,
             ),
             self.tcx()
                 .type_of(goal.predicate.projection_ty.def_id)
@@ -142,19 +142,19 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        if !drcx.substs_refs_may_unify(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs) {
+        if !drcx.args_refs_may_unify(goal_trait_ref.args, impl_trait_ref.skip_binder().args) {
             return Err(NoSolution);
         }
 
         ecx.probe(|r| CandidateKind::Candidate { name: "impl".into(), result: *r }).enter(|ecx| {
-            let impl_substs = ecx.fresh_substs_for_item(impl_def_id);
-            let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
+            let impl_args = ecx.fresh_args_for_item(impl_def_id);
+            let impl_trait_ref = impl_trait_ref.instantiate(tcx, impl_args);
 
             ecx.eq(goal.param_env, goal_trait_ref, impl_trait_ref)?;
 
             let where_clause_bounds = tcx
                 .predicates_of(impl_def_id)
-                .instantiate(tcx, impl_substs)
+                .instantiate(tcx, impl_args)
                 .predicates
                 .into_iter()
                 .map(|pred| goal.with(tcx, pred));
@@ -184,7 +184,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                         tcx,
                         guar,
                         tcx.type_of(goal.predicate.def_id())
-                            .subst(tcx, goal.predicate.projection_ty.substs),
+                            .instantiate(tcx, goal.predicate.projection_ty.args),
                     )
                     .into(),
                     ty::AssocKind::Type => Ty::new_error(tcx, guar).into(),
@@ -195,25 +195,25 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                 return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
             }
 
-            // Getting the right substitutions here is complex, e.g. given:
+            // Getting the right args here is complex, e.g. given:
             // - a goal `<Vec<u32> as Trait<i32>>::Assoc<u64>`
             // - the applicable impl `impl<T> Trait<i32> for Vec<T>`
             // - and the impl which defines `Assoc` being `impl<T, U> Trait<U> for Vec<T>`
             //
-            // We first rebase the goal substs onto the impl, going from `[Vec<u32>, i32, u64]`
+            // We first rebase the goal args onto the impl, going from `[Vec<u32>, i32, u64]`
             // to `[u32, u64]`.
             //
-            // And then map these substs to the substs of the defining impl of `Assoc`, going
+            // And then map these args to the args of the defining impl of `Assoc`, going
             // from `[u32, u64]` to `[u32, i32, u64]`.
-            let impl_substs_with_gat = goal.predicate.projection_ty.substs.rebase_onto(
+            let impl_args_with_gat = goal.predicate.projection_ty.args.rebase_onto(
                 tcx,
                 goal_trait_ref.def_id,
-                impl_substs,
+                impl_args,
             );
-            let substs = ecx.translate_substs(
+            let args = ecx.translate_args(
                 goal.param_env,
                 impl_def_id,
-                impl_substs_with_gat,
+                impl_args_with_gat,
                 assoc_def.defining_node,
             );
 
@@ -224,7 +224,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                 ty::AssocKind::Fn => unreachable!("we should never project to a fn"),
             };
 
-            ecx.eq(goal.param_env, goal.predicate.term, term.subst(tcx, substs))
+            ecx.eq(goal.param_env, goal.predicate.term, term.instantiate(tcx, args))
                 .expect("expected goal term to be fully unconstrained");
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
@@ -349,7 +349,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                 ty::Dynamic(_, _, _) => {
                     let dyn_metadata = tcx.require_lang_item(LangItem::DynMetadata, None);
                     tcx.type_of(dyn_metadata)
-                        .subst(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
+                        .instantiate(tcx, &[ty::GenericArg::from(goal.predicate.self_ty())])
                 }
 
                 ty::Alias(_, _) | ty::Param(_) | ty::Placeholder(..) => {
@@ -364,20 +364,18 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
                     tcx.types.unit
                 }
 
-                ty::Adt(def, substs) if def.is_struct() => {
-                    match def.non_enum_variant().tail_opt() {
-                        None => tcx.types.unit,
-                        Some(field_def) => {
-                            let self_ty = field_def.ty(tcx, substs);
-                            ecx.add_goal(goal.with(
-                                tcx,
-                                ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)),
-                            ));
-                            return ecx
-                                .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
-                        }
+                ty::Adt(def, args) if def.is_struct() => match def.non_enum_variant().tail_opt() {
+                    None => tcx.types.unit,
+                    Some(field_def) => {
+                        let self_ty = field_def.ty(tcx, args);
+                        ecx.add_goal(goal.with(
+                            tcx,
+                            ty::Binder::dummy(goal.predicate.with_self_ty(tcx, self_ty)),
+                        ));
+                        return ecx
+                            .evaluate_added_goals_and_make_canonical_response(Certainty::Yes);
                     }
-                }
+                },
                 ty::Adt(_, _) => tcx.types.unit,
 
                 ty::Tuple(elements) => match elements.last() {
@@ -412,7 +410,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         goal: Goal<'tcx, Self>,
     ) -> QueryResult<'tcx> {
         let self_ty = goal.predicate.self_ty();
-        let ty::Generator(def_id, substs, _) = *self_ty.kind() else {
+        let ty::Generator(def_id, args, _) = *self_ty.kind() else {
             return Err(NoSolution);
         };
 
@@ -422,7 +420,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
             return Err(NoSolution);
         }
 
-        let term = substs.as_generator().return_ty().into();
+        let term = args.as_generator().return_ty().into();
 
         Self::consider_implied_clause(
             ecx,
@@ -443,7 +441,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
         goal: Goal<'tcx, Self>,
     ) -> QueryResult<'tcx> {
         let self_ty = goal.predicate.self_ty();
-        let ty::Generator(def_id, substs, _) = *self_ty.kind() else {
+        let ty::Generator(def_id, args, _) = *self_ty.kind() else {
             return Err(NoSolution);
         };
 
@@ -453,7 +451,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
             return Err(NoSolution);
         }
 
-        let generator = substs.as_generator();
+        let generator = args.as_generator();
 
         let name = tcx.associated_item(goal.predicate.def_id()).name;
         let term = if name == sym::Return {
diff --git a/compiler/rustc_trait_selection/src/solve/trait_goals.rs b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
index 4066814509663..e7867eead1597 100644
--- a/compiler/rustc_trait_selection/src/solve/trait_goals.rs
+++ b/compiler/rustc_trait_selection/src/solve/trait_goals.rs
@@ -39,10 +39,9 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        if !drcx.substs_refs_may_unify(
-            goal.predicate.trait_ref.substs,
-            impl_trait_ref.skip_binder().substs,
-        ) {
+        if !drcx
+            .args_refs_may_unify(goal.predicate.trait_ref.args, impl_trait_ref.skip_binder().args)
+        {
             return Err(NoSolution);
         }
 
@@ -63,13 +62,13 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         };
 
         ecx.probe_candidate("impl").enter(|ecx| {
-            let impl_substs = ecx.fresh_substs_for_item(impl_def_id);
-            let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
+            let impl_args = ecx.fresh_args_for_item(impl_def_id);
+            let impl_trait_ref = impl_trait_ref.instantiate(tcx, impl_args);
 
             ecx.eq(goal.param_env, goal.predicate.trait_ref, impl_trait_ref)?;
             let where_clause_bounds = tcx
                 .predicates_of(impl_def_id)
-                .instantiate(tcx, impl_substs)
+                .instantiate(tcx, impl_args)
                 .predicates
                 .into_iter()
                 .map(|pred| goal.with(tcx, pred));
@@ -164,7 +163,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         ecx.probe_candidate("trait alias").enter(|ecx| {
             let nested_obligations = tcx
                 .predicates_of(goal.predicate.def_id())
-                .instantiate(tcx, goal.predicate.trait_ref.substs);
+                .instantiate(tcx, goal.predicate.trait_ref.args);
             ecx.add_goals(nested_obligations.predicates.into_iter().map(|p| goal.with(tcx, p)));
             ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
         })
@@ -337,7 +336,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         }
 
         let self_ty = goal.predicate.self_ty();
-        let ty::Generator(def_id, substs, _) = *self_ty.kind() else {
+        let ty::Generator(def_id, args, _) = *self_ty.kind() else {
             return Err(NoSolution);
         };
 
@@ -347,7 +346,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
             return Err(NoSolution);
         }
 
-        let generator = substs.as_generator();
+        let generator = args.as_generator();
         Self::consider_implied_clause(
             ecx,
             goal,
@@ -369,7 +368,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         let tcx = ecx.tcx();
         let a_ty = goal.predicate.self_ty();
-        let b_ty = goal.predicate.trait_ref.substs.type_at(1);
+        let b_ty = goal.predicate.trait_ref.args.type_at(1);
         if b_ty.is_ty_var() {
             return ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS);
         }
@@ -378,7 +377,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                 // Trait upcasting, or `dyn Trait + Auto + 'a` -> `dyn Trait + 'b`
                 (&ty::Dynamic(_, _, ty::Dyn), &ty::Dynamic(_, _, ty::Dyn)) => {
                     // Dyn upcasting is handled separately, since due to upcasting,
-                    // when there are two supertraits that differ by substs, we
+                    // when there are two supertraits that differ by args, we
                     // may return more than one query response.
                     Err(NoSolution)
                 }
@@ -415,7 +414,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                     ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
                 }
                 // Struct unsizing `Struct<T>` -> `Struct<U>` where `T: Unsize<U>`
-                (&ty::Adt(a_def, a_substs), &ty::Adt(b_def, b_substs))
+                (&ty::Adt(a_def, a_args), &ty::Adt(b_def, b_args))
                     if a_def.is_struct() && a_def.did() == b_def.did() =>
                 {
                     let unsizing_params = tcx.unsizing_params_for_adt(a_def.did());
@@ -428,17 +427,17 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
                     let tail_field = a_def.non_enum_variant().tail();
                     let tail_field_ty = tcx.type_of(tail_field.did);
 
-                    let a_tail_ty = tail_field_ty.subst(tcx, a_substs);
-                    let b_tail_ty = tail_field_ty.subst(tcx, b_substs);
+                    let a_tail_ty = tail_field_ty.instantiate(tcx, a_args);
+                    let b_tail_ty = tail_field_ty.instantiate(tcx, b_args);
 
                     // Substitute just the unsizing params from B into A. The type after
                     // this substitution must be equal to B. This is so we don't unsize
                     // unrelated type parameters.
-                    let new_a_substs =
-                        tcx.mk_substs_from_iter(a_substs.iter().enumerate().map(|(i, a)| {
-                            if unsizing_params.contains(i as u32) { b_substs[i] } else { a }
+                    let new_a_args =
+                        tcx.mk_args_from_iter(a_args.iter().enumerate().map(|(i, a)| {
+                            if unsizing_params.contains(i as u32) { b_args[i] } else { a }
                         }));
-                    let unsized_a_ty = Ty::new_adt(tcx, a_def, new_a_substs);
+                    let unsized_a_ty = Ty::new_adt(tcx, a_def, new_a_args);
 
                     // Finally, we require that `TailA: Unsize<TailB>` for the tail field
                     // types.
@@ -484,7 +483,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
         let tcx = ecx.tcx();
 
         let a_ty = goal.predicate.self_ty();
-        let b_ty = goal.predicate.trait_ref.substs.type_at(1);
+        let b_ty = goal.predicate.trait_ref.args.type_at(1);
         let ty::Dynamic(a_data, a_region, ty::Dyn) = *a_ty.kind() else {
             return vec![];
         };
@@ -598,17 +597,17 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
 
         // Erase regions because we compute layouts in `rustc_transmute`,
         // which will ICE for region vars.
-        let substs = ecx.tcx().erase_regions(goal.predicate.trait_ref.substs);
+        let args = ecx.tcx().erase_regions(goal.predicate.trait_ref.args);
 
         let Some(assume) =
-            rustc_transmute::Assume::from_const(ecx.tcx(), goal.param_env, substs.const_at(3))
+            rustc_transmute::Assume::from_const(ecx.tcx(), goal.param_env, args.const_at(3))
         else {
             return Err(NoSolution);
         };
 
         let certainty = ecx.is_transmutable(
-            rustc_transmute::Types { dst: substs.type_at(0), src: substs.type_at(1) },
-            substs.type_at(2),
+            rustc_transmute::Types { dst: args.type_at(0), src: args.type_at(1) },
+            args.type_at(2),
             assume,
         )?;
         ecx.evaluate_added_goals_and_make_canonical_response(certainty)
diff --git a/compiler/rustc_trait_selection/src/solve/weak_types.rs b/compiler/rustc_trait_selection/src/solve/weak_types.rs
index b095b54c554f1..2c176d4cfd663 100644
--- a/compiler/rustc_trait_selection/src/solve/weak_types.rs
+++ b/compiler/rustc_trait_selection/src/solve/weak_types.rs
@@ -12,7 +12,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         let weak_ty = goal.predicate.projection_ty;
         let expected = goal.predicate.term.ty().expect("no such thing as a const alias");
 
-        let actual = tcx.type_of(weak_ty.def_id).subst(tcx, weak_ty.substs);
+        let actual = tcx.type_of(weak_ty.def_id).instantiate(tcx, weak_ty.args);
         self.eq(goal.param_env, expected, actual)?;
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 67e7e5bfa53e2..27cd0f99f34bc 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -324,7 +324,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                 }
                 Ok(None) => {}
                 Err(SelectionError::Unimplemented) => {
-                    if self.is_param_no_infer(pred.skip_binder().trait_ref.substs) {
+                    if self.is_param_no_infer(pred.skip_binder().trait_ref.args) {
                         already_visited.remove(&pred);
                         self.add_user_pred(&mut user_computed_preds, pred.to_predicate(self.tcx));
                         predicates.push_back(pred);
@@ -334,7 +334,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                              {:?} {:?} {:?}",
                             ty,
                             pred,
-                            pred.skip_binder().trait_ref.substs
+                            pred.skip_binder().trait_ref.args
                         );
                         return None;
                     }
@@ -401,17 +401,17 @@ impl<'tcx> AutoTraitFinder<'tcx> {
             ) = (new_pred.kind().skip_binder(), old_pred.kind().skip_binder())
             {
                 if new_trait.def_id() == old_trait.def_id() {
-                    let new_substs = new_trait.trait_ref.substs;
-                    let old_substs = old_trait.trait_ref.substs;
+                    let new_args = new_trait.trait_ref.args;
+                    let old_args = old_trait.trait_ref.args;
 
-                    if !new_substs.types().eq(old_substs.types()) {
+                    if !new_args.types().eq(old_args.types()) {
                         // We can't compare lifetimes if the types are different,
                         // so skip checking `old_pred`.
                         return true;
                     }
 
                     for (new_region, old_region) in
-                        iter::zip(new_substs.regions(), old_substs.regions())
+                        iter::zip(new_args.regions(), old_args.regions())
                     {
                         match (*new_region, *old_region) {
                             // If both predicates have an `ReLateBound` (a HRTB) in the
@@ -564,8 +564,8 @@ impl<'tcx> AutoTraitFinder<'tcx> {
         finished_map
     }
 
-    fn is_param_no_infer(&self, substs: SubstsRef<'_>) -> bool {
-        self.is_of_param(substs.type_at(0)) && !substs.types().any(|t| t.has_infer_types())
+    fn is_param_no_infer(&self, args: GenericArgsRef<'_>) -> bool {
+        self.is_of_param(args.type_at(0)) && !args.types().any(|t| t.has_infer_types())
     }
 
     pub fn is_of_param(&self, ty: Ty<'_>) -> bool {
@@ -636,7 +636,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                     // an inference variable.
                     // Additionally, we check if we've seen this predicate before,
                     // to avoid rendering duplicate bounds to the user.
-                    if self.is_param_no_infer(p.skip_binder().projection_ty.substs)
+                    if self.is_param_no_infer(p.skip_binder().projection_ty.args)
                         && !p.term().skip_binder().has_infer_types()
                         && is_new_pred
                     {
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index dc72cd6517ac6..039e4ec9afdfc 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -96,9 +96,7 @@ pub fn overlapping_impls(
     let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
     let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
     let may_overlap = match (impl1_ref, impl2_ref) {
-        (Some(a), Some(b)) => {
-            drcx.substs_refs_may_unify(a.skip_binder().substs, b.skip_binder().substs)
-        }
+        (Some(a), Some(b)) => drcx.args_refs_may_unify(a.skip_binder().args, b.skip_binder().args),
         (None, None) => {
             let self_ty1 = tcx.type_of(impl1_def_id).skip_binder();
             let self_ty2 = tcx.type_of(impl2_def_id).skip_binder();
@@ -143,15 +141,15 @@ fn with_fresh_ty_vars<'cx, 'tcx>(
     impl_def_id: DefId,
 ) -> ty::ImplHeader<'tcx> {
     let tcx = selcx.tcx();
-    let impl_substs = selcx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
+    let impl_args = selcx.infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
 
     let header = ty::ImplHeader {
         impl_def_id,
-        self_ty: tcx.type_of(impl_def_id).subst(tcx, impl_substs),
-        trait_ref: tcx.impl_trait_ref(impl_def_id).map(|i| i.subst(tcx, impl_substs)),
+        self_ty: tcx.type_of(impl_def_id).instantiate(tcx, impl_args),
+        trait_ref: tcx.impl_trait_ref(impl_def_id).map(|i| i.instantiate(tcx, impl_args)),
         predicates: tcx
             .predicates_of(impl_def_id)
-            .instantiate(tcx, impl_substs)
+            .instantiate(tcx, impl_args)
             .iter()
             .map(|(c, _)| c.as_predicate())
             .collect(),
@@ -353,7 +351,7 @@ fn impl_intersection_has_negative_obligation(
         &infcx,
         ObligationCause::dummy(),
         impl_env,
-        tcx.impl_subject(impl1_def_id).subst_identity(),
+        tcx.impl_subject(impl1_def_id).instantiate_identity(),
     ) {
         Ok(s) => s,
         Err(err) => {
@@ -367,9 +365,9 @@ fn impl_intersection_has_negative_obligation(
 
     // Attempt to prove that impl2 applies, given all of the above.
     let selcx = &mut SelectionContext::new(&infcx);
-    let impl2_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl2_def_id);
+    let impl2_args = infcx.fresh_args_for_item(DUMMY_SP, impl2_def_id);
     let (subject2, normalization_obligations) =
-        impl_subject_and_oblig(selcx, impl_env, impl2_def_id, impl2_substs, |_, _| {
+        impl_subject_and_oblig(selcx, impl_env, impl2_def_id, impl2_args, |_, _| {
             ObligationCause::dummy()
         });
 
@@ -519,7 +517,7 @@ pub enum OrphanCheckErr<'tcx> {
 pub fn orphan_check(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Result<(), OrphanCheckErr<'_>> {
     // We only except this routine to be invoked on implementations
     // of a trait, not inherent implementations.
-    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst_identity();
+    let trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate_identity();
     debug!(?trait_ref);
 
     // If the *trait* is local to the crate, ok.
@@ -728,11 +726,11 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OrphanChecker<'tcx> {
 
             // For fundamental types, we just look inside of them.
             ty::Ref(_, ty, _) => ty.visit_with(self),
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 if self.def_id_is_local(def.did()) {
                     ControlFlow::Break(OrphanCheckEarlyExit::LocalTy(ty))
                 } else if def.is_fundamental() {
-                    substs.visit_with(self)
+                    args.visit_with(self)
                 } else {
                     self.found_non_local_ty(ty)
                 }
diff --git a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
index 8dc13b827e54b..3d0d3812d0c7e 100644
--- a/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
+++ b/compiler/rustc_trait_selection/src/traits/const_evaluatable.rs
@@ -191,7 +191,7 @@ fn satisfied_from_param_env<'tcx>(
             if let ty::ConstKind::Expr(e) = c.kind() {
                 e.visit_with(self)
             } else {
-                // FIXME(generic_const_exprs): This doesn't recurse into `<T as Trait<U>>::ASSOC`'s substs.
+                // FIXME(generic_const_exprs): This doesn't recurse into `<T as Trait<U>>::ASSOC`'s args.
                 // This is currently unobservable as `<T as Trait<{ U + 1 }>>::ASSOC` creates an anon const
                 // with its own `ConstEvaluatable` bound in the param env which we will visit separately.
                 //
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs
index f785c4eaf9dd4..fd813ca4ecb3f 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/ambiguity.rs
@@ -26,8 +26,8 @@ pub fn recompute_applicable_impls<'tcx>(
         let obligation_trait_ref =
             ocx.normalize(&ObligationCause::dummy(), param_env, placeholder_obligation.trait_ref);
 
-        let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
-        let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().subst(tcx, impl_substs);
+        let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
+        let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap().instantiate(tcx, impl_args);
         let impl_trait_ref = ocx.normalize(&ObligationCause::dummy(), param_env, impl_trait_ref);
 
         if let Err(_) =
@@ -36,7 +36,7 @@ pub fn recompute_applicable_impls<'tcx>(
             return false;
         }
 
-        let impl_predicates = tcx.predicates_of(impl_def_id).instantiate(tcx, impl_substs);
+        let impl_predicates = tcx.predicates_of(impl_def_id).instantiate(tcx, impl_args);
         ocx.register_obligations(impl_predicates.predicates.iter().map(|&predicate| {
             Obligation::new(tcx, ObligationCause::dummy(), param_env, predicate)
         }));
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
index 18d48b3b95fcd..a821d1be64b70 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs
@@ -1050,8 +1050,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         report_object_safety_error(self.tcx, span, trait_def_id, violations)
                     }
 
-                    ty::PredicateKind::ClosureKind(closure_def_id, closure_substs, kind) => {
-                        let found_kind = self.closure_kind(closure_substs).unwrap();
+                    ty::PredicateKind::ClosureKind(closure_def_id, closure_args, kind) => {
+                        let found_kind = self.closure_kind(closure_args).unwrap();
                         self.report_closure_error(&obligation, closure_def_id, found_kind, kind)
                     }
 
@@ -1627,14 +1627,14 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     ty::TermKind::Ty(_) => Ty::new_projection(
                         self.tcx,
                         data.projection_ty.def_id,
-                        data.projection_ty.substs,
+                        data.projection_ty.args,
                     )
                     .into(),
                     ty::TermKind::Const(ct) => ty::Const::new_unevaluated(
                         self.tcx,
                         ty::UnevaluatedConst {
                             def: data.projection_ty.def_id,
-                            substs: data.projection_ty.substs,
+                            args: data.projection_ty.args,
                         },
                         ct.ty(),
                     )
@@ -1972,7 +1972,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             traits.sort();
             traits.dedup();
             // FIXME: this could use a better heuristic, like just checking
-            // that substs[1..] is the same.
+            // that args[1..] is the same.
             let all_traits_equal = traits.len() == 1;
 
             let candidates: Vec<String> = candidates
@@ -2018,7 +2018,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         || self.tcx.is_automatically_derived(def_id)
                 })
                 .filter_map(|def_id| self.tcx.impl_trait_ref(def_id))
-                .map(ty::EarlyBinder::subst_identity)
+                .map(ty::EarlyBinder::instantiate_identity)
                 .filter(|trait_ref| {
                     let self_ty = trait_ref.self_ty();
                     // Avoid mentioning type parameters.
@@ -2267,7 +2267,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 // Pick the first substitution that still contains inference variables as the one
                 // we're going to emit an error for. If there are none (see above), fall back to
                 // a more general error.
-                let subst = data.trait_ref.substs.iter().find(|s| s.has_non_region_infer());
+                let subst = data.trait_ref.args.iter().find(|s| s.has_non_region_infer());
 
                 let mut err = if let Some(subst) = subst {
                     self.emit_inference_failure_err(
@@ -2292,7 +2292,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     &obligation.with(self.tcx, trait_ref),
                 );
                 let has_non_region_infer =
-                    trait_ref.skip_binder().substs.types().any(|t| !t.is_ty_or_numeric_infer());
+                    trait_ref.skip_binder().args.types().any(|t| !t.is_ty_or_numeric_infer());
                 // It doesn't make sense to talk about applicable impls if there are more
                 // than a handful of them.
                 if ambiguities.len() > 1 && ambiguities.len() < 10 && has_non_region_infer {
@@ -2330,7 +2330,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     self.suggest_fully_qualified_path(&mut err, def_id, span, trait_ref.def_id());
                 }
 
-                if let Some(ty::subst::GenericArgKind::Type(_)) = subst.map(|subst| subst.unpack())
+                if let Some(ty::GenericArgKind::Type(_)) = subst.map(|subst| subst.unpack())
                     && let Some(body_id) = self.tcx.hir().maybe_body_owned_by(obligation.cause.body_id)
                 {
                     let mut expr_finder = FindExprBySpan::new(span);
@@ -2389,7 +2389,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             // Otherwise, use a placeholder comment for the implementation.
                             let (message, impl_suggestion) = if non_blanket_impl_count == 1 {(
                                 "use the fully-qualified path to the only available implementation".to_string(),
-                                format!("<{} as ", self.tcx.type_of(impl_def_id).subst_identity())
+                                format!("<{} as ", self.tcx.type_of(impl_def_id).instantiate_identity())
                             )} else {(
                                 format!(
                                     "use a fully-qualified path to a specific available implementation ({} found)",
@@ -2466,7 +2466,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 }
                 let subst = data
                     .projection_ty
-                    .substs
+                    .args
                     .iter()
                     .chain(Some(data.term.into_arg()))
                     .find(|g| g.has_non_region_infer());
@@ -2829,9 +2829,9 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             if obligated_types.iter().any(|ot| ot == &self_ty) {
                 return true;
             }
-            if let ty::Adt(def, substs) = self_ty.kind()
-                && let [arg] = &substs[..]
-                && let ty::subst::GenericArgKind::Type(ty) = arg.unpack()
+            if let ty::Adt(def, args) = self_ty.kind()
+                && let [arg] = &args[..]
+                && let ty::GenericArgKind::Type(ty) = arg.unpack()
                 && let ty::Adt(inner_def, _) = ty.kind()
                 && inner_def == def
             {
@@ -2883,14 +2883,14 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         let trait_ref = self.tcx.erase_regions(self.tcx.erase_late_bound_regions(trait_ref));
 
         let src_and_dst = rustc_transmute::Types {
-            dst: trait_ref.substs.type_at(0),
-            src: trait_ref.substs.type_at(1),
+            dst: trait_ref.args.type_at(0),
+            src: trait_ref.args.type_at(1),
         };
-        let scope = trait_ref.substs.type_at(2);
+        let scope = trait_ref.args.type_at(2);
         let Some(assume) = rustc_transmute::Assume::from_const(
             self.infcx.tcx,
             obligation.param_env,
-            trait_ref.substs.const_at(3),
+            trait_ref.args.const_at(3),
         ) else {
             span_bug!(
                 span,
@@ -2905,8 +2905,8 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             assume,
         ) {
             Answer::No(reason) => {
-                let dst = trait_ref.substs.type_at(0);
-                let src = trait_ref.substs.type_at(1);
+                let dst = trait_ref.args.type_at(0);
+                let src = trait_ref.args.type_at(1);
                 let err_msg = format!(
                     "`{src}` cannot be safely transmuted into `{dst}` in the defining scope of `{scope}`"
                 );
@@ -3073,7 +3073,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
 
         // Note any argument mismatches
         let given_ty = params.skip_binder();
-        let expected_ty = trait_ref.skip_binder().substs.type_at(1);
+        let expected_ty = trait_ref.skip_binder().args.type_at(1);
         if let ty::Tuple(given) = given_ty.kind()
             && let ty::Tuple(expected) = expected_ty.kind()
         {
@@ -3288,7 +3288,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
 
         let mut not_tupled = false;
 
-        let found = match found_trait_ref.skip_binder().substs.type_at(1).kind() {
+        let found = match found_trait_ref.skip_binder().args.type_at(1).kind() {
             ty::Tuple(ref tys) => vec![ArgKind::empty(); tys.len()],
             _ => {
                 not_tupled = true;
@@ -3296,7 +3296,7 @@ impl<'tcx> InferCtxtPrivExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             }
         };
 
-        let expected_ty = expected_trait_ref.skip_binder().substs.type_at(1);
+        let expected_ty = expected_trait_ref.skip_binder().args.type_at(1);
         let expected = match expected_ty.kind() {
             ty::Tuple(ref tys) => {
                 tys.iter().map(|t| ArgKind::from_expected_ty(t, Some(span))).collect()
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
index b16d2eb5fc19e..fbe8d4a66803f 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/on_unimplemented.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::{struct_span_err, ErrorGuaranteed};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_middle::ty::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt};
 use rustc_parse_format::{ParseMode, Parser, Piece, Position};
 use rustc_span::symbol::{kw, sym, Symbol};
@@ -25,7 +25,7 @@ pub trait TypeErrCtxtExt<'tcx> {
         &self,
         trait_ref: ty::PolyTraitRef<'tcx>,
         obligation: &PredicateObligation<'tcx>,
-    ) -> Option<(DefId, SubstsRef<'tcx>)>;
+    ) -> Option<(DefId, GenericArgsRef<'tcx>)>;
 
     /*private*/
     fn describe_enclosure(&self, hir_id: hir::HirId) -> Option<&'static str>;
@@ -56,7 +56,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         &self,
         trait_ref: ty::PolyTraitRef<'tcx>,
         obligation: &PredicateObligation<'tcx>,
-    ) -> Option<(DefId, SubstsRef<'tcx>)> {
+    ) -> Option<(DefId, GenericArgsRef<'tcx>)> {
         let tcx = self.tcx;
         let param_env = obligation.param_env;
         let trait_ref = self.instantiate_binder_with_placeholders(trait_ref);
@@ -66,26 +66,23 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         let mut fuzzy_match_impls = vec![];
 
         self.tcx.for_each_relevant_impl(trait_ref.def_id, trait_self_ty, |def_id| {
-            let impl_substs = self.fresh_substs_for_item(obligation.cause.span, def_id);
-            let impl_trait_ref = tcx.impl_trait_ref(def_id).unwrap().subst(tcx, impl_substs);
+            let impl_args = self.fresh_args_for_item(obligation.cause.span, def_id);
+            let impl_trait_ref = tcx.impl_trait_ref(def_id).unwrap().instantiate(tcx, impl_args);
 
             let impl_self_ty = impl_trait_ref.self_ty();
 
             if self.can_eq(param_env, trait_self_ty, impl_self_ty) {
-                self_match_impls.push((def_id, impl_substs));
+                self_match_impls.push((def_id, impl_args));
 
-                if iter::zip(
-                    trait_ref.substs.types().skip(1),
-                    impl_trait_ref.substs.types().skip(1),
-                )
-                .all(|(u, v)| self.fuzzy_match_tys(u, v, false).is_some())
+                if iter::zip(trait_ref.args.types().skip(1), impl_trait_ref.args.types().skip(1))
+                    .all(|(u, v)| self.fuzzy_match_tys(u, v, false).is_some())
                 {
-                    fuzzy_match_impls.push((def_id, impl_substs));
+                    fuzzy_match_impls.push((def_id, impl_args));
                 }
             }
         });
 
-        let impl_def_id_and_substs = if self_match_impls.len() == 1 {
+        let impl_def_id_and_args = if self_match_impls.len() == 1 {
             self_match_impls[0]
         } else if fuzzy_match_impls.len() == 1 {
             fuzzy_match_impls[0]
@@ -93,8 +90,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             return None;
         };
 
-        tcx.has_attr(impl_def_id_and_substs.0, sym::rustc_on_unimplemented)
-            .then_some(impl_def_id_and_substs)
+        tcx.has_attr(impl_def_id_and_args.0, sym::rustc_on_unimplemented)
+            .then_some(impl_def_id_and_args)
     }
 
     /// Used to set on_unimplemented's `ItemContext`
@@ -143,9 +140,9 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         trait_ref: ty::PolyTraitRef<'tcx>,
         obligation: &PredicateObligation<'tcx>,
     ) -> OnUnimplementedNote {
-        let (def_id, substs) = self
+        let (def_id, args) = self
             .impl_similar_to(trait_ref, obligation)
-            .unwrap_or_else(|| (trait_ref.def_id(), trait_ref.skip_binder().substs));
+            .unwrap_or_else(|| (trait_ref.def_id(), trait_ref.skip_binder().args));
         let trait_ref = trait_ref.skip_binder();
 
         let mut flags = vec![];
@@ -192,14 +189,14 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 // signature with no type arguments resolved
                 flags.push((
                     sym::_Self,
-                    Some(self.tcx.type_of(def.did()).subst_identity().to_string()),
+                    Some(self.tcx.type_of(def.did()).instantiate_identity().to_string()),
                 ));
             }
 
             for param in generics.params.iter() {
                 let value = match param.kind {
                     GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
-                        substs[param.index as usize].to_string()
+                        args[param.index as usize].to_string()
                     }
                     GenericParamDefKind::Lifetime => continue,
                 };
@@ -207,13 +204,13 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 flags.push((name, Some(value)));
 
                 if let GenericParamDefKind::Type { .. } = param.kind {
-                    let param_ty = substs[param.index as usize].expect_ty();
+                    let param_ty = args[param.index as usize].expect_ty();
                     if let Some(def) = param_ty.ty_adt_def() {
                         // We also want to be able to select the parameter's
                         // original signature with no type arguments resolved
                         flags.push((
                             name,
-                            Some(self.tcx.type_of(def.did()).subst_identity().to_string()),
+                            Some(self.tcx.type_of(def.did()).instantiate_identity().to_string()),
                         ));
                     }
                 }
@@ -249,7 +246,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     // signature with no type arguments resolved
                     flags.push((
                         sym::_Self,
-                        Some(format!("[{}]", self.tcx.type_of(def.did()).subst_identity())),
+                        Some(format!("[{}]", self.tcx.type_of(def.did()).instantiate_identity())),
                     ));
                 }
                 if aty.is_integral() {
@@ -268,7 +265,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 if let Some(def) = aty.ty_adt_def() {
                     // We also want to be able to select the array's type's original
                     // signature with no type arguments resolved
-                    let def_ty = self.tcx.type_of(def.did()).subst_identity();
+                    let def_ty = self.tcx.type_of(def.did()).instantiate_identity();
                     flags.push((sym::_Self, Some(format!("[{def_ty}; _]"))));
                     if let Some(n) = len {
                         flags.push((sym::_Self, Some(format!("[{def_ty}; {n}]"))));
@@ -629,7 +626,7 @@ impl<'tcx> OnUnimplementedFormatString {
             .filter_map(|param| {
                 let value = match param.kind {
                     GenericParamDefKind::Type { .. } | GenericParamDefKind::Const { .. } => {
-                        trait_ref.substs[param.index as usize].to_string()
+                        trait_ref.args[param.index as usize].to_string()
                     }
                     GenericParamDefKind::Lifetime => return None,
                 };
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index 1a9e21c2bea13..2c78ae669074c 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -30,7 +30,7 @@ use rustc_middle::hir::map;
 use rustc_middle::ty::error::TypeError::{self, Sorts};
 use rustc_middle::ty::{
     self, suggest_arbitrary_trait_bound, suggest_constraining_type_param, AdtKind,
-    GeneratorDiagnosticData, GeneratorInteriorTypeCause, InferTy, InternalSubsts, IsSuggestable,
+    GeneratorDiagnosticData, GeneratorInteriorTypeCause, GenericArgs, InferTy, IsSuggestable,
     ToPredicate, Ty, TyCtxt, TypeAndMut, TypeFoldable, TypeFolder, TypeSuperFoldable,
     TypeVisitableExt, TypeckResults,
 };
@@ -670,7 +670,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     // this that we do in `suggest_restriction` and pull the
                     // `impl Trait` into a new generic if it shows up somewhere
                     // else in the predicate.
-                    if !trait_pred.skip_binder().trait_ref.substs[1..]
+                    if !trait_pred.skip_binder().trait_ref.args[1..]
                         .iter()
                         .all(|g| g.is_suggestable(self.tcx, false))
                     {
@@ -1183,21 +1183,21 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         let fn_sig = found.fn_sig(self.tcx);
                         Some((DefIdOrName::DefId(def_id), fn_sig.output(), fn_sig.inputs()))
                     }
-                    ty::Closure(def_id, substs) => {
-                        let fn_sig = substs.as_closure().sig();
+                    ty::Closure(def_id, args) => {
+                        let fn_sig = args.as_closure().sig();
                         Some((
                             DefIdOrName::DefId(def_id),
                             fn_sig.output(),
                             fn_sig.inputs().map_bound(|inputs| &inputs[1..]),
                         ))
                     }
-                    ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                        self.tcx.item_bounds(def_id).subst(self.tcx, substs).iter().find_map(
+                    ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                        self.tcx.item_bounds(def_id).instantiate(self.tcx, args).iter().find_map(
                             |pred| {
                                 if let ty::ClauseKind::Projection(proj) = pred.kind().skip_binder()
                         && Some(proj.projection_ty.def_id) == self.tcx.lang_items().fn_once_output()
-                        // args tuple will always be substs[1]
-                        && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind()
+                        // args tuple will always be args[1]
+                        && let ty::Tuple(args) = proj.projection_ty.args.type_at(1).kind()
                         {
                             Some((
                                 DefIdOrName::DefId(def_id),
@@ -1214,8 +1214,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                         data.iter().find_map(|pred| {
                             if let ty::ExistentialPredicate::Projection(proj) = pred.skip_binder()
                         && Some(proj.def_id) == self.tcx.lang_items().fn_once_output()
-                        // for existential projection, substs are shifted over by 1
-                        && let ty::Tuple(args) = proj.substs.type_at(0).kind()
+                        // for existential projection, args are shifted over by 1
+                        && let ty::Tuple(args) = proj.args.type_at(0).kind()
                         {
                             Some((
                                 DefIdOrName::Name("trait object"),
@@ -1242,8 +1242,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                             if let ty::ClauseKind::Projection(proj) = pred.kind().skip_binder()
                         && Some(proj.projection_ty.def_id) == self.tcx.lang_items().fn_once_output()
                         && proj.projection_ty.self_ty() == found
-                        // args tuple will always be substs[1]
-                        && let ty::Tuple(args) = proj.projection_ty.substs.type_at(1).kind()
+                        // args tuple will always be args[1]
+                        && let ty::Tuple(args) = proj.projection_ty.args.type_at(1).kind()
                         {
                             Some((
                                 name,
@@ -1699,7 +1699,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 }
                 if let Some(typeck_results) = &self.typeck_results
                         && let ty = typeck_results.expr_ty_adjusted(base)
-                        && let ty::FnDef(def_id, _substs) = ty.kind()
+                        && let ty::FnDef(def_id, _args) = ty.kind()
                         && let Some(hir::Node::Item(hir::Item { ident, span, vis_span, .. })) =
                             hir.get_if_local(*def_id)
                     {
@@ -1980,7 +1980,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             infcx: &InferCtxt<'tcx>,
             trait_ref: ty::PolyTraitRef<'tcx>,
         ) -> Ty<'tcx> {
-            let inputs = trait_ref.skip_binder().substs.type_at(1);
+            let inputs = trait_ref.skip_binder().args.type_at(1);
             let sig = match inputs.kind() {
                 ty::Tuple(inputs) if infcx.tcx.is_fn_trait(trait_ref.def_id()) => {
                     infcx.tcx.mk_fn_sig(
@@ -2061,12 +2061,12 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         {
             let expected_self =
                 self.tcx.anonymize_bound_vars(pred.kind().rebind(trait_pred.self_ty()));
-            let expected_substs = self
+            let expected_args = self
                 .tcx
-                .anonymize_bound_vars(pred.kind().rebind(trait_pred.trait_ref.substs));
+                .anonymize_bound_vars(pred.kind().rebind(trait_pred.trait_ref.args));
 
             // Find another predicate whose self-type is equal to the expected self type,
-            // but whose substs don't match.
+            // but whose args don't match.
             let other_pred = predicates.into_iter()
                 .enumerate()
                 .find(|(other_idx, (pred, _))| match pred.kind().skip_binder() {
@@ -2079,10 +2079,10 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 == self.tcx.anonymize_bound_vars(
                                     pred.kind().rebind(trait_pred.self_ty()),
                                 )
-                            // But the substs don't match (i.e. incompatible args)
-                            && expected_substs
+                            // But the args don't match (i.e. incompatible args)
+                            && expected_args
                                 != self.tcx.anonymize_bound_vars(
-                                    pred.kind().rebind(trait_pred.trait_ref.substs),
+                                    pred.kind().rebind(trait_pred.trait_ref.args),
                                 ) =>
                     {
                         true
@@ -3070,7 +3070,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 }
                                 err.note(msg.trim_end_matches(", ").to_string())
                             }
-                            ty::GeneratorWitnessMIR(def_id, substs) => {
+                            ty::GeneratorWitnessMIR(def_id, args) => {
                                 use std::fmt::Write;
 
                                 // FIXME: this is kind of an unusual format for rustc, can we make it more clear?
@@ -3079,7 +3079,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                                 let mut msg =
                                     "required because it captures the following types: ".to_owned();
                                 for bty in tcx.generator_hidden_types(*def_id) {
-                                    let ty = bty.subst(tcx, substs);
+                                    let ty = bty.instantiate(tcx, args);
                                     write!(msg, "`{}`, ", ty).unwrap();
                                 }
                                 err.note(msg.trim_end_matches(", ").to_string())
@@ -3407,7 +3407,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     Ty::new_projection(
                         self.tcx,
                         item_def_id,
-                        // Future::Output has no substs
+                        // Future::Output has no args
                         [trait_pred.self_ty()],
                     )
                 });
@@ -3448,7 +3448,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             _ => return,
         };
         if let ty::Float(_) = trait_ref.skip_binder().self_ty().kind()
-            && let ty::Infer(InferTy::IntVar(_)) = trait_ref.skip_binder().substs.type_at(1).kind()
+            && let ty::Infer(InferTy::IntVar(_)) = trait_ref.skip_binder().args.type_at(1).kind()
         {
             err.span_suggestion_verbose(
                 rhs_span.shrink_to_hi(),
@@ -3468,15 +3468,15 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         let Some(diagnostic_name) = self.tcx.get_diagnostic_name(trait_pred.def_id()) else {
             return;
         };
-        let (adt, substs) = match trait_pred.skip_binder().self_ty().kind() {
-            ty::Adt(adt, substs) if adt.did().is_local() => (adt, substs),
+        let (adt, args) = match trait_pred.skip_binder().self_ty().kind() {
+            ty::Adt(adt, args) if adt.did().is_local() => (adt, args),
             _ => return,
         };
         let can_derive = {
             let is_derivable_trait = match diagnostic_name {
                 sym::Default => !adt.is_enum(),
                 sym::PartialEq | sym::PartialOrd => {
-                    let rhs_ty = trait_pred.skip_binder().trait_ref.substs.type_at(1);
+                    let rhs_ty = trait_pred.skip_binder().trait_ref.args.type_at(1);
                     trait_pred.skip_binder().self_ty() == rhs_ty
                 }
                 sym::Eq | sym::Ord | sym::Clone | sym::Copy | sym::Hash | sym::Debug => true,
@@ -3485,8 +3485,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             is_derivable_trait &&
                 // Ensure all fields impl the trait.
                 adt.all_fields().all(|field| {
-                    let field_ty = field.ty(self.tcx, substs);
-                    let trait_substs = match diagnostic_name {
+                    let field_ty = field.ty(self.tcx, args);
+                    let trait_args = match diagnostic_name {
                         sym::PartialEq | sym::PartialOrd => {
                             Some(field_ty)
                         }
@@ -3495,7 +3495,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     let trait_pred = trait_pred.map_bound_ref(|tr| ty::TraitPredicate {
                         trait_ref: ty::TraitRef::new(self.tcx,
                             trait_pred.def_id(),
-                            [field_ty].into_iter().chain(trait_substs),
+                            [field_ty].into_iter().chain(trait_args),
                         ),
                         ..*tr
                     });
@@ -3530,7 +3530,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
     ) {
         if let ObligationCauseCode::ImplDerivedObligation(_) = obligation.cause.code()
             && self.tcx.is_diagnostic_item(sym::SliceIndex, trait_pred.skip_binder().trait_ref.def_id)
-            && let ty::Slice(_) = trait_pred.skip_binder().trait_ref.substs.type_at(1).kind()
+            && let ty::Slice(_) = trait_pred.skip_binder().trait_ref.args.type_at(1).kind()
             && let ty::Ref(_, inner_ty, _) = trait_pred.skip_binder().self_ty().kind()
             && let ty::Uint(ty::UintTy::Usize) = inner_ty.kind()
         {
@@ -3580,8 +3580,8 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             // trait_pred `S: Sum<<Self as Iterator>::Item>` and predicate `i32: Sum<&()>`
             let mut type_diffs = vec![];
             if let ObligationCauseCode::ExprBindingObligation(def_id, _, _, idx) = parent_code.deref()
-                && let Some(node_substs) = typeck_results.node_substs_opt(call_hir_id)
-                && let where_clauses = self.tcx.predicates_of(def_id).instantiate(self.tcx, node_substs)
+                && let Some(node_args) = typeck_results.node_args_opt(call_hir_id)
+                && let where_clauses = self.tcx.predicates_of(def_id).instantiate(self.tcx, node_args)
                 && let Some(where_pred) = where_clauses.predicates.get(*idx)
             {
                 if let Some(where_pred) = where_pred.as_trait_clause()
@@ -3595,7 +3595,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     );
 
                     let zipped =
-                        iter::zip(where_pred.trait_ref.substs, failed_pred.trait_ref.substs);
+                        iter::zip(where_pred.trait_ref.args, failed_pred.trait_ref.args);
                     for (expected, actual) in zipped {
                         self.probe(|_| {
                             match self
@@ -3686,7 +3686,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
         if let ty::PredicateKind::Clause(ty::ClauseKind::Trait(ty::TraitPredicate { trait_ref, .. }))
             = failed_pred.kind().skip_binder()
             && tcx.is_fn_trait(trait_ref.def_id)
-            && let [self_ty, found_ty] = trait_ref.substs.as_slice()
+            && let [self_ty, found_ty] = trait_ref.args.as_slice()
             && let Some(fn_ty) = self_ty.as_type().filter(|ty| ty.is_fn())
             && let fn_sig @ ty::FnSig {
                 abi: abi::Abi::Rust,
@@ -3706,7 +3706,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
 
             // Extract `<U as Deref>::Target` assoc type and check that it is `T`
             && let Some(deref_target_did) = tcx.lang_items().deref_target()
-            && let projection = Ty::new_projection(tcx,deref_target_did, tcx.mk_substs(&[ty::GenericArg::from(found_ty)]))
+            && let projection = Ty::new_projection(tcx,deref_target_did, tcx.mk_args(&[ty::GenericArg::from(found_ty)]))
             && let InferOk { value: deref_target, obligations } = infcx.at(&ObligationCause::dummy(), param_env).normalize(projection)
             && obligations.iter().all(|obligation| infcx.predicate_must_hold_modulo_regions(obligation))
             && infcx.can_eq(param_env, deref_target, target_ty)
@@ -3908,7 +3908,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             // Make `Self` be equivalent to the type of the call chain
             // expression we're looking at now, so that we can tell what
             // for example `Iterator::Item` is at this point in the chain.
-            let substs = InternalSubsts::for_item(self.tcx, trait_def_id, |param, _| {
+            let args = GenericArgs::for_item(self.tcx, trait_def_id, |param, _| {
                 match param.kind {
                     ty::GenericParamDefKind::Type { .. } => {
                         if param.index == 0 {
@@ -3926,7 +3926,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
             // This corresponds to `<ExprTy as Iterator>::Item = _`.
             let projection = ty::Binder::dummy(ty::PredicateKind::Clause(
                 ty::ClauseKind::Projection(ty::ProjectionPredicate {
-                    projection_ty: self.tcx.mk_alias_ty(proj.def_id, substs),
+                    projection_ty: self.tcx.mk_alias_ty(proj.def_id, args),
                     term: ty_var.into(),
                 }),
             ));
diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
index cf9d9315f60b2..9ddf8a09b58f0 100644
--- a/compiler/rustc_trait_selection/src/traits/fulfill.rs
+++ b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -8,7 +8,7 @@ use rustc_infer::traits::{PolyTraitObligation, SelectionError, TraitEngine};
 use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::error::{ExpectedFound, TypeError};
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Binder, Const, TypeVisitableExt};
 use std::marker::PhantomData;
 
@@ -410,8 +410,8 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
                     }
                 }
 
-                ty::PredicateKind::ClosureKind(_, closure_substs, kind) => {
-                    match self.selcx.infcx.closure_kind(closure_substs) {
+                ty::PredicateKind::ClosureKind(_, closure_args, kind) => {
+                    match self.selcx.infcx.closure_kind(closure_args) {
                         Some(closure_kind) => {
                             if closure_kind.extends(kind) {
                                 ProcessResult::Changed(vec![])
@@ -536,7 +536,7 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
                                 if let Ok(new_obligations) = infcx
                                     .at(&obligation.cause, obligation.param_env)
                                     .trace(c1, c2)
-                                    .eq(DefineOpaqueTypes::No, a.substs, b.substs)
+                                    .eq(DefineOpaqueTypes::No, a.args, b.args)
                                 {
                                     return ProcessResult::Changed(mk_pending(
                                         new_obligations.into_obligations(),
@@ -559,31 +559,30 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
 
                     let stalled_on = &mut pending_obligation.stalled_on;
 
-                    let mut evaluate = |c: Const<'tcx>| {
-                        if let ty::ConstKind::Unevaluated(unevaluated) = c.kind() {
-                            match self.selcx.infcx.try_const_eval_resolve(
-                                obligation.param_env,
-                                unevaluated,
-                                c.ty(),
-                                Some(obligation.cause.span),
-                            ) {
-                                Ok(val) => Ok(val),
-                                Err(e) => match e {
-                                    ErrorHandled::TooGeneric => {
-                                        stalled_on.extend(
-                                            unevaluated.substs.iter().filter_map(
+                    let mut evaluate =
+                        |c: Const<'tcx>| {
+                            if let ty::ConstKind::Unevaluated(unevaluated) = c.kind() {
+                                match self.selcx.infcx.try_const_eval_resolve(
+                                    obligation.param_env,
+                                    unevaluated,
+                                    c.ty(),
+                                    Some(obligation.cause.span),
+                                ) {
+                                    Ok(val) => Ok(val),
+                                    Err(e) => match e {
+                                        ErrorHandled::TooGeneric => {
+                                            stalled_on.extend(unevaluated.args.iter().filter_map(
                                                 TyOrConstInferVar::maybe_from_generic_arg,
-                                            ),
-                                        );
-                                        Err(ErrorHandled::TooGeneric)
-                                    }
-                                    _ => Err(e),
-                                },
+                                            ));
+                                            Err(ErrorHandled::TooGeneric)
+                                        }
+                                        _ => Err(e),
+                                    },
+                                }
+                            } else {
+                                Ok(c)
                             }
-                        } else {
-                            Ok(c)
-                        }
-                    };
+                        };
 
                     match (evaluate(c1), evaluate(c2)) {
                         (Ok(c1), Ok(c2)) => {
@@ -696,9 +695,9 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
                 // trait selection is because we don't have enough
                 // information about the types in the trait.
                 stalled_on.clear();
-                stalled_on.extend(substs_infer_vars(
+                stalled_on.extend(args_infer_vars(
                     &self.selcx,
-                    trait_obligation.predicate.map_bound(|pred| pred.trait_ref.substs),
+                    trait_obligation.predicate.map_bound(|pred| pred.trait_ref.args),
                 ));
 
                 debug!(
@@ -753,9 +752,9 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
             ProjectAndUnifyResult::Holds(os) => ProcessResult::Changed(mk_pending(os)),
             ProjectAndUnifyResult::FailedNormalization => {
                 stalled_on.clear();
-                stalled_on.extend(substs_infer_vars(
+                stalled_on.extend(args_infer_vars(
                     &self.selcx,
-                    project_obligation.predicate.map_bound(|pred| pred.projection_ty.substs),
+                    project_obligation.predicate.map_bound(|pred| pred.projection_ty.args),
                 ));
                 ProcessResult::Unchanged
             }
@@ -770,14 +769,14 @@ impl<'a, 'tcx> FulfillProcessor<'a, 'tcx> {
     }
 }
 
-/// Returns the set of inference variables contained in `substs`.
-fn substs_infer_vars<'a, 'tcx>(
+/// Returns the set of inference variables contained in `args`.
+fn args_infer_vars<'a, 'tcx>(
     selcx: &SelectionContext<'a, 'tcx>,
-    substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
+    args: ty::Binder<'tcx, GenericArgsRef<'tcx>>,
 ) -> impl Iterator<Item = TyOrConstInferVar<'tcx>> {
     selcx
         .infcx
-        .resolve_vars_if_possible(substs)
+        .resolve_vars_if_possible(args)
         .skip_binder() // ok because this check doesn't care about regions
         .iter()
         .filter(|arg| arg.has_non_region_infer())
diff --git a/compiler/rustc_trait_selection/src/traits/misc.rs b/compiler/rustc_trait_selection/src/traits/misc.rs
index e9cfd63e2eddc..ab07b10c65f58 100644
--- a/compiler/rustc_trait_selection/src/traits/misc.rs
+++ b/compiler/rustc_trait_selection/src/traits/misc.rs
@@ -43,7 +43,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
     self_type: Ty<'tcx>,
     parent_cause: ObligationCause<'tcx>,
 ) -> Result<(), CopyImplementationError<'tcx>> {
-    let (adt, substs) = match self_type.kind() {
+    let (adt, args) = match self_type.kind() {
         // These types used to have a builtin impl.
         // Now libcore provides that impl.
         ty::Uint(_)
@@ -56,7 +56,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
         | ty::Ref(_, _, hir::Mutability::Not)
         | ty::Array(..) => return Ok(()),
 
-        &ty::Adt(adt, substs) => (adt, substs),
+        &ty::Adt(adt, args) => (adt, args),
 
         _ => return Err(CopyImplementationError::NotAnAdt),
     };
@@ -66,7 +66,7 @@ pub fn type_allowed_to_implement_copy<'tcx>(
         param_env,
         self_type,
         adt,
-        substs,
+        args,
         parent_cause,
         hir::LangItem::Copy,
     )
@@ -91,7 +91,7 @@ pub fn type_allowed_to_implement_const_param_ty<'tcx>(
     self_type: Ty<'tcx>,
     parent_cause: ObligationCause<'tcx>,
 ) -> Result<(), ConstParamTyImplementationError<'tcx>> {
-    let (adt, substs) = match self_type.kind() {
+    let (adt, args) = match self_type.kind() {
         // `core` provides these impls.
         ty::Uint(_)
         | ty::Int(_)
@@ -103,7 +103,7 @@ pub fn type_allowed_to_implement_const_param_ty<'tcx>(
         | ty::Ref(.., hir::Mutability::Not)
         | ty::Tuple(_) => return Ok(()),
 
-        &ty::Adt(adt, substs) => (adt, substs),
+        &ty::Adt(adt, args) => (adt, args),
 
         _ => return Err(ConstParamTyImplementationError::NotAnAdtOrBuiltinAllowed),
     };
@@ -113,7 +113,7 @@ pub fn type_allowed_to_implement_const_param_ty<'tcx>(
         param_env,
         self_type,
         adt,
-        substs,
+        args,
         parent_cause,
         hir::LangItem::ConstParamTy,
     )
@@ -128,7 +128,7 @@ pub fn all_fields_implement_trait<'tcx>(
     param_env: ty::ParamEnv<'tcx>,
     self_type: Ty<'tcx>,
     adt: AdtDef<'tcx>,
-    substs: &'tcx List<GenericArg<'tcx>>,
+    args: &'tcx List<GenericArg<'tcx>>,
     parent_cause: ObligationCause<'tcx>,
     lang_item: LangItem,
 ) -> Result<(), Vec<(&'tcx ty::FieldDef, Ty<'tcx>, InfringingFieldsReason<'tcx>)>> {
@@ -141,7 +141,7 @@ pub fn all_fields_implement_trait<'tcx>(
             let infcx = tcx.infer_ctxt().build();
             let ocx = traits::ObligationCtxt::new(&infcx);
 
-            let unnormalized_ty = field.ty(tcx, substs);
+            let unnormalized_ty = field.ty(tcx, args);
             if unnormalized_ty.references_error() {
                 continue;
             }
@@ -154,11 +154,11 @@ pub fn all_fields_implement_trait<'tcx>(
 
             // FIXME(compiler-errors): This gives us better spans for bad
             // projection types like in issue-50480.
-            // If the ADT has substs, point to the cause we are given.
+            // If the ADT has args, point to the cause we are given.
             // If it does not, then this field probably doesn't normalize
             // to begin with, and point to the bad field's span instead.
             let normalization_cause = if field
-                .ty(tcx, traits::InternalSubsts::identity_for_item(tcx, adt.did()))
+                .ty(tcx, traits::GenericArgs::identity_for_item(tcx, adt.did()))
                 .has_non_region_param()
             {
                 parent_cause.clone()
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index f092e82175177..1c14599918419 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -32,7 +32,7 @@ use rustc_middle::query::Providers;
 use rustc_middle::ty::fold::TypeFoldable;
 use rustc_middle::ty::visit::{TypeVisitable, TypeVisitableExt};
 use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt, TypeFolder, TypeSuperVisitable};
-use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
@@ -61,13 +61,13 @@ pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError
 pub use self::specialize::specialization_graph::FutureCompatOverlapError;
 pub use self::specialize::specialization_graph::FutureCompatOverlapErrorKind;
 pub use self::specialize::{
-    specialization_graph, translate_substs, translate_substs_with_cause, OverlapError,
+    specialization_graph, translate_args, translate_args_with_cause, OverlapError,
 };
 pub use self::structural_match::search_for_structural_match_violation;
 pub use self::structural_normalize::StructurallyNormalizeExt;
 pub use self::util::elaborate;
 pub use self::util::{
-    check_substs_compatible, supertrait_def_ids, supertraits, transitive_bounds,
+    check_args_compatible, supertrait_def_ids, supertraits, transitive_bounds,
     transitive_bounds_that_define_assoc_item, SupertraitDefIds,
 };
 pub use self::util::{expand_trait_aliases, TraitAliasExpander};
@@ -454,7 +454,7 @@ pub fn impossible_predicates<'tcx>(tcx: TyCtxt<'tcx>, predicates: Vec<ty::Clause
 
 fn subst_and_check_impossible_predicates<'tcx>(
     tcx: TyCtxt<'tcx>,
-    key: (DefId, SubstsRef<'tcx>),
+    key: (DefId, GenericArgsRef<'tcx>),
 ) -> bool {
     debug!("subst_and_check_impossible_predicates(key={:?})", key);
 
@@ -521,7 +521,7 @@ fn is_impossible_method(tcx: TyCtxt<'_>, (impl_def_id, trait_item_def_id): (DefI
     let impl_trait_ref = tcx
         .impl_trait_ref(impl_def_id)
         .expect("expected impl to correspond to trait")
-        .subst_identity();
+        .instantiate_identity();
     let param_env = tcx.param_env(impl_def_id);
 
     let mut visitor = ReferencesOnlyParentGenerics { tcx, generics, trait_item_def_id };
@@ -531,7 +531,7 @@ fn is_impossible_method(tcx: TyCtxt<'_>, (impl_def_id, trait_item_def_id): (DefI
                 tcx,
                 ObligationCause::dummy_with_span(*span),
                 param_env,
-                ty::EarlyBinder::bind(*pred).subst(tcx, impl_trait_ref.substs),
+                ty::EarlyBinder::bind(*pred).instantiate(tcx, impl_trait_ref.args),
             )
         })
     });
diff --git a/compiler/rustc_trait_selection/src/traits/object_safety.rs b/compiler/rustc_trait_selection/src/traits/object_safety.rs
index c31944c162e6c..265a2ae7621ef 100644
--- a/compiler/rustc_trait_selection/src/traits/object_safety.rs
+++ b/compiler/rustc_trait_selection/src/traits/object_safety.rs
@@ -17,10 +17,10 @@ use rustc_errors::{DelayDm, FatalError, MultiSpan};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::subst::{GenericArg, InternalSubsts};
 use rustc_middle::ty::{
     self, EarlyBinder, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitor,
 };
+use rustc_middle::ty::{GenericArg, GenericArgs};
 use rustc_middle::ty::{ToPredicate, TypeVisitableExt};
 use rustc_session::lint::builtin::WHERE_CLAUSES_OBJECT_SAFETY;
 use rustc_span::symbol::Symbol;
@@ -270,7 +270,7 @@ fn bounds_reference_self(tcx: TyCtxt<'_>, trait_def_id: DefId) -> SmallVec<[Span
     tcx.associated_items(trait_def_id)
         .in_definition_order()
         .filter(|item| item.kind == ty::AssocKind::Type)
-        .flat_map(|item| tcx.explicit_item_bounds(item.def_id).subst_identity_iter_copied())
+        .flat_map(|item| tcx.explicit_item_bounds(item.def_id).instantiate_identity_iter_copied())
         .filter_map(|c| predicate_references_self(tcx, c))
         .collect()
 }
@@ -284,7 +284,7 @@ fn predicate_references_self<'tcx>(
     match predicate.kind().skip_binder() {
         ty::ClauseKind::Trait(ref data) => {
             // In the case of a trait predicate, we can skip the "self" type.
-            data.trait_ref.substs[1..].iter().any(has_self_ty).then_some(sp)
+            data.trait_ref.args[1..].iter().any(has_self_ty).then_some(sp)
         }
         ty::ClauseKind::Projection(ref data) => {
             // And similarly for projections. This should be redundant with
@@ -302,7 +302,7 @@ fn predicate_references_self<'tcx>(
             //
             // This is ALT2 in issue #56288, see that for discussion of the
             // possible alternatives.
-            data.projection_ty.substs[1..].iter().any(has_self_ty).then_some(sp)
+            data.projection_ty.args[1..].iter().any(has_self_ty).then_some(sp)
         }
         ty::ClauseKind::ConstArgHasType(_ct, ty) => has_self_ty(&ty.into()).then_some(sp),
 
@@ -414,7 +414,7 @@ fn virtual_call_violation_for_method<'tcx>(
     trait_def_id: DefId,
     method: ty::AssocItem,
 ) -> Option<MethodViolationCode> {
-    let sig = tcx.fn_sig(method.def_id).subst_identity();
+    let sig = tcx.fn_sig(method.def_id).instantiate_identity();
 
     // The method's first parameter must be named `self`
     if !method.fn_has_self_parameter {
@@ -586,7 +586,7 @@ fn virtual_call_violation_for_method<'tcx>(
             // allowed to have generic parameters so `auto trait Bound<T> {}`
             // would already have reported an error at the definition of the
             // auto trait.
-            if pred_trait_ref.substs.len() != 1 {
+            if pred_trait_ref.args.len() != 1 {
                 tcx.sess.diagnostic().delay_span_bug(
                     span,
                     "auto traits cannot have generic parameters",
@@ -612,11 +612,11 @@ fn receiver_for_self_ty<'tcx>(
     method_def_id: DefId,
 ) -> Ty<'tcx> {
     debug!("receiver_for_self_ty({:?}, {:?}, {:?})", receiver_ty, self_ty, method_def_id);
-    let substs = InternalSubsts::for_item(tcx, method_def_id, |param, _| {
+    let args = GenericArgs::for_item(tcx, method_def_id, |param, _| {
         if param.index == 0 { self_ty.into() } else { tcx.mk_param_from_def(param) }
     });
 
-    let result = EarlyBinder::bind(receiver_ty).subst(tcx, substs);
+    let result = EarlyBinder::bind(receiver_ty).instantiate(tcx, args);
     debug!(
         "receiver_for_self_ty({:?}, {:?}, {:?}) = {:?}",
         receiver_ty, self_ty, method_def_id, result
@@ -751,11 +751,11 @@ fn receiver_is_dispatchable<'tcx>(
         // U: Trait<Arg1, ..., ArgN>
         let trait_predicate = {
             let trait_def_id = method.trait_container(tcx).unwrap();
-            let substs = InternalSubsts::for_item(tcx, trait_def_id, |param, _| {
+            let args = GenericArgs::for_item(tcx, trait_def_id, |param, _| {
                 if param.index == 0 { unsized_self_ty.into() } else { tcx.mk_param_from_def(param) }
             });
 
-            ty::TraitRef::new(tcx, trait_def_id, substs).to_predicate(tcx)
+            ty::TraitRef::new(tcx, trait_def_id, args).to_predicate(tcx)
         };
 
         let caller_bounds =
diff --git a/compiler/rustc_trait_selection/src/traits/project.rs b/compiler/rustc_trait_selection/src/traits/project.rs
index 4ccfb54ff7ce5..e137ed9cda8e8 100644
--- a/compiler/rustc_trait_selection/src/traits/project.rs
+++ b/compiler/rustc_trait_selection/src/traits/project.rs
@@ -1,8 +1,8 @@
 //! Code for projecting associated types out of trait references.
 
-use super::check_substs_compatible;
+use super::check_args_compatible;
 use super::specialization_graph;
-use super::translate_substs;
+use super::translate_args;
 use super::util;
 use super::ImplSourceUserDefinedData;
 use super::MismatchedProjectionTypes;
@@ -524,7 +524,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
         // ```
         // for<'a> fn(<T as Foo>::One<'a, Box<dyn Bar<'a, Item=<T as Foo>::Two<'a>>>>)
         // ```
-        // We normalize the substs on the projection before the projecting, but
+        // We normalize the args on the projection before the projecting, but
         // if we're naive, we'll
         //   replace bound vars on inner, project inner, replace placeholders on inner,
         //   replace bound vars on outer, project outer, replace placeholders on outer
@@ -539,7 +539,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
         //
         // On the other hand, this does add a bit of complexity, since we only
         // replace bound vars if the current type is a `Projection` and we need
-        // to make sure we don't forget to fold the substs regardless.
+        // to make sure we don't forget to fold the args regardless.
 
         match kind {
             ty::Opaque => {
@@ -558,9 +558,9 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                             );
                         }
 
-                        let substs = data.substs.fold_with(self);
+                        let args = data.args.fold_with(self);
                         let generic_ty = self.interner().type_of(data.def_id);
-                        let concrete_ty = generic_ty.subst(self.interner(), substs);
+                        let concrete_ty = generic_ty.instantiate(self.interner(), args);
                         self.depth += 1;
                         let folded_ty = self.fold_ty(concrete_ty);
                         self.depth -= 1;
@@ -660,11 +660,8 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
             ty::Weak => {
                 let infcx = self.selcx.infcx;
                 self.obligations.extend(
-                    infcx
-                        .tcx
-                        .predicates_of(data.def_id)
-                        .instantiate_own(infcx.tcx, data.substs)
-                        .map(|(mut predicate, span)| {
+                    infcx.tcx.predicates_of(data.def_id).instantiate_own(infcx.tcx, data.args).map(
+                        |(mut predicate, span)| {
                             if data.has_escaping_bound_vars() {
                                 (predicate, ..) = BoundVarReplacer::replace_bound_vars(
                                     infcx,
@@ -677,9 +674,10 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
                                 ObligationCauseCode::TypeAlias(code, span, data.def_id)
                             });
                             Obligation::new(infcx.tcx, cause, self.param_env, predicate)
-                        }),
+                        },
+                    ),
                 );
-                infcx.tcx.type_of(data.def_id).subst(infcx.tcx, data.substs).fold_with(self)
+                infcx.tcx.type_of(data.def_id).instantiate(infcx.tcx, data.args).fold_with(self)
             }
 
             ty::Inherent if !data.has_escaping_bound_vars() => {
@@ -1337,7 +1335,7 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
         });
     }
 
-    let substs = compute_inherent_assoc_ty_substs(
+    let args = compute_inherent_assoc_ty_args(
         selcx,
         param_env,
         alias_ty,
@@ -1347,7 +1345,7 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
     );
 
     // Register the obligations arising from the impl and from the associated type itself.
-    let predicates = tcx.predicates_of(alias_ty.def_id).instantiate(tcx, substs);
+    let predicates = tcx.predicates_of(alias_ty.def_id).instantiate(tcx, args);
     for (predicate, span) in predicates {
         let predicate = normalize_with_depth_to(
             selcx,
@@ -1381,7 +1379,7 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
         ));
     }
 
-    let ty = tcx.type_of(alias_ty.def_id).subst(tcx, substs);
+    let ty = tcx.type_of(alias_ty.def_id).instantiate(tcx, args);
 
     let mut ty = selcx.infcx.resolve_vars_if_possible(ty);
     if ty.has_projections() {
@@ -1391,20 +1389,20 @@ pub fn normalize_inherent_projection<'a, 'b, 'tcx>(
     ty
 }
 
-pub fn compute_inherent_assoc_ty_substs<'a, 'b, 'tcx>(
+pub fn compute_inherent_assoc_ty_args<'a, 'b, 'tcx>(
     selcx: &'a mut SelectionContext<'b, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     alias_ty: ty::AliasTy<'tcx>,
     cause: ObligationCause<'tcx>,
     depth: usize,
     obligations: &mut Vec<PredicateObligation<'tcx>>,
-) -> ty::SubstsRef<'tcx> {
+) -> ty::GenericArgsRef<'tcx> {
     let tcx = selcx.tcx();
 
     let impl_def_id = tcx.parent(alias_ty.def_id);
-    let impl_substs = selcx.infcx.fresh_substs_for_item(cause.span, impl_def_id);
+    let impl_args = selcx.infcx.fresh_args_for_item(cause.span, impl_def_id);
 
-    let impl_ty = tcx.type_of(impl_def_id).subst(tcx, impl_substs);
+    let impl_ty = tcx.type_of(impl_def_id).instantiate(tcx, impl_args);
     let impl_ty =
         normalize_with_depth_to(selcx, param_env, cause.clone(), depth + 1, impl_ty, obligations);
 
@@ -1423,7 +1421,7 @@ pub fn compute_inherent_assoc_ty_substs<'a, 'b, 'tcx>(
         }
     }
 
-    alias_ty.rebase_substs_onto_impl(impl_substs, tcx)
+    alias_ty.rebase_args_onto_impl(impl_args, tcx)
 }
 
 enum Projected<'tcx> {
@@ -1495,20 +1493,18 @@ fn project<'cx, 'tcx>(
         ProjectionCandidateSet::None => {
             let tcx = selcx.tcx();
             let term = match tcx.def_kind(obligation.predicate.def_id) {
-                DefKind::AssocTy => Ty::new_projection(
-                    tcx,
-                    obligation.predicate.def_id,
-                    obligation.predicate.substs,
-                )
-                .into(),
+                DefKind::AssocTy => {
+                    Ty::new_projection(tcx, obligation.predicate.def_id, obligation.predicate.args)
+                        .into()
+                }
                 DefKind::AssocConst => ty::Const::new_unevaluated(
                     tcx,
                     ty::UnevaluatedConst::new(
                         obligation.predicate.def_id,
-                        obligation.predicate.substs,
+                        obligation.predicate.args,
                     ),
                     tcx.type_of(obligation.predicate.def_id)
-                        .subst(tcx, obligation.predicate.substs),
+                        .instantiate(tcx, obligation.predicate.args),
                 )
                 .into(),
                 kind => {
@@ -1567,7 +1563,7 @@ fn assemble_candidates_from_trait_def<'cx, 'tcx>(
     let bounds = match *obligation.predicate.self_ty().kind() {
         // Excluding IATs and type aliases here as they don't have meaningful item bounds.
         ty::Alias(ty::Projection | ty::Opaque, ref data) => {
-            tcx.item_bounds(data.def_id).subst(tcx, data.substs)
+            tcx.item_bounds(data.def_id).instantiate(tcx, data.args)
         }
         ty::Infer(ty::TyVar(_)) => {
             // If the self-type is an inference variable, then it MAY wind up
@@ -2017,12 +2013,12 @@ fn confirm_generator_candidate<'cx, 'tcx>(
     obligation: &ProjectionTyObligation<'tcx>,
     nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let ty::Generator(_, substs, _) =
+    let ty::Generator(_, args, _) =
         selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
     else {
         unreachable!()
     };
-    let gen_sig = substs.as_generator().poly_sig();
+    let gen_sig = args.as_generator().poly_sig();
     let Normalized { value: gen_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2054,7 +2050,7 @@ fn confirm_generator_candidate<'cx, 'tcx>(
         };
 
         ty::ProjectionPredicate {
-            projection_ty: tcx.mk_alias_ty(obligation.predicate.def_id, trait_ref.substs),
+            projection_ty: tcx.mk_alias_ty(obligation.predicate.def_id, trait_ref.args),
             term: ty.into(),
         }
     });
@@ -2069,12 +2065,12 @@ fn confirm_future_candidate<'cx, 'tcx>(
     obligation: &ProjectionTyObligation<'tcx>,
     nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let ty::Generator(_, substs, _) =
+    let ty::Generator(_, args, _) =
         selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
     else {
         unreachable!()
     };
-    let gen_sig = substs.as_generator().poly_sig();
+    let gen_sig = args.as_generator().poly_sig();
     let Normalized { value: gen_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2098,7 +2094,7 @@ fn confirm_future_candidate<'cx, 'tcx>(
         debug_assert_eq!(tcx.associated_item(obligation.predicate.def_id).name, sym::Output);
 
         ty::ProjectionPredicate {
-            projection_ty: tcx.mk_alias_ty(obligation.predicate.def_id, trait_ref.substs),
+            projection_ty: tcx.mk_alias_ty(obligation.predicate.def_id, trait_ref.args),
             term: return_ty.into(),
         }
     });
@@ -2115,7 +2111,7 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
 ) -> Progress<'tcx> {
     let tcx = selcx.tcx();
     let self_ty = obligation.predicate.self_ty();
-    let substs = tcx.mk_substs(&[self_ty.into()]);
+    let args = tcx.mk_args(&[self_ty.into()]);
     let lang_items = tcx.lang_items();
     let item_def_id = obligation.predicate.def_id;
     let trait_def_id = tcx.trait_of_item(item_def_id).unwrap();
@@ -2155,7 +2151,7 @@ fn confirm_builtin_candidate<'cx, 'tcx>(
     };
 
     let predicate =
-        ty::ProjectionPredicate { projection_ty: tcx.mk_alias_ty(item_def_id, substs), term };
+        ty::ProjectionPredicate { projection_ty: tcx.mk_alias_ty(item_def_id, args), term };
 
     confirm_param_env_candidate(selcx, obligation, ty::Binder::dummy(predicate), false)
         .with_addl_obligations(obligations)
@@ -2187,11 +2183,11 @@ fn confirm_closure_candidate<'cx, 'tcx>(
     obligation: &ProjectionTyObligation<'tcx>,
     nested: Vec<PredicateObligation<'tcx>>,
 ) -> Progress<'tcx> {
-    let ty::Closure(_, substs) = selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
+    let ty::Closure(_, args) = selcx.infcx.shallow_resolve(obligation.predicate.self_ty()).kind()
     else {
         unreachable!()
     };
-    let closure_sig = substs.as_closure().sig();
+    let closure_sig = args.as_closure().sig();
     let Normalized { value: closure_sig, obligations } = normalize_with_depth(
         selcx,
         obligation.param_env,
@@ -2228,7 +2224,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
         flag,
     )
     .map_bound(|(trait_ref, ret_type)| ty::ProjectionPredicate {
-        projection_ty: tcx.mk_alias_ty(fn_once_output_def_id, trait_ref.substs),
+        projection_ty: tcx.mk_alias_ty(fn_once_output_def_id, trait_ref.args),
         term: ret_type.into(),
     });
 
@@ -2312,7 +2308,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
 ) -> Progress<'tcx> {
     let tcx = selcx.tcx();
 
-    let ImplSourceUserDefinedData { impl_def_id, substs, mut nested } = impl_impl_source;
+    let ImplSourceUserDefinedData { impl_def_id, args, mut nested } = impl_impl_source;
     let assoc_item_id = obligation.predicate.def_id;
     let trait_def_id = tcx.trait_id_of_impl(impl_def_id).unwrap();
 
@@ -2336,23 +2332,22 @@ fn confirm_impl_candidate<'cx, 'tcx>(
     // If we're trying to normalize `<Vec<u32> as X>::A<S>` using
     //`impl<T> X for Vec<T> { type A<Y> = Box<Y>; }`, then:
     //
-    // * `obligation.predicate.substs` is `[Vec<u32>, S]`
-    // * `substs` is `[u32]`
-    // * `substs` ends up as `[u32, S]`
-    let substs = obligation.predicate.substs.rebase_onto(tcx, trait_def_id, substs);
-    let substs =
-        translate_substs(selcx.infcx, param_env, impl_def_id, substs, assoc_ty.defining_node);
+    // * `obligation.predicate.args` is `[Vec<u32>, S]`
+    // * `args` is `[u32]`
+    // * `args` ends up as `[u32, S]`
+    let args = obligation.predicate.args.rebase_onto(tcx, trait_def_id, args);
+    let args = translate_args(selcx.infcx, param_env, impl_def_id, args, assoc_ty.defining_node);
     let ty = tcx.type_of(assoc_ty.item.def_id);
     let is_const = matches!(tcx.def_kind(assoc_ty.item.def_id), DefKind::AssocConst);
     let term: ty::EarlyBinder<ty::Term<'tcx>> = if is_const {
         let did = assoc_ty.item.def_id;
-        let identity_substs = crate::traits::InternalSubsts::identity_for_item(tcx, did);
-        let uv = ty::UnevaluatedConst::new(did, identity_substs);
+        let identity_args = crate::traits::GenericArgs::identity_for_item(tcx, did);
+        let uv = ty::UnevaluatedConst::new(did, identity_args);
         ty.map_bound(|ty| ty::Const::new_unevaluated(tcx, uv, ty).into())
     } else {
         ty.map_bound(|ty| ty.into())
     };
-    if !check_substs_compatible(tcx, assoc_ty.item, substs) {
+    if !check_args_compatible(tcx, assoc_ty.item, args) {
         let err = Ty::new_error_with_message(
             tcx,
             obligation.cause.span,
@@ -2361,7 +2356,7 @@ fn confirm_impl_candidate<'cx, 'tcx>(
         Progress { term: err.into(), obligations: nested }
     } else {
         assoc_ty_own_obligations(selcx, obligation, &mut nested);
-        Progress { term: term.subst(tcx, substs), obligations: nested }
+        Progress { term: term.instantiate(tcx, args), obligations: nested }
     }
 }
 
@@ -2375,7 +2370,7 @@ fn assoc_ty_own_obligations<'cx, 'tcx>(
     let tcx = selcx.tcx();
     let predicates = tcx
         .predicates_of(obligation.predicate.def_id)
-        .instantiate_own(tcx, obligation.predicate.substs);
+        .instantiate_own(tcx, obligation.predicate.args);
     for (predicate, span) in predicates {
         let normalized = normalize_with_depth_to(
             selcx,
diff --git a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
index 709c3f432e609..ef989d8c9d689 100644
--- a/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/dropck_outlives.rs
@@ -49,8 +49,8 @@ pub fn trivial_dropck_outlives<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> bool {
         // (T1..Tn) and closures have same properties as T1..Tn --
         // check if *all* of them are trivial.
         ty::Tuple(tys) => tys.iter().all(|t| trivial_dropck_outlives(tcx, t)),
-        ty::Closure(_, ref substs) => {
-            trivial_dropck_outlives(tcx, substs.as_closure().tupled_upvars_ty())
+        ty::Closure(_, ref args) => {
+            trivial_dropck_outlives(tcx, args.as_closure().tupled_upvars_ty())
         }
 
         ty::Adt(def, _) => {
@@ -237,8 +237,8 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             Ok::<_, NoSolution>(())
         })?,
 
-        ty::Closure(_, substs) => {
-            if !substs.as_closure().is_valid() {
+        ty::Closure(_, args) => {
+            if !args.as_closure().is_valid() {
                 // By the time this code runs, all type variables ought to
                 // be fully resolved.
 
@@ -250,14 +250,14 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             }
 
             rustc_data_structures::stack::ensure_sufficient_stack(|| {
-                for ty in substs.as_closure().upvar_tys() {
+                for ty in args.as_closure().upvar_tys() {
                     dtorck_constraint_for_ty_inner(tcx, span, for_ty, depth + 1, ty, constraints)?;
                 }
                 Ok::<_, NoSolution>(())
             })?
         }
 
-        ty::Generator(_, substs, _movability) => {
+        ty::Generator(_, args, _movability) => {
             // rust-lang/rust#49918: types can be constructed, stored
             // in the interior, and sit idle when generator yields
             // (and is subsequently dropped).
@@ -281,7 +281,7 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             // derived from lifetimes attached to the upvars and resume
             // argument, and we *do* incorporate those here.
 
-            if !substs.as_generator().is_valid() {
+            if !args.as_generator().is_valid() {
                 // By the time this code runs, all type variables ought to
                 // be fully resolved.
                 tcx.sess.delay_span_bug(
@@ -292,28 +292,25 @@ pub fn dtorck_constraint_for_ty_inner<'tcx>(
             }
 
             constraints.outlives.extend(
-                substs
-                    .as_generator()
-                    .upvar_tys()
-                    .map(|t| -> ty::subst::GenericArg<'tcx> { t.into() }),
+                args.as_generator().upvar_tys().map(|t| -> ty::GenericArg<'tcx> { t.into() }),
             );
-            constraints.outlives.push(substs.as_generator().resume_ty().into());
+            constraints.outlives.push(args.as_generator().resume_ty().into());
         }
 
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             let DropckConstraint { dtorck_types, outlives, overflows } =
                 tcx.at(span).adt_dtorck_constraint(def.did())?;
             // FIXME: we can try to recursively `dtorck_constraint_on_ty`
             // there, but that needs some way to handle cycles.
             constraints
                 .dtorck_types
-                .extend(dtorck_types.iter().map(|t| EarlyBinder::bind(*t).subst(tcx, substs)));
+                .extend(dtorck_types.iter().map(|t| EarlyBinder::bind(*t).instantiate(tcx, args)));
             constraints
                 .outlives
-                .extend(outlives.iter().map(|t| EarlyBinder::bind(*t).subst(tcx, substs)));
+                .extend(outlives.iter().map(|t| EarlyBinder::bind(*t).instantiate(tcx, args)));
             constraints
                 .overflows
-                .extend(overflows.iter().map(|t| EarlyBinder::bind(*t).subst(tcx, substs)));
+                .extend(overflows.iter().map(|t| EarlyBinder::bind(*t).instantiate(tcx, args)));
         }
 
         // Objects must be alive in order for their destructor
diff --git a/compiler/rustc_trait_selection/src/traits/query/normalize.rs b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
index 7fe79fd865ce3..ab301b593c21b 100644
--- a/compiler/rustc_trait_selection/src/traits/query/normalize.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/normalize.rs
@@ -217,7 +217,7 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
         };
 
         // See note in `rustc_trait_selection::traits::project` about why we
-        // wait to fold the substs.
+        // wait to fold the args.
 
         // Wrap this in a closure so we don't accidentally return from the outer function
         let res = match kind {
@@ -227,7 +227,7 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
                     Reveal::UserFacing => ty.try_super_fold_with(self)?,
 
                     Reveal::All => {
-                        let substs = data.substs.try_fold_with(self)?;
+                        let args = data.args.try_fold_with(self)?;
                         let recursion_limit = self.interner().recursion_limit();
                         if !recursion_limit.value_within_limit(self.anon_depth) {
                             // A closure or generator may have itself as in its upvars.
@@ -243,14 +243,14 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
                         }
 
                         let generic_ty = self.interner().type_of(data.def_id);
-                        let concrete_ty = generic_ty.subst(self.interner(), substs);
+                        let concrete_ty = generic_ty.instantiate(self.interner(), args);
                         self.anon_depth += 1;
                         if concrete_ty == ty {
                             bug!(
-                                "infinite recursion generic_ty: {:#?}, substs: {:#?}, \
+                                "infinite recursion generic_ty: {:#?}, args: {:#?}, \
                                  concrete_ty: {:#?}, ty: {:#?}",
                                 generic_ty,
-                                substs,
+                                args,
                                 concrete_ty,
                                 ty
                             );
diff --git a/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs b/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
index 44671a07659bd..420d632655338 100644
--- a/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
+++ b/compiler/rustc_trait_selection/src/traits/query/type_op/ascribe_user_type.rs
@@ -4,7 +4,7 @@ use rustc_hir::def_id::{DefId, CRATE_DEF_ID};
 use rustc_infer::traits::Obligation;
 use rustc_middle::traits::query::NoSolution;
 use rustc_middle::traits::{ObligationCause, ObligationCauseCode};
-use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, UserSelfTy, UserSubsts, UserType};
+use rustc_middle::ty::{self, ParamEnvAnd, Ty, TyCtxt, UserArgs, UserSelfTy, UserType};
 
 pub use rustc_middle::traits::query::type_op::AscribeUserType;
 use rustc_span::{Span, DUMMY_SP};
@@ -47,8 +47,8 @@ pub fn type_op_ascribe_user_type_with_span<'tcx>(
     let span = span.unwrap_or(DUMMY_SP);
     match user_ty {
         UserType::Ty(user_ty) => relate_mir_and_user_ty(ocx, param_env, span, mir_ty, user_ty)?,
-        UserType::TypeOf(def_id, user_substs) => {
-            relate_mir_and_user_substs(ocx, param_env, span, mir_ty, def_id, user_substs)?
+        UserType::TypeOf(def_id, user_args) => {
+            relate_mir_and_user_args(ocx, param_env, span, mir_ty, def_id, user_args)?
         }
     };
     Ok(())
@@ -74,20 +74,20 @@ fn relate_mir_and_user_ty<'tcx>(
 }
 
 #[instrument(level = "debug", skip(ocx, param_env, span))]
-fn relate_mir_and_user_substs<'tcx>(
+fn relate_mir_and_user_args<'tcx>(
     ocx: &ObligationCtxt<'_, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     span: Span,
     mir_ty: Ty<'tcx>,
     def_id: DefId,
-    user_substs: UserSubsts<'tcx>,
+    user_args: UserArgs<'tcx>,
 ) -> Result<(), NoSolution> {
     let param_env = param_env.without_const();
-    let UserSubsts { user_self_ty, substs } = user_substs;
+    let UserArgs { user_self_ty, args } = user_args;
     let tcx = ocx.infcx.tcx;
     let cause = ObligationCause::dummy_with_span(span);
 
-    let ty = tcx.type_of(def_id).subst(tcx, substs);
+    let ty = tcx.type_of(def_id).instantiate(tcx, args);
     let ty = ocx.normalize(&cause, param_env, ty);
     debug!("relate_type_and_user_type: ty of def-id is {:?}", ty);
 
@@ -98,7 +98,7 @@ fn relate_mir_and_user_substs<'tcx>(
     // Also, normalize the `instantiated_predicates`
     // because otherwise we wind up with duplicate "type
     // outlives" error messages.
-    let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, substs);
+    let instantiated_predicates = tcx.predicates_of(def_id).instantiate(tcx, args);
 
     debug!(?instantiated_predicates);
     for (instantiated_predicate, predicate_span) in instantiated_predicates {
@@ -116,7 +116,7 @@ fn relate_mir_and_user_substs<'tcx>(
 
     if let Some(UserSelfTy { impl_def_id, self_ty }) = user_self_ty {
         let self_ty = ocx.normalize(&cause, param_env, self_ty);
-        let impl_self_ty = tcx.type_of(impl_def_id).subst(tcx, substs);
+        let impl_self_ty = tcx.type_of(impl_def_id).instantiate(tcx, args);
         let impl_self_ty = ocx.normalize(&cause, param_env, impl_self_ty);
 
         ocx.eq(&cause, param_env, self_ty, impl_self_ty)?;
@@ -128,9 +128,9 @@ fn relate_mir_and_user_substs<'tcx>(
 
     // In addition to proving the predicates, we have to
     // prove that `ty` is well-formed -- this is because
-    // the WF of `ty` is predicated on the substs being
+    // the WF of `ty` is predicated on the args being
     // well-formed, and we haven't proven *that*. We don't
-    // want to prove the WF of types from  `substs` directly because they
+    // want to prove the WF of types from  `args` directly because they
     // haven't been normalized.
     //
     // FIXME(nmatsakis): Well, perhaps we should normalize
diff --git a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
index eb603cf37376d..aa195d70a9f6d 100644
--- a/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs
@@ -209,7 +209,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         obligation: &PolyTraitObligation<'tcx>,
         candidates: &mut SelectionCandidateSet<'tcx>,
     ) {
-        // Okay to skip binder because the substs on generator types never
+        // Okay to skip binder because the args on generator types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
         let self_ty = obligation.self_ty().skip_binder();
@@ -261,14 +261,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             return;
         };
 
-        // Okay to skip binder because the substs on closure types never
+        // Okay to skip binder because the args on closure types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters
         match *obligation.self_ty().skip_binder().kind() {
-            ty::Closure(def_id, closure_substs) => {
+            ty::Closure(def_id, closure_args) => {
                 let is_const = self.tcx().is_const_fn_raw(def_id);
                 debug!(?kind, ?obligation, "assemble_unboxed_candidates");
-                match self.infcx.closure_kind(closure_substs) {
+                match self.infcx.closure_kind(closure_args) {
                     Some(closure_kind) => {
                         debug!(?closure_kind, "assemble_unboxed_candidates");
                         if closure_kind.extends(kind) {
@@ -351,7 +351,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         }
 
         let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::ForLookup };
-        let obligation_substs = obligation.predicate.skip_binder().trait_ref.substs;
+        let obligation_args = obligation.predicate.skip_binder().trait_ref.args;
         self.tcx().for_each_relevant_impl(
             obligation.predicate.def_id(),
             obligation.predicate.skip_binder().trait_ref.self_ty(),
@@ -360,9 +360,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 // consider a "quick reject". This avoids creating more types
                 // and so forth that we need to.
                 let impl_trait_ref = self.tcx().impl_trait_ref(impl_def_id).unwrap();
-                if !drcx
-                    .substs_refs_may_unify(obligation_substs, impl_trait_ref.skip_binder().substs)
-                {
+                if !drcx.args_refs_may_unify(obligation_args, impl_trait_ref.skip_binder().args) {
                     return;
                 }
                 if self.reject_fn_ptr_impls(
@@ -374,7 +372,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 }
 
                 self.infcx.probe(|_| {
-                    if let Ok(_substs) = self.match_impl(impl_def_id, impl_trait_ref, obligation) {
+                    if let Ok(_args) = self.match_impl(impl_def_id, impl_trait_ref, obligation) {
                         candidates.vec.push(ImplCandidate(impl_def_id));
                     }
                 });
@@ -650,7 +648,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             let ty = traits::normalize_projection_type(
                 self,
                 param_env,
-                tcx.mk_alias_ty(tcx.lang_items().deref_target()?, trait_ref.substs),
+                tcx.mk_alias_ty(tcx.lang_items().deref_target()?, trait_ref.args),
                 cause.clone(),
                 0,
                 // We're *intentionally* throwing these away,
@@ -688,7 +686,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // Don't add any candidates if there are bound regions.
             return;
         };
-        let target = obligation.predicate.skip_binder().trait_ref.substs.type_at(1);
+        let target = obligation.predicate.skip_binder().trait_ref.args.type_at(1);
 
         debug!(?source, ?target, "assemble_candidates_for_unsizing");
 
diff --git a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
index 01452986f5a23..2cb2895b47642 100644
--- a/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/confirmation.rs
@@ -13,7 +13,7 @@ use rustc_infer::infer::LateBoundRegionConversionTime::HigherRankedType;
 use rustc_infer::infer::{DefineOpaqueTypes, InferOk};
 use rustc_middle::traits::SelectionOutputTypeParameterMismatch;
 use rustc_middle::ty::{
-    self, Binder, GenericParamDefKind, InternalSubsts, SubstsRef, ToPolyTraitRef, ToPredicate,
+    self, Binder, GenericArgs, GenericArgsRef, GenericParamDefKind, ToPolyTraitRef, ToPredicate,
     TraitPredicate, TraitRef, Ty, TyCtxt, TypeVisitableExt,
 };
 use rustc_span::def_id::DefId;
@@ -158,15 +158,16 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             self.infcx.instantiate_binder_with_placeholders(trait_predicate).trait_ref;
         let placeholder_self_ty = placeholder_trait_predicate.self_ty();
         let placeholder_trait_predicate = ty::Binder::dummy(placeholder_trait_predicate);
-        let (def_id, substs) = match *placeholder_self_ty.kind() {
+        let (def_id, args) = match *placeholder_self_ty.kind() {
             // Excluding IATs and type aliases here as they don't have meaningful item bounds.
-            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                (def_id, substs)
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                (def_id, args)
             }
             _ => bug!("projection candidate for unexpected type: {:?}", placeholder_self_ty),
         };
 
-        let candidate_predicate = tcx.item_bounds(def_id).map_bound(|i| i[idx]).subst(tcx, substs);
+        let candidate_predicate =
+            tcx.item_bounds(def_id).map_bound(|i| i[idx]).instantiate(tcx, args);
         let candidate = candidate_predicate
             .as_trait_clause()
             .expect("projection candidate is not a trait predicate")
@@ -190,7 +191,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         })?);
 
         if let ty::Alias(ty::Projection, ..) = placeholder_self_ty.kind() {
-            let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
+            let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, args);
             for (predicate, _) in predicates {
                 let normalized = normalize_with_depth_to(
                     self,
@@ -298,8 +299,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     .collect(),
                 Condition::IfTransmutable { src, dst } => {
                     let trait_def_id = obligation.predicate.def_id();
-                    let scope = predicate.trait_ref.substs.type_at(2);
-                    let assume_const = predicate.trait_ref.substs.const_at(3);
+                    let scope = predicate.trait_ref.args.type_at(2);
+                    let assume_const = predicate.trait_ref.args.const_at(3);
                     let make_obl = |from_ty, to_ty| {
                         let trait_ref1 = ty::TraitRef::new(
                             tcx,
@@ -342,19 +343,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let Some(assume) = rustc_transmute::Assume::from_const(
             self.infcx.tcx,
             obligation.param_env,
-            predicate.trait_ref.substs.const_at(3),
+            predicate.trait_ref.args.const_at(3),
         ) else {
             return Err(Unimplemented);
         };
 
-        let dst = predicate.trait_ref.substs.type_at(0);
-        let src = predicate.trait_ref.substs.type_at(1);
+        let dst = predicate.trait_ref.args.type_at(0);
+        let src = predicate.trait_ref.args.type_at(1);
         debug!(?src, ?dst);
         let mut transmute_env = rustc_transmute::TransmuteTypeEnv::new(self.infcx);
         let maybe_transmutable = transmute_env.is_transmutable(
             obligation.cause.clone(),
             rustc_transmute::Types { dst, src },
-            predicate.trait_ref.substs.type_at(2),
+            predicate.trait_ref.args.type_at(2),
             assume,
         );
 
@@ -402,7 +403,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 obligation.recursion_depth + 1,
                 obligation.param_env,
                 trait_def_id,
-                &trait_ref.substs,
+                &trait_ref.args,
                 obligation.predicate,
             );
 
@@ -433,12 +434,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         // First, create the substitutions by matching the impl again,
         // this time not in a probe.
-        let substs = self.rematch_impl(impl_def_id, obligation);
-        debug!(?substs, "impl substs");
+        let args = self.rematch_impl(impl_def_id, obligation);
+        debug!(?args, "impl args");
         ensure_sufficient_stack(|| {
             self.vtable_impl(
                 impl_def_id,
-                substs,
+                args,
                 &obligation.cause,
                 obligation.recursion_depth + 1,
                 obligation.param_env,
@@ -450,33 +451,33 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
     fn vtable_impl(
         &mut self,
         impl_def_id: DefId,
-        substs: Normalized<'tcx, SubstsRef<'tcx>>,
+        args: Normalized<'tcx, GenericArgsRef<'tcx>>,
         cause: &ObligationCause<'tcx>,
         recursion_depth: usize,
         param_env: ty::ParamEnv<'tcx>,
         parent_trait_pred: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
     ) -> ImplSourceUserDefinedData<'tcx, PredicateObligation<'tcx>> {
-        debug!(?impl_def_id, ?substs, ?recursion_depth, "vtable_impl");
+        debug!(?impl_def_id, ?args, ?recursion_depth, "vtable_impl");
 
         let mut impl_obligations = self.impl_or_trait_obligations(
             cause,
             recursion_depth,
             param_env,
             impl_def_id,
-            &substs.value,
+            &args.value,
             parent_trait_pred,
         );
 
         debug!(?impl_obligations, "vtable_impl");
 
         // Because of RFC447, the impl-trait-ref and obligations
-        // are sufficient to determine the impl substs, without
+        // are sufficient to determine the impl args, without
         // relying on projections in the impl-trait-ref.
         //
         // e.g., `impl<U: Tr, V: Iterator<Item=U>> Foo<<U as Tr>::T> for V`
-        impl_obligations.extend(substs.obligations);
+        impl_obligations.extend(args.obligations);
 
-        ImplSourceUserDefinedData { impl_def_id, substs: substs.value, nested: impl_obligations }
+        ImplSourceUserDefinedData { impl_def_id, args: args.value, nested: impl_obligations }
     }
 
     fn confirm_object_candidate(
@@ -531,7 +532,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // will be checked in the code below.
         for super_trait in tcx
             .super_predicates_of(trait_predicate.def_id())
-            .instantiate(tcx, trait_predicate.trait_ref.substs)
+            .instantiate(tcx, trait_predicate.trait_ref.args)
             .predicates
             .into_iter()
         {
@@ -569,68 +570,65 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             // higher-ranked things.
             // Prevent, e.g., `dyn Iterator<Item = str>`.
             for bound in self.tcx().item_bounds(assoc_type).transpose_iter() {
-                let subst_bound =
-                    if defs.count() == 0 {
-                        bound.subst(tcx, trait_predicate.trait_ref.substs)
-                    } else {
-                        let mut substs = smallvec::SmallVec::with_capacity(defs.count());
-                        substs.extend(trait_predicate.trait_ref.substs.iter());
-                        let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
-                            smallvec::SmallVec::with_capacity(
-                                bound.skip_binder().kind().bound_vars().len() + defs.count(),
-                            );
-                        bound_vars.extend(bound.skip_binder().kind().bound_vars().into_iter());
-                        InternalSubsts::fill_single(&mut substs, defs, &mut |param, _| match param
-                            .kind
-                        {
-                            GenericParamDefKind::Type { .. } => {
-                                let kind = ty::BoundTyKind::Param(param.def_id, param.name);
-                                let bound_var = ty::BoundVariableKind::Ty(kind);
-                                bound_vars.push(bound_var);
-                                Ty::new_bound(
-                                    tcx,
-                                    ty::INNERMOST,
-                                    ty::BoundTy {
-                                        var: ty::BoundVar::from_usize(bound_vars.len() - 1),
-                                        kind,
-                                    },
-                                )
-                                .into()
-                            }
-                            GenericParamDefKind::Lifetime => {
-                                let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
-                                let bound_var = ty::BoundVariableKind::Region(kind);
-                                bound_vars.push(bound_var);
-                                ty::Region::new_late_bound(
-                                    tcx,
-                                    ty::INNERMOST,
-                                    ty::BoundRegion {
-                                        var: ty::BoundVar::from_usize(bound_vars.len() - 1),
-                                        kind,
-                                    },
-                                )
-                                .into()
-                            }
-                            GenericParamDefKind::Const { .. } => {
-                                let bound_var = ty::BoundVariableKind::Const;
-                                bound_vars.push(bound_var);
-                                ty::Const::new_bound(
-                                    tcx,
-                                    ty::INNERMOST,
-                                    ty::BoundVar::from_usize(bound_vars.len() - 1),
-                                    tcx.type_of(param.def_id)
-                                        .no_bound_vars()
-                                        .expect("const parameter types cannot be generic"),
-                                )
-                                .into()
-                            }
-                        });
-                        let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);
-                        let assoc_ty_substs = tcx.mk_substs(&substs);
-                        let bound =
-                            bound.map_bound(|b| b.kind().skip_binder()).subst(tcx, assoc_ty_substs);
-                        ty::Binder::bind_with_vars(bound, bound_vars).to_predicate(tcx)
-                    };
+                let subst_bound = if defs.count() == 0 {
+                    bound.instantiate(tcx, trait_predicate.trait_ref.args)
+                } else {
+                    let mut args = smallvec::SmallVec::with_capacity(defs.count());
+                    args.extend(trait_predicate.trait_ref.args.iter());
+                    let mut bound_vars: smallvec::SmallVec<[ty::BoundVariableKind; 8]> =
+                        smallvec::SmallVec::with_capacity(
+                            bound.skip_binder().kind().bound_vars().len() + defs.count(),
+                        );
+                    bound_vars.extend(bound.skip_binder().kind().bound_vars().into_iter());
+                    GenericArgs::fill_single(&mut args, defs, &mut |param, _| match param.kind {
+                        GenericParamDefKind::Type { .. } => {
+                            let kind = ty::BoundTyKind::Param(param.def_id, param.name);
+                            let bound_var = ty::BoundVariableKind::Ty(kind);
+                            bound_vars.push(bound_var);
+                            Ty::new_bound(
+                                tcx,
+                                ty::INNERMOST,
+                                ty::BoundTy {
+                                    var: ty::BoundVar::from_usize(bound_vars.len() - 1),
+                                    kind,
+                                },
+                            )
+                            .into()
+                        }
+                        GenericParamDefKind::Lifetime => {
+                            let kind = ty::BoundRegionKind::BrNamed(param.def_id, param.name);
+                            let bound_var = ty::BoundVariableKind::Region(kind);
+                            bound_vars.push(bound_var);
+                            ty::Region::new_late_bound(
+                                tcx,
+                                ty::INNERMOST,
+                                ty::BoundRegion {
+                                    var: ty::BoundVar::from_usize(bound_vars.len() - 1),
+                                    kind,
+                                },
+                            )
+                            .into()
+                        }
+                        GenericParamDefKind::Const { .. } => {
+                            let bound_var = ty::BoundVariableKind::Const;
+                            bound_vars.push(bound_var);
+                            ty::Const::new_bound(
+                                tcx,
+                                ty::INNERMOST,
+                                ty::BoundVar::from_usize(bound_vars.len() - 1),
+                                tcx.type_of(param.def_id)
+                                    .no_bound_vars()
+                                    .expect("const parameter types cannot be generic"),
+                            )
+                            .into()
+                        }
+                    });
+                    let bound_vars = tcx.mk_bound_variable_kinds(&bound_vars);
+                    let assoc_ty_args = tcx.mk_args(&args);
+                    let bound =
+                        bound.map_bound(|b| b.kind().skip_binder()).instantiate(tcx, assoc_ty_args);
+                    ty::Binder::bind_with_vars(bound, bound_vars).to_predicate(tcx)
+                };
                 let normalized_bound = normalize_with_depth_to(
                     self,
                     obligation.param_env,
@@ -685,8 +683,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         if obligation.is_const() && !is_const {
             // function is a trait method
-            if let ty::FnDef(def_id, substs) = self_ty.kind() && let Some(trait_id) = tcx.trait_of_item(*def_id) {
-                let trait_ref = TraitRef::from_method(tcx, trait_id, *substs);
+            if let ty::FnDef(def_id, args) = self_ty.kind() && let Some(trait_id) = tcx.trait_of_item(*def_id) {
+                let trait_ref = TraitRef::from_method(tcx, trait_id, *args);
                 let poly_trait_pred = Binder::dummy(trait_ref).with_constness(ty::BoundConstness::ConstIfConst);
                 let obligation = Obligation::new(tcx, cause.clone(), obligation.param_env, poly_trait_pred);
                 nested.push(obligation);
@@ -718,14 +716,14 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         let predicate = self.infcx.instantiate_binder_with_placeholders(obligation.predicate);
         let trait_ref = predicate.trait_ref;
         let trait_def_id = trait_ref.def_id;
-        let substs = trait_ref.substs;
+        let args = trait_ref.args;
 
         let trait_obligations = self.impl_or_trait_obligations(
             &obligation.cause,
             obligation.recursion_depth,
             obligation.param_env,
             trait_def_id,
-            &substs,
+            &args,
             obligation.predicate,
         );
 
@@ -738,17 +736,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
     ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
-        // Okay to skip binder because the substs on generator types never
+        // Okay to skip binder because the args on generator types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
         let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
-        let ty::Generator(generator_def_id, substs, _) = *self_ty.kind() else {
+        let ty::Generator(generator_def_id, args, _) = *self_ty.kind() else {
             bug!("closure candidate for non-closure {:?}", obligation);
         };
 
-        debug!(?obligation, ?generator_def_id, ?substs, "confirm_generator_candidate");
+        debug!(?obligation, ?generator_def_id, ?args, "confirm_generator_candidate");
 
-        let gen_sig = substs.as_generator().poly_sig();
+        let gen_sig = args.as_generator().poly_sig();
 
         // NOTE: The self-type is a generator type and hence is
         // in fact unparameterized (or at least does not reference any
@@ -777,17 +775,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
     ) -> Result<Vec<PredicateObligation<'tcx>>, SelectionError<'tcx>> {
-        // Okay to skip binder because the substs on generator types never
+        // Okay to skip binder because the args on generator types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
         let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
-        let ty::Generator(generator_def_id, substs, _) = *self_ty.kind() else {
+        let ty::Generator(generator_def_id, args, _) = *self_ty.kind() else {
             bug!("closure candidate for non-closure {:?}", obligation);
         };
 
-        debug!(?obligation, ?generator_def_id, ?substs, "confirm_future_candidate");
+        debug!(?obligation, ?generator_def_id, ?args, "confirm_future_candidate");
 
-        let gen_sig = substs.as_generator().poly_sig();
+        let gen_sig = args.as_generator().poly_sig();
 
         let trait_ref = super::util::future_trait_ref_and_outputs(
             self.tcx(),
@@ -813,22 +811,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             .fn_trait_kind_from_def_id(obligation.predicate.def_id())
             .unwrap_or_else(|| bug!("closure candidate for non-fn trait {:?}", obligation));
 
-        // Okay to skip binder because the substs on closure types never
+        // Okay to skip binder because the args on closure types never
         // touch bound regions, they just capture the in-scope
         // type/region parameters.
         let self_ty = self.infcx.shallow_resolve(obligation.self_ty().skip_binder());
-        let ty::Closure(closure_def_id, substs) = *self_ty.kind() else {
+        let ty::Closure(closure_def_id, args) = *self_ty.kind() else {
             bug!("closure candidate for non-closure {:?}", obligation);
         };
 
-        let trait_ref = self.closure_trait_ref_unnormalized(obligation, substs);
+        let trait_ref = self.closure_trait_ref_unnormalized(obligation, args);
         let mut nested = self.confirm_poly_trait_refs(obligation, trait_ref)?;
 
         debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
 
         nested.push(obligation.with(
             self.tcx(),
-            ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, substs, kind)),
+            ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, args, kind)),
         ));
 
         Ok(nested)
@@ -905,7 +903,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // `assemble_candidates_for_unsizing` should ensure there are no late-bound
         // regions here. See the comment there for more details.
         let source = self.infcx.shallow_resolve(obligation.self_ty().no_bound_vars().unwrap());
-        let target = obligation.predicate.skip_binder().trait_ref.substs.type_at(1);
+        let target = obligation.predicate.skip_binder().trait_ref.args.type_at(1);
         let target = self.infcx.shallow_resolve(target);
 
         debug!(?source, ?target, "confirm_trait_upcasting_unsize_candidate");
@@ -1008,7 +1006,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // `assemble_candidates_for_unsizing` should ensure there are no late-bound
         // regions here. See the comment there for more details.
         let source = self.infcx.shallow_resolve(obligation.self_ty().no_bound_vars().unwrap());
-        let target = obligation.predicate.skip_binder().trait_ref.substs.type_at(1);
+        let target = obligation.predicate.skip_binder().trait_ref.args.type_at(1);
         let target = self.infcx.shallow_resolve(target);
 
         debug!(?source, ?target, "confirm_builtin_unsize_candidate");
@@ -1116,7 +1114,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             }
 
             // `Struct<T>` -> `Struct<U>`
-            (&ty::Adt(def, substs_a), &ty::Adt(_, substs_b)) => {
+            (&ty::Adt(def, args_a), &ty::Adt(_, args_b)) => {
                 let unsizing_params = tcx.unsizing_params_for_adt(def.did());
                 if unsizing_params.is_empty() {
                     return Err(Unimplemented);
@@ -1133,7 +1131,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     obligation.param_env,
                     obligation.cause.clone(),
                     obligation.recursion_depth + 1,
-                    tail_field_ty.subst(tcx, substs_a),
+                    tail_field_ty.instantiate(tcx, args_a),
                     &mut nested,
                 );
                 let target_tail = normalize_with_depth_to(
@@ -1141,16 +1139,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     obligation.param_env,
                     obligation.cause.clone(),
                     obligation.recursion_depth + 1,
-                    tail_field_ty.subst(tcx, substs_b),
+                    tail_field_ty.instantiate(tcx, args_b),
                     &mut nested,
                 );
 
                 // Check that the source struct with the target's
                 // unsizing parameters is equal to the target.
-                let substs = tcx.mk_substs_from_iter(substs_a.iter().enumerate().map(|(i, k)| {
-                    if unsizing_params.contains(i as u32) { substs_b[i] } else { k }
-                }));
-                let new_struct = Ty::new_adt(tcx, def, substs);
+                let args =
+                    tcx.mk_args_from_iter(args_a.iter().enumerate().map(|(i, k)| {
+                        if unsizing_params.contains(i as u32) { args_b[i] } else { k }
+                    }));
+                let new_struct = Ty::new_adt(tcx, def, args);
                 let InferOk { obligations, .. } = self
                     .infcx
                     .at(&obligation.cause, obligation.param_env)
@@ -1230,8 +1229,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 trait_pred.trait_ref.def_id = drop_trait;
                 trait_pred
             });
-            let substs = self.rematch_impl(impl_def_id, &new_obligation);
-            debug!(?substs, "impl substs");
+            let args = self.rematch_impl(impl_def_id, &new_obligation);
+            debug!(?args, "impl args");
 
             let cause = obligation.derived_cause(|derived| {
                 ImplDerivedObligation(Box::new(ImplDerivedObligationCause {
@@ -1244,7 +1243,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             let obligations = ensure_sufficient_stack(|| {
                 self.vtable_impl(
                     impl_def_id,
-                    substs,
+                    args,
                     &cause,
                     new_obligation.recursion_depth + 1,
                     new_obligation.param_env,
@@ -1256,7 +1255,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
 
         // We want to confirm the ADT's fields if we have an ADT
         let mut stack = match *self_ty.skip_binder().kind() {
-            ty::Adt(def, substs) => def.all_fields().map(|f| f.ty(tcx, substs)).collect(),
+            ty::Adt(def, args) => def.all_fields().map(|f| f.ty(tcx, args)).collect(),
             _ => vec![self_ty.skip_binder()],
         };
 
@@ -1289,20 +1288,20 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 ty::Tuple(tys) => {
                     stack.extend(tys.iter());
                 }
-                ty::Closure(_, substs) => {
-                    stack.push(substs.as_closure().tupled_upvars_ty());
+                ty::Closure(_, args) => {
+                    stack.push(args.as_closure().tupled_upvars_ty());
                 }
-                ty::Generator(_, substs, _) => {
-                    let generator = substs.as_generator();
+                ty::Generator(_, args, _) => {
+                    let generator = args.as_generator();
                     stack.extend([generator.tupled_upvars_ty(), generator.witness()]);
                 }
                 ty::GeneratorWitness(tys) => {
                     stack.extend(tcx.erase_late_bound_regions(tys).to_vec());
                 }
-                ty::GeneratorWitnessMIR(def_id, substs) => {
+                ty::GeneratorWitnessMIR(def_id, args) => {
                     let tcx = self.tcx();
                     stack.extend(tcx.generator_hidden_types(def_id).map(|bty| {
-                        let ty = bty.subst(tcx, substs);
+                        let ty = bty.instantiate(tcx, args);
                         debug_assert!(!ty.has_late_bound_regions());
                         ty
                     }))
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 7f31ab751191d..56d5d698d909d 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -40,7 +40,7 @@ use rustc_middle::mir::interpret::ErrorHandled;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
 use rustc_middle::ty::fold::BottomUpFolder;
 use rustc_middle::ty::relate::TypeRelation;
-use rustc_middle::ty::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, EarlyBinder, PolyProjectionPredicate, ToPolyTraitRef, ToPredicate};
 use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable, TypeVisitableExt};
 use rustc_span::symbol::sym;
@@ -843,8 +843,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                     }
                 }
 
-                ty::PredicateKind::ClosureKind(_, closure_substs, kind) => {
-                    match self.infcx.closure_kind(closure_substs) {
+                ty::PredicateKind::ClosureKind(_, closure_args, kind) => {
+                    match self.infcx.closure_kind(closure_args) {
                         Some(closure_kind) => {
                             if closure_kind.extends(kind) {
                                 Ok(EvaluatedToOk)
@@ -895,7 +895,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                                     .infcx
                                     .at(&obligation.cause, obligation.param_env)
                                     .trace(c1, c2)
-                                    .eq(DefineOpaqueTypes::No, a.substs, b.substs)
+                                    .eq(DefineOpaqueTypes::No, a.args, b.args)
                                 {
                                     return self.evaluate_predicates_recursively(
                                         previous_stack,
@@ -1194,7 +1194,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // terms of `Fn` etc, but we could probably make this more
         // precise still.
         let unbound_input_types =
-            stack.fresh_trait_pred.skip_binder().trait_ref.substs.types().any(|ty| ty.is_fresh());
+            stack.fresh_trait_pred.skip_binder().trait_ref.args.types().any(|ty| ty.is_fresh());
 
         if unbound_input_types
             && stack.iter().skip(1).any(|prev| {
@@ -1635,9 +1635,9 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         debug!(?placeholder_trait_predicate);
 
         let tcx = self.infcx.tcx;
-        let (def_id, substs) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
-            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
-                (def_id, substs)
+        let (def_id, args) = match *placeholder_trait_predicate.trait_ref.self_ty().kind() {
+            ty::Alias(ty::Projection | ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
+                (def_id, args)
             }
             _ => {
                 span_bug!(
@@ -1648,7 +1648,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                 );
             }
         };
-        let bounds = tcx.item_bounds(def_id).subst(tcx, substs);
+        let bounds = tcx.item_bounds(def_id).instantiate(tcx, args);
 
         // The bounds returned by `item_bounds` may contain duplicates after
         // normalization, so try to deduplicate when possible to avoid
@@ -1785,11 +1785,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         if is_match {
             let generics = self.tcx().generics_of(obligation.predicate.def_id);
             // FIXME(generic-associated-types): Addresses aggressive inference in #92917.
-            // If this type is a GAT, and of the GAT substs resolve to something new,
+            // If this type is a GAT, and of the GAT args resolve to something new,
             // that means that we must have newly inferred something about the GAT.
             // We should give up in that case.
             if !generics.params.is_empty()
-                && obligation.predicate.substs[generics.parent_count..]
+                && obligation.predicate.args[generics.parent_count..]
                     .iter()
                     .any(|&p| p.has_non_region_infer() && self.infcx.shallow_resolve(p) != p)
             {
@@ -2127,13 +2127,13 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 obligation.predicate.rebind(tys.last().map_or_else(Vec::new, |&last| vec![last])),
             ),
 
-            ty::Adt(def, substs) => {
+            ty::Adt(def, args) => {
                 let sized_crit = def.sized_constraint(self.tcx());
                 // (*) binder moved here
                 Where(
                     obligation
                         .predicate
-                        .rebind(sized_crit.subst_iter_copied(self.tcx(), substs).collect()),
+                        .rebind(sized_crit.arg_iter_copied(self.tcx(), args).collect()),
                 )
             }
 
@@ -2190,20 +2190,20 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 Where(obligation.predicate.rebind(tys.iter().collect()))
             }
 
-            ty::Generator(_, substs, hir::Movability::Movable) => {
+            ty::Generator(_, args, hir::Movability::Movable) => {
                 if self.tcx().features().generator_clone {
                     let resolved_upvars =
-                        self.infcx.shallow_resolve(substs.as_generator().tupled_upvars_ty());
+                        self.infcx.shallow_resolve(args.as_generator().tupled_upvars_ty());
                     let resolved_witness =
-                        self.infcx.shallow_resolve(substs.as_generator().witness());
+                        self.infcx.shallow_resolve(args.as_generator().witness());
                     if resolved_upvars.is_ty_var() || resolved_witness.is_ty_var() {
                         // Not yet resolved.
                         Ambiguous
                     } else {
-                        let all = substs
+                        let all = args
                             .as_generator()
                             .upvar_tys()
-                            .chain(iter::once(substs.as_generator().witness()))
+                            .chain(iter::once(args.as_generator().witness()))
                             .collect::<Vec<_>>();
                         Where(obligation.predicate.rebind(all))
                     }
@@ -2227,24 +2227,24 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 Where(ty::Binder::bind_with_vars(witness_tys.to_vec(), all_vars))
             }
 
-            ty::GeneratorWitnessMIR(def_id, ref substs) => {
+            ty::GeneratorWitnessMIR(def_id, ref args) => {
                 let hidden_types = bind_generator_hidden_types_above(
                     self.infcx,
                     def_id,
-                    substs,
+                    args,
                     obligation.predicate.bound_vars(),
                 );
                 Where(hidden_types)
             }
 
-            ty::Closure(_, substs) => {
+            ty::Closure(_, args) => {
                 // (*) binder moved here
-                let ty = self.infcx.shallow_resolve(substs.as_closure().tupled_upvars_ty());
+                let ty = self.infcx.shallow_resolve(args.as_closure().tupled_upvars_ty());
                 if let ty::Infer(ty::TyVar(_)) = ty.kind() {
                     // Not yet resolved.
                     Ambiguous
                 } else {
-                    Where(obligation.predicate.rebind(substs.as_closure().upvar_tys().collect()))
+                    Where(obligation.predicate.rebind(args.as_closure().upvar_tys().collect()))
                 }
             }
 
@@ -2321,14 +2321,14 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 t.rebind(tys.iter().collect())
             }
 
-            ty::Closure(_, ref substs) => {
-                let ty = self.infcx.shallow_resolve(substs.as_closure().tupled_upvars_ty());
+            ty::Closure(_, ref args) => {
+                let ty = self.infcx.shallow_resolve(args.as_closure().tupled_upvars_ty());
                 t.rebind(vec![ty])
             }
 
-            ty::Generator(_, ref substs, _) => {
-                let ty = self.infcx.shallow_resolve(substs.as_generator().tupled_upvars_ty());
-                let witness = substs.as_generator().witness();
+            ty::Generator(_, ref args, _) => {
+                let ty = self.infcx.shallow_resolve(args.as_generator().tupled_upvars_ty());
+                let witness = args.as_generator().witness();
                 t.rebind([ty].into_iter().chain(iter::once(witness)).collect())
             }
 
@@ -2337,18 +2337,18 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 types.map_bound(|types| types.to_vec())
             }
 
-            ty::GeneratorWitnessMIR(def_id, ref substs) => {
-                bind_generator_hidden_types_above(self.infcx, def_id, substs, t.bound_vars())
+            ty::GeneratorWitnessMIR(def_id, ref args) => {
+                bind_generator_hidden_types_above(self.infcx, def_id, args, t.bound_vars())
             }
 
             // For `PhantomData<T>`, we pass `T`.
-            ty::Adt(def, substs) if def.is_phantom_data() => t.rebind(substs.types().collect()),
+            ty::Adt(def, args) if def.is_phantom_data() => t.rebind(args.types().collect()),
 
-            ty::Adt(def, substs) => {
-                t.rebind(def.all_fields().map(|f| f.ty(self.tcx(), substs)).collect())
+            ty::Adt(def, args) => {
+                t.rebind(def.all_fields().map(|f| f.ty(self.tcx(), args)).collect())
             }
 
-            ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+            ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
                 let ty = self.tcx().type_of(def_id);
                 if ty.skip_binder().references_error() {
                     return Err(SelectionError::OpaqueTypeAutoTraitLeakageUnknown(def_id));
@@ -2356,7 +2356,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                 // We can resolve the `impl Trait` to its concrete type,
                 // which enforces a DAG between the functions requiring
                 // the auto trait bounds in question.
-                t.rebind(vec![ty.subst(self.tcx(), substs)])
+                t.rebind(vec![ty.instantiate(self.tcx(), args)])
             }
         })
     }
@@ -2428,10 +2428,10 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         &mut self,
         impl_def_id: DefId,
         obligation: &PolyTraitObligation<'tcx>,
-    ) -> Normalized<'tcx, SubstsRef<'tcx>> {
+    ) -> Normalized<'tcx, GenericArgsRef<'tcx>> {
         let impl_trait_ref = self.tcx().impl_trait_ref(impl_def_id).unwrap();
         match self.match_impl(impl_def_id, impl_trait_ref, obligation) {
-            Ok(substs) => substs,
+            Ok(args) => args,
             Err(()) => {
                 // FIXME: A rematch may fail when a candidate cache hit occurs
                 // on thefreshened form of the trait predicate, but the match
@@ -2447,7 +2447,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
                         impl_def_id, obligation
                     ),
                 );
-                let value = self.infcx.fresh_substs_for_item(obligation.cause.span, impl_def_id);
+                let value = self.infcx.fresh_args_for_item(obligation.cause.span, impl_def_id);
                 let err = Ty::new_error(self.tcx(), guar);
                 let value = value.fold_with(&mut BottomUpFolder {
                     tcx: self.tcx(),
@@ -2466,14 +2466,14 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         impl_def_id: DefId,
         impl_trait_ref: EarlyBinder<ty::TraitRef<'tcx>>,
         obligation: &PolyTraitObligation<'tcx>,
-    ) -> Result<Normalized<'tcx, SubstsRef<'tcx>>, ()> {
+    ) -> Result<Normalized<'tcx, GenericArgsRef<'tcx>>, ()> {
         let placeholder_obligation =
             self.infcx.instantiate_binder_with_placeholders(obligation.predicate);
         let placeholder_obligation_trait_ref = placeholder_obligation.trait_ref;
 
-        let impl_substs = self.infcx.fresh_substs_for_item(obligation.cause.span, impl_def_id);
+        let impl_args = self.infcx.fresh_args_for_item(obligation.cause.span, impl_def_id);
 
-        let impl_trait_ref = impl_trait_ref.subst(self.tcx(), impl_substs);
+        let impl_trait_ref = impl_trait_ref.instantiate(self.tcx(), impl_args);
         if impl_trait_ref.references_error() {
             return Err(());
         }
@@ -2515,7 +2515,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
             return Err(());
         }
 
-        Ok(Normalized { value: impl_substs, obligations: nested_obligations })
+        Ok(Normalized { value: impl_args, obligations: nested_obligations })
     }
 
     /// Normalize `where_clause_trait_ref` and try to match it against
@@ -2580,9 +2580,9 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
     fn closure_trait_ref_unnormalized(
         &mut self,
         obligation: &PolyTraitObligation<'tcx>,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> ty::PolyTraitRef<'tcx> {
-        let closure_sig = substs.as_closure().sig();
+        let closure_sig = args.as_closure().sig();
 
         debug!(?closure_sig);
 
@@ -2615,8 +2615,8 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         cause: &ObligationCause<'tcx>,
         recursion_depth: usize,
         param_env: ty::ParamEnv<'tcx>,
-        def_id: DefId,           // of impl or trait
-        substs: SubstsRef<'tcx>, // for impl or trait
+        def_id: DefId,              // of impl or trait
+        args: GenericArgsRef<'tcx>, // for impl or trait
         parent_trait_pred: ty::Binder<'tcx, ty::TraitPredicate<'tcx>>,
     ) -> Vec<PredicateObligation<'tcx>> {
         let tcx = self.tcx();
@@ -2637,7 +2637,7 @@ impl<'tcx> SelectionContext<'_, 'tcx> {
         // that order.
         let predicates = tcx.predicates_of(def_id);
         assert_eq!(predicates.parent, None);
-        let predicates = predicates.instantiate_own(tcx, substs);
+        let predicates = predicates.instantiate_own(tcx, args);
         let mut obligations = Vec::with_capacity(predicates.len());
         for (index, (predicate, span)) in predicates.into_iter().enumerate() {
             let cause =
@@ -2990,7 +2990,7 @@ pub enum ProjectionMatchesProjection {
 fn bind_generator_hidden_types_above<'tcx>(
     infcx: &InferCtxt<'tcx>,
     def_id: DefId,
-    substs: ty::SubstsRef<'tcx>,
+    args: ty::GenericArgsRef<'tcx>,
     bound_vars: &ty::List<ty::BoundVariableKind>,
 ) -> ty::Binder<'tcx, Vec<Ty<'tcx>>> {
     let tcx = infcx.tcx;
@@ -3006,7 +3006,7 @@ fn bind_generator_hidden_types_above<'tcx>(
         // Deduplicate tys to avoid repeated work.
         .filter(|bty| seen_tys.insert(*bty))
         .map(|bty| {
-            let mut ty = bty.subst(tcx, substs);
+            let mut ty = bty.instantiate(tcx, args);
 
             // Only remap erased regions if we use them.
             if considering_regions {
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
index 6d001467b447b..b61b209654c1d 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/mod.rs
@@ -23,7 +23,7 @@ use rustc_data_structures::fx::FxIndexSet;
 use rustc_errors::{error_code, DelayDm, Diagnostic};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::ty::{self, ImplSubject, Ty, TyCtxt, TypeVisitableExt};
-use rustc_middle::ty::{InternalSubsts, SubstsRef};
+use rustc_middle::ty::{GenericArgs, GenericArgsRef};
 use rustc_session::lint::builtin::COHERENCE_LEAK_CHECK;
 use rustc_session::lint::builtin::ORDER_DEPENDENT_TRAIT_OBJECTS;
 use rustc_span::{Span, DUMMY_SP};
@@ -48,7 +48,7 @@ pub struct OverlapError<'tcx> {
 /// When we have selected one impl, but are actually using item definitions from
 /// a parent impl providing a default, we need a way to translate between the
 /// type parameters of the two impls. Here the `source_impl` is the one we've
-/// selected, and `source_substs` is a substitution of its generics.
+/// selected, and `source_args` is a substitution of its generics.
 /// And `target_node` is the impl/trait we're actually going to get the
 /// definition from. The resulting substitution will map from `target_node`'s
 /// generics to `source_impl`'s generics as instantiated by `source_subst`.
@@ -76,51 +76,46 @@ pub struct OverlapError<'tcx> {
 /// through associated type projection. We deal with such cases by using
 /// *fulfillment* to relate the two impls, requiring that all projections are
 /// resolved.
-pub fn translate_substs<'tcx>(
+pub fn translate_args<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     source_impl: DefId,
-    source_substs: SubstsRef<'tcx>,
+    source_args: GenericArgsRef<'tcx>,
     target_node: specialization_graph::Node,
-) -> SubstsRef<'tcx> {
-    translate_substs_with_cause(
-        infcx,
-        param_env,
-        source_impl,
-        source_substs,
-        target_node,
-        |_, _| ObligationCause::dummy(),
-    )
+) -> GenericArgsRef<'tcx> {
+    translate_args_with_cause(infcx, param_env, source_impl, source_args, target_node, |_, _| {
+        ObligationCause::dummy()
+    })
 }
 
-/// Like [translate_substs], but obligations from the parent implementation
+/// Like [translate_args], but obligations from the parent implementation
 /// are registered with the provided `ObligationCause`.
 ///
 /// This is for reporting *region* errors from those bounds. Type errors should
 /// not happen because the specialization graph already checks for those, and
 /// will result in an ICE.
-pub fn translate_substs_with_cause<'tcx>(
+pub fn translate_args_with_cause<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     source_impl: DefId,
-    source_substs: SubstsRef<'tcx>,
+    source_args: GenericArgsRef<'tcx>,
     target_node: specialization_graph::Node,
     cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
-) -> SubstsRef<'tcx> {
+) -> GenericArgsRef<'tcx> {
     debug!(
-        "translate_substs({:?}, {:?}, {:?}, {:?})",
-        param_env, source_impl, source_substs, target_node
+        "translate_args({:?}, {:?}, {:?}, {:?})",
+        param_env, source_impl, source_args, target_node
     );
     let source_trait_ref =
-        infcx.tcx.impl_trait_ref(source_impl).unwrap().subst(infcx.tcx, &source_substs);
+        infcx.tcx.impl_trait_ref(source_impl).unwrap().instantiate(infcx.tcx, &source_args);
 
     // translate the Self and Param parts of the substitution, since those
     // vary across impls
-    let target_substs = match target_node {
+    let target_args = match target_node {
         specialization_graph::Node::Impl(target_impl) => {
             // no need to translate if we're targeting the impl we started with
             if source_impl == target_impl {
-                return source_substs;
+                return source_args;
             }
 
             fulfill_implication(infcx, param_env, source_trait_ref, source_impl, target_impl, cause)
@@ -131,11 +126,11 @@ pub fn translate_substs_with_cause<'tcx>(
                     )
                 })
         }
-        specialization_graph::Node::Trait(..) => source_trait_ref.substs,
+        specialization_graph::Node::Trait(..) => source_trait_ref.args,
     };
 
     // directly inherent the method generics, since those do not vary across impls
-    source_substs.rebase_onto(infcx.tcx, source_impl, target_substs)
+    source_args.rebase_onto(infcx.tcx, source_impl, target_args)
 }
 
 /// Is `impl1` a specialization of `impl2`?
@@ -172,7 +167,7 @@ pub(super) fn specializes(tcx: TyCtxt<'_>, (impl1_def_id, impl2_def_id): (DefId,
 
     // create a parameter environment corresponding to a (placeholder) instantiation of impl1
     let penv = tcx.param_env(impl1_def_id);
-    let impl1_trait_ref = tcx.impl_trait_ref(impl1_def_id).unwrap().subst_identity();
+    let impl1_trait_ref = tcx.impl_trait_ref(impl1_def_id).unwrap().instantiate_identity();
 
     // Create an infcx, taking the predicates of impl1 as assumptions:
     let infcx = tcx.infer_ctxt().build();
@@ -196,7 +191,7 @@ fn fulfill_implication<'tcx>(
     source_impl: DefId,
     target_impl: DefId,
     error_cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
-) -> Result<SubstsRef<'tcx>, ()> {
+) -> Result<GenericArgsRef<'tcx>, ()> {
     debug!(
         "fulfill_implication({:?}, trait_ref={:?} |- {:?} applies)",
         param_env, source_trait_ref, target_impl
@@ -221,9 +216,9 @@ fn fulfill_implication<'tcx>(
     let source_trait = ImplSubject::Trait(source_trait_ref);
 
     let selcx = &mut SelectionContext::new(&infcx);
-    let target_substs = infcx.fresh_substs_for_item(DUMMY_SP, target_impl);
+    let target_args = infcx.fresh_args_for_item(DUMMY_SP, target_impl);
     let (target_trait, obligations) =
-        util::impl_subject_and_oblig(selcx, param_env, target_impl, target_substs, error_cause);
+        util::impl_subject_and_oblig(selcx, param_env, target_impl, target_args, error_cause);
 
     // do the impls unify? If not, no specialization.
     let Ok(InferOk { obligations: more_obligations, .. }) = infcx
@@ -259,7 +254,7 @@ fn fulfill_implication<'tcx>(
 
     // Now resolve the *substitution* we built for the target earlier, replacing
     // the inference variables inside with whatever we got from fulfillment.
-    Ok(infcx.resolve_vars_if_possible(target_substs))
+    Ok(infcx.resolve_vars_if_possible(target_args))
 }
 
 /// Query provider for `specialization_graph_of`.
@@ -467,21 +462,21 @@ fn report_conflicting_impls<'tcx>(
 pub(crate) fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Option<String> {
     use std::fmt::Write;
 
-    let trait_ref = tcx.impl_trait_ref(impl_def_id)?.subst_identity();
+    let trait_ref = tcx.impl_trait_ref(impl_def_id)?.instantiate_identity();
     let mut w = "impl".to_owned();
 
-    let substs = InternalSubsts::identity_for_item(tcx, impl_def_id);
+    let args = GenericArgs::identity_for_item(tcx, impl_def_id);
 
     // FIXME: Currently only handles ?Sized.
     //        Needs to support ?Move and ?DynSized when they are implemented.
     let mut types_without_default_bounds = FxIndexSet::default();
     let sized_trait = tcx.lang_items().sized_trait();
 
-    if !substs.is_empty() {
-        types_without_default_bounds.extend(substs.types());
+    if !args.is_empty() {
+        types_without_default_bounds.extend(args.types());
         w.push('<');
         w.push_str(
-            &substs
+            &args
                 .iter()
                 .map(|k| k.to_string())
                 .filter(|k| k != "'_")
@@ -495,7 +490,7 @@ pub(crate) fn to_pretty_impl_header(tcx: TyCtxt<'_>, impl_def_id: DefId) -> Opti
         w,
         " {} for {}",
         trait_ref.print_only_trait_path(),
-        tcx.type_of(impl_def_id).subst_identity()
+        tcx.type_of(impl_def_id).instantiate_identity()
     )
     .unwrap();
 
diff --git a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
index aa5c624f471ff..e9a592bdee799 100644
--- a/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
+++ b/compiler/rustc_trait_selection/src/traits/specialize/specialization_graph.rs
@@ -180,7 +180,7 @@ impl<'tcx> ChildrenExt<'tcx> for Children {
             if le && !ge {
                 debug!(
                     "descending as child of TraitRef {:?}",
-                    tcx.impl_trait_ref(possible_sibling).unwrap().subst_identity()
+                    tcx.impl_trait_ref(possible_sibling).unwrap().instantiate_identity()
                 );
 
                 // The impl specializes `possible_sibling`.
@@ -188,7 +188,7 @@ impl<'tcx> ChildrenExt<'tcx> for Children {
             } else if ge && !le {
                 debug!(
                     "placing as parent of TraitRef {:?}",
-                    tcx.impl_trait_ref(possible_sibling).unwrap().subst_identity()
+                    tcx.impl_trait_ref(possible_sibling).unwrap().instantiate_identity()
                 );
 
                 replace_children.push(possible_sibling);
diff --git a/compiler/rustc_trait_selection/src/traits/structural_match.rs b/compiler/rustc_trait_selection/src/traits/structural_match.rs
index 420f8c5dceb50..0864e4dc84199 100644
--- a/compiler/rustc_trait_selection/src/traits/structural_match.rs
+++ b/compiler/rustc_trait_selection/src/traits/structural_match.rs
@@ -62,8 +62,8 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for Search<'tcx> {
     fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         debug!("Search visiting ty: {:?}", ty);
 
-        let (adt_def, substs) = match *ty.kind() {
-            ty::Adt(adt_def, substs) => (adt_def, substs),
+        let (adt_def, args) = match *ty.kind() {
+            ty::Adt(adt_def, args) => (adt_def, args),
             ty::Param(_) => {
                 return ControlFlow::Break(ty);
             }
@@ -157,15 +157,15 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for Search<'tcx> {
         // instead looks directly at its fields outside
         // this match), so we skip super_visit_with.
         //
-        // (Must not recur on substs for `PhantomData<T>` cf
+        // (Must not recur on args for `PhantomData<T>` cf
         // rust-lang/rust#55028 and rust-lang/rust#55837; but also
-        // want to skip substs when only uses of generic are
+        // want to skip args when only uses of generic are
         // behind unsafe pointers `*const T`/`*mut T`.)
 
         // even though we skip super_visit_with, we must recur on
         // fields of ADT.
         let tcx = self.tcx;
-        adt_def.all_fields().map(|field| field.ty(tcx, substs)).try_for_each(|field_ty| {
+        adt_def.all_fields().map(|field| field.ty(tcx, args)).try_for_each(|field_ty| {
             let ty = self.tcx.normalize_erasing_regions(ty::ParamEnv::empty(), field_ty);
             debug!("structural-match ADT: field_ty={:?}, ty={:?}", field_ty, ty);
             ty.visit_with(self)
diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs
index 302b6cacf2ccf..7b34908c4bed4 100644
--- a/compiler/rustc_trait_selection/src/traits/util.rs
+++ b/compiler/rustc_trait_selection/src/traits/util.rs
@@ -4,7 +4,7 @@ use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::Diagnostic;
 use rustc_hir::def_id::DefId;
 use rustc_infer::infer::InferOk;
-use rustc_middle::ty::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, ImplSubject, ToPredicate, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::Span;
 use smallvec::SmallVec;
@@ -194,24 +194,24 @@ impl Iterator for SupertraitDefIds<'_> {
 // Other
 ///////////////////////////////////////////////////////////////////////////
 
-/// Instantiate all bound parameters of the impl subject with the given substs,
+/// Instantiate all bound parameters of the impl subject with the given args,
 /// returning the resulting subject and all obligations that arise.
 /// The obligations are closed under normalization.
 pub fn impl_subject_and_oblig<'a, 'tcx>(
     selcx: &mut SelectionContext<'a, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     impl_def_id: DefId,
-    impl_substs: SubstsRef<'tcx>,
+    impl_args: GenericArgsRef<'tcx>,
     cause: impl Fn(usize, Span) -> ObligationCause<'tcx>,
 ) -> (ImplSubject<'tcx>, impl Iterator<Item = PredicateObligation<'tcx>>) {
     let subject = selcx.tcx().impl_subject(impl_def_id);
-    let subject = subject.subst(selcx.tcx(), impl_substs);
+    let subject = subject.instantiate(selcx.tcx(), impl_args);
 
     let InferOk { value: subject, obligations: normalization_obligations1 } =
         selcx.infcx.at(&ObligationCause::dummy(), param_env).normalize(subject);
 
     let predicates = selcx.tcx().predicates_of(impl_def_id);
-    let predicates = predicates.instantiate(selcx.tcx(), impl_substs);
+    let predicates = predicates.instantiate(selcx.tcx(), impl_args);
     let InferOk { value: predicates, obligations: normalization_obligations2 } =
         selcx.infcx.at(&ObligationCause::dummy(), param_env).normalize(predicates);
     let impl_obligations = super::predicates_for_generics(cause, param_env, predicates);
@@ -303,13 +303,13 @@ pub enum TupleArgumentsFlag {
     No,
 }
 
-// Verify that the trait item and its implementation have compatible substs lists
-pub fn check_substs_compatible<'tcx>(
+// Verify that the trait item and its implementation have compatible args lists
+pub fn check_args_compatible<'tcx>(
     tcx: TyCtxt<'tcx>,
     assoc_item: ty::AssocItem,
-    substs: ty::SubstsRef<'tcx>,
+    args: ty::GenericArgsRef<'tcx>,
 ) -> bool {
-    fn check_substs_compatible_inner<'tcx>(
+    fn check_args_compatible_inner<'tcx>(
         tcx: TyCtxt<'tcx>,
         generics: &'tcx ty::Generics,
         args: &'tcx [ty::GenericArg<'tcx>],
@@ -322,7 +322,7 @@ pub fn check_substs_compatible<'tcx>(
 
         if let Some(parent) = generics.parent
             && let parent_generics = tcx.generics_of(parent)
-            && !check_substs_compatible_inner(tcx, parent_generics, parent_args) {
+            && !check_args_compatible_inner(tcx, parent_generics, parent_args) {
             return false;
         }
 
@@ -339,7 +339,7 @@ pub fn check_substs_compatible<'tcx>(
     }
 
     let generics = tcx.generics_of(assoc_item.def_id);
-    // Chop off any additional substs (RPITIT) substs
-    let substs = &substs[0..generics.count().min(substs.len())];
-    check_substs_compatible_inner(tcx, generics, substs)
+    // Chop off any additional args (RPITIT) args
+    let args = &args[0..generics.count().min(args.len())];
+    check_args_compatible_inner(tcx, generics, args)
 }
diff --git a/compiler/rustc_trait_selection/src/traits/vtable.rs b/compiler/rustc_trait_selection/src/traits/vtable.rs
index 1f83f1f44bcbd..78816fed01739 100644
--- a/compiler/rustc_trait_selection/src/traits/vtable.rs
+++ b/compiler/rustc_trait_selection/src/traits/vtable.rs
@@ -6,7 +6,7 @@ use rustc_infer::traits::util::PredicateSet;
 use rustc_infer::traits::ImplSource;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::visit::TypeVisitableExt;
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::{self, GenericParamDefKind, ToPredicate, Ty, TyCtxt, VtblEntry};
 use rustc_span::{sym, Span};
 use smallvec::SmallVec;
@@ -241,12 +241,12 @@ fn vtable_entries<'tcx>(
                     debug!("vtable_entries: trait_method={:?}", def_id);
 
                     // The method may have some early-bound lifetimes; add regions for those.
-                    let substs = trait_ref.map_bound(|trait_ref| {
-                        InternalSubsts::for_item(tcx, def_id, |param, _| match param.kind {
+                    let args = trait_ref.map_bound(|trait_ref| {
+                        GenericArgs::for_item(tcx, def_id, |param, _| match param.kind {
                             GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
                             GenericParamDefKind::Type { .. }
                             | GenericParamDefKind::Const { .. } => {
-                                trait_ref.substs[param.index as usize]
+                                trait_ref.args[param.index as usize]
                             }
                         })
                     });
@@ -254,14 +254,14 @@ fn vtable_entries<'tcx>(
                     // The trait type may have higher-ranked lifetimes in it;
                     // erase them if they appear, so that we get the type
                     // at some particular call site.
-                    let substs = tcx
-                        .normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), substs);
+                    let args =
+                        tcx.normalize_erasing_late_bound_regions(ty::ParamEnv::reveal_all(), args);
 
                     // It's possible that the method relies on where-clauses that
                     // do not hold for this particular set of type parameters.
                     // Note that this method could then never be called, so we
                     // do not want to try and codegen it, in that case (see #23435).
-                    let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
+                    let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, args);
                     if impossible_predicates(
                         tcx,
                         predicates.map(|(predicate, _)| predicate).collect(),
@@ -274,7 +274,7 @@ fn vtable_entries<'tcx>(
                         tcx,
                         ty::ParamEnv::reveal_all(),
                         def_id,
-                        substs,
+                        args,
                     )
                     .expect("resolution failed during building vtable representation");
                     VtblEntry::Method(instance)
diff --git a/compiler/rustc_trait_selection/src/traits/wf.rs b/compiler/rustc_trait_selection/src/traits/wf.rs
index d81722ce22a12..b327dd2e15026 100644
--- a/compiler/rustc_trait_selection/src/traits/wf.rs
+++ b/compiler/rustc_trait_selection/src/traits/wf.rs
@@ -2,8 +2,8 @@ use crate::infer::InferCtxt;
 use crate::traits;
 use rustc_hir as hir;
 use rustc_hir::lang_items::LangItem;
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
+use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_span::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_span::{Span, DUMMY_SP};
 
@@ -341,7 +341,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         let trait_ref = &trait_pred.trait_ref;
 
         // Negative trait predicates don't require supertraits to hold, just
-        // that their substs are WF.
+        // that their args are WF.
         if trait_pred.polarity == ty::ImplPolarity::Negative {
             self.compute_negative_trait_pred(trait_ref);
             return;
@@ -349,9 +349,9 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
         // if the trait predicate is not const, the wf obligations should not be const as well.
         let obligations = if trait_pred.constness == ty::BoundConstness::NotConst {
-            self.nominal_obligations_without_const(trait_ref.def_id, trait_ref.substs)
+            self.nominal_obligations_without_const(trait_ref.def_id, trait_ref.args)
         } else {
-            self.nominal_obligations(trait_ref.def_id, trait_ref.substs)
+            self.nominal_obligations(trait_ref.def_id, trait_ref.args)
         };
 
         debug!("compute_trait_pred obligations {:?}", obligations);
@@ -383,7 +383,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
 
         self.out.extend(
             trait_ref
-                .substs
+                .args
                 .iter()
                 .enumerate()
                 .filter(|(_, arg)| {
@@ -416,7 +416,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     // Compute the obligations that are required for `trait_ref` to be WF,
     // given that it is a *negative* trait predicate.
     fn compute_negative_trait_pred(&mut self, trait_ref: &ty::TraitRef<'tcx>) {
-        for arg in trait_ref.substs {
+        for arg in trait_ref.args {
             self.compute(arg);
         }
     }
@@ -427,7 +427,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         // A projection is well-formed if
         //
         // (a) its predicates hold (*)
-        // (b) its substs are wf
+        // (b) its args are wf
         //
         // (*) The predicates of an associated type include the predicates of
         //     the trait that it's contained in. For example, given
@@ -446,17 +446,17 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         //     `i32: Copy`
         // ]
         // Projection types do not require const predicates.
-        let obligations = self.nominal_obligations_without_const(data.def_id, data.substs);
+        let obligations = self.nominal_obligations_without_const(data.def_id, data.args);
         self.out.extend(obligations);
 
-        self.compute_projection_substs(data.substs);
+        self.compute_projection_args(data.args);
     }
 
     fn compute_inherent_projection(&mut self, data: ty::AliasTy<'tcx>) {
         // An inherent projection is well-formed if
         //
         // (a) its predicates hold (*)
-        // (b) its substs are wf
+        // (b) its args are wf
         //
         // (*) The predicates of an inherent associated type include the
         //     predicates of the impl that it's contained in.
@@ -464,7 +464,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         if !data.self_ty().has_escaping_bound_vars() {
             // FIXME(inherent_associated_types): Should this happen inside of a snapshot?
             // FIXME(inherent_associated_types): This is incompatible with the new solver and lazy norm!
-            let substs = traits::project::compute_inherent_assoc_ty_substs(
+            let args = traits::project::compute_inherent_assoc_ty_args(
                 &mut traits::SelectionContext::new(self.infcx),
                 self.param_env,
                 data,
@@ -473,22 +473,21 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                 &mut self.out,
             );
             // Inherent projection types do not require const predicates.
-            let obligations = self.nominal_obligations_without_const(data.def_id, substs);
+            let obligations = self.nominal_obligations_without_const(data.def_id, args);
             self.out.extend(obligations);
         }
 
-        self.compute_projection_substs(data.substs);
+        self.compute_projection_args(data.args);
     }
 
-    fn compute_projection_substs(&mut self, substs: SubstsRef<'tcx>) {
+    fn compute_projection_args(&mut self, args: GenericArgsRef<'tcx>) {
         let tcx = self.tcx();
         let cause = self.cause(traits::WellFormed(None));
         let param_env = self.param_env;
         let depth = self.recursion_depth;
 
         self.out.extend(
-            substs
-                .iter()
+            args.iter()
                 .filter(|arg| {
                     matches!(arg.unpack(), GenericArgKind::Type(..) | GenericArgKind::Const(..))
                 })
@@ -541,7 +540,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     match ct.kind() {
                         ty::ConstKind::Unevaluated(uv) => {
                             if !ct.has_escaping_bound_vars() {
-                                let obligations = self.nominal_obligations(uv.def, uv.substs);
+                                let obligations = self.nominal_obligations(uv.def, uv.args);
                                 self.out.extend(obligations);
 
                                 let predicate = ty::Binder::dummy(ty::PredicateKind::Clause(
@@ -661,14 +660,14 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     self.compute_inherent_projection(data);
                 }
 
-                ty::Adt(def, substs) => {
+                ty::Adt(def, args) => {
                     // WfNominalType
-                    let obligations = self.nominal_obligations(def.did(), substs);
+                    let obligations = self.nominal_obligations(def.did(), args);
                     self.out.extend(obligations);
                 }
 
-                ty::FnDef(did, substs) => {
-                    let obligations = self.nominal_obligations_without_const(did, substs);
+                ty::FnDef(did, args) => {
+                    let obligations = self.nominal_obligations_without_const(did, args);
                     self.out.extend(obligations);
                 }
 
@@ -688,7 +687,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     }
                 }
 
-                ty::Generator(did, substs, ..) => {
+                ty::Generator(did, args, ..) => {
                     // Walk ALL the types in the generator: this will
                     // include the upvar types as well as the yield
                     // type. Note that this is mildly distinct from
@@ -696,11 +695,11 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // about the signature of the closure. We don't
                     // have the problem of implied bounds here since
                     // generators don't take arguments.
-                    let obligations = self.nominal_obligations(did, substs);
+                    let obligations = self.nominal_obligations(did, args);
                     self.out.extend(obligations);
                 }
 
-                ty::Closure(did, substs) => {
+                ty::Closure(did, args) => {
                     // Only check the upvar types for WF, not the rest
                     // of the types within. This is needed because we
                     // capture the signature and it may not be WF
@@ -723,7 +722,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // fn(&'a T) }`, as discussed in #25860.
                     walker.skip_current_subtree(); // subtree handled below
                     // FIXME(eddyb) add the type to `walker` instead of recursing.
-                    self.compute(substs.as_closure().tupled_upvars_ty().into());
+                    self.compute(args.as_closure().tupled_upvars_ty().into());
                     // Note that we cannot skip the generic types
                     // types. Normally, within the fn
                     // body where they are created, the generics will
@@ -739,7 +738,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // can cause compiler crashes when the user abuses unsafe
                     // code to procure such a closure.
                     // See tests/ui/type-alias-impl-trait/wf_check_closures.rs
-                    let obligations = self.nominal_obligations(did, substs);
+                    let obligations = self.nominal_obligations(did, args);
                     self.out.extend(obligations);
                 }
 
@@ -748,18 +747,18 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                     // types appearing in the fn signature
                 }
 
-                ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+                ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
                     // All of the requirements on type parameters
                     // have already been checked for `impl Trait` in
                     // return position. We do need to check type-alias-impl-trait though.
                     if self.tcx().is_type_alias_impl_trait(def_id) {
-                        let obligations = self.nominal_obligations(def_id, substs);
+                        let obligations = self.nominal_obligations(def_id, args);
                         self.out.extend(obligations);
                     }
                 }
 
-                ty::Alias(ty::Weak, ty::AliasTy { def_id, substs, .. }) => {
-                    let obligations = self.nominal_obligations(def_id, substs);
+                ty::Alias(ty::Weak, ty::AliasTy { def_id, args, .. }) => {
+                    let obligations = self.nominal_obligations(def_id, args);
                     self.out.extend(obligations);
                 }
 
@@ -826,7 +825,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     fn nominal_obligations_inner(
         &mut self,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
         remap_constness: bool,
     ) -> Vec<traits::PredicateObligation<'tcx>> {
         let predicates = self.tcx().predicates_of(def_id);
@@ -837,7 +836,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
             origins.extend(iter::repeat(parent).take(head.predicates.len()));
         }
 
-        let predicates = predicates.instantiate(self.tcx(), substs);
+        let predicates = predicates.instantiate(self.tcx(), args);
         trace!("{:#?}", predicates);
         debug_assert_eq!(predicates.predicates.len(), origins.len());
 
@@ -867,17 +866,17 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
     fn nominal_obligations(
         &mut self,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Vec<traits::PredicateObligation<'tcx>> {
-        self.nominal_obligations_inner(def_id, substs, false)
+        self.nominal_obligations_inner(def_id, args, false)
     }
 
     fn nominal_obligations_without_const(
         &mut self,
         def_id: DefId,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Vec<traits::PredicateObligation<'tcx>> {
-        self.nominal_obligations_inner(def_id, substs, true)
+        self.nominal_obligations_inner(def_id, args, true)
     }
 
     fn from_object_ty(
diff --git a/compiler/rustc_traits/src/dropck_outlives.rs b/compiler/rustc_traits/src/dropck_outlives.rs
index f35c14eeac801..074764f0c4e2e 100644
--- a/compiler/rustc_traits/src/dropck_outlives.rs
+++ b/compiler/rustc_traits/src/dropck_outlives.rs
@@ -4,7 +4,7 @@ use rustc_infer::infer::canonical::{Canonical, QueryResponse};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::query::{DropckConstraint, DropckOutlivesResult};
-use rustc_middle::ty::InternalSubsts;
+use rustc_middle::ty::GenericArgs;
 use rustc_middle::ty::TyCtxt;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
 use rustc_trait_selection::traits::query::dropck_outlives::{
@@ -41,11 +41,11 @@ pub(crate) fn adt_dtorck_constraint(
     } else if def.is_phantom_data() {
         // The first generic parameter here is guaranteed to be a type because it's
         // `PhantomData`.
-        let substs = InternalSubsts::identity_for_item(tcx, def_id);
-        assert_eq!(substs.len(), 1);
+        let args = GenericArgs::identity_for_item(tcx, def_id);
+        assert_eq!(args.len(), 1);
         let result = DropckConstraint {
             outlives: vec![],
-            dtorck_types: vec![substs.type_at(0)],
+            dtorck_types: vec![args.type_at(0)],
             overflows: vec![],
         };
         debug!("dtorck_constraint: {:?} => {:?}", def, result);
@@ -54,7 +54,7 @@ pub(crate) fn adt_dtorck_constraint(
 
     let mut result = DropckConstraint::empty();
     for field in def.all_fields() {
-        let fty = tcx.type_of(field.did).subst_identity();
+        let fty = tcx.type_of(field.did).instantiate_identity();
         dtorck_constraint_for_ty_inner(tcx, span, fty, 0, fty, &mut result)?;
     }
     result.outlives.extend(tcx.destructor_constraints(def));
diff --git a/compiler/rustc_traits/src/normalize_projection_ty.rs b/compiler/rustc_traits/src/normalize_projection_ty.rs
index 83828f177bc84..0dbac56b47dd4 100644
--- a/compiler/rustc_traits/src/normalize_projection_ty.rs
+++ b/compiler/rustc_traits/src/normalize_projection_ty.rs
@@ -58,7 +58,7 @@ fn normalize_weak_ty<'tcx>(
     tcx.infer_ctxt().enter_canonical_trait_query(
         &goal,
         |ocx, ParamEnvAnd { param_env, value: goal }| {
-            let obligations = tcx.predicates_of(goal.def_id).instantiate_own(tcx, goal.substs).map(
+            let obligations = tcx.predicates_of(goal.def_id).instantiate_own(tcx, goal.args).map(
                 |(predicate, span)| {
                     traits::Obligation::new(
                         tcx,
@@ -69,7 +69,7 @@ fn normalize_weak_ty<'tcx>(
                 },
             );
             ocx.register_obligations(obligations);
-            let normalized_ty = tcx.type_of(goal.def_id).subst(tcx, goal.substs);
+            let normalized_ty = tcx.type_of(goal.def_id).instantiate(tcx, goal.args);
             Ok(NormalizationResult { normalized_ty })
         },
     )
diff --git a/compiler/rustc_transmute/src/layout/tree.rs b/compiler/rustc_transmute/src/layout/tree.rs
index be434eb7d00d3..8bd268182560a 100644
--- a/compiler/rustc_transmute/src/layout/tree.rs
+++ b/compiler/rustc_transmute/src/layout/tree.rs
@@ -175,8 +175,8 @@ pub(crate) mod rustc {
     use rustc_middle::ty::layout::LayoutError;
     use rustc_middle::ty::util::Discr;
     use rustc_middle::ty::AdtDef;
+    use rustc_middle::ty::GenericArgsRef;
     use rustc_middle::ty::ParamEnv;
-    use rustc_middle::ty::SubstsRef;
     use rustc_middle::ty::VariantDef;
     use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
     use rustc_span::ErrorGuaranteed;
@@ -297,7 +297,7 @@ pub(crate) mod rustc {
                         .fold(Tree::unit(), |tree, elt| tree.then(elt)))
                 }
 
-                ty::Adt(adt_def, substs_ref) => {
+                ty::Adt(adt_def, args_ref) => {
                     use rustc_middle::ty::AdtKind;
 
                     // If the layout is ill-specified, halt.
@@ -316,7 +316,7 @@ pub(crate) mod rustc {
                         AdtKind::Struct => Self::from_repr_c_variant(
                             ty,
                             *adt_def,
-                            substs_ref,
+                            args_ref,
                             &layout_summary,
                             None,
                             adt_def.non_enum_variant(),
@@ -330,7 +330,7 @@ pub(crate) mod rustc {
                                 tree = tree.or(Self::from_repr_c_variant(
                                     ty,
                                     *adt_def,
-                                    substs_ref,
+                                    args_ref,
                                     &layout_summary,
                                     Some(discr),
                                     adt_def.variant(idx),
@@ -351,7 +351,7 @@ pub(crate) mod rustc {
                             let mut tree = Tree::uninhabited();
 
                             for field in adt_def.all_fields() {
-                                let variant_ty = field.ty(tcx, substs_ref);
+                                let variant_ty = field.ty(tcx, args_ref);
                                 let variant_layout = layout_of(tcx, variant_ty)?;
                                 let padding_needed = ty_layout.size() - variant_layout.size();
                                 let variant = Self::def(Def::Field(field))
@@ -383,7 +383,7 @@ pub(crate) mod rustc {
         fn from_repr_c_variant(
             ty: Ty<'tcx>,
             adt_def: AdtDef<'tcx>,
-            substs_ref: SubstsRef<'tcx>,
+            args_ref: GenericArgsRef<'tcx>,
             layout_summary: &LayoutSummary,
             discr: Option<Discr<'tcx>>,
             variant_def: &'tcx VariantDef,
@@ -427,7 +427,7 @@ pub(crate) mod rustc {
             // Next come fields.
             let fields_span = trace_span!("treeifying fields").entered();
             for field_def in variant_def.fields.iter() {
-                let field_ty = field_def.ty(tcx, substs_ref);
+                let field_ty = field_def.ty(tcx, args_ref);
                 let _span = trace_span!("treeifying field", field = ?field_ty).entered();
 
                 // begin with the field's visibility
diff --git a/compiler/rustc_ty_utils/src/abi.rs b/compiler/rustc_ty_utils/src/abi.rs
index 55484f5c72e2b..d0a7414b4ff62 100644
--- a/compiler/rustc_ty_utils/src/abi.rs
+++ b/compiler/rustc_ty_utils/src/abi.rs
@@ -51,12 +51,12 @@ fn fn_sig_for_fn_abi<'tcx>(
             //
             // We normalize the `fn_sig` again after substituting at a later point.
             let mut sig = match *ty.kind() {
-                ty::FnDef(def_id, substs) => tcx
+                ty::FnDef(def_id, args) => tcx
                     .fn_sig(def_id)
                     .map_bound(|fn_sig| {
                         tcx.normalize_erasing_regions(tcx.param_env(def_id), fn_sig)
                     })
-                    .subst(tcx, substs),
+                    .instantiate(tcx, args),
                 _ => unreachable!(),
             };
 
@@ -71,8 +71,8 @@ fn fn_sig_for_fn_abi<'tcx>(
             }
             sig
         }
-        ty::Closure(def_id, substs) => {
-            let sig = substs.as_closure().sig();
+        ty::Closure(def_id, args) => {
+            let sig = args.as_closure().sig();
 
             let bound_vars = tcx.mk_bound_variable_kinds_from_iter(
                 sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
@@ -82,7 +82,7 @@ fn fn_sig_for_fn_abi<'tcx>(
                 kind: ty::BoundRegionKind::BrEnv,
             };
             let env_region = ty::Region::new_late_bound(tcx, ty::INNERMOST, br);
-            let env_ty = tcx.closure_env_ty(def_id, substs, env_region).unwrap();
+            let env_ty = tcx.closure_env_ty(def_id, args, env_region).unwrap();
 
             let sig = sig.skip_binder();
             ty::Binder::bind_with_vars(
@@ -96,8 +96,8 @@ fn fn_sig_for_fn_abi<'tcx>(
                 bound_vars,
             )
         }
-        ty::Generator(did, substs, _) => {
-            let sig = substs.as_generator().poly_sig();
+        ty::Generator(did, args, _) => {
+            let sig = args.as_generator().poly_sig();
 
             let bound_vars = tcx.mk_bound_variable_kinds_from_iter(
                 sig.bound_vars().iter().chain(iter::once(ty::BoundVariableKind::Region(ty::BrEnv))),
@@ -111,8 +111,8 @@ fn fn_sig_for_fn_abi<'tcx>(
 
             let pin_did = tcx.require_lang_item(LangItem::Pin, None);
             let pin_adt_ref = tcx.adt_def(pin_did);
-            let pin_substs = tcx.mk_substs(&[env_ty.into()]);
-            let env_ty = Ty::new_adt(tcx, pin_adt_ref, pin_substs);
+            let pin_args = tcx.mk_args(&[env_ty.into()]);
+            let env_ty = Ty::new_adt(tcx, pin_adt_ref, pin_args);
 
             let sig = sig.skip_binder();
             // The `FnSig` and the `ret_ty` here is for a generators main
@@ -123,8 +123,8 @@ fn fn_sig_for_fn_abi<'tcx>(
                 // The signature should be `Future::poll(_, &mut Context<'_>) -> Poll<Output>`
                 let poll_did = tcx.require_lang_item(LangItem::Poll, None);
                 let poll_adt_ref = tcx.adt_def(poll_did);
-                let poll_substs = tcx.mk_substs(&[sig.return_ty.into()]);
-                let ret_ty = Ty::new_adt(tcx, poll_adt_ref, poll_substs);
+                let poll_args = tcx.mk_args(&[sig.return_ty.into()]);
+                let ret_ty = Ty::new_adt(tcx, poll_adt_ref, poll_args);
 
                 // We have to replace the `ResumeTy` that is used for type and borrow checking
                 // with `&mut Context<'_>` which is used in codegen.
@@ -145,8 +145,8 @@ fn fn_sig_for_fn_abi<'tcx>(
                 // The signature should be `Generator::resume(_, Resume) -> GeneratorState<Yield, Return>`
                 let state_did = tcx.require_lang_item(LangItem::GeneratorState, None);
                 let state_adt_ref = tcx.adt_def(state_did);
-                let state_substs = tcx.mk_substs(&[sig.yield_ty.into(), sig.return_ty.into()]);
-                let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_substs);
+                let state_args = tcx.mk_args(&[sig.yield_ty.into(), sig.return_ty.into()]);
+                let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args);
 
                 (sig.resume_ty, ret_ty)
             };
diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index ed4f6d972c208..4a54423217422 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -5,7 +5,7 @@ use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_hir::definitions::DefPathData;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::query::Providers;
-use rustc_middle::ty::{self, ImplTraitInTraitData, InternalSubsts, Ty, TyCtxt};
+use rustc_middle::ty::{self, GenericArgs, ImplTraitInTraitData, Ty, TyCtxt};
 use rustc_span::symbol::kw;
 
 pub fn provide(providers: &mut Providers) {
@@ -290,7 +290,7 @@ fn associated_type_for_impl_trait_in_trait(
     trait_assoc_ty.type_of(ty::EarlyBinder::bind(Ty::new_opaque(
         tcx,
         opaque_ty_def_id.to_def_id(),
-        InternalSubsts::identity_for_item(tcx, opaque_ty_def_id),
+        GenericArgs::identity_for_item(tcx, opaque_ty_def_id),
     )));
 
     trait_assoc_ty.is_type_alias_impl_trait(false);
diff --git a/compiler/rustc_ty_utils/src/consts.rs b/compiler/rustc_ty_utils/src/consts.rs
index 426c98012b3fb..5f754d90b6dcc 100644
--- a/compiler/rustc_ty_utils/src/consts.rs
+++ b/compiler/rustc_ty_utils/src/consts.rs
@@ -42,7 +42,7 @@ pub(crate) fn destructure_const<'tcx>(
             (field_consts, None)
         }
         ty::Adt(def, _) if def.variants().is_empty() => bug!("unreachable"),
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             let (variant_idx, branches) = if def.is_enum() {
                 let (head, rest) = branches.split_first().unwrap();
                 (VariantIdx::from_u32(head.unwrap_leaf().try_to_u32().unwrap()), rest)
@@ -53,7 +53,7 @@ pub(crate) fn destructure_const<'tcx>(
             let mut field_consts = Vec::with_capacity(fields.len());
 
             for (field, field_valtree) in iter::zip(fields, branches) {
-                let field_ty = field.ty(tcx, substs);
+                let field_ty = field.ty(tcx, args);
                 let field_const = ty::Const::new_value(tcx, *field_valtree, field_ty);
                 field_consts.push(field_const);
             }
@@ -133,8 +133,8 @@ fn recurse_build<'tcx>(
             let val = ty::ValTree::zst();
             ty::Const::new_value(tcx, val, node.ty)
         }
-        &ExprKind::NamedConst { def_id, substs, user_ty: _ } => {
-            let uneval = ty::UnevaluatedConst::new(def_id, substs);
+        &ExprKind::NamedConst { def_id, args, user_ty: _ } => {
+            let uneval = ty::UnevaluatedConst::new(def_id, args);
             ty::Const::new_unevaluated(tcx, uneval, node.ty)
         }
         ExprKind::ConstParam { param, .. } => ty::Const::new_param(tcx, *param, node.ty),
@@ -306,8 +306,9 @@ impl<'a, 'tcx> IsThirPolymorphic<'a, 'tcx> {
         }
 
         match expr.kind {
-            thir::ExprKind::NamedConst { substs, .. }
-            | thir::ExprKind::ConstBlock { substs, .. } => substs.has_non_region_param(),
+            thir::ExprKind::NamedConst { args, .. } | thir::ExprKind::ConstBlock { args, .. } => {
+                args.has_non_region_param()
+            }
             thir::ExprKind::ConstParam { .. } => true,
             thir::ExprKind::Repeat { value, count } => {
                 self.visit_expr(&self.thir()[value]);
diff --git a/compiler/rustc_ty_utils/src/implied_bounds.rs b/compiler/rustc_ty_utils/src/implied_bounds.rs
index 2822595a8a7fa..be063a097c02d 100644
--- a/compiler/rustc_ty_utils/src/implied_bounds.rs
+++ b/compiler/rustc_ty_utils/src/implied_bounds.rs
@@ -13,7 +13,7 @@ pub fn provide(providers: &mut Providers) {
 fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'tcx>, Span)] {
     match tcx.def_kind(def_id) {
         DefKind::Fn => {
-            let sig = tcx.fn_sig(def_id).subst_identity();
+            let sig = tcx.fn_sig(def_id).instantiate_identity();
             let liberated_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
             tcx.arena.alloc_from_iter(itertools::zip_eq(
                 liberated_sig.inputs_and_output,
@@ -21,7 +21,7 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
             ))
         }
         DefKind::AssocFn => {
-            let sig = tcx.fn_sig(def_id).subst_identity();
+            let sig = tcx.fn_sig(def_id).instantiate_identity();
             let liberated_sig = tcx.liberate_late_bound_regions(def_id.to_def_id(), sig);
             let mut assumed_wf_types: Vec<_> =
                 tcx.assumed_wf_types(tcx.local_parent(def_id)).into();
@@ -35,8 +35,8 @@ fn assumed_wf_types<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx [(Ty<'
             // Trait arguments and the self type for trait impls or only the self type for
             // inherent impls.
             let tys = match tcx.impl_trait_ref(def_id) {
-                Some(trait_ref) => trait_ref.skip_binder().substs.types().collect(),
-                None => vec![tcx.type_of(def_id).subst_identity()],
+                Some(trait_ref) => trait_ref.skip_binder().args.types().collect(),
+                None => vec![tcx.type_of(def_id).instantiate_identity()],
             };
 
             let mut impl_spans = impl_spans(tcx, def_id);
diff --git a/compiler/rustc_ty_utils/src/instance.rs b/compiler/rustc_ty_utils/src/instance.rs
index b5e85e6d65f62..16b1836ba9faf 100644
--- a/compiler/rustc_ty_utils/src/instance.rs
+++ b/compiler/rustc_ty_utils/src/instance.rs
@@ -3,19 +3,19 @@ use rustc_hir::def_id::DefId;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::CodegenObligationError;
-use rustc_middle::ty::subst::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, Instance, TyCtxt, TypeVisitableExt};
 use rustc_span::sym;
 use rustc_trait_selection::traits;
-use traits::{translate_substs, Reveal};
+use traits::{translate_args, Reveal};
 
 use crate::errors::UnexpectedFnPtrAssociatedItem;
 
 fn resolve_instance<'tcx>(
     tcx: TyCtxt<'tcx>,
-    key: ty::ParamEnvAnd<'tcx, (DefId, SubstsRef<'tcx>)>,
+    key: ty::ParamEnvAnd<'tcx, (DefId, GenericArgsRef<'tcx>)>,
 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
-    let (param_env, (def, substs)) = key.into_parts();
+    let (param_env, (def, args)) = key.into_parts();
 
     let result = if let Some(trait_def_id) = tcx.trait_of_item(def) {
         debug!(" => associated item, attempting to find impl in param_env {:#?}", param_env);
@@ -24,19 +24,19 @@ fn resolve_instance<'tcx>(
             def,
             param_env,
             trait_def_id,
-            tcx.normalize_erasing_regions(param_env, substs),
+            tcx.normalize_erasing_regions(param_env, args),
         )
     } else {
         let ty = tcx.type_of(def);
-        let item_type = tcx.subst_and_normalize_erasing_regions(substs, param_env, ty);
+        let item_type = tcx.subst_and_normalize_erasing_regions(args, param_env, ty);
 
         let def = match *item_type.kind() {
             ty::FnDef(def_id, ..) if tcx.is_intrinsic(def_id) => {
                 debug!(" => intrinsic");
                 ty::InstanceDef::Intrinsic(def)
             }
-            ty::FnDef(def_id, substs) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => {
-                let ty = substs.type_at(0);
+            ty::FnDef(def_id, args) if Some(def_id) == tcx.lang_items().drop_in_place_fn() => {
+                let ty = args.type_at(0);
 
                 if ty.needs_drop(tcx, param_env) {
                     debug!(" => nontrivial drop glue");
@@ -63,7 +63,7 @@ fn resolve_instance<'tcx>(
                 ty::InstanceDef::Item(def)
             }
         };
-        Ok(Some(Instance { def, substs }))
+        Ok(Some(Instance { def, args }))
     };
     debug!("inner_resolve_instance: result={:?}", result);
     result
@@ -74,11 +74,11 @@ fn resolve_associated_item<'tcx>(
     trait_item_id: DefId,
     param_env: ty::ParamEnv<'tcx>,
     trait_id: DefId,
-    rcvr_substs: SubstsRef<'tcx>,
+    rcvr_args: GenericArgsRef<'tcx>,
 ) -> Result<Option<Instance<'tcx>>, ErrorGuaranteed> {
-    debug!(?trait_item_id, ?param_env, ?trait_id, ?rcvr_substs, "resolve_associated_item");
+    debug!(?trait_item_id, ?param_env, ?trait_id, ?rcvr_args, "resolve_associated_item");
 
-    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
+    let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_args);
 
     let vtbl = match tcx.codegen_select_candidate((param_env, trait_ref)) {
         Ok(vtbl) => vtbl,
@@ -102,9 +102,9 @@ fn resolve_associated_item<'tcx>(
         traits::ImplSource::UserDefined(impl_data) => {
             debug!(
                 "resolving ImplSource::UserDefined: {:?}, {:?}, {:?}, {:?}",
-                param_env, trait_item_id, rcvr_substs, impl_data
+                param_env, trait_item_id, rcvr_args, impl_data
             );
-            assert!(!rcvr_substs.has_infer());
+            assert!(!rcvr_args.has_infer());
             assert!(!trait_ref.has_infer());
 
             let trait_def_id = tcx.trait_id_of_impl(impl_data.impl_def_id).unwrap();
@@ -117,15 +117,15 @@ fn resolve_associated_item<'tcx>(
                 });
             let infcx = tcx.infer_ctxt().build();
             let param_env = param_env.with_reveal_all_normalized(tcx);
-            let substs = rcvr_substs.rebase_onto(tcx, trait_def_id, impl_data.substs);
-            let substs = translate_substs(
+            let args = rcvr_args.rebase_onto(tcx, trait_def_id, impl_data.args);
+            let args = translate_args(
                 &infcx,
                 param_env,
                 impl_data.impl_def_id,
-                substs,
+                args,
                 leaf_def.defining_node,
             );
-            let substs = infcx.tcx.erase_regions(substs);
+            let args = infcx.tcx.erase_regions(args);
 
             // Since this is a trait item, we need to see if the item is either a trait default item
             // or a specialization because we can't resolve those unless we can `Reveal::All`.
@@ -159,7 +159,7 @@ fn resolve_associated_item<'tcx>(
                 return Err(guard);
             }
 
-            let substs = tcx.erase_regions(substs);
+            let args = tcx.erase_regions(args);
 
             // Check if we just resolved an associated `const` declaration from
             // a `trait` to an associated `const` definition in an `impl`, where
@@ -175,14 +175,11 @@ fn resolve_associated_item<'tcx>(
                 ))?;
             }
 
-            Some(ty::Instance::new(leaf_def.item.def_id, substs))
+            Some(ty::Instance::new(leaf_def.item.def_id, args))
         }
         traits::ImplSource::Object(ref data) => {
             traits::get_vtable_index_of_object_method(tcx, data, trait_item_id).map(|index| {
-                Instance {
-                    def: ty::InstanceDef::Virtual(trait_item_id, index),
-                    substs: rcvr_substs,
-                }
+                Instance { def: ty::InstanceDef::Virtual(trait_item_id, index), args: rcvr_args }
             })
         }
         traits::ImplSource::Builtin(..) => {
@@ -205,14 +202,14 @@ fn resolve_associated_item<'tcx>(
 
                     Some(Instance {
                         def: ty::InstanceDef::CloneShim(trait_item_id, self_ty),
-                        substs: rcvr_substs,
+                        args: rcvr_args,
                     })
                 } else {
                     assert_eq!(name, sym::clone_from);
 
                     // Use the default `fn clone_from` from `trait Clone`.
-                    let substs = tcx.erase_regions(rcvr_substs);
-                    Some(ty::Instance::new(trait_item_id, substs))
+                    let args = tcx.erase_regions(rcvr_args);
+                    Some(ty::Instance::new(trait_item_id, args))
                 }
             } else if Some(trait_ref.def_id) == lang_items.fn_ptr_trait() {
                 if lang_items.fn_ptr_addr() == Some(trait_item_id) {
@@ -222,7 +219,7 @@ fn resolve_associated_item<'tcx>(
                     }
                     Some(Instance {
                         def: ty::InstanceDef::FnPtrAddrShim(trait_item_id, self_ty),
-                        substs: rcvr_substs,
+                        args: rcvr_args,
                     })
                 } else {
                     tcx.sess.emit_fatal(UnexpectedFnPtrAssociatedItem {
@@ -230,22 +227,20 @@ fn resolve_associated_item<'tcx>(
                     })
                 }
             } else if Some(trait_ref.def_id) == lang_items.future_trait() {
-                let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind()
-                else {
+                let ty::Generator(generator_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
                     bug!()
                 };
                 if Some(trait_item_id) == tcx.lang_items().future_poll_fn() {
                     // `Future::poll` is generated by the compiler.
-                    Some(Instance { def: ty::InstanceDef::Item(generator_def_id), substs: substs })
+                    Some(Instance { def: ty::InstanceDef::Item(generator_def_id), args: args })
                 } else {
                     // All other methods are default methods of the `Future` trait.
                     // (this assumes that `ImplSource::Builtin` is only used for methods on `Future`)
                     debug_assert!(tcx.defaultness(trait_item_id).has_value());
-                    Some(Instance::new(trait_item_id, rcvr_substs))
+                    Some(Instance::new(trait_item_id, rcvr_args))
                 }
             } else if Some(trait_ref.def_id) == lang_items.gen_trait() {
-                let ty::Generator(generator_def_id, substs, _) = *rcvr_substs.type_at(0).kind()
-                else {
+                let ty::Generator(generator_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
                     bug!()
                 };
                 if cfg!(debug_assertions) && tcx.item_name(trait_item_id) != sym::resume {
@@ -259,7 +254,7 @@ fn resolve_associated_item<'tcx>(
                         tcx.item_name(trait_item_id)
                     )
                 }
-                Some(Instance { def: ty::InstanceDef::Item(generator_def_id), substs })
+                Some(Instance { def: ty::InstanceDef::Item(generator_def_id), args })
             } else if tcx.fn_trait_kind_from_def_id(trait_ref.def_id).is_some() {
                 // FIXME: This doesn't check for malformed libcore that defines, e.g.,
                 // `trait Fn { fn call_once(&self) { .. } }`. This is mostly for extension
@@ -277,14 +272,14 @@ fn resolve_associated_item<'tcx>(
                         tcx.item_name(trait_item_id)
                     )
                 }
-                match *rcvr_substs.type_at(0).kind() {
-                    ty::Closure(closure_def_id, substs) => {
+                match *rcvr_args.type_at(0).kind() {
+                    ty::Closure(closure_def_id, args) => {
                         let trait_closure_kind = tcx.fn_trait_kind_from_def_id(trait_id).unwrap();
-                        Instance::resolve_closure(tcx, closure_def_id, substs, trait_closure_kind)
+                        Instance::resolve_closure(tcx, closure_def_id, args, trait_closure_kind)
                     }
                     ty::FnDef(..) | ty::FnPtr(..) => Some(Instance {
-                        def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_substs.type_at(0)),
-                        substs: rcvr_substs,
+                        def: ty::InstanceDef::FnPtrShim(trait_item_id, rcvr_args.type_at(0)),
+                        args: rcvr_args,
                     }),
                     _ => bug!(
                         "no built-in definition for `{trait_ref}::{}` for non-fn type",
diff --git a/compiler/rustc_ty_utils/src/layout.rs b/compiler/rustc_ty_utils/src/layout.rs
index 1cbbdedde974a..d858fa5a97c18 100644
--- a/compiler/rustc_ty_utils/src/layout.rs
+++ b/compiler/rustc_ty_utils/src/layout.rs
@@ -8,7 +8,7 @@ use rustc_middle::ty::layout::{
     IntegerExt, LayoutCx, LayoutError, LayoutOf, TyAndLayout, MAX_SIMD_LANES,
 };
 use rustc_middle::ty::{
-    self, subst::SubstsRef, AdtDef, EarlyBinder, ReprOptions, Ty, TyCtxt, TypeVisitableExt,
+    self, AdtDef, EarlyBinder, GenericArgsRef, ReprOptions, Ty, TyCtxt, TypeVisitableExt,
 };
 use rustc_session::{DataTypeKind, FieldInfo, FieldKind, SizeKind, VariantInfo};
 use rustc_span::symbol::Symbol;
@@ -299,10 +299,10 @@ fn layout_of_uncached<'tcx>(
             tcx.mk_layout(unit)
         }
 
-        ty::Generator(def_id, substs, _) => generator_layout(cx, ty, def_id, substs)?,
+        ty::Generator(def_id, args, _) => generator_layout(cx, ty, def_id, args)?,
 
-        ty::Closure(_, ref substs) => {
-            let tys = substs.as_closure().upvar_tys();
+        ty::Closure(_, ref args) => {
+            let tys = args.as_closure().upvar_tys();
             univariant(
                 &tys.map(|ty| Ok(cx.layout_of(ty)?.layout)).try_collect::<IndexVec<_, _>>()?,
                 &ReprOptions::default(),
@@ -322,7 +322,7 @@ fn layout_of_uncached<'tcx>(
         }
 
         // SIMD vector types.
-        ty::Adt(def, substs) if def.repr().simd() => {
+        ty::Adt(def, args) if def.repr().simd() => {
             if !def.is_struct() {
                 // Should have yielded E0517 by now.
                 tcx.sess.delay_span_bug(
@@ -349,12 +349,12 @@ fn layout_of_uncached<'tcx>(
             }
 
             // Type of the first ADT field:
-            let f0_ty = fields[FieldIdx::from_u32(0)].ty(tcx, substs);
+            let f0_ty = fields[FieldIdx::from_u32(0)].ty(tcx, args);
 
             // Heterogeneous SIMD vectors are not supported:
             // (should be caught by typeck)
             for fi in fields {
-                if fi.ty(tcx, substs) != f0_ty {
+                if fi.ty(tcx, args) != f0_ty {
                     tcx.sess.delay_span_bug(
                         DUMMY_SP,
                         "#[repr(simd)] was applied to an ADT with heterogeneous field type",
@@ -435,7 +435,7 @@ fn layout_of_uncached<'tcx>(
         }
 
         // ADTs.
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             // Cache the field layouts.
             let variants = def
                 .variants()
@@ -443,7 +443,7 @@ fn layout_of_uncached<'tcx>(
                 .map(|v| {
                     v.fields
                         .iter()
-                        .map(|field| Ok(cx.layout_of(field.ty(tcx, substs))?.layout))
+                        .map(|field| Ok(cx.layout_of(field.ty(tcx, args))?.layout))
                         .try_collect::<IndexVec<_, _>>()
                 })
                 .try_collect::<IndexVec<VariantIdx, _>>()?;
@@ -482,7 +482,7 @@ fn layout_of_uncached<'tcx>(
             let maybe_unsized = def.is_struct()
                 && def.non_enum_variant().tail_opt().is_some_and(|last_field| {
                     let param_env = tcx.param_env(def.did());
-                    !tcx.type_of(last_field.did).subst_identity().is_sized(tcx, param_env)
+                    !tcx.type_of(last_field.did).instantiate_identity().is_sized(tcx, param_env)
                 });
 
             let Some(layout) = cx.layout_of_struct_or_enum(
@@ -502,7 +502,7 @@ fn layout_of_uncached<'tcx>(
             // If the struct tail is sized and can be unsized, check that unsizing doesn't move the fields around.
             if cfg!(debug_assertions)
                 && maybe_unsized
-                && def.non_enum_variant().tail().ty(tcx, substs).is_sized(tcx, cx.param_env)
+                && def.non_enum_variant().tail().ty(tcx, args).is_sized(tcx, cx.param_env)
             {
                 let mut variants = variants;
                 let tail_replacement = cx.layout_of(Ty::new_slice(tcx, tcx.types.u8)).unwrap();
@@ -696,11 +696,11 @@ fn generator_layout<'tcx>(
     cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
     ty: Ty<'tcx>,
     def_id: hir::def_id::DefId,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
 ) -> Result<Layout<'tcx>, &'tcx LayoutError<'tcx>> {
     use SavedLocalEligibility::*;
     let tcx = cx.tcx;
-    let subst_field = |ty: Ty<'tcx>| EarlyBinder::bind(ty).subst(tcx, substs);
+    let subst_field = |ty: Ty<'tcx>| EarlyBinder::bind(ty).instantiate(tcx, args);
 
     let Some(info) = tcx.generator_layout(def_id) else {
         return Err(error(cx, LayoutError::Unknown(ty)));
@@ -710,7 +710,7 @@ fn generator_layout<'tcx>(
     // Build a prefix layout, including "promoting" all ineligible
     // locals as part of the prefix. We compute the layout of all of
     // these fields at once to get optimal packing.
-    let tag_index = substs.as_generator().prefix_tys().count();
+    let tag_index = args.as_generator().prefix_tys().count();
 
     // `info.variant_fields` already accounts for the reserved variants, so no need to add them.
     let max_discr = (info.variant_fields.len() - 1) as u128;
@@ -726,7 +726,7 @@ fn generator_layout<'tcx>(
         .map(|local| subst_field(info.field_tys[local].ty))
         .map(|ty| Ty::new_maybe_uninit(tcx, ty))
         .map(|ty| Ok(cx.layout_of(ty)?.layout));
-    let prefix_layouts = substs
+    let prefix_layouts = args
         .as_generator()
         .prefix_tys()
         .map(|ty| Ok(cx.layout_of(ty)?.layout))
@@ -934,11 +934,11 @@ fn record_layout_for_printing_outlined<'tcx>(
             record(adt_kind.into(), adt_packed, opt_discr_size, variant_infos);
         }
 
-        ty::Generator(def_id, substs, _) => {
+        ty::Generator(def_id, args, _) => {
             debug!("print-type-size t: `{:?}` record generator", layout.ty);
             // Generators always have a begin/poisoned/end state with additional suspend points
             let (variant_infos, opt_discr_size) =
-                variant_info_for_generator(cx, layout, def_id, substs);
+                variant_info_for_generator(cx, layout, def_id, args);
             record(DataTypeKind::Generator, false, opt_discr_size, variant_infos);
         }
 
@@ -1028,7 +1028,7 @@ fn variant_info_for_generator<'tcx>(
     cx: &LayoutCx<'tcx, TyCtxt<'tcx>>,
     layout: TyAndLayout<'tcx>,
     def_id: DefId,
-    substs: ty::SubstsRef<'tcx>,
+    args: ty::GenericArgsRef<'tcx>,
 ) -> (Vec<VariantInfo>, Option<Size>) {
     let Variants::Multiple { tag, ref tag_encoding, tag_field, .. } = layout.variants else {
         return (vec![], None);
@@ -1038,7 +1038,7 @@ fn variant_info_for_generator<'tcx>(
     let upvar_names = cx.tcx.closure_saved_names_of_captured_variables(def_id);
 
     let mut upvars_size = Size::ZERO;
-    let upvar_fields: Vec<_> = substs
+    let upvar_fields: Vec<_> = args
         .as_generator()
         .upvar_tys()
         .zip(upvar_names)
@@ -1113,7 +1113,7 @@ fn variant_info_for_generator<'tcx>(
             }
 
             VariantInfo {
-                name: Some(Symbol::intern(&ty::GeneratorSubsts::variant_name(variant_idx))),
+                name: Some(Symbol::intern(&ty::GeneratorArgs::variant_name(variant_idx))),
                 kind: SizeKind::Exact,
                 size: variant_size.bytes(),
                 align: variant_layout.align.abi.bytes(),
diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index 9d593dc5e04ee..3e6dfc1304f11 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -3,8 +3,8 @@
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def_id::DefId;
 use rustc_middle::query::Providers;
-use rustc_middle::ty::subst::SubstsRef;
 use rustc_middle::ty::util::{needs_drop_components, AlwaysRequiresDrop};
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, EarlyBinder, Ty, TyCtxt};
 use rustc_session::Limit;
 use rustc_span::{sym, DUMMY_SP};
@@ -80,7 +80,7 @@ impl<'tcx, F> NeedsDropTypes<'tcx, F> {
 
 impl<'tcx, F, I> Iterator for NeedsDropTypes<'tcx, F>
 where
-    F: Fn(ty::AdtDef<'tcx>, SubstsRef<'tcx>) -> NeedsDropResult<I>,
+    F: Fn(ty::AdtDef<'tcx>, GenericArgsRef<'tcx>) -> NeedsDropResult<I>,
     I: Iterator<Item = Ty<'tcx>>,
 {
     type Item = NeedsDropResult<Ty<'tcx>>;
@@ -119,15 +119,15 @@ where
 
                     _ if component.is_copy_modulo_regions(tcx, self.param_env) => (),
 
-                    ty::Closure(_, substs) => {
-                        queue_type(self, substs.as_closure().tupled_upvars_ty());
+                    ty::Closure(_, args) => {
+                        queue_type(self, args.as_closure().tupled_upvars_ty());
                     }
 
-                    ty::Generator(def_id, substs, _) => {
-                        let substs = substs.as_generator();
-                        queue_type(self, substs.tupled_upvars_ty());
+                    ty::Generator(def_id, args, _) => {
+                        let args = args.as_generator();
+                        queue_type(self, args.tupled_upvars_ty());
 
-                        let witness = substs.witness();
+                        let witness = args.witness();
                         let interior_tys = match witness.kind() {
                             &ty::GeneratorWitness(tys) => tcx.erase_late_bound_regions(tys),
                             _ => {
@@ -147,8 +147,8 @@ where
                     // Check for a `Drop` impl and whether this is a union or
                     // `ManuallyDrop`. If it's a struct or enum without a `Drop`
                     // impl then check whether the field types need `Drop`.
-                    ty::Adt(adt_def, substs) => {
-                        let tys = match (self.adt_components)(adt_def, substs) {
+                    ty::Adt(adt_def, args) => {
+                        let tys = match (self.adt_components)(adt_def, args) {
                             Err(e) => return Some(Err(e)),
                             Ok(tys) => tys,
                         };
@@ -210,7 +210,7 @@ fn drop_tys_helper<'tcx>(
             match subty.kind() {
                 ty::Adt(adt_id, subst) => {
                     for subty in tcx.adt_drop_tys(adt_id.did())? {
-                        vec.push(EarlyBinder::bind(subty).subst(tcx, subst));
+                        vec.push(EarlyBinder::bind(subty).instantiate(tcx, subst));
                     }
                 }
                 _ => vec.push(subty),
@@ -219,7 +219,7 @@ fn drop_tys_helper<'tcx>(
         })
     }
 
-    let adt_components = move |adt_def: ty::AdtDef<'tcx>, substs: SubstsRef<'tcx>| {
+    let adt_components = move |adt_def: ty::AdtDef<'tcx>, args: GenericArgsRef<'tcx>| {
         if adt_def.is_manually_drop() {
             debug!("drop_tys_helper: `{:?}` is manually drop", adt_def);
             Ok(Vec::new())
@@ -235,7 +235,7 @@ fn drop_tys_helper<'tcx>(
                     // Since the destructor is insignificant, we just want to make sure all of
                     // the passed in type parameters are also insignificant.
                     // Eg: Vec<T> dtor is insignificant when T=i32 but significant when T=Mutex.
-                    Ok(substs.types().collect())
+                    Ok(args.types().collect())
                 }
             }
         } else if adt_def.is_union() {
@@ -243,8 +243,8 @@ fn drop_tys_helper<'tcx>(
             Ok(Vec::new())
         } else {
             let field_tys = adt_def.all_fields().map(|field| {
-                let r = tcx.type_of(field.did).subst(tcx, substs);
-                debug!("drop_tys_helper: Subst into {:?} with {:?} getting {:?}", field, substs, r);
+                let r = tcx.type_of(field.did).instantiate(tcx, args);
+                debug!("drop_tys_helper: Subst into {:?} with {:?} getting {:?}", field, args, r);
                 r
             });
             if only_significant {
@@ -295,10 +295,10 @@ fn adt_drop_tys<'tcx>(
     // significant.
     let adt_has_dtor =
         |adt_def: ty::AdtDef<'tcx>| adt_def.destructor(tcx).map(|_| DtorType::Significant);
-    // `tcx.type_of(def_id)` identical to `tcx.make_adt(def, identity_substs)`
+    // `tcx.type_of(def_id)` identical to `tcx.make_adt(def, identity_args)`
     drop_tys_helper(
         tcx,
-        tcx.type_of(def_id).subst_identity(),
+        tcx.type_of(def_id).instantiate_identity(),
         tcx.param_env(def_id),
         adt_has_dtor,
         false,
@@ -307,7 +307,7 @@ fn adt_drop_tys<'tcx>(
     .map(|components| tcx.mk_type_list(&components))
 }
 // If `def_id` refers to a generic ADT, the queries above and below act as if they had been handed
-// a `tcx.make_ty(def, identity_substs)` and as such it is legal to substitute the generic parameters
+// a `tcx.make_ty(def, identity_args)` and as such it is legal to substitute the generic parameters
 // of the ADT into the outputted `ty`s.
 fn adt_significant_drop_tys(
     tcx: TyCtxt<'_>,
@@ -315,7 +315,7 @@ fn adt_significant_drop_tys(
 ) -> Result<&ty::List<Ty<'_>>, AlwaysRequiresDrop> {
     drop_tys_helper(
         tcx,
-        tcx.type_of(def_id).subst_identity(), // identical to `tcx.make_adt(def, identity_substs)`
+        tcx.type_of(def_id).instantiate_identity(), // identical to `tcx.make_adt(def, identity_args)`
         tcx.param_env(def_id),
         adt_consider_insignificant_dtor(tcx),
         true,
diff --git a/compiler/rustc_ty_utils/src/opaque_types.rs b/compiler/rustc_ty_utils/src/opaque_types.rs
index 87dfacc4c2da6..06a30677d2005 100644
--- a/compiler/rustc_ty_utils/src/opaque_types.rs
+++ b/compiler/rustc_ty_utils/src/opaque_types.rs
@@ -7,7 +7,7 @@ use rustc_middle::ty::util::{CheckRegions, NotUniqueParam};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_middle::ty::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use rustc_span::Span;
-use rustc_trait_selection::traits::check_substs_compatible;
+use rustc_trait_selection::traits::check_args_compatible;
 use std::ops::ControlFlow;
 
 use crate::errors::{DuplicateArg, NotParam};
@@ -45,7 +45,7 @@ impl<'tcx> OpaqueTypeCollector<'tcx> {
     fn parent_trait_ref(&self) -> Option<ty::TraitRef<'tcx>> {
         let parent = self.parent()?;
         if matches!(self.tcx.def_kind(parent), DefKind::Impl { .. }) {
-            Some(self.tcx.impl_trait_ref(parent)?.subst_identity())
+            Some(self.tcx.impl_trait_ref(parent)?.instantiate_identity())
         } else {
             None
         }
@@ -159,19 +159,19 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
 
                 self.opaques.push(alias_ty.def_id.expect_local());
 
-                match self.tcx.uses_unique_generic_params(alias_ty.substs, CheckRegions::Bound) {
+                match self.tcx.uses_unique_generic_params(alias_ty.args, CheckRegions::Bound) {
                     Ok(()) => {
                         // FIXME: implement higher kinded lifetime bounds on nested opaque types. They are not
                         // supported at all, so this is sound to do, but once we want to support them, you'll
                         // start seeing the error below.
 
                         // Collect opaque types nested within the associated type bounds of this opaque type.
-                        // We use identity substs here, because we already know that the opaque type uses
+                        // We use identity args here, because we already know that the opaque type uses
                         // only generic parameters, and thus substituting would not give us more information.
                         for (pred, span) in self
                             .tcx
                             .explicit_item_bounds(alias_ty.def_id)
-                            .subst_identity_iter_copied()
+                            .instantiate_identity_iter_copied()
                         {
                             trace!(?pred);
                             self.visit_spanned(span, pred);
@@ -196,7 +196,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
             ty::Alias(ty::Weak, alias_ty) if alias_ty.def_id.is_local() => {
                 self.tcx
                     .type_of(alias_ty.def_id)
-                    .subst(self.tcx, alias_ty.substs)
+                    .instantiate(self.tcx, alias_ty.args)
                     .visit_with(self)?;
             }
             ty::Alias(ty::Projection, alias_ty) => {
@@ -222,22 +222,22 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                                 continue;
                             }
 
-                            let impl_substs = alias_ty.substs.rebase_onto(
+                            let impl_args = alias_ty.args.rebase_onto(
                                 self.tcx,
                                 parent_trait_ref.def_id,
-                                ty::InternalSubsts::identity_for_item(self.tcx, parent),
+                                ty::GenericArgs::identity_for_item(self.tcx, parent),
                             );
 
-                            if check_substs_compatible(self.tcx, assoc, impl_substs) {
+                            if check_args_compatible(self.tcx, assoc, impl_args) {
                                 return self
                                     .tcx
                                     .type_of(assoc.def_id)
-                                    .subst(self.tcx, impl_substs)
+                                    .instantiate(self.tcx, impl_args)
                                     .visit_with(self);
                             } else {
                                 self.tcx.sess.delay_span_bug(
                                     self.tcx.def_span(assoc.def_id),
-                                    "item had incorrect substs",
+                                    "item had incorrect args",
                                 );
                             }
                         }
@@ -250,15 +250,15 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for OpaqueTypeCollector<'tcx> {
                 }
                 for variant in def.variants().iter() {
                     for field in variant.fields.iter() {
-                        // Don't use the `ty::Adt` substs, we either
-                        // * found the opaque in the substs
+                        // Don't use the `ty::Adt` args, we either
+                        // * found the opaque in the args
                         // * will find the opaque in the unsubstituted fields
                         // The only other situation that can occur is that after substituting,
                         // some projection resolves to an opaque that we would have otherwise
                         // not found. While we could substitute and walk those, that would mean we
                         // would have to walk all substitutions of an Adt, which can quickly
                         // degenerate into looking at an exponential number of types.
-                        let ty = self.tcx.type_of(field.did).subst_identity();
+                        let ty = self.tcx.type_of(field.did).instantiate_identity();
                         self.visit_spanned(self.tcx.def_span(field.did), ty);
                     }
                 }
@@ -276,7 +276,7 @@ fn opaque_types_defined_by<'tcx>(tcx: TyCtxt<'tcx>, item: LocalDefId) -> &'tcx [
     match kind {
         // Walk over the signature of the function-like to find the opaques.
         DefKind::AssocFn | DefKind::Fn => {
-            let ty_sig = tcx.fn_sig(item).subst_identity();
+            let ty_sig = tcx.fn_sig(item).instantiate_identity();
             let hir_sig = tcx.hir().get_by_def_id(item).fn_sig().unwrap();
             // Walk over the inputs and outputs manually in order to get good spans for them.
             collector.visit_spanned(hir_sig.decl.output.span(), ty_sig.output());
@@ -291,15 +291,15 @@ fn opaque_types_defined_by<'tcx>(tcx: TyCtxt<'tcx>, item: LocalDefId) -> &'tcx [
                 Some(ty) => ty.span,
                 _ => tcx.def_span(item),
             };
-            collector.visit_spanned(span, tcx.type_of(item).subst_identity());
+            collector.visit_spanned(span, tcx.type_of(item).instantiate_identity());
             collector.collect_body_and_predicate_taits();
         }
         // We're also doing this for `AssocTy` for the wf checks in `check_opaque_meets_bounds`
         DefKind::TyAlias | DefKind::AssocTy => {
-            tcx.type_of(item).subst_identity().visit_with(&mut collector);
+            tcx.type_of(item).instantiate_identity().visit_with(&mut collector);
         }
         DefKind::OpaqueTy => {
-            for (pred, span) in tcx.explicit_item_bounds(item).subst_identity_iter_copied() {
+            for (pred, span) in tcx.explicit_item_bounds(item).instantiate_identity_iter_copied() {
                 collector.visit_spanned(span, pred);
             }
         }
diff --git a/compiler/rustc_ty_utils/src/representability.rs b/compiler/rustc_ty_utils/src/representability.rs
index 0b5e27c2c743f..f34e0df2c75ef 100644
--- a/compiler/rustc_ty_utils/src/representability.rs
+++ b/compiler/rustc_ty_utils/src/representability.rs
@@ -31,7 +31,7 @@ fn representability(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Representability {
             }
             Representability::Representable
         }
-        DefKind::Field => representability_ty(tcx, tcx.type_of(def_id).subst_identity()),
+        DefKind::Field => representability_ty(tcx, tcx.type_of(def_id).instantiate_identity()),
         def_kind => bug!("unexpected {def_kind:?}"),
     }
 }
@@ -68,14 +68,14 @@ representability_adt_ty(Bar<..>) is in the cycle and representability(Bar) is
 *not* in the cycle.
 */
 fn representability_adt_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> Representability {
-    let ty::Adt(adt, substs) = ty.kind() else { bug!("expected adt") };
+    let ty::Adt(adt, args) = ty.kind() else { bug!("expected adt") };
     if let Some(def_id) = adt.did().as_local() {
         rtry!(tcx.representability(def_id));
     }
     // At this point, we know that the item of the ADT type is representable;
     // but the type parameters may cause a cycle with an upstream type
     let params_in_repr = tcx.params_in_repr(adt.did());
-    for (i, subst) in substs.iter().enumerate() {
+    for (i, subst) in args.iter().enumerate() {
         if let ty::GenericArgKind::Type(ty) = subst.unpack() {
             if params_in_repr.contains(i as u32) {
                 rtry!(representability_ty(tcx, ty));
@@ -91,7 +91,11 @@ fn params_in_repr(tcx: TyCtxt<'_>, def_id: LocalDefId) -> BitSet<u32> {
     let mut params_in_repr = BitSet::new_empty(generics.params.len());
     for variant in adt_def.variants() {
         for field in variant.fields.iter() {
-            params_in_repr_ty(tcx, tcx.type_of(field.did).subst_identity(), &mut params_in_repr);
+            params_in_repr_ty(
+                tcx,
+                tcx.type_of(field.did).instantiate_identity(),
+                &mut params_in_repr,
+            );
         }
     }
     params_in_repr
@@ -99,9 +103,9 @@ fn params_in_repr(tcx: TyCtxt<'_>, def_id: LocalDefId) -> BitSet<u32> {
 
 fn params_in_repr_ty<'tcx>(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>, params_in_repr: &mut BitSet<u32>) {
     match *ty.kind() {
-        ty::Adt(adt, substs) => {
+        ty::Adt(adt, args) => {
             let inner_params_in_repr = tcx.params_in_repr(adt.did());
-            for (i, subst) in substs.iter().enumerate() {
+            for (i, subst) in args.iter().enumerate() {
                 if let ty::GenericArgKind::Type(ty) = subst.unpack() {
                     if inner_params_in_repr.contains(i as u32) {
                         params_in_repr_ty(tcx, ty, params_in_repr);
diff --git a/compiler/rustc_ty_utils/src/ty.rs b/compiler/rustc_ty_utils/src/ty.rs
index 43e3c99fb5778..c228938126e57 100644
--- a/compiler/rustc_ty_utils/src/ty.rs
+++ b/compiler/rustc_ty_utils/src/ty.rs
@@ -37,12 +37,12 @@ fn sized_constraint_for_ty<'tcx>(
             Some(&ty) => sized_constraint_for_ty(tcx, adtdef, ty),
         },
 
-        Adt(adt, substs) => {
+        Adt(adt, args) => {
             // recursive case
             let adt_tys = adt.sized_constraint(tcx);
             debug!("sized_constraint_for_ty({:?}) intermediate = {:?}", ty, adt_tys);
             adt_tys
-                .subst_iter_copied(tcx, substs)
+                .arg_iter_copied(tcx, args)
                 .flat_map(|ty| sized_constraint_for_ty(tcx, adtdef, ty))
                 .collect()
         }
@@ -100,12 +100,10 @@ fn adt_sized_constraint(tcx: TyCtxt<'_>, def_id: DefId) -> &[Ty<'_>] {
     }
     let def = tcx.adt_def(def_id);
 
-    let result = tcx.mk_type_list_from_iter(
-        def.variants()
-            .iter()
-            .filter_map(|v| v.tail_opt())
-            .flat_map(|f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did).subst_identity())),
-    );
+    let result =
+        tcx.mk_type_list_from_iter(def.variants().iter().filter_map(|v| v.tail_opt()).flat_map(
+            |f| sized_constraint_for_ty(tcx, def, tcx.type_of(f.did).instantiate_identity()),
+        ));
 
     debug!("adt_sized_constraint: {:?} => {:?}", def, result);
 
@@ -133,7 +131,7 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     if tcx.def_kind(def_id) == DefKind::AssocFn
         && tcx.associated_item(def_id).container == ty::AssocItemContainer::TraitContainer
     {
-        let sig = tcx.fn_sig(def_id).subst_identity();
+        let sig = tcx.fn_sig(def_id).instantiate_identity();
         // We accounted for the binder of the fn sig, so skip the binder.
         sig.skip_binder().visit_with(&mut ImplTraitInTraitFinder {
             tcx,
@@ -282,7 +280,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
             // If we're lowering to associated item, install the opaque type which is just
             // the `type_of` of the trait's associated item. If we're using the old lowering
             // strategy, then just reinterpret the associated type like an opaque :^)
-            let default_ty = self.tcx.type_of(shifted_alias_ty.def_id).subst(self.tcx, shifted_alias_ty.substs);
+            let default_ty = self.tcx.type_of(shifted_alias_ty.def_id).instantiate(self.tcx, shifted_alias_ty.args);
 
             self.predicates.push(
                 ty::Binder::bind_with_vars(
@@ -299,7 +297,7 @@ impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ImplTraitInTraitFinder<'_, 'tcx> {
             for bound in self
                 .tcx
                 .item_bounds(unshifted_alias_ty.def_id)
-                .subst_iter(self.tcx, unshifted_alias_ty.substs)
+                .arg_iter(self.tcx, unshifted_alias_ty.args)
             {
                 bound.visit_with(self);
             }
@@ -352,8 +350,8 @@ fn issue33140_self_ty(tcx: TyCtxt<'_>, def_id: DefId) -> Option<EarlyBinder<Ty<'
     }
 
     // impl must be `impl Trait for dyn Marker1 + Marker2 + ...`
-    if trait_ref.substs.len() != 1 {
-        debug!("issue33140_self_ty - impl has substs!");
+    if trait_ref.args.len() != 1 {
+        debug!("issue33140_self_ty - impl has args!");
         return None;
     }
 
@@ -409,7 +407,7 @@ fn unsizing_params_for_adt<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> BitSet<u32
     };
 
     let mut unsizing_params = BitSet::new_empty(num_params);
-    for arg in tcx.type_of(tail_field.did).subst_identity().walk() {
+    for arg in tcx.type_of(tail_field.did).instantiate_identity().walk() {
         if let Some(i) = maybe_unsizing_param_idx(arg) {
             unsizing_params.insert(i);
         }
@@ -418,7 +416,7 @@ fn unsizing_params_for_adt<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> BitSet<u32
     // Ensure none of the other fields mention the parameters used
     // in unsizing.
     for field in prefix_fields {
-        for arg in tcx.type_of(field.did).subst_identity().walk() {
+        for arg in tcx.type_of(field.did).instantiate_identity().walk() {
             if let Some(i) = maybe_unsizing_param_idx(arg) {
                 unsizing_params.remove(i);
             }
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index 9ca26d18ae1b6..a7cd7aa2c4fb6 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -40,7 +40,7 @@ pub trait HashStableContext {}
 
 pub trait Interner: Sized {
     type AdtDef: Clone + Debug + Hash + Ord;
-    type SubstsRef: Clone + DebugWithInfcx<Self> + Hash + Ord;
+    type GenericArgsRef: Clone + DebugWithInfcx<Self> + Hash + Ord;
     type DefId: Clone + Debug + Hash + Ord;
     type Binder<T>;
     type Ty: Clone + DebugWithInfcx<Self> + Hash + Ord;
diff --git a/compiler/rustc_type_ir/src/sty.rs b/compiler/rustc_type_ir/src/sty.rs
index 416e8a3d2d269..b134845dab04c 100644
--- a/compiler/rustc_type_ir/src/sty.rs
+++ b/compiler/rustc_type_ir/src/sty.rs
@@ -74,11 +74,11 @@ pub enum TyKind<I: Interner> {
     /// Algebraic data types (ADT). For example: structures, enumerations and unions.
     ///
     /// For example, the type `List<i32>` would be represented using the `AdtDef`
-    /// for `struct List<T>` and the substs `[i32]`.
+    /// for `struct List<T>` and the args `[i32]`.
     ///
     /// Note that generic parameters in fields only get lazily substituted
-    /// by using something like `adt_def.all_fields().map(|field| field.ty(tcx, substs))`.
-    Adt(I::AdtDef, I::SubstsRef),
+    /// by using something like `adt_def.all_fields().map(|field| field.ty(tcx, args))`.
+    Adt(I::AdtDef, I::GenericArgsRef),
 
     /// An unsized FFI type that is opaque to Rust. Written as `extern type T`.
     Foreign(I::DefId),
@@ -110,7 +110,7 @@ pub enum TyKind<I: Interner> {
     /// fn foo() -> i32 { 1 }
     /// let bar = foo; // bar: fn() -> i32 {foo}
     /// ```
-    FnDef(I::DefId, I::SubstsRef),
+    FnDef(I::DefId, I::GenericArgsRef),
 
     /// A pointer to a function. Written as `fn() -> i32`.
     ///
@@ -130,20 +130,20 @@ pub enum TyKind<I: Interner> {
 
     /// The anonymous type of a closure. Used to represent the type of `|a| a`.
     ///
-    /// Closure substs contain both the - potentially substituted - generic parameters
+    /// Closure args contain both the - potentially substituted - generic parameters
     /// of its parent and some synthetic parameters. See the documentation for
-    /// `ClosureSubsts` for more details.
-    Closure(I::DefId, I::SubstsRef),
+    /// `ClosureArgs` for more details.
+    Closure(I::DefId, I::GenericArgsRef),
 
     /// The anonymous type of a generator. Used to represent the type of
     /// `|a| yield a`.
     ///
-    /// For more info about generator substs, visit the documentation for
-    /// `GeneratorSubsts`.
-    Generator(I::DefId, I::SubstsRef, I::Movability),
+    /// For more info about generator args, visit the documentation for
+    /// `GeneratorArgs`.
+    Generator(I::DefId, I::GenericArgsRef, I::Movability),
 
     /// A type representing the types stored inside a generator.
-    /// This should only appear as part of the `GeneratorSubsts`.
+    /// This should only appear as part of the `GeneratorArgs`.
     ///
     /// Note that the captured variables for generators are stored separately
     /// using a tuple in the same way as for closures.
@@ -168,7 +168,7 @@ pub enum TyKind<I: Interner> {
     GeneratorWitness(I::BinderListTy),
 
     /// A type representing the types stored inside a generator.
-    /// This should only appear as part of the `GeneratorSubsts`.
+    /// This should only appear as part of the `GeneratorArgs`.
     ///
     /// Unlike upvars, the witness can reference lifetimes from
     /// inside of the generator itself. To deal with them in
@@ -176,7 +176,7 @@ pub enum TyKind<I: Interner> {
     /// lifetimes bound by the witness itself.
     ///
     /// This variant is only using when `drop_tracking_mir` is set.
-    /// This contains the `DefId` and the `SubstsRef` of the generator.
+    /// This contains the `DefId` and the `GenericArgsRef` of the generator.
     /// The actual witness types are computed on MIR by the `mir_generator_witnesses` query.
     ///
     /// Looking at the following example, the witness for this generator
@@ -191,7 +191,7 @@ pub enum TyKind<I: Interner> {
     /// }
     /// # ;
     /// ```
-    GeneratorWitnessMIR(I::DefId, I::SubstsRef),
+    GeneratorWitnessMIR(I::DefId, I::GenericArgsRef),
 
     /// The never type `!`.
     Never,
@@ -587,7 +587,7 @@ impl<I: Interner, E: TyEncoder> Encodable<E> for TyKind<I>
 where
     I::ErrorGuaranteed: Encodable<E>,
     I::AdtDef: Encodable<E>,
-    I::SubstsRef: Encodable<E>,
+    I::GenericArgsRef: Encodable<E>,
     I::DefId: Encodable<E>,
     I::Ty: Encodable<E>,
     I::Const: Encodable<E>,
@@ -621,9 +621,9 @@ where
             Float(f) => e.emit_enum_variant(disc, |e| {
                 f.encode(e);
             }),
-            Adt(adt, substs) => e.emit_enum_variant(disc, |e| {
+            Adt(adt, args) => e.emit_enum_variant(disc, |e| {
                 adt.encode(e);
-                substs.encode(e);
+                args.encode(e);
             }),
             Foreign(def_id) => e.emit_enum_variant(disc, |e| {
                 def_id.encode(e);
@@ -644,9 +644,9 @@ where
                 t.encode(e);
                 m.encode(e);
             }),
-            FnDef(def_id, substs) => e.emit_enum_variant(disc, |e| {
+            FnDef(def_id, args) => e.emit_enum_variant(disc, |e| {
                 def_id.encode(e);
-                substs.encode(e);
+                args.encode(e);
             }),
             FnPtr(polyfnsig) => e.emit_enum_variant(disc, |e| {
                 polyfnsig.encode(e);
@@ -656,25 +656,25 @@ where
                 r.encode(e);
                 repr.encode(e);
             }),
-            Closure(def_id, substs) => e.emit_enum_variant(disc, |e| {
+            Closure(def_id, args) => e.emit_enum_variant(disc, |e| {
                 def_id.encode(e);
-                substs.encode(e);
+                args.encode(e);
             }),
-            Generator(def_id, substs, m) => e.emit_enum_variant(disc, |e| {
+            Generator(def_id, args, m) => e.emit_enum_variant(disc, |e| {
                 def_id.encode(e);
-                substs.encode(e);
+                args.encode(e);
                 m.encode(e);
             }),
             GeneratorWitness(b) => e.emit_enum_variant(disc, |e| {
                 b.encode(e);
             }),
-            GeneratorWitnessMIR(def_id, substs) => e.emit_enum_variant(disc, |e| {
+            GeneratorWitnessMIR(def_id, args) => e.emit_enum_variant(disc, |e| {
                 def_id.encode(e);
-                substs.encode(e);
+                args.encode(e);
             }),
             Never => e.emit_enum_variant(disc, |_| {}),
-            Tuple(substs) => e.emit_enum_variant(disc, |e| {
-                substs.encode(e);
+            Tuple(args) => e.emit_enum_variant(disc, |e| {
+                args.encode(e);
             }),
             Alias(k, p) => e.emit_enum_variant(disc, |e| {
                 k.encode(e);
@@ -705,7 +705,7 @@ impl<I: Interner, D: TyDecoder<I = I>> Decodable<D> for TyKind<I>
 where
     I::ErrorGuaranteed: Decodable<D>,
     I::AdtDef: Decodable<D>,
-    I::SubstsRef: Decodable<D>,
+    I::GenericArgsRef: Decodable<D>,
     I::DefId: Decodable<D>,
     I::Ty: Decodable<D>,
     I::Const: Decodable<D>,
@@ -772,7 +772,7 @@ impl<CTX: HashStableContext, I: Interner> HashStable<CTX> for TyKind<I>
 where
     I::AdtDef: HashStable<CTX>,
     I::DefId: HashStable<CTX>,
-    I::SubstsRef: HashStable<CTX>,
+    I::GenericArgsRef: HashStable<CTX>,
     I::Ty: HashStable<CTX>,
     I::Const: HashStable<CTX>,
     I::TypeAndMut: HashStable<CTX>,
@@ -809,9 +809,9 @@ where
             Float(f) => {
                 f.hash_stable(__hcx, __hasher);
             }
-            Adt(adt, substs) => {
+            Adt(adt, args) => {
                 adt.hash_stable(__hcx, __hasher);
-                substs.hash_stable(__hcx, __hasher);
+                args.hash_stable(__hcx, __hasher);
             }
             Foreign(def_id) => {
                 def_id.hash_stable(__hcx, __hasher);
@@ -832,9 +832,9 @@ where
                 t.hash_stable(__hcx, __hasher);
                 m.hash_stable(__hcx, __hasher);
             }
-            FnDef(def_id, substs) => {
+            FnDef(def_id, args) => {
                 def_id.hash_stable(__hcx, __hasher);
-                substs.hash_stable(__hcx, __hasher);
+                args.hash_stable(__hcx, __hasher);
             }
             FnPtr(polyfnsig) => {
                 polyfnsig.hash_stable(__hcx, __hasher);
@@ -844,25 +844,25 @@ where
                 r.hash_stable(__hcx, __hasher);
                 repr.hash_stable(__hcx, __hasher);
             }
-            Closure(def_id, substs) => {
+            Closure(def_id, args) => {
                 def_id.hash_stable(__hcx, __hasher);
-                substs.hash_stable(__hcx, __hasher);
+                args.hash_stable(__hcx, __hasher);
             }
-            Generator(def_id, substs, m) => {
+            Generator(def_id, args, m) => {
                 def_id.hash_stable(__hcx, __hasher);
-                substs.hash_stable(__hcx, __hasher);
+                args.hash_stable(__hcx, __hasher);
                 m.hash_stable(__hcx, __hasher);
             }
             GeneratorWitness(b) => {
                 b.hash_stable(__hcx, __hasher);
             }
-            GeneratorWitnessMIR(def_id, substs) => {
+            GeneratorWitnessMIR(def_id, args) => {
                 def_id.hash_stable(__hcx, __hasher);
-                substs.hash_stable(__hcx, __hasher);
+                args.hash_stable(__hcx, __hasher);
             }
             Never => {}
-            Tuple(substs) => {
-                substs.hash_stable(__hcx, __hasher);
+            Tuple(args) => {
+                args.hash_stable(__hcx, __hasher);
             }
             Alias(k, p) => {
                 k.hash_stable(__hcx, __hasher);
@@ -1167,7 +1167,7 @@ impl<I: Interner> Clone for ConstKind<I> {
 /// These are regions that are stored behind a binder and must be substituted
 /// with some concrete region before being used. There are two kind of
 /// bound regions: early-bound, which are bound in an item's `Generics`,
-/// and are substituted by an `InternalSubsts`, and late-bound, which are part of
+/// and are substituted by an `GenericArgs`, and late-bound, which are part of
 /// higher-ranked types (e.g., `for<'a> fn(&'a ())`), and are substituted by
 /// the likes of `liberate_late_bound_regions`. The distinction exists
 /// because higher-ranked lifetimes aren't supported in all places. See [1][2].
diff --git a/src/librustdoc/clean/auto_trait.rs b/src/librustdoc/clean/auto_trait.rs
index 92bae551644b6..68d636b360ac7 100644
--- a/src/librustdoc/clean/auto_trait.rs
+++ b/src/librustdoc/clean/auto_trait.rs
@@ -137,7 +137,7 @@ where
     pub(crate) fn get_auto_trait_impls(&mut self, item_def_id: DefId) -> Vec<Item> {
         let tcx = self.cx.tcx;
         let param_env = tcx.param_env(item_def_id);
-        let ty = tcx.type_of(item_def_id).subst_identity();
+        let ty = tcx.type_of(item_def_id).instantiate_identity();
         let f = auto_trait::AutoTraitFinder::new(tcx);
 
         debug!("get_auto_trait_impls({:?})", ty);
diff --git a/src/librustdoc/clean/blanket_impl.rs b/src/librustdoc/clean/blanket_impl.rs
index c4ac5466164fc..f5e02940c82e6 100644
--- a/src/librustdoc/clean/blanket_impl.rs
+++ b/src/librustdoc/clean/blanket_impl.rs
@@ -38,12 +38,12 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     continue;
                 }
                 let infcx = cx.tcx.infer_ctxt().build();
-                let substs = infcx.fresh_substs_for_item(DUMMY_SP, item_def_id);
-                let impl_ty = ty.subst(infcx.tcx, substs);
-                let param_env = EarlyBinder::bind(param_env).subst(infcx.tcx, substs);
+                let args = infcx.fresh_args_for_item(DUMMY_SP, item_def_id);
+                let impl_ty = ty.instantiate(infcx.tcx, args);
+                let param_env = EarlyBinder::bind(param_env).instantiate(infcx.tcx, args);
 
-                let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
-                let impl_trait_ref = trait_ref.subst(infcx.tcx, impl_substs);
+                let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
+                let impl_trait_ref = trait_ref.instantiate(infcx.tcx, impl_args);
 
                 // Require the type the impl is implemented on to match
                 // our type, and ignore the impl if there was a mismatch.
@@ -67,7 +67,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                 let predicates = cx
                     .tcx
                     .predicates_of(impl_def_id)
-                    .instantiate(cx.tcx, impl_substs)
+                    .instantiate(cx.tcx, impl_args)
                     .predicates
                     .into_iter()
                     .chain(Some(ty::Binder::dummy(impl_trait_ref).to_predicate(infcx.tcx)));
@@ -108,11 +108,11 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                         // the post-inference `trait_ref`, as it's more accurate.
                         trait_: Some(clean_trait_ref_with_bindings(
                             cx,
-                            ty::Binder::dummy(trait_ref.subst_identity()),
+                            ty::Binder::dummy(trait_ref.instantiate_identity()),
                             ThinVec::new(),
                         )),
                         for_: clean_middle_ty(
-                            ty::Binder::dummy(ty.subst_identity()),
+                            ty::Binder::dummy(ty.instantiate_identity()),
                             cx,
                             None,
                             None,
@@ -125,7 +125,7 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             .collect::<Vec<_>>(),
                         polarity: ty::ImplPolarity::Positive,
                         kind: ImplKind::Blanket(Box::new(clean_middle_ty(
-                            ty::Binder::dummy(trait_ref.subst_identity().self_ty()),
+                            ty::Binder::dummy(trait_ref.instantiate_identity().self_ty()),
                             cx,
                             None,
                             None,
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 870cfa93058aa..a98d466cd81c6 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -226,7 +226,7 @@ pub(crate) fn build_external_trait(cx: &mut DocContext<'_>, did: DefId) -> clean
 }
 
 fn build_external_function<'tcx>(cx: &mut DocContext<'tcx>, did: DefId) -> Box<clean::Function> {
-    let sig = cx.tcx.fn_sig(did).subst_identity();
+    let sig = cx.tcx.fn_sig(did).instantiate_identity();
 
     let late_bound_regions = sig.bound_vars().into_iter().filter_map(|var| match var {
         ty::BoundVariableKind::Region(ty::BrNamed(_, name)) if name != kw::UnderscoreLifetime => {
@@ -279,7 +279,7 @@ fn build_union(cx: &mut DocContext<'_>, did: DefId) -> clean::Union {
 fn build_type_alias(cx: &mut DocContext<'_>, did: DefId) -> Box<clean::Typedef> {
     let predicates = cx.tcx.explicit_predicates_of(did);
     let type_ = clean_middle_ty(
-        ty::Binder::dummy(cx.tcx.type_of(did).subst_identity()),
+        ty::Binder::dummy(cx.tcx.type_of(did).instantiate_identity()),
         cx,
         Some(did),
         None,
@@ -391,7 +391,7 @@ pub(crate) fn build_impl(
     let for_ = match &impl_item {
         Some(impl_) => clean_ty(impl_.self_ty, cx),
         None => clean_middle_ty(
-            ty::Binder::dummy(tcx.type_of(did).subst_identity()),
+            ty::Binder::dummy(tcx.type_of(did).instantiate_identity()),
             cx,
             Some(did),
             None,
@@ -634,7 +634,7 @@ pub(crate) fn print_inlined_const(tcx: TyCtxt<'_>, did: DefId) -> String {
 fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
     clean::Constant {
         type_: clean_middle_ty(
-            ty::Binder::dummy(cx.tcx.type_of(def_id).subst_identity()),
+            ty::Binder::dummy(cx.tcx.type_of(def_id).instantiate_identity()),
             cx,
             Some(def_id),
             None,
@@ -646,7 +646,7 @@ fn build_const(cx: &mut DocContext<'_>, def_id: DefId) -> clean::Constant {
 fn build_static(cx: &mut DocContext<'_>, did: DefId, mutable: bool) -> clean::Static {
     clean::Static {
         type_: clean_middle_ty(
-            ty::Binder::dummy(cx.tcx.type_of(did).subst_identity()),
+            ty::Binder::dummy(cx.tcx.type_of(did).instantiate_identity()),
             cx,
             Some(did),
             None,
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index d26de77a78d38..d62c4b707e169 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -24,7 +24,6 @@ use rustc_infer::infer::region_constraints::{Constraint, RegionConstraintData};
 use rustc_middle::metadata::Reexport;
 use rustc_middle::middle::resolve_bound_vars as rbv;
 use rustc_middle::ty::fold::TypeFolder;
-use rustc_middle::ty::InternalSubsts;
 use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, AdtKind, EarlyBinder, Ty, TyCtxt};
 use rustc_middle::{bug, span_bug};
@@ -201,7 +200,7 @@ pub(crate) fn clean_trait_ref_with_bindings<'tcx>(
     }
     inline::record_extern_fqn(cx, trait_ref.def_id(), kind);
     let path =
-        external_path(cx, trait_ref.def_id(), true, bindings, trait_ref.map_bound(|tr| tr.substs));
+        external_path(cx, trait_ref.def_id(), true, bindings, trait_ref.map_bound(|tr| tr.args));
 
     debug!(?trait_ref);
 
@@ -239,7 +238,7 @@ fn clean_lifetime<'tcx>(lifetime: &hir::Lifetime, cx: &mut DocContext<'tcx>) ->
         | rbv::ResolvedArg::Free(_, node_id),
     ) = def
     {
-        if let Some(lt) = cx.substs.get(&node_id).and_then(|p| p.as_lt()).cloned() {
+        if let Some(lt) = cx.args.get(&node_id).and_then(|p| p.as_lt()).cloned() {
             return lt;
         }
     }
@@ -250,7 +249,7 @@ pub(crate) fn clean_const<'tcx>(constant: &hir::ConstArg, cx: &mut DocContext<'t
     let def_id = cx.tcx.hir().body_owner_def_id(constant.value.body).to_def_id();
     Constant {
         type_: clean_middle_ty(
-            ty::Binder::dummy(cx.tcx.type_of(def_id).subst_identity()),
+            ty::Binder::dummy(cx.tcx.type_of(def_id).instantiate_identity()),
             cx,
             Some(def_id),
             None,
@@ -442,7 +441,7 @@ fn clean_projection<'tcx>(
         let bounds = cx
             .tcx
             .explicit_item_bounds(ty.skip_binder().def_id)
-            .subst_iter_copied(cx.tcx, ty.skip_binder().substs)
+            .arg_iter_copied(cx.tcx, ty.skip_binder().args)
             .map(|(pred, _)| pred)
             .collect::<Vec<_>>();
         return clean_middle_opaque_bounds(cx, bounds);
@@ -481,9 +480,9 @@ fn projection_to_path_segment<'tcx>(
     PathSegment {
         name: item.name,
         args: GenericArgs::AngleBracketed {
-            args: substs_to_args(
+            args: ty_args_to_args(
                 cx,
-                ty.map_bound(|ty| &ty.substs[generics.parent_count..]),
+                ty.map_bound(|ty| &ty.args[generics.parent_count..]),
                 false,
                 None,
             )
@@ -504,7 +503,7 @@ fn clean_generic_param_def<'tcx>(
         ty::GenericParamDefKind::Type { has_default, synthetic, .. } => {
             let default = if has_default {
                 Some(clean_middle_ty(
-                    ty::Binder::dummy(cx.tcx.type_of(def.def_id).subst_identity()),
+                    ty::Binder::dummy(cx.tcx.type_of(def.def_id).instantiate_identity()),
                     cx,
                     Some(def.def_id),
                     None,
@@ -538,7 +537,7 @@ fn clean_generic_param_def<'tcx>(
                 )),
                 default: match has_default {
                     true => Some(Box::new(
-                        cx.tcx.const_param_default(def.def_id).subst_identity().to_string(),
+                        cx.tcx.const_param_default(def.def_id).instantiate_identity().to_string(),
                     )),
                     false => None,
                 },
@@ -1243,7 +1242,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
     let kind = match assoc_item.kind {
         ty::AssocKind::Const => {
             let ty = clean_middle_ty(
-                ty::Binder::dummy(tcx.type_of(assoc_item.def_id).subst_identity()),
+                ty::Binder::dummy(tcx.type_of(assoc_item.def_id).instantiate_identity()),
                 cx,
                 Some(assoc_item.def_id),
                 None,
@@ -1260,7 +1259,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
             }
         }
         ty::AssocKind::Fn => {
-            let sig = tcx.fn_sig(assoc_item.def_id).subst_identity();
+            let sig = tcx.fn_sig(assoc_item.def_id).instantiate_identity();
 
             let late_bound_regions = sig.bound_vars().into_iter().filter_map(|var| match var {
                 ty::BoundVariableKind::Region(ty::BrNamed(_, name))
@@ -1283,7 +1282,9 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
 
             if assoc_item.fn_has_self_parameter {
                 let self_ty = match assoc_item.container {
-                    ty::ImplContainer => tcx.type_of(assoc_item.container_id(tcx)).subst_identity(),
+                    ty::ImplContainer => {
+                        tcx.type_of(assoc_item.container_id(tcx)).instantiate_identity()
+                    }
                     ty::TraitContainer => tcx.types.self_param,
                 };
                 let self_arg_ty = sig.input(0).skip_binder();
@@ -1339,7 +1340,7 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
             let mut predicates = tcx.explicit_predicates_of(assoc_item.def_id).predicates;
             if let ty::TraitContainer = assoc_item.container {
                 let bounds =
-                    tcx.explicit_item_bounds(assoc_item.def_id).subst_identity_iter_copied();
+                    tcx.explicit_item_bounds(assoc_item.def_id).instantiate_identity_iter_copied();
                 predicates = tcx.arena.alloc_from_iter(bounds.chain(predicates.iter().copied()));
             }
             let mut generics = clean_ty_generics(
@@ -1442,7 +1443,9 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                     AssocTypeItem(
                         Box::new(Typedef {
                             type_: clean_middle_ty(
-                                ty::Binder::dummy(tcx.type_of(assoc_item.def_id).subst_identity()),
+                                ty::Binder::dummy(
+                                    tcx.type_of(assoc_item.def_id).instantiate_identity(),
+                                ),
                                 cx,
                                 Some(assoc_item.def_id),
                                 None,
@@ -1459,7 +1462,9 @@ pub(crate) fn clean_middle_assoc_item<'tcx>(
                 AssocTypeItem(
                     Box::new(Typedef {
                         type_: clean_middle_ty(
-                            ty::Binder::dummy(tcx.type_of(assoc_item.def_id).subst_identity()),
+                            ty::Binder::dummy(
+                                tcx.type_of(assoc_item.def_id).instantiate_identity(),
+                            ),
                             cx,
                             Some(assoc_item.def_id),
                             None,
@@ -1485,7 +1490,7 @@ fn clean_qpath<'tcx>(hir_ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type
     match qpath {
         hir::QPath::Resolved(None, path) => {
             if let Res::Def(DefKind::TyParam, did) = path.res {
-                if let Some(new_ty) = cx.substs.get(&did).and_then(|p| p.as_ty()).cloned() {
+                if let Some(new_ty) = cx.args.get(&did).and_then(|p| p.as_ty()).cloned() {
                     return new_ty;
                 }
                 if let Some(bounds) = cx.impl_trait_bounds.remove(&did.into()) {
@@ -1576,7 +1581,7 @@ fn maybe_expand_private_type_alias<'tcx>(
     let hir::ItemKind::TyAlias(ty, generics) = alias else { return None };
 
     let provided_params = &path.segments.last().expect("segments were empty");
-    let mut substs = DefIdMap::default();
+    let mut args = DefIdMap::default();
     let generic_args = provided_params.args();
 
     let mut indices: hir::GenericParamCount = Default::default();
@@ -1600,7 +1605,7 @@ fn maybe_expand_private_type_alias<'tcx>(
                     } else {
                         Lifetime::elided()
                     };
-                    substs.insert(param.def_id.to_def_id(), SubstParam::Lifetime(cleaned));
+                    args.insert(param.def_id.to_def_id(), SubstParam::Lifetime(cleaned));
                 }
                 indices.lifetimes += 1;
             }
@@ -1617,10 +1622,9 @@ fn maybe_expand_private_type_alias<'tcx>(
                     _ => None,
                 });
                 if let Some(ty) = type_ {
-                    substs.insert(param.def_id.to_def_id(), SubstParam::Type(clean_ty(ty, cx)));
+                    args.insert(param.def_id.to_def_id(), SubstParam::Type(clean_ty(ty, cx)));
                 } else if let Some(default) = *default {
-                    substs
-                        .insert(param.def_id.to_def_id(), SubstParam::Type(clean_ty(default, cx)));
+                    args.insert(param.def_id.to_def_id(), SubstParam::Type(clean_ty(default, cx)));
                 }
                 indices.types += 1;
             }
@@ -1637,7 +1641,7 @@ fn maybe_expand_private_type_alias<'tcx>(
                     _ => None,
                 });
                 if let Some(ct) = const_ {
-                    substs.insert(
+                    args.insert(
                         param.def_id.to_def_id(),
                         SubstParam::Constant(clean_const(ct, cx)),
                     );
@@ -1648,7 +1652,7 @@ fn maybe_expand_private_type_alias<'tcx>(
         }
     }
 
-    Some(cx.enter_alias(substs, def_id.to_def_id(), |cx| clean_ty(ty, cx)))
+    Some(cx.enter_alias(args, def_id.to_def_id(), |cx| clean_ty(ty, cx)))
 }
 
 pub(crate) fn clean_ty<'tcx>(ty: &hir::Ty<'tcx>, cx: &mut DocContext<'tcx>) -> Type {
@@ -1817,14 +1821,14 @@ fn can_elide_trait_object_lifetime_bound<'tcx>(
 #[derive(Debug)]
 pub(crate) enum ContainerTy<'tcx> {
     Ref(ty::Region<'tcx>),
-    Regular { ty: DefId, substs: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>, arg: usize },
+    Regular { ty: DefId, args: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>, arg: usize },
 }
 
 impl<'tcx> ContainerTy<'tcx> {
     fn object_lifetime_default(self, tcx: TyCtxt<'tcx>) -> ObjectLifetimeDefault<'tcx> {
         match self {
             Self::Ref(region) => ObjectLifetimeDefault::Arg(region),
-            Self::Regular { ty: container, substs, arg: index } => {
+            Self::Regular { ty: container, args, arg: index } => {
                 let (DefKind::Struct
                 | DefKind::Union
                 | DefKind::Enum
@@ -1843,7 +1847,7 @@ impl<'tcx> ContainerTy<'tcx> {
                 match default {
                     rbv::ObjectLifetimeDefault::Param(lifetime) => {
                         let index = generics.param_def_id_to_index[&lifetime];
-                        let arg = substs.skip_binder()[index as usize].expect_region();
+                        let arg = args.skip_binder()[index as usize].expect_region();
                         ObjectLifetimeDefault::Arg(arg)
                     }
                     rbv::ObjectLifetimeDefault::Empty => ObjectLifetimeDefault::Empty,
@@ -1909,7 +1913,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 abi: sig.abi(),
             }))
         }
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             let did = def.did();
             let kind = match def.adt_kind() {
                 AdtKind::Struct => ItemType::Struct,
@@ -1917,7 +1921,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 AdtKind::Enum => ItemType::Enum,
             };
             inline::record_extern_fqn(cx, did, kind);
-            let path = external_path(cx, did, false, ThinVec::new(), bound_ty.rebind(substs));
+            let path = external_path(cx, did, false, ThinVec::new(), bound_ty.rebind(args));
             Type::Path { path }
         }
         ty::Foreign(did) => {
@@ -1927,7 +1931,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 did,
                 false,
                 ThinVec::new(),
-                ty::Binder::dummy(InternalSubsts::empty()),
+                ty::Binder::dummy(ty::GenericArgs::empty()),
             );
             Type::Path { path }
         }
@@ -1940,10 +1944,10 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 .principal_def_id()
                 .or_else(|| dids.next())
                 .unwrap_or_else(|| panic!("found trait object `{bound_ty:?}` with no traits?"));
-            let substs = match obj.principal() {
-                Some(principal) => principal.map_bound(|p| p.substs),
-                // marker traits have no substs.
-                _ => ty::Binder::dummy(InternalSubsts::empty()),
+            let args = match obj.principal() {
+                Some(principal) => principal.map_bound(|p| p.args),
+                // marker traits have no args.
+                _ => ty::Binder::dummy(ty::GenericArgs::empty()),
             };
 
             inline::record_extern_fqn(cx, did, ItemType::Trait);
@@ -1952,7 +1956,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
 
             let mut bounds = dids
                 .map(|did| {
-                    let empty = ty::Binder::dummy(InternalSubsts::empty());
+                    let empty = ty::Binder::dummy(ty::GenericArgs::empty());
                     let path = external_path(cx, did, false, ThinVec::new(), empty);
                     inline::record_extern_fqn(cx, did, ItemType::Trait);
                     PolyTrait { trait_: path, generic_params: Vec::new() }
@@ -1966,7 +1970,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                         pb.map_bound(|pb| {
                             pb
                                 // HACK(compiler-errors): Doesn't actually matter what self
-                                // type we put here, because we're only using the GAT's substs.
+                                // type we put here, because we're only using the GAT's args.
                                 .with_self_ty(cx.tcx, cx.tcx.types.self_param)
                                 .projection_ty
                         }),
@@ -1992,7 +1996,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 .collect();
             let late_bound_regions = late_bound_regions.into_iter().collect();
 
-            let path = external_path(cx, did, false, bindings, substs);
+            let path = external_path(cx, did, false, bindings, args);
             bounds.insert(0, PolyTrait { trait_: path, generic_params: late_bound_regions });
 
             DynTrait(bounds, lifetime)
@@ -2013,9 +2017,9 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 assoc: PathSegment {
                     name: cx.tcx.associated_item(alias_ty.skip_binder().def_id).name,
                     args: GenericArgs::AngleBracketed {
-                        args: substs_to_args(
+                        args: ty_args_to_args(
                             cx,
-                            alias_ty.map_bound(|ty| ty.substs.as_slice()),
+                            alias_ty.map_bound(|ty| ty.args.as_slice()),
                             true,
                             None,
                         )
@@ -2038,11 +2042,11 @@ pub(crate) fn clean_middle_ty<'tcx>(
                     data.def_id,
                     false,
                     ThinVec::new(),
-                    bound_ty.rebind(data.substs),
+                    bound_ty.rebind(data.args),
                 );
                 Type::Path { path }
             } else {
-                let ty = cx.tcx.type_of(data.def_id).subst(cx.tcx, data.substs);
+                let ty = cx.tcx.type_of(data.def_id).instantiate(cx.tcx, data.args);
                 clean_middle_ty(bound_ty.rebind(ty), cx, None, None)
             }
         }
@@ -2055,11 +2059,10 @@ pub(crate) fn clean_middle_ty<'tcx>(
             }
         }
 
-        ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => {
+        ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
             // If it's already in the same alias, don't get an infinite loop.
             if cx.current_type_aliases.contains_key(&def_id) {
-                let path =
-                    external_path(cx, def_id, false, ThinVec::new(), bound_ty.rebind(substs));
+                let path = external_path(cx, def_id, false, ThinVec::new(), bound_ty.rebind(args));
                 Type::Path { path }
             } else {
                 *cx.current_type_aliases.entry(def_id).or_insert(0) += 1;
@@ -2068,7 +2071,7 @@ pub(crate) fn clean_middle_ty<'tcx>(
                 let bounds = cx
                     .tcx
                     .explicit_item_bounds(def_id)
-                    .subst_iter_copied(cx.tcx, substs)
+                    .arg_iter_copied(cx.tcx, args)
                     .map(|(bound, _)| bound)
                     .collect::<Vec<_>>();
                 let ty = clean_middle_opaque_bounds(cx, bounds);
@@ -2161,7 +2164,7 @@ pub(crate) fn clean_middle_field<'tcx>(field: &ty::FieldDef, cx: &mut DocContext
         field.did,
         field.name,
         clean_middle_ty(
-            ty::Binder::dummy(cx.tcx.type_of(field.did).subst_identity()),
+            ty::Binder::dummy(cx.tcx.type_of(field.did).instantiate_identity()),
             cx,
             Some(field.did),
             None,
@@ -2562,7 +2565,7 @@ fn clean_impl<'tcx>(
     let type_alias =
         for_.def_id(&cx.cache).and_then(|alias_def_id: DefId| match tcx.def_kind(alias_def_id) {
             DefKind::TyAlias => Some(clean_middle_ty(
-                ty::Binder::dummy(tcx.type_of(def_id).subst_identity()),
+                ty::Binder::dummy(tcx.type_of(def_id).instantiate_identity()),
                 cx,
                 Some(def_id.to_def_id()),
                 None,
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index eccc881d6b185..cfe62407fd35d 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1221,7 +1221,7 @@ pub(crate) enum GenericBound {
 impl GenericBound {
     pub(crate) fn maybe_sized(cx: &mut DocContext<'_>) -> GenericBound {
         let did = cx.tcx.require_lang_item(LangItem::Sized, None);
-        let empty = ty::Binder::dummy(ty::InternalSubsts::empty());
+        let empty = ty::Binder::dummy(ty::GenericArgs::empty());
         let path = external_path(cx, did, false, ThinVec::new(), empty);
         inline::record_extern_fqn(cx, did, ItemType::Trait);
         GenericBound::TraitBound(
diff --git a/src/librustdoc/clean/utils.rs b/src/librustdoc/clean/utils.rs
index d6a970fba398c..df9da9e7c7fd4 100644
--- a/src/librustdoc/clean/utils.rs
+++ b/src/librustdoc/clean/utils.rs
@@ -16,8 +16,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, LOCAL_CRATE};
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ConstValue;
-use rustc_middle::ty::subst::{GenericArgKind, SubstsRef};
-use rustc_middle::ty::{self, TyCtxt};
+use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, TyCtxt};
 use rustc_span::symbol::{kw, sym, Symbol};
 use std::fmt::Write as _;
 use std::mem;
@@ -71,20 +70,16 @@ pub(crate) fn krate(cx: &mut DocContext<'_>) -> Crate {
     Crate { module, external_traits: cx.external_traits.clone() }
 }
 
-pub(crate) fn substs_to_args<'tcx>(
+pub(crate) fn ty_args_to_args<'tcx>(
     cx: &mut DocContext<'tcx>,
-    substs: ty::Binder<'tcx, &'tcx [ty::subst::GenericArg<'tcx>]>,
+    args: ty::Binder<'tcx, &'tcx [ty::GenericArg<'tcx>]>,
     mut skip_first: bool,
     container: Option<DefId>,
 ) -> Vec<GenericArg> {
     let mut ret_val =
-        Vec::with_capacity(substs.skip_binder().len().saturating_sub(if skip_first {
-            1
-        } else {
-            0
-        }));
+        Vec::with_capacity(args.skip_binder().len().saturating_sub(if skip_first { 1 } else { 0 }));
 
-    ret_val.extend(substs.iter().enumerate().filter_map(|(index, kind)| {
+    ret_val.extend(args.iter().enumerate().filter_map(|(index, kind)| {
         match kind.skip_binder().unpack() {
             GenericArgKind::Lifetime(lt) => {
                 Some(GenericArg::Lifetime(clean_middle_region(lt).unwrap_or(Lifetime::elided())))
@@ -99,7 +94,7 @@ pub(crate) fn substs_to_args<'tcx>(
                 None,
                 container.map(|container| crate::clean::ContainerTy::Regular {
                     ty: container,
-                    substs,
+                    args,
                     arg: index,
                 }),
             ))),
@@ -116,12 +111,12 @@ fn external_generic_args<'tcx>(
     did: DefId,
     has_self: bool,
     bindings: ThinVec<TypeBinding>,
-    substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
+    ty_args: ty::Binder<'tcx, GenericArgsRef<'tcx>>,
 ) -> GenericArgs {
-    let args = substs_to_args(cx, substs.map_bound(|substs| &substs[..]), has_self, Some(did));
+    let args = ty_args_to_args(cx, ty_args.map_bound(|args| &args[..]), has_self, Some(did));
 
     if cx.tcx.fn_trait_kind_from_def_id(did).is_some() {
-        let ty = substs
+        let ty = ty_args
             .iter()
             .nth(if has_self { 1 } else { 0 })
             .unwrap()
@@ -149,7 +144,7 @@ pub(super) fn external_path<'tcx>(
     did: DefId,
     has_self: bool,
     bindings: ThinVec<TypeBinding>,
-    substs: ty::Binder<'tcx, SubstsRef<'tcx>>,
+    args: ty::Binder<'tcx, GenericArgsRef<'tcx>>,
 ) -> Path {
     let def_kind = cx.tcx.def_kind(did);
     let name = cx.tcx.item_name(did);
@@ -157,7 +152,7 @@ pub(super) fn external_path<'tcx>(
         res: Res::Def(def_kind, did),
         segments: thin_vec![PathSegment {
             name,
-            args: external_generic_args(cx, did, has_self, bindings, substs),
+            args: external_generic_args(cx, did, has_self, bindings, args),
         }],
     }
 }
@@ -252,7 +247,7 @@ pub(crate) fn name_from_pat(p: &hir::Pat<'_>) -> Symbol {
 
 pub(crate) fn print_const(cx: &DocContext<'_>, n: ty::Const<'_>) -> String {
     match n.kind() {
-        ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, substs: _ }) => {
+        ty::ConstKind::Unevaluated(ty::UnevaluatedConst { def, args: _ }) => {
             let s = if let Some(def) = def.as_local() {
                 print_const_expr(cx.tcx, cx.tcx.hir().body_owned_by(def))
             } else {
@@ -277,7 +272,7 @@ pub(crate) fn print_evaluated_const(
     underscores_and_type: bool,
 ) -> Option<String> {
     tcx.const_eval_poly(def_id).ok().and_then(|val| {
-        let ty = tcx.type_of(def_id).subst_identity();
+        let ty = tcx.type_of(def_id).instantiate_identity();
         match (val, ty.kind()) {
             (_, &ty::Ref(..)) => None,
             (ConstValue::Scalar(_), &ty::Adt(_, _)) => None,
diff --git a/src/librustdoc/core.rs b/src/librustdoc/core.rs
index 9687b8b18878e..1bd40aea823ea 100644
--- a/src/librustdoc/core.rs
+++ b/src/librustdoc/core.rs
@@ -45,7 +45,7 @@ pub(crate) struct DocContext<'tcx> {
     // The current set of parameter substitutions,
     // for expanding type aliases at the HIR level:
     /// Table `DefId` of type, lifetime, or const parameter -> substituted type, lifetime, or const
-    pub(crate) substs: DefIdMap<clean::SubstParam>,
+    pub(crate) args: DefIdMap<clean::SubstParam>,
     pub(crate) current_type_aliases: DefIdMap<usize>,
     /// Table synthetic type parameter for `impl Trait` in argument position -> bounds
     pub(crate) impl_trait_bounds: FxHashMap<ImplTraitParam, Vec<clean::GenericBound>>,
@@ -85,17 +85,17 @@ impl<'tcx> DocContext<'tcx> {
     /// the substitutions for a type alias' RHS.
     pub(crate) fn enter_alias<F, R>(
         &mut self,
-        substs: DefIdMap<clean::SubstParam>,
+        args: DefIdMap<clean::SubstParam>,
         def_id: DefId,
         f: F,
     ) -> R
     where
         F: FnOnce(&mut Self) -> R,
     {
-        let old_substs = mem::replace(&mut self.substs, substs);
+        let old_args = mem::replace(&mut self.args, args);
         *self.current_type_aliases.entry(def_id).or_insert(0) += 1;
         let r = f(self);
-        self.substs = old_substs;
+        self.args = old_args;
         if let Some(count) = self.current_type_aliases.get_mut(&def_id) {
             *count -= 1;
             if *count == 0 {
@@ -340,7 +340,7 @@ pub(crate) fn run_global_ctxt(
         param_env: ParamEnv::empty(),
         external_traits: Default::default(),
         active_extern_traits: Default::default(),
-        substs: Default::default(),
+        args: Default::default(),
         current_type_aliases: Default::default(),
         impl_trait_bounds: Default::default(),
         generated_synthetics: Default::default(),
diff --git a/src/librustdoc/formats/cache.rs b/src/librustdoc/formats/cache.rs
index dac762e9ff9f6..6b48936cc59d0 100644
--- a/src/librustdoc/formats/cache.rs
+++ b/src/librustdoc/formats/cache.rs
@@ -473,7 +473,7 @@ impl<'a, 'tcx> DocFolder for CacheBuilder<'a, 'tcx> {
                 | clean::BorrowedRef { type_: box clean::Type::Path { ref path }, .. } => {
                     dids.insert(path.def_id());
                     if let Some(generics) = path.generics() &&
-                        let ty::Adt(adt, _) = self.tcx.type_of(path.def_id()).subst_identity().kind() &&
+                        let ty::Adt(adt, _) = self.tcx.type_of(path.def_id()).instantiate_identity().kind() &&
                         adt.is_fundamental() {
                         for ty in generics {
                             if let Some(did) = ty.def_id(self.cache) {
diff --git a/src/librustdoc/html/render/type_layout.rs b/src/librustdoc/html/render/type_layout.rs
index 0bc32ea5a20b7..377daaeb9d487 100644
--- a/src/librustdoc/html/render/type_layout.rs
+++ b/src/librustdoc/html/render/type_layout.rs
@@ -39,7 +39,7 @@ pub(crate) fn document_type_layout<'a, 'cx: 'a>(
 
         let tcx = cx.tcx();
         let param_env = tcx.param_env(ty_def_id);
-        let ty = tcx.type_of(ty_def_id).subst_identity();
+        let ty = tcx.type_of(ty_def_id).instantiate_identity();
         let type_layout = tcx.layout_of(param_env.and(ty));
 
         let variants =
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 6df2b9735519f..91f3729bfa243 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -298,7 +298,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
         let ty_res = self.resolve_path(&path, TypeNS, item_id, module_id).ok_or_else(no_res)?;
 
         match ty_res {
-            Res::Def(DefKind::Enum, did) => match tcx.type_of(did).subst_identity().kind() {
+            Res::Def(DefKind::Enum, did) => match tcx.type_of(did).instantiate_identity().kind() {
                 ty::Adt(def, _) if def.is_enum() => {
                     if let Some(variant) = def.variants().iter().find(|v| v.name == variant_name)
                         && let Some(field) = variant.fields.iter().find(|f| f.name == variant_field_name) {
@@ -493,7 +493,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
     /// This is used for resolving type aliases.
     fn def_id_to_res(&self, ty_id: DefId) -> Option<Res> {
         use PrimitiveType::*;
-        Some(match *self.cx.tcx.type_of(ty_id).subst_identity().kind() {
+        Some(match *self.cx.tcx.type_of(ty_id).instantiate_identity().kind() {
             ty::Bool => Res::Primitive(Bool),
             ty::Char => Res::Primitive(Char),
             ty::Int(ity) => Res::Primitive(ity.into()),
@@ -601,7 +601,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                 debug!("looking for associated item named {} for item {:?}", item_name, did);
                 // Checks if item_name is a variant of the `SomeItem` enum
                 if ns == TypeNS && def_kind == DefKind::Enum {
-                    match tcx.type_of(did).subst_identity().kind() {
+                    match tcx.type_of(did).instantiate_identity().kind() {
                         ty::Adt(adt_def, _) => {
                             for variant in adt_def.variants() {
                                 if variant.name == item_name {
@@ -635,7 +635,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                     // To handle that properly resolve() would have to support
                     // something like [`ambi_fn`](<SomeStruct as SomeTrait>::ambi_fn)
                     assoc_items = resolve_associated_trait_item(
-                        tcx.type_of(did).subst_identity(),
+                        tcx.type_of(did).instantiate_identity(),
                         module_id,
                         item_name,
                         ns,
@@ -671,7 +671,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                 // they also look like associated items (`module::Type::Variant`),
                 // because they are real Rust syntax (unlike the intra-doc links
                 // field syntax) and are handled by the compiler's resolver.
-                let def = match tcx.type_of(did).subst_identity().kind() {
+                let def = match tcx.type_of(did).instantiate_identity().kind() {
                     ty::Adt(def, _) if !def.is_enum() => def,
                     _ => return Vec::new(),
                 };
@@ -1810,7 +1810,7 @@ fn resolution_failure(
                         Res::Primitive(_) => None,
                     };
                     let is_struct_variant = |did| {
-                        if let ty::Adt(def, _) = tcx.type_of(did).subst_identity().kind()
+                        if let ty::Adt(def, _) = tcx.type_of(did).instantiate_identity().kind()
                         && def.is_enum()
                         && let Some(variant) = def.variants().iter().find(|v| v.name == res.name(tcx)) {
                             // ctor is `None` if variant is a struct
diff --git a/src/librustdoc/passes/collect_trait_impls.rs b/src/librustdoc/passes/collect_trait_impls.rs
index fbf827cce0984..ff89d4e088735 100644
--- a/src/librustdoc/passes/collect_trait_impls.rs
+++ b/src/librustdoc/passes/collect_trait_impls.rs
@@ -103,11 +103,11 @@ pub(crate) fn collect_trait_impls(mut krate: Crate, cx: &mut DocContext<'_>) ->
                     // nothing to do with the inherent impl.
                     //
                     // Rustdoc currently uses these `impl` block as a source of
-                    // the `Ty`, as well as the `ParamEnv`, `SubstsRef`, and
+                    // the `Ty`, as well as the `ParamEnv`, `GenericArgsRef`, and
                     // `Generics`. To avoid relying on the `impl` block, these
                     // things would need to be created from wholecloth, in a
                     // form that is valid for use in type inference.
-                    let ty = tcx.type_of(def_id).subst_identity();
+                    let ty = tcx.type_of(def_id).instantiate_identity();
                     match ty.kind() {
                         ty::Slice(ty)
                         | ty::Ref(_, ty, _)
diff --git a/src/librustdoc/scrape_examples.rs b/src/librustdoc/scrape_examples.rs
index d2fa7769bbd2f..647d835884015 100644
--- a/src/librustdoc/scrape_examples.rs
+++ b/src/librustdoc/scrape_examples.rs
@@ -169,7 +169,7 @@ where
                 };
 
                 let ident_span = path.ident.span;
-                (tcx.type_of(def_id).subst_identity(), call_span, ident_span)
+                (tcx.type_of(def_id).instantiate_identity(), call_span, ident_span)
             }
             _ => {
                 return;
diff --git a/src/tools/clippy/clippy_lints/src/assertions_on_result_states.rs b/src/tools/clippy/clippy_lints/src/assertions_on_result_states.rs
index f6d6c23bb6ed2..2980c9d6db3d2 100644
--- a/src/tools/clippy/clippy_lints/src/assertions_on_result_states.rs
+++ b/src/tools/clippy/clippy_lints/src/assertions_on_result_states.rs
@@ -47,7 +47,7 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
             && let result_type_with_refs = cx.typeck_results().expr_ty(recv)
             && let result_type = result_type_with_refs.peel_refs()
             && is_type_diagnostic_item(cx, result_type, sym::Result)
-            && let ty::Adt(_, substs) = result_type.kind()
+            && let ty::Adt(_, args) = result_type.kind()
         {
             if !is_copy(cx, result_type) {
                 if result_type_with_refs != result_type {
@@ -61,7 +61,7 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
             let semicolon = if is_expr_final_block_expr(cx.tcx, e) {";"} else {""};
             let mut app = Applicability::MachineApplicable;
             match method_segment.ident.as_str() {
-                "is_ok" if type_suitable_to_unwrap(cx, substs.type_at(1)) => {
+                "is_ok" if type_suitable_to_unwrap(cx, args.type_at(1)) => {
                     span_lint_and_sugg(
                         cx,
                         ASSERTIONS_ON_RESULT_STATES,
@@ -75,7 +75,7 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
                         app,
                     );
                 }
-                "is_err" if type_suitable_to_unwrap(cx, substs.type_at(0)) => {
+                "is_err" if type_suitable_to_unwrap(cx, args.type_at(0)) => {
                     span_lint_and_sugg(
                         cx,
                         ASSERTIONS_ON_RESULT_STATES,
diff --git a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
index e8775b0814448..d984fddc57ae2 100644
--- a/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
+++ b/src/tools/clippy/clippy_lints/src/bool_assert_comparison.rs
@@ -61,7 +61,7 @@ fn is_impl_not_trait_with_bool_out<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -
             )
         })
         .map_or(false, |assoc_item| {
-            let proj = Ty::new_projection(cx.tcx,assoc_item.def_id, cx.tcx.mk_substs_trait(ty, []));
+            let proj = Ty::new_projection(cx.tcx,assoc_item.def_id, cx.tcx.mk_args_trait(ty, []));
             let nty = cx.tcx.normalize_erasing_regions(cx.param_env, proj);
 
             nty.is_bool()
diff --git a/src/tools/clippy/clippy_lints/src/casts/as_ptr_cast_mut.rs b/src/tools/clippy/clippy_lints/src/casts/as_ptr_cast_mut.rs
index 1633ffd589c38..fa1550a0ef9b8 100644
--- a/src/tools/clippy/clippy_lints/src/casts/as_ptr_cast_mut.rs
+++ b/src/tools/clippy/clippy_lints/src/casts/as_ptr_cast_mut.rs
@@ -17,7 +17,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, cast_expr: &Expr<'_>,
         && let ExprKind::MethodCall(method_name, receiver, [], _) = cast_expr.peel_blocks().kind
         && method_name.ident.name == rustc_span::sym::as_ptr
         && let Some(as_ptr_did) = cx.typeck_results().type_dependent_def_id(cast_expr.peel_blocks().hir_id)
-        && let as_ptr_sig = cx.tcx.fn_sig(as_ptr_did).subst_identity()
+        && let as_ptr_sig = cx.tcx.fn_sig(as_ptr_did).instantiate_identity()
         && let Some(first_param_ty) = as_ptr_sig.skip_binder().inputs().iter().next()
         && let ty::Ref(_, _, Mutability::Not) = first_param_ty.kind()
         && let Some(recv) = snippet_opt(cx, receiver.span)
diff --git a/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs b/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs
index 6c8ee296c7510..5bf467efa0f14 100644
--- a/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs
+++ b/src/tools/clippy/clippy_lints/src/casts/cast_ptr_alignment.rs
@@ -66,7 +66,7 @@ fn is_used_as_unaligned(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
             if matches!(name.ident.as_str(), "read_unaligned" | "write_unaligned")
                 && let Some(def_id) = cx.typeck_results().type_dependent_def_id(parent.hir_id)
                 && let Some(def_id) = cx.tcx.impl_of_method(def_id)
-                && cx.tcx.type_of(def_id).subst_identity().is_unsafe_ptr()
+                && cx.tcx.type_of(def_id).instantiate_identity().is_unsafe_ptr()
             {
                 true
             } else {
diff --git a/src/tools/clippy/clippy_lints/src/copy_iterator.rs b/src/tools/clippy/clippy_lints/src/copy_iterator.rs
index 0fc11523298f1..5d04ad0112d50 100644
--- a/src/tools/clippy/clippy_lints/src/copy_iterator.rs
+++ b/src/tools/clippy/clippy_lints/src/copy_iterator.rs
@@ -43,7 +43,7 @@ impl<'tcx> LateLintPass<'tcx> for CopyIterator {
                 of_trait: Some(ref trait_ref),
                 ..
             }) = item.kind;
-            let ty = cx.tcx.type_of(item.owner_id).subst_identity();
+            let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
             if is_copy(cx, ty);
             if let Some(trait_id) = trait_ref.trait_def_id();
             if cx.tcx.is_diagnostic_item(sym::Iterator, trait_id);
diff --git a/src/tools/clippy/clippy_lints/src/default.rs b/src/tools/clippy/clippy_lints/src/default.rs
index 80c22742ba442..763ad0264ad91 100644
--- a/src/tools/clippy/clippy_lints/src/default.rs
+++ b/src/tools/clippy/clippy_lints/src/default.rs
@@ -150,7 +150,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
                     .fields
                     .iter()
                     .all(|field| {
-                        is_copy(cx, cx.tcx.type_of(field.did).subst_identity())
+                        is_copy(cx, cx.tcx.type_of(field.did).instantiate_identity())
                     });
                 if !has_drop(cx, binding_type) || all_fields_are_copy;
                 then {
@@ -219,11 +219,11 @@ impl<'tcx> LateLintPass<'tcx> for Default {
 
                 // give correct suggestion if generics are involved (see #6944)
                 let binding_type = if_chain! {
-                    if let ty::Adt(adt_def, substs) = binding_type.kind();
-                    if !substs.is_empty();
+                    if let ty::Adt(adt_def, args) = binding_type.kind();
+                    if !args.is_empty();
                     then {
                         let adt_def_ty_name = cx.tcx.item_name(adt_def.did());
-                        let generic_args = substs.iter().collect::<Vec<_>>();
+                        let generic_args = args.iter().collect::<Vec<_>>();
                         let tys_str = generic_args
                             .iter()
                             .map(ToString::to_string)
diff --git a/src/tools/clippy/clippy_lints/src/default_numeric_fallback.rs b/src/tools/clippy/clippy_lints/src/default_numeric_fallback.rs
index e53a9877b20ca..9217edcef071d 100644
--- a/src/tools/clippy/clippy_lints/src/default_numeric_fallback.rs
+++ b/src/tools/clippy/clippy_lints/src/default_numeric_fallback.rs
@@ -141,7 +141,7 @@ impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
 
             ExprKind::MethodCall(_, receiver, args, _) => {
                 if let Some(def_id) = self.cx.typeck_results().type_dependent_def_id(expr.hir_id) {
-                    let fn_sig = self.cx.tcx.fn_sig(def_id).subst_identity().skip_binder();
+                    let fn_sig = self.cx.tcx.fn_sig(def_id).instantiate_identity().skip_binder();
                     for (expr, bound) in iter::zip(std::iter::once(*receiver).chain(args.iter()), fn_sig.inputs()) {
                         self.ty_bounds.push((*bound).into());
                         self.visit_expr(expr);
@@ -167,7 +167,7 @@ impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
                                     .iter()
                                     .find_map(|f_def| {
                                         if f_def.ident(self.cx.tcx) == field.ident
-                                            { Some(self.cx.tcx.type_of(f_def.did).subst_identity()) }
+                                            { Some(self.cx.tcx.type_of(f_def.did).instantiate_identity()) }
                                         else { None }
                                     });
                             self.ty_bounds.push(bound.into());
@@ -213,9 +213,9 @@ impl<'a, 'tcx> Visitor<'tcx> for NumericFallbackVisitor<'a, 'tcx> {
 
 fn fn_sig_opt<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId) -> Option<PolyFnSig<'tcx>> {
     let node_ty = cx.typeck_results().node_type_opt(hir_id)?;
-    // We can't use `Ty::fn_sig` because it automatically performs substs, this may result in FNs.
+    // We can't use `Ty::fn_sig` because it automatically performs args, this may result in FNs.
     match node_ty.kind() {
-        ty::FnDef(def_id, _) => Some(cx.tcx.fn_sig(*def_id).subst_identity()),
+        ty::FnDef(def_id, _) => Some(cx.tcx.fn_sig(*def_id).instantiate_identity()),
         ty::FnPtr(fn_sig) => Some(*fn_sig),
         _ => None,
     }
diff --git a/src/tools/clippy/clippy_lints/src/dereference.rs b/src/tools/clippy/clippy_lints/src/dereference.rs
index 73556c1053ecd..0e7efd53390c8 100644
--- a/src/tools/clippy/clippy_lints/src/dereference.rs
+++ b/src/tools/clippy/clippy_lints/src/dereference.rs
@@ -739,7 +739,7 @@ fn walk_parents<'tcx>(
                 span,
                 ..
             }) if span.ctxt() == ctxt => {
-                let ty = cx.tcx.type_of(owner_id.def_id).subst_identity();
+                let ty = cx.tcx.type_of(owner_id.def_id).instantiate_identity();
                 Some(ty_auto_deref_stability(cx.tcx, cx.param_env, ty, precedence).position_for_result(cx))
             },
 
@@ -763,7 +763,7 @@ fn walk_parents<'tcx>(
             }) if span.ctxt() == ctxt => {
                 let output = cx
                     .tcx
-                    .erase_late_bound_regions(cx.tcx.fn_sig(owner_id).subst_identity().output());
+                    .erase_late_bound_regions(cx.tcx.fn_sig(owner_id).instantiate_identity().output());
                 Some(ty_auto_deref_stability(cx.tcx, cx.param_env, output, precedence).position_for_result(cx))
             },
 
@@ -785,7 +785,7 @@ fn walk_parents<'tcx>(
                             cx.tcx,
                             // Use the param_env of the target type.
                             cx.tcx.param_env(adt.did()),
-                            cx.tcx.type_of(field_def.did).subst_identity(),
+                            cx.tcx.type_of(field_def.did).instantiate_identity(),
                             precedence,
                         )
                         .position_for_arg()
@@ -808,7 +808,7 @@ fn walk_parents<'tcx>(
                         } else {
                             let output = cx
                                 .tcx
-                                .erase_late_bound_regions(cx.tcx.fn_sig(owner_id).subst_identity().output());
+                                .erase_late_bound_regions(cx.tcx.fn_sig(owner_id).instantiate_identity().output());
                             ty_auto_deref_stability(cx.tcx, cx.param_env, output, precedence).position_for_result(cx)
                         },
                     )
@@ -879,9 +879,9 @@ fn walk_parents<'tcx>(
                             && let ty::Ref(_, sub_ty, _) = *arg_ty.kind()
                             && let subs = cx
                                 .typeck_results()
-                                .node_substs_opt(parent.hir_id).map(|subs| &subs[1..]).unwrap_or_default()
+                                .node_args_opt(parent.hir_id).map(|subs| &subs[1..]).unwrap_or_default()
                             && let impl_ty = if cx.tcx.fn_sig(fn_id)
-                                .subst_identity()
+                                .instantiate_identity()
                                 .skip_binder()
                                 .inputs()[0].is_ref()
                             {
@@ -905,7 +905,7 @@ fn walk_parents<'tcx>(
                         return Some(Position::MethodReceiver);
                     }
                     args.iter().position(|arg| arg.hir_id == child_id).map(|i| {
-                        let ty = cx.tcx.fn_sig(fn_id).subst_identity().input(i + 1);
+                        let ty = cx.tcx.fn_sig(fn_id).instantiate_identity().input(i + 1);
                         // `e.hir_id == child_id` for https://github.com/rust-lang/rust-clippy/issues/9739
                         // `method.args.is_none()` for https://github.com/rust-lang/rust-clippy/issues/9782
                         if e.hir_id == child_id
@@ -1124,10 +1124,10 @@ fn needless_borrow_impl_arg_position<'tcx>(
     let sized_trait_def_id = cx.tcx.lang_items().sized_trait();
 
     let Some(callee_def_id) = fn_def_id(cx, parent) else { return Position::Other(precedence) };
-    let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder();
-    let substs_with_expr_ty = cx
+    let fn_sig = cx.tcx.fn_sig(callee_def_id).instantiate_identity().skip_binder();
+    let args_with_expr_ty = cx
         .typeck_results()
-        .node_substs(if let ExprKind::Call(callee, _) = parent.kind {
+        .node_args(if let ExprKind::Call(callee, _) = parent.kind {
             callee.hir_id
         } else {
             parent.hir_id
@@ -1181,9 +1181,9 @@ fn needless_borrow_impl_arg_position<'tcx>(
         return Position::Other(precedence);
     }
 
-    // `substs_with_referent_ty` can be constructed outside of `check_referent` because the same
+    // `args_with_referent_ty` can be constructed outside of `check_referent` because the same
     // elements are modified each time `check_referent` is called.
-    let mut substs_with_referent_ty = substs_with_expr_ty.to_vec();
+    let mut args_with_referent_ty = args_with_expr_ty.to_vec();
 
     let mut check_reference_and_referent = |reference, referent| {
         let referent_ty = cx.typeck_results().expr_ty(referent);
@@ -1207,7 +1207,7 @@ fn needless_borrow_impl_arg_position<'tcx>(
             fn_sig,
             arg_index,
             &projection_predicates,
-            &mut substs_with_referent_ty,
+            &mut args_with_referent_ty,
         ) {
             return false;
         }
@@ -1216,14 +1216,14 @@ fn needless_borrow_impl_arg_position<'tcx>(
             if let ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder()
                 && cx.tcx.is_diagnostic_item(sym::IntoIterator, trait_predicate.trait_ref.def_id)
                 && let ty::Param(param_ty) = trait_predicate.self_ty().kind()
-                && let GenericArgKind::Type(ty) = substs_with_referent_ty[param_ty.index as usize].unpack()
+                && let GenericArgKind::Type(ty) = args_with_referent_ty[param_ty.index as usize].unpack()
                 && ty.is_array()
                 && !msrv.meets(msrvs::ARRAY_INTO_ITERATOR)
             {
                 return false;
             }
 
-            let predicate = EarlyBinder::bind(predicate).subst(cx.tcx, &substs_with_referent_ty);
+            let predicate = EarlyBinder::bind(predicate).instantiate(cx.tcx, &args_with_referent_ty);
             let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate);
             let infcx = cx.tcx.infer_ctxt().build();
             infcx.predicate_must_hold_modulo_regions(&obligation)
@@ -1252,7 +1252,7 @@ fn has_ref_mut_self_method(cx: &LateContext<'_>, trait_def_id: DefId) -> bool {
         .in_definition_order()
         .any(|assoc_item| {
             if assoc_item.fn_has_self_parameter {
-                let self_ty = cx.tcx.fn_sig(assoc_item.def_id).subst_identity().skip_binder().inputs()[0];
+                let self_ty = cx.tcx.fn_sig(assoc_item.def_id).instantiate_identity().skip_binder().inputs()[0];
                 matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Mut))
             } else {
                 false
@@ -1323,7 +1323,7 @@ fn referent_used_exactly_once<'tcx>(
     }
 }
 
-// Iteratively replaces `param_ty` with `new_ty` in `substs`, and similarly for each resulting
+// Iteratively replaces `param_ty` with `new_ty` in `args`, and similarly for each resulting
 // projected type that is a type parameter. Returns `false` if replacing the types would have an
 // effect on the function signature beyond substituting `new_ty` for `param_ty`.
 // See: https://github.com/rust-lang/rust-clippy/pull/9136#discussion_r927212757
@@ -1334,11 +1334,11 @@ fn replace_types<'tcx>(
     fn_sig: FnSig<'tcx>,
     arg_index: usize,
     projection_predicates: &[ProjectionPredicate<'tcx>],
-    substs: &mut [ty::GenericArg<'tcx>],
+    args: &mut [ty::GenericArg<'tcx>],
 ) -> bool {
-    let mut replaced = BitSet::new_empty(substs.len());
+    let mut replaced = BitSet::new_empty(args.len());
 
-    let mut deque = VecDeque::with_capacity(substs.len());
+    let mut deque = VecDeque::with_capacity(args.len());
     deque.push_back((param_ty, new_ty));
 
     while let Some((param_ty, new_ty)) = deque.pop_front() {
@@ -1352,7 +1352,7 @@ fn replace_types<'tcx>(
             return false;
         }
 
-        substs[param_ty.index as usize] = ty::GenericArg::from(new_ty);
+        args[param_ty.index as usize] = ty::GenericArg::from(new_ty);
 
         // The `replaced.insert(...)` check provides some protection against infinite loops.
         if replaced.insert(param_ty.index) {
@@ -1367,7 +1367,7 @@ fn replace_types<'tcx>(
                     ));
 
                     if let Ok(projected_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, projection)
-                        && substs[term_param_ty.index as usize] != ty::GenericArg::from(projected_ty)
+                        && args[term_param_ty.index as usize] != ty::GenericArg::from(projected_ty)
                     {
                         deque.push_back((*term_param_ty, projected_ty));
                     }
@@ -1442,7 +1442,7 @@ fn ty_auto_deref_stability<'tcx>(
             ty::Adt(..) if ty.has_placeholders() || ty.has_opaque_types() => {
                 Position::ReborrowStable(precedence).into()
             },
-            ty::Adt(_, substs) if substs.has_non_region_param() => {
+            ty::Adt(_, args) if args.has_non_region_param() => {
                 TyPosition::new_deref_stable_for_result(precedence, ty)
             },
             ty::Bool
diff --git a/src/tools/clippy/clippy_lints/src/derivable_impls.rs b/src/tools/clippy/clippy_lints/src/derivable_impls.rs
index 020ffe7f8fa22..71b5104bed8e6 100644
--- a/src/tools/clippy/clippy_lints/src/derivable_impls.rs
+++ b/src/tools/clippy/clippy_lints/src/derivable_impls.rs
@@ -10,7 +10,7 @@ use rustc_hir::{
 };
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::adjustment::{Adjust, PointerCoercion};
-use rustc_middle::ty::{self, Adt, AdtDef, SubstsRef, Ty, TypeckResults};
+use rustc_middle::ty::{self, Adt, AdtDef, GenericArgsRef, Ty, TypeckResults};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::sym;
 
@@ -80,7 +80,7 @@ fn is_path_self(e: &Expr<'_>) -> bool {
 fn contains_trait_object(ty: Ty<'_>) -> bool {
     match ty.kind() {
         ty::Ref(_, ty, _) => contains_trait_object(*ty),
-        ty::Adt(def, substs) => def.is_box() && substs[0].as_type().map_or(false, contains_trait_object),
+        ty::Adt(def, args) => def.is_box() && args[0].as_type().map_or(false, contains_trait_object),
         ty::Dynamic(..) => true,
         _ => false,
     }
@@ -92,18 +92,18 @@ fn check_struct<'tcx>(
     self_ty: &hir::Ty<'_>,
     func_expr: &Expr<'_>,
     adt_def: AdtDef<'_>,
-    substs: SubstsRef<'_>,
+    ty_args: GenericArgsRef<'_>,
     typeck_results: &'tcx TypeckResults<'tcx>,
 ) {
     if let TyKind::Path(QPath::Resolved(_, p)) = self_ty.kind {
         if let Some(PathSegment { args, .. }) = p.segments.last() {
             let args = args.map(|a| a.args).unwrap_or(&[]);
 
-            // substs contains the generic parameters of the type declaration, while args contains the arguments
+            // ty_args contains the generic parameters of the type declaration, while args contains the arguments
             // used at instantiation time. If both len are not equal, it means that some parameters were not
             // provided (which means that the default values were used); in this case we will not risk
             // suggesting too broad a rewrite. We won't either if any argument is a type or a const.
-            if substs.len() != args.len() || args.iter().any(|arg| !matches!(arg, GenericArg::Lifetime(_))) {
+            if ty_args.len() != args.len() || args.iter().any(|arg| !matches!(arg, GenericArg::Lifetime(_))) {
                 return;
             }
         }
@@ -214,7 +214,7 @@ impl<'tcx> LateLintPass<'tcx> for DerivableImpls {
             if let Some(Node::ImplItem(impl_item)) = cx.tcx.hir().find(impl_item_hir);
             if let ImplItemKind::Fn(_, b) = &impl_item.kind;
             if let Body { value: func_expr, .. } = cx.tcx.hir().body(*b);
-            if let &Adt(adt_def, substs) = cx.tcx.type_of(item.owner_id).subst_identity().kind();
+            if let &Adt(adt_def, args) = cx.tcx.type_of(item.owner_id).instantiate_identity().kind();
             if let attrs = cx.tcx.hir().attrs(item.hir_id());
             if !attrs.iter().any(|attr| attr.doc_str().is_some());
             if let child_attrs = cx.tcx.hir().attrs(impl_item_hir);
@@ -222,7 +222,7 @@ impl<'tcx> LateLintPass<'tcx> for DerivableImpls {
 
             then {
                 if adt_def.is_struct() {
-                    check_struct(cx, item, self_ty, func_expr, adt_def, substs, cx.tcx.typeck_body(*b));
+                    check_struct(cx, item, self_ty, func_expr, adt_def, args, cx.tcx.typeck_body(*b));
                 } else if adt_def.is_enum() && self.msrv.meets(msrvs::DEFAULT_ENUM_ATTRIBUTE) {
                     check_enum(cx, item, func_expr, adt_def);
                 }
diff --git a/src/tools/clippy/clippy_lints/src/derive.rs b/src/tools/clippy/clippy_lints/src/derive.rs
index a005a360e9cef..78e7f93e2bfd9 100644
--- a/src/tools/clippy/clippy_lints/src/derive.rs
+++ b/src/tools/clippy/clippy_lints/src/derive.rs
@@ -211,7 +211,7 @@ impl<'tcx> LateLintPass<'tcx> for Derive {
             ..
         }) = item.kind
         {
-            let ty = cx.tcx.type_of(item.owner_id).subst_identity();
+            let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
             let is_automatically_derived = cx.tcx.has_attr(item.owner_id, sym::automatically_derived);
 
             check_hash_peq(cx, item.span, trait_ref, ty, is_automatically_derived);
@@ -252,7 +252,7 @@ fn check_hash_peq<'tcx>(
 
                 // Only care about `impl PartialEq<Foo> for Foo`
                 // For `impl PartialEq<B> for A, input_types is [A, B]
-                if trait_ref.subst_identity().substs.type_at(1) == ty {
+                if trait_ref.instantiate_identity().args.type_at(1) == ty {
                     span_lint_and_then(
                         cx,
                         DERIVED_HASH_WITH_MANUAL_EQ,
@@ -300,7 +300,7 @@ fn check_ord_partial_ord<'tcx>(
 
                 // Only care about `impl PartialOrd<Foo> for Foo`
                 // For `impl PartialOrd<B> for A, input_types is [A, B]
-                if trait_ref.subst_identity().substs.type_at(1) == ty {
+                if trait_ref.instantiate_identity().args.type_at(1) == ty {
                     let mess = if partial_ord_is_automatically_derived {
                         "you are implementing `Ord` explicitly but have derived `PartialOrd`"
                     } else {
@@ -347,7 +347,7 @@ fn check_copy_clone<'tcx>(cx: &LateContext<'tcx>, item: &Item<'_>, trait_ref: &h
             let has_copy_impl = cx.tcx.all_local_trait_impls(()).get(&copy_id).map_or(false, |impls| {
                 impls
                     .iter()
-                    .any(|&id| matches!(cx.tcx.type_of(id).subst_identity().kind(), ty::Adt(adt, _) if ty_adt.did() == adt.did()))
+                    .any(|&id| matches!(cx.tcx.type_of(id).instantiate_identity().kind(), ty::Adt(adt, _) if ty_adt.did() == adt.did()))
             });
             if !has_copy_impl {
                 return;
@@ -464,7 +464,7 @@ impl<'tcx> Visitor<'tcx> for UnsafeVisitor<'_, 'tcx> {
 /// Implementation of the `DERIVE_PARTIAL_EQ_WITHOUT_EQ` lint.
 fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_ref: &hir::TraitRef<'_>, ty: Ty<'tcx>) {
     if_chain! {
-        if let ty::Adt(adt, substs) = ty.kind();
+        if let ty::Adt(adt, args) = ty.kind();
         if cx.tcx.visibility(adt.did()).is_public();
         if let Some(eq_trait_def_id) = cx.tcx.get_diagnostic_item(sym::Eq);
         if let Some(def_id) = trait_ref.trait_def_id();
@@ -474,7 +474,7 @@ fn check_partial_eq_without_eq<'tcx>(cx: &LateContext<'tcx>, span: Span, trait_r
         // If all of our fields implement `Eq`, we can implement `Eq` too
         if adt
             .all_fields()
-            .map(|f| f.ty(cx.tcx, substs))
+            .map(|f| f.ty(cx.tcx, args))
             .all(|ty| implements_trait_with_env(cx.tcx, param_env, ty, eq_trait_def_id, []));
         then {
             span_lint_and_sugg(
diff --git a/src/tools/clippy/clippy_lints/src/empty_enum.rs b/src/tools/clippy/clippy_lints/src/empty_enum.rs
index d94664daa5619..1701d061128b9 100644
--- a/src/tools/clippy/clippy_lints/src/empty_enum.rs
+++ b/src/tools/clippy/clippy_lints/src/empty_enum.rs
@@ -49,7 +49,7 @@ impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
         }
 
         if let ItemKind::Enum(..) = item.kind {
-            let ty = cx.tcx.type_of(item.owner_id).subst_identity();
+            let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
             let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
             if adt.variants().is_empty() {
                 span_lint_and_help(
diff --git a/src/tools/clippy/clippy_lints/src/enum_clike.rs b/src/tools/clippy/clippy_lints/src/enum_clike.rs
index d85650712db82..96c5c7fc50931 100644
--- a/src/tools/clippy/clippy_lints/src/enum_clike.rs
+++ b/src/tools/clippy/clippy_lints/src/enum_clike.rs
@@ -45,7 +45,7 @@ impl<'tcx> LateLintPass<'tcx> for UnportableVariant {
             for var in def.variants {
                 if let Some(anon_const) = &var.disr_expr {
                     let def_id = cx.tcx.hir().body_owner_def_id(anon_const.body);
-                    let mut ty = cx.tcx.type_of(def_id.to_def_id()).subst_identity();
+                    let mut ty = cx.tcx.type_of(def_id.to_def_id()).instantiate_identity();
                     let constant = cx
                         .tcx
                         .const_eval_poly(def_id.to_def_id())
diff --git a/src/tools/clippy/clippy_lints/src/eta_reduction.rs b/src/tools/clippy/clippy_lints/src/eta_reduction.rs
index 58e62d1f3d377..22e10accd357f 100644
--- a/src/tools/clippy/clippy_lints/src/eta_reduction.rs
+++ b/src/tools/clippy/clippy_lints/src/eta_reduction.rs
@@ -11,7 +11,7 @@ use rustc_hir::{Closure, Expr, ExprKind, Param, PatKind, Unsafety};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, AutoBorrow};
 use rustc_middle::ty::binding::BindingMode;
-use rustc_middle::ty::{self, EarlyBinder, SubstsRef, Ty, TypeVisitableExt};
+use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TypeVisitableExt};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::symbol::sym;
 
@@ -108,18 +108,18 @@ impl<'tcx> LateLintPass<'tcx> for EtaReduction {
             if check_inputs(cx, body.params, None, args);
             let callee_ty = cx.typeck_results().expr_ty_adjusted(callee);
             let call_ty = cx.typeck_results().type_dependent_def_id(body.value.hir_id)
-                .map_or(callee_ty, |id| cx.tcx.type_of(id).subst_identity());
+                .map_or(callee_ty, |id| cx.tcx.type_of(id).instantiate_identity());
             if check_sig(cx, closure_ty, call_ty);
-            let substs = cx.typeck_results().node_substs(callee.hir_id);
+            let args = cx.typeck_results().node_args(callee.hir_id);
             // This fixes some false positives that I don't entirely understand
-            if substs.is_empty() || !cx.typeck_results().expr_ty(expr).has_late_bound_regions();
+            if args.is_empty() || !cx.typeck_results().expr_ty(expr).has_late_bound_regions();
             // A type param function ref like `T::f` is not 'static, however
             // it is if cast like `T::f as fn()`. This seems like a rustc bug.
-            if !substs.types().any(|t| matches!(t.kind(), ty::Param(_)));
+            if !args.types().any(|t| matches!(t.kind(), ty::Param(_)));
             let callee_ty_unadjusted = cx.typeck_results().expr_ty(callee).peel_refs();
             if !is_type_diagnostic_item(cx, callee_ty_unadjusted, sym::Arc);
             if !is_type_diagnostic_item(cx, callee_ty_unadjusted, sym::Rc);
-            if let ty::Closure(_, substs) = *closure_ty.kind();
+            if let ty::Closure(_, args) = *closure_ty.kind();
             // Don't lint if this is an inclusive range expression.
             // They desugar to a call to `RangeInclusiveNew` which would have odd suggestions. (#10684)
             if !matches!(higher::Range::hir(body.value), Some(higher::Range {
@@ -131,7 +131,7 @@ impl<'tcx> LateLintPass<'tcx> for EtaReduction {
                 span_lint_and_then(cx, REDUNDANT_CLOSURE, expr.span, "redundant closure", |diag| {
                     if let Some(mut snippet) = snippet_opt(cx, callee.span) {
                         if let Some(fn_mut_id) = cx.tcx.lang_items().fn_mut_trait()
-                            && let args = cx.tcx.erase_late_bound_regions(substs.as_closure().sig()).inputs()
+                            && let args = cx.tcx.erase_late_bound_regions(args.as_closure().sig()).inputs()
                             && implements_trait(
                                    cx,
                                    callee_ty.peel_refs(),
@@ -160,12 +160,12 @@ impl<'tcx> LateLintPass<'tcx> for EtaReduction {
             if let ExprKind::MethodCall(path, receiver, args, _) = body.value.kind;
             if check_inputs(cx, body.params, Some(receiver), args);
             let method_def_id = cx.typeck_results().type_dependent_def_id(body.value.hir_id).unwrap();
-            let substs = cx.typeck_results().node_substs(body.value.hir_id);
-            let call_ty = cx.tcx.type_of(method_def_id).subst(cx.tcx, substs);
+            let args = cx.typeck_results().node_args(body.value.hir_id);
+            let call_ty = cx.tcx.type_of(method_def_id).instantiate(cx.tcx, args);
             if check_sig(cx, closure_ty, call_ty);
             then {
                 span_lint_and_then(cx, REDUNDANT_CLOSURE_FOR_METHOD_CALLS, expr.span, "redundant closure", |diag| {
-                    let name = get_ufcs_type_name(cx, method_def_id, substs);
+                    let name = get_ufcs_type_name(cx, method_def_id, args);
                     diag.span_suggestion(
                         expr.span,
                         "replace the closure with the method itself",
@@ -228,14 +228,14 @@ fn check_sig<'tcx>(cx: &LateContext<'tcx>, closure_ty: Ty<'tcx>, call_ty: Ty<'tc
     if !closure_ty.has_late_bound_regions() {
         return true;
     }
-    let ty::Closure(_, substs) = closure_ty.kind() else {
+    let ty::Closure(_, args) = closure_ty.kind() else {
         return false;
     };
-    let closure_sig = cx.tcx.signature_unclosure(substs.as_closure().sig(), Unsafety::Normal);
+    let closure_sig = cx.tcx.signature_unclosure(args.as_closure().sig(), Unsafety::Normal);
     cx.tcx.erase_late_bound_regions(closure_sig) == cx.tcx.erase_late_bound_regions(call_sig)
 }
 
-fn get_ufcs_type_name<'tcx>(cx: &LateContext<'tcx>, method_def_id: DefId, substs: SubstsRef<'tcx>) -> String {
+fn get_ufcs_type_name<'tcx>(cx: &LateContext<'tcx>, method_def_id: DefId, args: GenericArgsRef<'tcx>) -> String {
     let assoc_item = cx.tcx.associated_item(method_def_id);
     let def_id = assoc_item.container_id(cx.tcx);
     match assoc_item.container {
@@ -251,7 +251,7 @@ fn get_ufcs_type_name<'tcx>(cx: &LateContext<'tcx>, method_def_id: DefId, substs
                 | ty::Ref(..)
                 | ty::Slice(_)
                 | ty::Tuple(_) => {
-                    format!("<{}>", EarlyBinder::bind(ty).subst(cx.tcx, substs))
+                    format!("<{}>", EarlyBinder::bind(ty).instantiate(cx.tcx, args))
                 },
                 _ => ty.to_string(),
             }
diff --git a/src/tools/clippy/clippy_lints/src/from_over_into.rs b/src/tools/clippy/clippy_lints/src/from_over_into.rs
index 92d67ef359dca..35061fc64c95d 100644
--- a/src/tools/clippy/clippy_lints/src/from_over_into.rs
+++ b/src/tools/clippy/clippy_lints/src/from_over_into.rs
@@ -76,9 +76,9 @@ impl<'tcx> LateLintPass<'tcx> for FromOverInto {
             && let Some(into_trait_seg) = hir_trait_ref.path.segments.last()
             // `impl Into<target_ty> for self_ty`
             && let Some(GenericArgs { args: [GenericArg::Type(target_ty)], .. }) = into_trait_seg.args
-            && let Some(middle_trait_ref) = cx.tcx.impl_trait_ref(item.owner_id).map(ty::EarlyBinder::subst_identity)
+            && let Some(middle_trait_ref) = cx.tcx.impl_trait_ref(item.owner_id).map(ty::EarlyBinder::instantiate_identity)
             && cx.tcx.is_diagnostic_item(sym::Into, middle_trait_ref.def_id)
-            && !matches!(middle_trait_ref.substs.type_at(1).kind(), ty::Alias(ty::Opaque, _))
+            && !matches!(middle_trait_ref.args.type_at(1).kind(), ty::Alias(ty::Opaque, _))
         {
             span_lint_and_then(
                 cx,
diff --git a/src/tools/clippy/clippy_lints/src/functions/must_use.rs b/src/tools/clippy/clippy_lints/src/functions/must_use.rs
index d0ad26282642c..1b173de856b90 100644
--- a/src/tools/clippy/clippy_lints/src/functions/must_use.rs
+++ b/src/tools/clippy/clippy_lints/src/functions/must_use.rs
@@ -198,14 +198,14 @@ fn is_mutable_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>, tys: &mut DefIdSet)
     match *ty.kind() {
         // primitive types are never mutable
         ty::Bool | ty::Char | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Str => false,
-        ty::Adt(adt, substs) => {
+        ty::Adt(adt, args) => {
             tys.insert(adt.did()) && !ty.is_freeze(cx.tcx, cx.param_env)
                 || KNOWN_WRAPPER_TYS
                     .iter()
                     .any(|&sym| cx.tcx.is_diagnostic_item(sym, adt.did()))
-                    && substs.types().any(|ty| is_mutable_ty(cx, ty, tys))
+                    && args.types().any(|ty| is_mutable_ty(cx, ty, tys))
         },
-        ty::Tuple(substs) => substs.iter().any(|ty| is_mutable_ty(cx, ty, tys)),
+        ty::Tuple(args) => args.iter().any(|ty| is_mutable_ty(cx, ty, tys)),
         ty::Array(ty, _) | ty::Slice(ty) => is_mutable_ty(cx, ty, tys),
         ty::RawPtr(ty::TypeAndMut { ty, mutbl }) | ty::Ref(_, ty, mutbl) => {
             mutbl == hir::Mutability::Mut || is_mutable_ty(cx, ty, tys)
diff --git a/src/tools/clippy/clippy_lints/src/functions/result.rs b/src/tools/clippy/clippy_lints/src/functions/result.rs
index fa2a9b30c058d..90fc0d4f662e1 100644
--- a/src/tools/clippy/clippy_lints/src/functions/result.rs
+++ b/src/tools/clippy/clippy_lints/src/functions/result.rs
@@ -21,11 +21,11 @@ fn result_err_ty<'tcx>(
 ) -> Option<(&'tcx hir::Ty<'tcx>, Ty<'tcx>)> {
     if !in_external_macro(cx.sess(), item_span)
         && let hir::FnRetTy::Return(hir_ty) = decl.output
-        && let ty = cx.tcx.erase_late_bound_regions(cx.tcx.fn_sig(id).subst_identity().output())
+        && let ty = cx.tcx.erase_late_bound_regions(cx.tcx.fn_sig(id).instantiate_identity().output())
         && is_type_diagnostic_item(cx, ty, sym::Result)
-        && let ty::Adt(_, substs) = ty.kind()
+        && let ty::Adt(_, args) = ty.kind()
     {
-        let err_ty = substs.type_at(1);
+        let err_ty = args.type_at(1);
         Some((hir_ty, err_ty))
     } else {
         None
diff --git a/src/tools/clippy/clippy_lints/src/future_not_send.rs b/src/tools/clippy/clippy_lints/src/future_not_send.rs
index 818ebd1134de0..e54429aee8e8e 100644
--- a/src/tools/clippy/clippy_lints/src/future_not_send.rs
+++ b/src/tools/clippy/clippy_lints/src/future_not_send.rs
@@ -63,10 +63,10 @@ impl<'tcx> LateLintPass<'tcx> for FutureNotSend {
             return;
         }
         let ret_ty = return_ty(cx, cx.tcx.hir().local_def_id_to_hir_id(fn_def_id).expect_owner());
-        if let ty::Alias(ty::Opaque, AliasTy { def_id, substs, .. }) = *ret_ty.kind() {
+        if let ty::Alias(ty::Opaque, AliasTy { def_id, args, .. }) = *ret_ty.kind() {
             let preds = cx.tcx.explicit_item_bounds(def_id);
             let mut is_future = false;
-            for (p, _span) in preds.subst_iter_copied(cx.tcx, substs) {
+            for (p, _span) in preds.arg_iter_copied(cx.tcx, args) {
                 if let Some(trait_pred) = p.as_trait_clause() {
                     if Some(trait_pred.skip_binder().trait_ref.def_id) == cx.tcx.lang_items().future_trait() {
                         is_future = true;
diff --git a/src/tools/clippy/clippy_lints/src/implicit_saturating_sub.rs b/src/tools/clippy/clippy_lints/src/implicit_saturating_sub.rs
index 1e99b6faa6ca5..b99d454468174 100644
--- a/src/tools/clippy/clippy_lints/src/implicit_saturating_sub.rs
+++ b/src/tools/clippy/clippy_lints/src/implicit_saturating_sub.rs
@@ -102,7 +102,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub {
                             if let Some(const_id) = cx.typeck_results().type_dependent_def_id(cond_num_val.hir_id);
                             if let Some(impl_id) = cx.tcx.impl_of_method(const_id);
                             if let None = cx.tcx.impl_trait_ref(impl_id); // An inherent impl
-                            if cx.tcx.type_of(impl_id).subst_identity().is_integral();
+                            if cx.tcx.type_of(impl_id).instantiate_identity().is_integral();
                             then {
                                 print_lint_and_sugg(cx, var_name, expr)
                             }
@@ -115,7 +115,7 @@ impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub {
                             if let Some(func_id) = cx.typeck_results().type_dependent_def_id(func.hir_id);
                             if let Some(impl_id) = cx.tcx.impl_of_method(func_id);
                             if let None = cx.tcx.impl_trait_ref(impl_id); // An inherent impl
-                            if cx.tcx.type_of(impl_id).subst_identity().is_integral();
+                            if cx.tcx.type_of(impl_id).instantiate_identity().is_integral();
                             then {
                                 print_lint_and_sugg(cx, var_name, expr)
                             }
diff --git a/src/tools/clippy/clippy_lints/src/inherent_impl.rs b/src/tools/clippy/clippy_lints/src/inherent_impl.rs
index 7c41699f307aa..3ac40401e8981 100644
--- a/src/tools/clippy/clippy_lints/src/inherent_impl.rs
+++ b/src/tools/clippy/clippy_lints/src/inherent_impl.rs
@@ -66,7 +66,7 @@ impl<'tcx> LateLintPass<'tcx> for MultipleInherentImpl {
             )
         }) {
             for impl_id in impl_ids.iter().map(|id| id.expect_local()) {
-                let impl_ty = cx.tcx.type_of(impl_id).subst_identity();
+                let impl_ty = cx.tcx.type_of(impl_id).instantiate_identity();
                 match type_map.entry(impl_ty) {
                     Entry::Vacant(e) => {
                         // Store the id for the first impl block of this type. The span is retrieved lazily.
diff --git a/src/tools/clippy/clippy_lints/src/iter_not_returning_iterator.rs b/src/tools/clippy/clippy_lints/src/iter_not_returning_iterator.rs
index c924d7361ce3b..bb100ec632e65 100644
--- a/src/tools/clippy/clippy_lints/src/iter_not_returning_iterator.rs
+++ b/src/tools/clippy/clippy_lints/src/iter_not_returning_iterator.rs
@@ -68,7 +68,7 @@ fn check_sig(cx: &LateContext<'_>, name: &str, sig: &FnSig<'_>, fn_id: LocalDefI
     if sig.decl.implicit_self.has_implicit_self() {
         let ret_ty = cx
             .tcx
-            .erase_late_bound_regions(cx.tcx.fn_sig(fn_id).subst_identity().output());
+            .erase_late_bound_regions(cx.tcx.fn_sig(fn_id).instantiate_identity().output());
         let ret_ty = cx
             .tcx
             .try_normalize_erasing_regions(cx.param_env, ret_ty)
diff --git a/src/tools/clippy/clippy_lints/src/large_enum_variant.rs b/src/tools/clippy/clippy_lints/src/large_enum_variant.rs
index 1c99bd2f3d02e..693218f8a9c54 100644
--- a/src/tools/clippy/clippy_lints/src/large_enum_variant.rs
+++ b/src/tools/clippy/clippy_lints/src/large_enum_variant.rs
@@ -83,7 +83,7 @@ impl<'tcx> LateLintPass<'tcx> for LargeEnumVariant {
             return;
         }
         if let ItemKind::Enum(ref def, _) = item.kind {
-            let ty = cx.tcx.type_of(item.owner_id).subst_identity();
+            let ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
             let Adt(adt, subst) = ty.kind() else {
                 panic!("already checked whether this is an enum")
             };
@@ -169,8 +169,8 @@ impl<'tcx> LateLintPass<'tcx> for LargeEnumVariant {
 }
 
 fn maybe_copy<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
-    if let Adt(_def, substs) = ty.kind()
-        && substs.types().next().is_some()
+    if let Adt(_def, args) = ty.kind()
+        && args.types().next().is_some()
         && let Some(copy_trait) = cx.tcx.lang_items().copy_trait()
     {
         return cx.tcx.non_blanket_impls_for_ty(copy_trait, ty).next().is_some();
diff --git a/src/tools/clippy/clippy_lints/src/len_zero.rs b/src/tools/clippy/clippy_lints/src/len_zero.rs
index 17bd89efaee03..83fa25c795a00 100644
--- a/src/tools/clippy/clippy_lints/src/len_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/len_zero.rs
@@ -145,7 +145,7 @@ impl<'tcx> LateLintPass<'tcx> for LenZero {
             if let Some(local_id) = ty_id.as_local();
             let ty_hir_id = cx.tcx.hir().local_def_id_to_hir_id(local_id);
             if !is_lint_allowed(cx, LEN_WITHOUT_IS_EMPTY, ty_hir_id);
-            if let Some(output) = parse_len_output(cx, cx.tcx.fn_sig(item.owner_id).subst_identity().skip_binder());
+            if let Some(output) = parse_len_output(cx, cx.tcx.fn_sig(item.owner_id).instantiate_identity().skip_binder());
             then {
                 let (name, kind) = match cx.tcx.hir().find(ty_hir_id) {
                     Some(Node::ForeignItem(x)) => (x.ident.name, "extern type"),
@@ -425,7 +425,7 @@ fn check_for_is_empty(
             if !(is_empty.fn_has_self_parameter
                 && check_is_empty_sig(
                     cx,
-                    cx.tcx.fn_sig(is_empty.def_id).subst_identity().skip_binder(),
+                    cx.tcx.fn_sig(is_empty.def_id).instantiate_identity().skip_binder(),
                     self_kind,
                     output,
                 )) =>
diff --git a/src/tools/clippy/clippy_lints/src/let_underscore.rs b/src/tools/clippy/clippy_lints/src/let_underscore.rs
index e661418092080..b7a470020805a 100644
--- a/src/tools/clippy/clippy_lints/src/let_underscore.rs
+++ b/src/tools/clippy/clippy_lints/src/let_underscore.rs
@@ -5,7 +5,7 @@ use clippy_utils::{is_must_use_func_call, paths};
 use rustc_hir::{Local, PatKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::IsSuggestable;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{BytePos, Span};
diff --git a/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs b/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
index 5c5a4cfce8844..a84a0a6eeb82a 100644
--- a/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
+++ b/src/tools/clippy/clippy_lints/src/loops/explicit_iter_loop.rs
@@ -125,7 +125,7 @@ fn is_ref_iterable<'tcx>(
         }
 
         let res_ty = cx.tcx.erase_regions(EarlyBinder::bind(req_res_ty)
-            .subst(cx.tcx, typeck.node_substs(call_expr.hir_id)));
+            .instantiate(cx.tcx, typeck.node_args(call_expr.hir_id)));
         let mutbl = if let ty::Ref(_, _, mutbl) = *req_self_ty.kind() {
             Some(mutbl)
         } else {
diff --git a/src/tools/clippy/clippy_lints/src/loops/missing_spin_loop.rs b/src/tools/clippy/clippy_lints/src/loops/missing_spin_loop.rs
index 8412875b11b7e..0e49f08d89890 100644
--- a/src/tools/clippy/clippy_lints/src/loops/missing_spin_loop.rs
+++ b/src/tools/clippy/clippy_lints/src/loops/missing_spin_loop.rs
@@ -35,7 +35,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, cond: &'tcx Expr<'_>, body: &'
         if let ExprKind::Block(Block { stmts: [], expr: None, ..}, _) = body.kind;
         if let ExprKind::MethodCall(method, callee, ..) = unpack_cond(cond).kind;
         if [sym::load, sym::compare_exchange, sym::compare_exchange_weak].contains(&method.ident.name);
-        if let ty::Adt(def, _substs) = cx.typeck_results().expr_ty(callee).kind();
+        if let ty::Adt(def, _args) = cx.typeck_results().expr_ty(callee).kind();
         if cx.tcx.is_diagnostic_item(sym::AtomicBool, def.did());
         then {
             span_lint_and_sugg(
diff --git a/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs b/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
index cb446567506af..2c20e9e86933d 100644
--- a/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
+++ b/src/tools/clippy/clippy_lints/src/loops/needless_range_loop.rs
@@ -370,7 +370,7 @@ impl<'a, 'tcx> Visitor<'tcx> for VarVisitor<'a, 'tcx> {
             ExprKind::MethodCall(_, receiver, args, _) => {
                 let def_id = self.cx.typeck_results().type_dependent_def_id(expr.hir_id).unwrap();
                 for (ty, expr) in iter::zip(
-                    self.cx.tcx.fn_sig(def_id).subst_identity().inputs().skip_binder(),
+                    self.cx.tcx.fn_sig(def_id).instantiate_identity().inputs().skip_binder(),
                     std::iter::once(receiver).chain(args.iter()),
                 ) {
                     self.prefer_mutable = false;
diff --git a/src/tools/clippy/clippy_lints/src/manual_bits.rs b/src/tools/clippy/clippy_lints/src/manual_bits.rs
index 4629b22d1717f..6c7c57ba1d6b6 100644
--- a/src/tools/clippy/clippy_lints/src/manual_bits.rs
+++ b/src/tools/clippy/clippy_lints/src/manual_bits.rs
@@ -110,7 +110,7 @@ fn get_size_of_ty<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<
         if let Some(def_id) = cx.qpath_res(count_func_qpath, count_func.hir_id).opt_def_id();
         if cx.tcx.is_diagnostic_item(sym::mem_size_of, def_id);
         then {
-            cx.typeck_results().node_substs(count_func.hir_id).types().next().map(|resolved_ty| (*real_ty, resolved_ty))
+            cx.typeck_results().node_args(count_func.hir_id).types().next().map(|resolved_ty| (*real_ty, resolved_ty))
         } else {
             None
         }
diff --git a/src/tools/clippy/clippy_lints/src/manual_slice_size_calculation.rs b/src/tools/clippy/clippy_lints/src/manual_slice_size_calculation.rs
index 703a6b25840b1..f97600b53e4d9 100644
--- a/src/tools/clippy/clippy_lints/src/manual_slice_size_calculation.rs
+++ b/src/tools/clippy/clippy_lints/src/manual_slice_size_calculation.rs
@@ -92,7 +92,7 @@ fn simplify_half<'tcx>(
         && let ExprKind::Path(ref func_qpath) = func.kind
         && let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id()
         && cx.tcx.is_diagnostic_item(sym::mem_size_of, def_id)
-        && let Some(ty2) = cx.typeck_results().node_substs(func.hir_id).types().next()
+        && let Some(ty2) = cx.typeck_results().node_args(func.hir_id).types().next()
         // T1 == T2?
         && *ty1 == ty2
     {
diff --git a/src/tools/clippy/clippy_lints/src/map_unit_fn.rs b/src/tools/clippy/clippy_lints/src/map_unit_fn.rs
index edcab6968cbe0..75605fb30918d 100644
--- a/src/tools/clippy/clippy_lints/src/map_unit_fn.rs
+++ b/src/tools/clippy/clippy_lints/src/map_unit_fn.rs
@@ -104,7 +104,7 @@ fn is_unit_function(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
     let ty = cx.typeck_results().expr_ty(expr);
 
     if let ty::FnDef(id, _) = *ty.kind() {
-        if let Some(fn_type) = cx.tcx.fn_sig(id).subst_identity().no_bound_vars() {
+        if let Some(fn_type) = cx.tcx.fn_sig(id).instantiate_identity().no_bound_vars() {
             return is_unit_type(fn_type.output());
         }
     }
diff --git a/src/tools/clippy/clippy_lints/src/matches/match_as_ref.rs b/src/tools/clippy/clippy_lints/src/matches/match_as_ref.rs
index 2818f030b7a63..29c6e11134f87 100644
--- a/src/tools/clippy/clippy_lints/src/matches/match_as_ref.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/match_as_ref.rs
@@ -27,10 +27,10 @@ pub(crate) fn check(cx: &LateContext<'_>, ex: &Expr<'_>, arms: &[Arm<'_>], expr:
             let input_ty = cx.typeck_results().expr_ty(ex);
 
             let cast = if_chain! {
-                if let ty::Adt(_, substs) = input_ty.kind();
-                let input_ty = substs.type_at(0);
-                if let ty::Adt(_, substs) = output_ty.kind();
-                let output_ty = substs.type_at(0);
+                if let ty::Adt(_, args) = input_ty.kind();
+                let input_ty = args.type_at(0);
+                if let ty::Adt(_, args) = output_ty.kind();
+                let output_ty = args.type_at(0);
                 if let ty::Ref(_, output_ty, _) = *output_ty.kind();
                 if input_ty != output_ty;
                 then {
diff --git a/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs b/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs
index 479cfd835126c..039c2134cf816 100644
--- a/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/redundant_pattern_match.rs
@@ -12,7 +12,7 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::LangItem::{self, OptionNone, OptionSome, PollPending, PollReady, ResultErr, ResultOk};
 use rustc_hir::{Arm, Expr, ExprKind, Node, Pat, PatKind, QPath, UnOp};
 use rustc_lint::LateContext;
-use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
+use rustc_middle::ty::{self, GenericArgKind, Ty};
 use rustc_span::{sym, Symbol};
 
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
diff --git a/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs b/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
index d06bcdaa27f0a..4efe93d4b5424 100644
--- a/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/rest_pat_in_fully_bound_struct.rs
@@ -10,7 +10,7 @@ pub(crate) fn check(cx: &LateContext<'_>, pat: &Pat<'_>) {
         if !pat.span.from_expansion();
         if let PatKind::Struct(QPath::Resolved(_, path), fields, true) = pat.kind;
         if let Some(def_id) = path.res.opt_def_id();
-        let ty = cx.tcx.type_of(def_id).subst_identity();
+        let ty = cx.tcx.type_of(def_id).instantiate_identity();
         if let ty::Adt(def, _) = ty.kind();
         if def.is_struct() || def.is_union();
         if fields.len() == def.non_enum_variant().fields.len();
diff --git a/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs b/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
index 37528d9f7f200..02500fac293e5 100644
--- a/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
+++ b/src/tools/clippy/clippy_lints/src/matches/significant_drop_in_scrutinee.rs
@@ -6,7 +6,7 @@ use rustc_errors::{Applicability, Diagnostic};
 use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_hir::{Arm, Expr, ExprKind, MatchSource};
 use rustc_lint::{LateContext, LintContext};
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{Ty, TypeAndMut};
 use rustc_span::Span;
 
diff --git a/src/tools/clippy/clippy_lints/src/methods/bytes_count_to_len.rs b/src/tools/clippy/clippy_lints/src/methods/bytes_count_to_len.rs
index 46a20ad412baf..649fc46e4adf1 100644
--- a/src/tools/clippy/clippy_lints/src/methods/bytes_count_to_len.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/bytes_count_to_len.rs
@@ -17,7 +17,7 @@ pub(super) fn check<'tcx>(
     if_chain! {
         if let Some(bytes_id) = cx.typeck_results().type_dependent_def_id(count_recv.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(bytes_id);
-        if cx.tcx.type_of(impl_id).subst_identity().is_str();
+        if cx.tcx.type_of(impl_id).instantiate_identity().is_str();
         let ty = cx.typeck_results().expr_ty(bytes_recv).peel_refs();
         if ty.is_str() || is_type_lang_item(cx, ty, hir::LangItem::String);
         then {
diff --git a/src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs b/src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs
index 7711aa78b2391..fb10f782f7aa2 100644
--- a/src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/case_sensitive_file_extension_comparisons.rs
@@ -30,7 +30,7 @@ pub(super) fn check<'tcx>(
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if cx.tcx.type_of(impl_id).subst_identity().is_str();
+        if cx.tcx.type_of(impl_id).instantiate_identity().is_str();
         if let ExprKind::Lit(Spanned { node: LitKind::Str(ext_literal, ..), ..}) = arg.kind;
         if (2..=6).contains(&ext_literal.as_str().len());
         let ext_str = ext_literal.as_str();
diff --git a/src/tools/clippy/clippy_lints/src/methods/err_expect.rs b/src/tools/clippy/clippy_lints/src/methods/err_expect.rs
index ae03da0d3f9ce..4ab06bf2ae872 100644
--- a/src/tools/clippy/clippy_lints/src/methods/err_expect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/err_expect.rs
@@ -47,7 +47,7 @@ pub(super) fn check(
 /// Given a `Result<T, E>` type, return its data (`T`).
 fn get_data_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
     match ty.kind() {
-        ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::Result) => substs.types().next(),
+        ty::Adt(_, args) if is_type_diagnostic_item(cx, ty, sym::Result) => args.types().next(),
         _ => None,
     }
 }
diff --git a/src/tools/clippy/clippy_lints/src/methods/expect_fun_call.rs b/src/tools/clippy/clippy_lints/src/methods/expect_fun_call.rs
index 92d21bb893262..9af11f08c2613 100644
--- a/src/tools/clippy/clippy_lints/src/methods/expect_fun_call.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/expect_fun_call.rs
@@ -70,7 +70,7 @@ pub(super) fn check<'tcx>(
                 if let hir::ExprKind::Path(ref p) = fun.kind {
                     match cx.qpath_res(p, fun.hir_id) {
                         hir::def::Res::Def(hir::def::DefKind::Fn | hir::def::DefKind::AssocFn, def_id) => matches!(
-                            cx.tcx.fn_sig(def_id).subst_identity().output().skip_binder().kind(),
+                            cx.tcx.fn_sig(def_id).instantiate_identity().output().skip_binder().kind(),
                             ty::Ref(re, ..) if re.is_static(),
                         ),
                         _ => false,
@@ -84,7 +84,7 @@ pub(super) fn check<'tcx>(
                     .type_dependent_def_id(arg.hir_id)
                     .map_or(false, |method_id| {
                         matches!(
-                            cx.tcx.fn_sig(method_id).subst_identity().output().skip_binder().kind(),
+                            cx.tcx.fn_sig(method_id).instantiate_identity().output().skip_binder().kind(),
                             ty::Ref(re, ..) if re.is_static()
                         )
                     })
diff --git a/src/tools/clippy/clippy_lints/src/methods/flat_map_option.rs b/src/tools/clippy/clippy_lints/src/methods/flat_map_option.rs
index 615bde9413349..4737a101345a3 100644
--- a/src/tools/clippy/clippy_lints/src/methods/flat_map_option.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/flat_map_option.rs
@@ -15,7 +15,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>, arg
     }
     let arg_ty = cx.typeck_results().expr_ty_adjusted(arg);
     let sig = match arg_ty.kind() {
-        ty::Closure(_, substs) => substs.as_closure().sig(),
+        ty::Closure(_, args) => args.as_closure().sig(),
         _ if arg_ty.is_fn() => arg_ty.fn_sig(cx.tcx),
         _ => return,
     };
diff --git a/src/tools/clippy/clippy_lints/src/methods/get_first.rs b/src/tools/clippy/clippy_lints/src/methods/get_first.rs
index 945bbf53bcf35..ee063adac64af 100644
--- a/src/tools/clippy/clippy_lints/src/methods/get_first.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/get_first.rs
@@ -19,7 +19,7 @@ pub(super) fn check<'tcx>(
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if cx.tcx.type_of(impl_id).subst_identity().is_slice();
+        if cx.tcx.type_of(impl_id).instantiate_identity().is_slice();
         if let Some(_) = is_slice_of_primitives(cx, recv);
         if let hir::ExprKind::Lit(Spanned { node: LitKind::Int(0, _), .. }) = arg.kind;
         then {
diff --git a/src/tools/clippy/clippy_lints/src/methods/implicit_clone.rs b/src/tools/clippy/clippy_lints/src/methods/implicit_clone.rs
index 5a78a41687725..043425300d8bc 100644
--- a/src/tools/clippy/clippy_lints/src/methods/implicit_clone.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/implicit_clone.rs
@@ -54,7 +54,7 @@ pub fn is_clone_like(cx: &LateContext<'_>, method_name: &str, method_def_id: hir
             .tcx
             .impl_of_method(method_def_id)
             .filter(|&impl_did| {
-                cx.tcx.type_of(impl_did).subst_identity().is_slice() && cx.tcx.impl_trait_ref(impl_did).is_none()
+                cx.tcx.type_of(impl_did).instantiate_identity().is_slice() && cx.tcx.impl_trait_ref(impl_did).is_none()
             })
             .is_some(),
         _ => false,
diff --git a/src/tools/clippy/clippy_lints/src/methods/inefficient_to_string.rs b/src/tools/clippy/clippy_lints/src/methods/inefficient_to_string.rs
index 424482859ee87..37da52dc7336f 100644
--- a/src/tools/clippy/clippy_lints/src/methods/inefficient_to_string.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/inefficient_to_string.rs
@@ -23,9 +23,9 @@ pub fn check(
         if args.is_empty() && method_name == sym::to_string;
         if let Some(to_string_meth_did) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if match_def_path(cx, to_string_meth_did, &paths::TO_STRING_METHOD);
-        if let Some(substs) = cx.typeck_results().node_substs_opt(expr.hir_id);
+        if let Some(args) = cx.typeck_results().node_args_opt(expr.hir_id);
         let arg_ty = cx.typeck_results().expr_ty_adjusted(receiver);
-        let self_ty = substs.type_at(0);
+        let self_ty = args.type_at(0);
         let (deref_self_ty, deref_count) = walk_ptrs_ty_depth(self_ty);
         if deref_count >= 1;
         if specializes_tostring(cx, deref_self_ty);
@@ -64,8 +64,8 @@ fn specializes_tostring(cx: &LateContext<'_>, ty: Ty<'_>) -> bool {
         return true;
     }
 
-    if let ty::Adt(adt, substs) = ty.kind() {
-        cx.tcx.is_diagnostic_item(sym::Cow, adt.did()) && substs.type_at(1).is_str()
+    if let ty::Adt(adt, args) = ty.kind() {
+        cx.tcx.is_diagnostic_item(sym::Cow, adt.did()) && args.type_at(1).is_str()
     } else {
         false
     }
diff --git a/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs b/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs
index b9a0ec779961e..3031193e53122 100644
--- a/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/manual_ok_or.rs
@@ -21,7 +21,7 @@ pub(super) fn check<'tcx>(
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).subst_identity(), sym::Option);
+        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::Option);
         if let ExprKind::Call(err_path, [err_arg]) = or_expr.kind;
         if is_res_lang_ctor(cx, path_res(cx, err_path), ResultErr);
         if is_ok_wrapping(cx, map_expr);
diff --git a/src/tools/clippy/clippy_lints/src/methods/map_clone.rs b/src/tools/clippy/clippy_lints/src/methods/map_clone.rs
index 2b26ef0141096..880efe60c1a34 100644
--- a/src/tools/clippy/clippy_lints/src/methods/map_clone.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/map_clone.rs
@@ -19,7 +19,7 @@ pub(super) fn check(cx: &LateContext<'_>, e: &hir::Expr<'_>, recv: &hir::Expr<'_
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id);
         if cx.tcx.impl_of_method(method_id)
-            .map_or(false, |id| is_type_diagnostic_item(cx, cx.tcx.type_of(id).subst_identity(), sym::Option))
+            .map_or(false, |id| is_type_diagnostic_item(cx, cx.tcx.type_of(id).instantiate_identity(), sym::Option))
             || is_diag_trait_item(cx, method_id, sym::Iterator);
         if let hir::ExprKind::Closure(&hir::Closure{ body, .. }) = arg.kind;
         then {
diff --git a/src/tools/clippy/clippy_lints/src/methods/map_collect_result_unit.rs b/src/tools/clippy/clippy_lints/src/methods/map_collect_result_unit.rs
index a0300d278709d..042bab805b889 100644
--- a/src/tools/clippy/clippy_lints/src/methods/map_collect_result_unit.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/map_collect_result_unit.rs
@@ -15,8 +15,8 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, iter: &hir::Expr
     let collect_ret_ty = cx.typeck_results().expr_ty(expr);
     if_chain! {
         if is_type_diagnostic_item(cx, collect_ret_ty, sym::Result);
-        if let ty::Adt(_, substs) = collect_ret_ty.kind();
-        if let Some(result_t) = substs.types().next();
+        if let ty::Adt(_, args) = collect_ret_ty.kind();
+        if let Some(result_t) = args.types().next();
         if result_t.is_unit();
         // get parts for snippet
         then {
diff --git a/src/tools/clippy/clippy_lints/src/methods/map_err_ignore.rs b/src/tools/clippy/clippy_lints/src/methods/map_err_ignore.rs
index a5beb291f3263..fbb83c8ce5635 100644
--- a/src/tools/clippy/clippy_lints/src/methods/map_err_ignore.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/map_err_ignore.rs
@@ -9,7 +9,7 @@ use super::MAP_ERR_IGNORE;
 pub(super) fn check(cx: &LateContext<'_>, e: &Expr<'_>, arg: &Expr<'_>) {
     if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
         && let Some(impl_id) = cx.tcx.impl_of_method(method_id)
-        && is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).subst_identity(), sym::Result)
+        && is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::Result)
         && let ExprKind::Closure(&Closure {
             capture_clause: CaptureBy::Ref,
             body,
diff --git a/src/tools/clippy/clippy_lints/src/methods/map_flatten.rs b/src/tools/clippy/clippy_lints/src/methods/map_flatten.rs
index 361ffcb5ef3fb..950902d455b6f 100644
--- a/src/tools/clippy/clippy_lints/src/methods/map_flatten.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/map_flatten.rs
@@ -59,7 +59,7 @@ fn is_map_to_option(cx: &LateContext<'_>, map_arg: &Expr<'_>) -> bool {
     match map_closure_ty.kind() {
         ty::Closure(_, _) | ty::FnDef(_, _) | ty::FnPtr(_) => {
             let map_closure_sig = match map_closure_ty.kind() {
-                ty::Closure(_, substs) => substs.as_closure().sig(),
+                ty::Closure(_, args) => args.as_closure().sig(),
                 _ => map_closure_ty.fn_sig(cx.tcx),
             };
             let map_closure_return_ty = cx.tcx.erase_late_bound_regions(map_closure_sig.output());
diff --git a/src/tools/clippy/clippy_lints/src/methods/mod.rs b/src/tools/clippy/clippy_lints/src/methods/mod.rs
index 24dbe8c1d7518..9ab78c6f8e05e 100644
--- a/src/tools/clippy/clippy_lints/src/methods/mod.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/mod.rs
@@ -3508,11 +3508,11 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
         let name = impl_item.ident.name.as_str();
         let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id()).def_id;
         let item = cx.tcx.hir().expect_item(parent);
-        let self_ty = cx.tcx.type_of(item.owner_id).subst_identity();
+        let self_ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
 
         let implements_trait = matches!(item.kind, hir::ItemKind::Impl(hir::Impl { of_trait: Some(_), .. }));
         if let hir::ImplItemKind::Fn(ref sig, id) = impl_item.kind {
-            let method_sig = cx.tcx.fn_sig(impl_item.owner_id).subst_identity();
+            let method_sig = cx.tcx.fn_sig(impl_item.owner_id).instantiate_identity();
             let method_sig = cx.tcx.erase_late_bound_regions(method_sig);
             let first_arg_ty_opt = method_sig.inputs().iter().next().copied();
             // if this impl block implements a trait, lint in trait definition instead
@@ -4113,8 +4113,8 @@ impl SelfKind {
             } else if ty.is_box() {
                 ty.boxed_ty() == parent_ty
             } else if is_type_diagnostic_item(cx, ty, sym::Rc) || is_type_diagnostic_item(cx, ty, sym::Arc) {
-                if let ty::Adt(_, substs) = ty.kind() {
-                    substs.types().next().map_or(false, |t| t == parent_ty)
+                if let ty::Adt(_, args) = ty.kind() {
+                    args.types().next().map_or(false, |t| t == parent_ty)
                 } else {
                     false
                 }
diff --git a/src/tools/clippy/clippy_lints/src/methods/mut_mutex_lock.rs b/src/tools/clippy/clippy_lints/src/methods/mut_mutex_lock.rs
index d0aa39d06275a..fe024ee8dff97 100644
--- a/src/tools/clippy/clippy_lints/src/methods/mut_mutex_lock.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/mut_mutex_lock.rs
@@ -15,7 +15,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'tcx>, recv: &'
         if let ty::Ref(_, _, Mutability::Mut) = cx.typeck_results().expr_ty(recv).kind();
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(ex.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).subst_identity(), sym::Mutex);
+        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::Mutex);
         then {
             span_lint_and_sugg(
                 cx,
diff --git a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
index 8ca7af8107f67..f34f1cf27045c 100644
--- a/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/needless_collect.rs
@@ -163,7 +163,7 @@ fn check_collect_into_intoiterator<'tcx>(
             // that contains `collect_expr`
             let inputs = cx
                 .tcx
-                .liberate_late_bound_regions(id, cx.tcx.fn_sig(id).subst_identity())
+                .liberate_late_bound_regions(id, cx.tcx.fn_sig(id).instantiate_identity())
                 .inputs();
 
             // map IntoIterator generic bounds to their signature
@@ -201,7 +201,7 @@ fn check_collect_into_intoiterator<'tcx>(
 /// Checks if the given method call matches the expected signature of `([&[mut]] self) -> bool`
 fn is_is_empty_sig(cx: &LateContext<'_>, call_id: HirId) -> bool {
     cx.typeck_results().type_dependent_def_id(call_id).map_or(false, |id| {
-        let sig = cx.tcx.fn_sig(id).subst_identity().skip_binder();
+        let sig = cx.tcx.fn_sig(id).instantiate_identity().skip_binder();
         sig.inputs().len() == 1 && sig.output().is_bool()
     })
 }
@@ -215,7 +215,7 @@ fn iterates_same_ty<'tcx>(cx: &LateContext<'tcx>, iter_ty: Ty<'tcx>, collect_ty:
         && let Some(into_iter_item_proj) = make_projection(cx.tcx, into_iter_trait, item, [collect_ty])
         && let Ok(into_iter_item_ty) = cx.tcx.try_normalize_erasing_regions(
             cx.param_env,
-            Ty::new_projection(cx.tcx,into_iter_item_proj.def_id, into_iter_item_proj.substs)
+            Ty::new_projection(cx.tcx,into_iter_item_proj.def_id, into_iter_item_proj.args)
         )
     {
         iter_item_ty == into_iter_item_ty
@@ -229,7 +229,7 @@ fn iterates_same_ty<'tcx>(cx: &LateContext<'tcx>, iter_ty: Ty<'tcx>, collect_ty:
 fn is_contains_sig(cx: &LateContext<'_>, call_id: HirId, iter_expr: &Expr<'_>) -> bool {
     let typeck = cx.typeck_results();
     if let Some(id) = typeck.type_dependent_def_id(call_id)
-        && let sig = cx.tcx.fn_sig(id).subst_identity()
+        && let sig = cx.tcx.fn_sig(id).instantiate_identity()
         && sig.skip_binder().output().is_bool()
         && let [_, search_ty] = *sig.skip_binder().inputs()
         && let ty::Ref(_, search_ty, Mutability::Not) = *cx.tcx.erase_late_bound_regions(sig.rebind(search_ty)).kind()
@@ -237,11 +237,11 @@ fn is_contains_sig(cx: &LateContext<'_>, call_id: HirId, iter_expr: &Expr<'_>) -
         && let Some(iter_item) = cx.tcx
             .associated_items(iter_trait)
             .find_by_name_and_kind(cx.tcx, Ident::with_dummy_span(Symbol::intern("Item")), AssocKind::Type, iter_trait)
-        && let substs = cx.tcx.mk_substs(&[GenericArg::from(typeck.expr_ty_adjusted(iter_expr))])
-        && let proj_ty = Ty::new_projection(cx.tcx,iter_item.def_id, substs)
+        && let args = cx.tcx.mk_args(&[GenericArg::from(typeck.expr_ty_adjusted(iter_expr))])
+        && let proj_ty = Ty::new_projection(cx.tcx,iter_item.def_id, args)
         && let Ok(item_ty) = cx.tcx.try_normalize_erasing_regions(cx.param_env, proj_ty)
     {
-        item_ty == EarlyBinder::bind(search_ty).subst(cx.tcx, cx.typeck_results().node_substs(call_id))
+        item_ty == EarlyBinder::bind(search_ty).instantiate(cx.tcx, cx.typeck_results().node_args(call_id))
     } else {
         false
     }
diff --git a/src/tools/clippy/clippy_lints/src/methods/ok_expect.rs b/src/tools/clippy/clippy_lints/src/methods/ok_expect.rs
index 646fc4a7bcf37..f2ef42933df62 100644
--- a/src/tools/clippy/clippy_lints/src/methods/ok_expect.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/ok_expect.rs
@@ -33,7 +33,7 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr
 /// Given a `Result<T, E>` type, return its error type (`E`).
 fn get_error_type<'a>(cx: &LateContext<'_>, ty: Ty<'a>) -> Option<Ty<'a>> {
     match ty.kind() {
-        ty::Adt(_, substs) if is_type_diagnostic_item(cx, ty, sym::Result) => substs.types().nth(1),
+        ty::Adt(_, args) if is_type_diagnostic_item(cx, ty, sym::Result) => args.types().nth(1),
         _ => None,
     }
 }
diff --git a/src/tools/clippy/clippy_lints/src/methods/open_options.rs b/src/tools/clippy/clippy_lints/src/methods/open_options.rs
index bd625a6914c3c..1c664e76d74f5 100644
--- a/src/tools/clippy/clippy_lints/src/methods/open_options.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/open_options.rs
@@ -11,7 +11,7 @@ use super::NONSENSICAL_OPEN_OPTIONS;
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, recv: &'tcx Expr<'_>) {
     if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
         && let Some(impl_id) = cx.tcx.impl_of_method(method_id)
-        && match_type(cx, cx.tcx.type_of(impl_id).subst_identity(), &paths::OPEN_OPTIONS)
+        && match_type(cx, cx.tcx.type_of(impl_id).instantiate_identity(), &paths::OPEN_OPTIONS)
     {
         let mut options = Vec::new();
         get_open_options(cx, recv, &mut options);
diff --git a/src/tools/clippy/clippy_lints/src/methods/path_buf_push_overwrite.rs b/src/tools/clippy/clippy_lints/src/methods/path_buf_push_overwrite.rs
index 0284d9dea3032..1c07d2a3a59c2 100644
--- a/src/tools/clippy/clippy_lints/src/methods/path_buf_push_overwrite.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/path_buf_push_overwrite.rs
@@ -14,7 +14,7 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, arg: &'t
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).subst_identity(), sym::PathBuf);
+        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::PathBuf);
         if let ExprKind::Lit(lit) = arg.kind;
         if let LitKind::Str(ref path_lit, _) = lit.node;
         if let pushed_path = Path::new(path_lit.as_str());
diff --git a/src/tools/clippy/clippy_lints/src/methods/stable_sort_primitive.rs b/src/tools/clippy/clippy_lints/src/methods/stable_sort_primitive.rs
index b5fd0ad8ce524..0f4c97022dbe5 100644
--- a/src/tools/clippy/clippy_lints/src/methods/stable_sort_primitive.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/stable_sort_primitive.rs
@@ -10,7 +10,7 @@ use super::STABLE_SORT_PRIMITIVE;
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, recv: &'tcx Expr<'_>) {
     if let Some(method_id) = cx.typeck_results().type_dependent_def_id(e.hir_id)
         && let Some(impl_id) = cx.tcx.impl_of_method(method_id)
-        && cx.tcx.type_of(impl_id).subst_identity().is_slice()
+        && cx.tcx.type_of(impl_id).instantiate_identity().is_slice()
         && let Some(slice_type) = is_slice_of_primitives(cx, recv)
     {
         span_lint_and_then(
diff --git a/src/tools/clippy/clippy_lints/src/methods/suspicious_splitn.rs b/src/tools/clippy/clippy_lints/src/methods/suspicious_splitn.rs
index 90ca66bd70c50..3cb2719e4a032 100644
--- a/src/tools/clippy/clippy_lints/src/methods/suspicious_splitn.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/suspicious_splitn.rs
@@ -13,7 +13,7 @@ pub(super) fn check(cx: &LateContext<'_>, method_name: &str, expr: &Expr<'_>, se
         if let Some(call_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(call_id);
         if cx.tcx.impl_trait_ref(impl_id).is_none();
-        let self_ty = cx.tcx.type_of(impl_id).subst_identity();
+        let self_ty = cx.tcx.type_of(impl_id).instantiate_identity();
         if self_ty.is_slice() || self_ty.is_str();
         then {
             // Ignore empty slice and string literals when used with a literal count.
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs
index 67618f7038add..e62a65a27125f 100644
--- a/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_sort_by.rs
@@ -6,7 +6,7 @@ use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{Closure, Expr, ExprKind, Mutability, Param, Pat, PatKind, Path, PathSegment, QPath};
 use rustc_lint::LateContext;
-use rustc_middle::ty::{self, subst::GenericArgKind};
+use rustc_middle::ty::{self, GenericArgKind};
 use rustc_span::sym;
 use rustc_span::symbol::Ident;
 use std::iter;
@@ -118,7 +118,7 @@ fn detect_lint(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg: &Exp
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if cx.tcx.type_of(impl_id).subst_identity().is_slice();
+        if cx.tcx.type_of(impl_id).instantiate_identity().is_slice();
         if let ExprKind::Closure(&Closure { body, .. }) = arg.kind;
         if let closure_body = cx.tcx.hir().body(body);
         if let &[
diff --git a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
index 6bd5e9e88c846..21e2638e5b92b 100644
--- a/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -13,7 +13,7 @@ use rustc_infer::infer::TyCtxtInferExt;
 use rustc_lint::LateContext;
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
-use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
+use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgsRef};
 use rustc_middle::ty::{self, ClauseKind, EarlyBinder, ParamTy, ProjectionPredicate, TraitPredicate, Ty};
 use rustc_span::{sym, Symbol};
 use rustc_trait_selection::traits::{query::evaluate_obligation::InferCtxtExt as _, Obligation, ObligationCause};
@@ -250,8 +250,8 @@ fn check_other_call_arg<'tcx>(
 ) -> bool {
     if_chain! {
         if let Some((maybe_call, maybe_arg)) = skip_addr_of_ancestors(cx, expr);
-        if let Some((callee_def_id, _, recv, call_args)) = get_callee_substs_and_args(cx, maybe_call);
-        let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder();
+        if let Some((callee_def_id, _, recv, call_args)) = get_callee_generic_args_and_args(cx, maybe_call);
+        let fn_sig = cx.tcx.fn_sig(callee_def_id).instantiate_identity().skip_binder();
         if let Some(i) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == maybe_arg.hir_id);
         if let Some(input) = fn_sig.inputs().get(i);
         let (input, n_refs) = peel_mid_ty_refs(*input);
@@ -315,26 +315,26 @@ fn skip_addr_of_ancestors<'tcx>(
 }
 
 /// Checks whether an expression is a function or method call and, if so, returns its `DefId`,
-/// `Substs`, and arguments.
-fn get_callee_substs_and_args<'tcx>(
+/// `GenericArgs`, and arguments.
+fn get_callee_generic_args_and_args<'tcx>(
     cx: &LateContext<'tcx>,
     expr: &'tcx Expr<'tcx>,
-) -> Option<(DefId, SubstsRef<'tcx>, Option<&'tcx Expr<'tcx>>, &'tcx [Expr<'tcx>])> {
+) -> Option<(DefId, GenericArgsRef<'tcx>, Option<&'tcx Expr<'tcx>>, &'tcx [Expr<'tcx>])> {
     if_chain! {
         if let ExprKind::Call(callee, args) = expr.kind;
         let callee_ty = cx.typeck_results().expr_ty(callee);
         if let ty::FnDef(callee_def_id, _) = callee_ty.kind();
         then {
-            let substs = cx.typeck_results().node_substs(callee.hir_id);
-            return Some((*callee_def_id, substs, None, args));
+            let generic_args = cx.typeck_results().node_args(callee.hir_id);
+            return Some((*callee_def_id, generic_args, None, args));
         }
     }
     if_chain! {
         if let ExprKind::MethodCall(_, recv, args, _) = expr.kind;
         if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         then {
-            let substs = cx.typeck_results().node_substs(expr.hir_id);
-            return Some((method_def_id, substs, Some(recv), args));
+            let generic_args = cx.typeck_results().node_args(expr.hir_id);
+            return Some((method_def_id, generic_args, Some(recv), args));
         }
     }
     None
@@ -388,17 +388,17 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                 }
             }
             Node::Expr(parent_expr) => {
-                if let Some((callee_def_id, call_substs, recv, call_args)) = get_callee_substs_and_args(cx, parent_expr)
+                if let Some((callee_def_id, call_generic_args, recv, call_args)) = get_callee_generic_args_and_args(cx, parent_expr)
                 {
-                    // FIXME: the `subst_identity()` below seems incorrect, since we eventually
+                    // FIXME: the `instantiate_identity()` below seems incorrect, since we eventually
                     // call `tcx.try_subst_and_normalize_erasing_regions` further down
                     // (i.e., we are explicitly not in the identity context).
-                    let fn_sig = cx.tcx.fn_sig(callee_def_id).subst_identity().skip_binder();
+                    let fn_sig = cx.tcx.fn_sig(callee_def_id).instantiate_identity().skip_binder();
                     if let Some(arg_index) = recv.into_iter().chain(call_args).position(|arg| arg.hir_id == expr.hir_id)
                         && let Some(param_ty) = fn_sig.inputs().get(arg_index)
                         && let ty::Param(ParamTy { index: param_index , ..}) = param_ty.kind()
                         // https://github.com/rust-lang/rust-clippy/issues/9504 and https://github.com/rust-lang/rust-clippy/issues/10021
-                        && (*param_index as usize) < call_substs.len()
+                        && (*param_index as usize) < call_generic_args.len()
                     {
                         if fn_sig
                             .inputs()
@@ -422,8 +422,8 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                             }
                         });
 
-                        let new_subst = cx.tcx.mk_substs_from_iter(
-                            call_substs.iter()
+                        let new_subst = cx.tcx.mk_args_from_iter(
+                            call_generic_args.iter()
                                 .enumerate()
                                 .map(|(i, t)|
                                      if i == (*param_index as usize) {
@@ -433,7 +433,7 @@ fn can_change_type<'a>(cx: &LateContext<'a>, mut expr: &'a Expr<'a>, mut ty: Ty<
                                      }));
 
                         if trait_predicates.any(|predicate| {
-                            let predicate = EarlyBinder::bind(predicate).subst(cx.tcx, new_subst);
+                            let predicate = EarlyBinder::bind(predicate).instantiate(cx.tcx, new_subst);
                             let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate);
                             !cx.tcx.infer_ctxt().build().predicate_must_hold_modulo_regions(&obligation)
                         }) {
@@ -500,8 +500,8 @@ fn is_to_string_on_string_like<'a>(
         return false;
     }
 
-    if let Some(substs) = cx.typeck_results().node_substs_opt(call_expr.hir_id)
-        && let [generic_arg] = substs.as_slice()
+    if let Some(args) = cx.typeck_results().node_args_opt(call_expr.hir_id)
+        && let [generic_arg] = args.as_slice()
         && let GenericArgKind::Type(ty) = generic_arg.unpack()
         && let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
         && let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef)
diff --git a/src/tools/clippy/clippy_lints/src/methods/utils.rs b/src/tools/clippy/clippy_lints/src/methods/utils.rs
index c96d69226972f..9f1f73e602185 100644
--- a/src/tools/clippy/clippy_lints/src/methods/utils.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/utils.rs
@@ -143,7 +143,7 @@ impl<'cx, 'tcx> Visitor<'tcx> for CloneOrCopyVisitor<'cx, 'tcx> {
                         if_chain! {
                             if args.iter().all(|arg| !self.is_binding(arg));
                             if let Some(method_def_id) = self.cx.typeck_results().type_dependent_def_id(parent.hir_id);
-                            let method_ty = self.cx.tcx.type_of(method_def_id).subst_identity();
+                            let method_ty = self.cx.tcx.type_of(method_def_id).instantiate_identity();
                             let self_ty = method_ty.fn_sig(self.cx.tcx).input(0).skip_binder();
                             if matches!(self_ty.kind(), ty::Ref(_, _, Mutability::Not));
                             then {
diff --git a/src/tools/clippy/clippy_lints/src/methods/vec_resize_to_zero.rs b/src/tools/clippy/clippy_lints/src/methods/vec_resize_to_zero.rs
index b0cfc163fd08b..73072718678eb 100644
--- a/src/tools/clippy/clippy_lints/src/methods/vec_resize_to_zero.rs
+++ b/src/tools/clippy/clippy_lints/src/methods/vec_resize_to_zero.rs
@@ -20,7 +20,7 @@ pub(super) fn check<'tcx>(
     if_chain! {
         if let Some(method_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
         if let Some(impl_id) = cx.tcx.impl_of_method(method_id);
-        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).subst_identity(), sym::Vec);
+        if is_type_diagnostic_item(cx, cx.tcx.type_of(impl_id).instantiate_identity(), sym::Vec);
         if let ExprKind::Lit(Spanned { node: LitKind::Int(0, _), .. }) = count_arg.kind;
         if let ExprKind::Lit(Spanned { node: LitKind::Int(..), .. }) = default_arg.kind;
         then {
diff --git a/src/tools/clippy/clippy_lints/src/mut_key.rs b/src/tools/clippy/clippy_lints/src/mut_key.rs
index 309f67521a3b4..5878f899541ae 100644
--- a/src/tools/clippy/clippy_lints/src/mut_key.rs
+++ b/src/tools/clippy/clippy_lints/src/mut_key.rs
@@ -139,7 +139,7 @@ impl MutableKeyType {
     }
 
     fn check_sig(&self, cx: &LateContext<'_>, fn_def_id: LocalDefId, decl: &hir::FnDecl<'_>) {
-        let fn_sig = cx.tcx.fn_sig(fn_def_id).subst_identity();
+        let fn_sig = cx.tcx.fn_sig(fn_def_id).instantiate_identity();
         for (hir_ty, ty) in iter::zip(decl.inputs, fn_sig.inputs().skip_binder()) {
             self.check_ty_(cx, hir_ty.span, *ty);
         }
@@ -150,7 +150,7 @@ impl MutableKeyType {
     // generics (because the compiler cannot ensure immutability for unknown types).
     fn check_ty_<'tcx>(&self, cx: &LateContext<'tcx>, span: Span, ty: Ty<'tcx>) {
         let ty = ty.peel_refs();
-        if let Adt(def, substs) = ty.kind() {
+        if let Adt(def, args) = ty.kind() {
             let is_keyed_type = [sym::HashMap, sym::BTreeMap, sym::HashSet, sym::BTreeSet]
                 .iter()
                 .any(|diag_item| cx.tcx.is_diagnostic_item(*diag_item, def.did()));
@@ -158,7 +158,7 @@ impl MutableKeyType {
                 return;
             }
 
-            let subst_ty = substs.type_at(0);
+            let subst_ty = args.type_at(0);
             // Determines if a type contains interior mutability which would affect its implementation of
             // [`Hash`] or [`Ord`].
             if is_interior_mut_ty(cx, subst_ty)
diff --git a/src/tools/clippy/clippy_lints/src/mut_reference.rs b/src/tools/clippy/clippy_lints/src/mut_reference.rs
index e91aac41bc485..4b20aecad4a19 100644
--- a/src/tools/clippy/clippy_lints/src/mut_reference.rs
+++ b/src/tools/clippy/clippy_lints/src/mut_reference.rs
@@ -51,8 +51,8 @@ impl<'tcx> LateLintPass<'tcx> for UnnecessaryMutPassed {
             },
             ExprKind::MethodCall(path, receiver, arguments, _) => {
                 let def_id = cx.typeck_results().type_dependent_def_id(e.hir_id).unwrap();
-                let substs = cx.typeck_results().node_substs(e.hir_id);
-                let method_type = cx.tcx.type_of(def_id).subst(cx.tcx, substs);
+                let args = cx.typeck_results().node_args(e.hir_id);
+                let method_type = cx.tcx.type_of(def_id).instantiate(cx.tcx, args);
                 check_arguments(
                     cx,
                     std::iter::once(receiver).chain(arguments.iter()).collect(),
diff --git a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
index f11d5773d0413..55b6e1606ee40 100644
--- a/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
+++ b/src/tools/clippy/clippy_lints/src/needless_pass_by_value.rs
@@ -140,7 +140,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
             ctx
         };
 
-        let fn_sig = cx.tcx.fn_sig(fn_def_id).subst_identity();
+        let fn_sig = cx.tcx.fn_sig(fn_def_id).instantiate_identity();
         let fn_sig = cx.tcx.liberate_late_bound_regions(fn_def_id.to_def_id(), fn_sig);
 
         for (idx, ((input, &ty), arg)) in decl.inputs.iter().zip(fn_sig.inputs()).zip(body.params).enumerate() {
@@ -170,7 +170,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByValue {
                     !preds.is_empty() && {
                         let ty_empty_region = Ty::new_imm_ref(cx.tcx,cx.tcx.lifetimes.re_erased, ty);
                         preds.iter().all(|t| {
-                            let ty_params = t.trait_ref.substs.iter().skip(1).collect::<Vec<_>>();
+                            let ty_params = t.trait_ref.args.iter().skip(1).collect::<Vec<_>>();
                             implements_trait(cx, ty_empty_region, t.def_id(), &ty_params)
                         })
                     },
diff --git a/src/tools/clippy/clippy_lints/src/new_without_default.rs b/src/tools/clippy/clippy_lints/src/new_without_default.rs
index 653b1a8a05f66..cf7cd671dcabe 100644
--- a/src/tools/clippy/clippy_lints/src/new_without_default.rs
+++ b/src/tools/clippy/clippy_lints/src/new_without_default.rs
@@ -98,14 +98,14 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
                             if name == sym::new;
                             if cx.effective_visibilities.is_reachable(impl_item.owner_id.def_id);
                             let self_def_id = cx.tcx.hir().get_parent_item(id.into());
-                            let self_ty = cx.tcx.type_of(self_def_id).subst_identity();
+                            let self_ty = cx.tcx.type_of(self_def_id).instantiate_identity();
                             if self_ty == return_ty(cx, id);
                             if let Some(default_trait_id) = cx.tcx.get_diagnostic_item(sym::Default);
                             then {
                                 if self.impling_types.is_none() {
                                     let mut impls = HirIdSet::default();
                                     cx.tcx.for_each_impl(default_trait_id, |d| {
-                                        let ty = cx.tcx.type_of(d).subst_identity();
+                                        let ty = cx.tcx.type_of(d).instantiate_identity();
                                         if let Some(ty_def) = ty.ty_adt_def() {
                                             if let Some(local_def_id) = ty_def.did().as_local() {
                                                 impls.insert(cx.tcx.hir().local_def_id_to_hir_id(local_def_id));
@@ -119,7 +119,7 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
                                 // generics
                                 if_chain! {
                                     if let Some(ref impling_types) = self.impling_types;
-                                    let self_def = cx.tcx.type_of(self_def_id).subst_identity();
+                                    let self_def = cx.tcx.type_of(self_def_id).instantiate_identity();
                                     if let Some(self_def) = self_def.ty_adt_def();
                                     if let Some(self_local_did) = self_def.did().as_local();
                                     let self_id = cx.tcx.hir().local_def_id_to_hir_id(self_local_did);
diff --git a/src/tools/clippy/clippy_lints/src/non_copy_const.rs b/src/tools/clippy/clippy_lints/src/non_copy_const.rs
index 75f1e95276a69..12d4f33d428a7 100644
--- a/src/tools/clippy/clippy_lints/src/non_copy_const.rs
+++ b/src/tools/clippy/clippy_lints/src/non_copy_const.rs
@@ -158,7 +158,7 @@ fn is_value_unfrozen_raw<'tcx>(
                 val.unwrap_branch().iter().any(|field| inner(cx, *field, ty))
             },
             ty::Adt(def, _) if def.is_union() => false,
-            ty::Adt(def, substs) if def.is_enum() => {
+            ty::Adt(def, args) if def.is_enum() => {
                 let (&variant_index, fields) = val.unwrap_branch().split_first().unwrap();
                 let variant_index =
                     VariantIdx::from_u32(variant_index.unwrap_leaf().try_to_u32().ok().unwrap());
@@ -166,10 +166,10 @@ fn is_value_unfrozen_raw<'tcx>(
                     def.variants()[variant_index]
                         .fields
                         .iter()
-                        .map(|field| field.ty(cx.tcx, substs))).any(|(field, ty)| inner(cx, field, ty))
+                        .map(|field| field.ty(cx.tcx, args))).any(|(field, ty)| inner(cx, field, ty))
             }
-            ty::Adt(def, substs) => {
-                val.unwrap_branch().iter().zip(def.non_enum_variant().fields.iter().map(|field| field.ty(cx.tcx, substs))).any(|(field, ty)| inner(cx, *field, ty))
+            ty::Adt(def, args) => {
+                val.unwrap_branch().iter().zip(def.non_enum_variant().fields.iter().map(|field| field.ty(cx.tcx, args))).any(|(field, ty)| inner(cx, *field, ty))
             }
             ty::Tuple(tys) => val.unwrap_branch().iter().zip(tys).any(|(field, ty)| inner(cx, *field, ty)),
             _ => false,
@@ -206,8 +206,8 @@ fn is_value_unfrozen_raw<'tcx>(
 
 fn is_value_unfrozen_poly<'tcx>(cx: &LateContext<'tcx>, body_id: BodyId, ty: Ty<'tcx>) -> bool {
     let def_id = body_id.hir_id.owner.to_def_id();
-    let substs = ty::InternalSubsts::identity_for_item(cx.tcx, def_id);
-    let instance = ty::Instance::new(def_id, substs);
+    let args = ty::GenericArgs::identity_for_item(cx.tcx, def_id);
+    let instance = ty::Instance::new(def_id, args);
     let cid = rustc_middle::mir::interpret::GlobalId { instance, promoted: None };
     let param_env = cx.tcx.param_env(def_id).with_reveal_all_normalized(cx.tcx);
     let result = cx.tcx.const_eval_global_id_for_typeck(param_env, cid, None);
@@ -215,9 +215,9 @@ fn is_value_unfrozen_poly<'tcx>(cx: &LateContext<'tcx>, body_id: BodyId, ty: Ty<
 }
 
 fn is_value_unfrozen_expr<'tcx>(cx: &LateContext<'tcx>, hir_id: HirId, def_id: DefId, ty: Ty<'tcx>) -> bool {
-    let substs = cx.typeck_results().node_substs(hir_id);
+    let args = cx.typeck_results().node_args(hir_id);
 
-    let result = const_eval_resolve(cx.tcx, cx.param_env, ty::UnevaluatedConst::new(def_id, substs), None);
+    let result = const_eval_resolve(cx.tcx, cx.param_env, ty::UnevaluatedConst::new(def_id, args), None);
     is_value_unfrozen_raw(cx, result, ty)
 }
 
@@ -228,7 +228,7 @@ pub fn const_eval_resolve<'tcx>(
     ct: ty::UnevaluatedConst<'tcx>,
     span: Option<Span>,
 ) -> EvalToValTreeResult<'tcx> {
-    match ty::Instance::resolve(tcx, param_env, ct.def, ct.substs) {
+    match ty::Instance::resolve(tcx, param_env, ct.def, ct.args) {
         Ok(Some(instance)) => {
             let cid = GlobalId { instance, promoted: None };
             tcx.const_eval_global_id_for_typeck(param_env, cid, span)
@@ -347,7 +347,7 @@ impl<'tcx> LateLintPass<'tcx> for NonCopyConst {
                                 // and, in that case, the definition is *not* generic.
                                 cx.tcx.normalize_erasing_regions(
                                     cx.tcx.param_env(of_trait_def_id),
-                                    cx.tcx.type_of(of_assoc_item).subst_identity(),
+                                    cx.tcx.type_of(of_assoc_item).instantiate_identity(),
                                 ),
                             ))
                             .is_err();
diff --git a/src/tools/clippy/clippy_lints/src/non_send_fields_in_send_ty.rs b/src/tools/clippy/clippy_lints/src/non_send_fields_in_send_ty.rs
index 7eaa7db78a470..c5e777c207028 100644
--- a/src/tools/clippy/clippy_lints/src/non_send_fields_in_send_ty.rs
+++ b/src/tools/clippy/clippy_lints/src/non_send_fields_in_send_ty.rs
@@ -7,7 +7,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::{FieldDef, Item, ItemKind, Node};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
+use rustc_middle::ty::{self, GenericArgKind, Ty};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::sym;
 
@@ -90,8 +90,8 @@ impl<'tcx> LateLintPass<'tcx> for NonSendFieldInSendTy {
             if send_trait == trait_id;
             if hir_impl.polarity == ImplPolarity::Positive;
             if let Some(ty_trait_ref) = cx.tcx.impl_trait_ref(item.owner_id);
-            if let self_ty = ty_trait_ref.subst_identity().self_ty();
-            if let ty::Adt(adt_def, impl_trait_substs) = self_ty.kind();
+            if let self_ty = ty_trait_ref.instantiate_identity().self_ty();
+            if let ty::Adt(adt_def, impl_trait_args) = self_ty.kind();
             then {
                 let mut non_send_fields = Vec::new();
 
@@ -104,7 +104,7 @@ impl<'tcx> LateLintPass<'tcx> for NonSendFieldInSendTy {
                                 .as_local()
                                 .map(|local_def_id| hir_map.local_def_id_to_hir_id(local_def_id));
                             if !is_lint_allowed(cx, NON_SEND_FIELDS_IN_SEND_TY, field_hir_id);
-                            if let field_ty = field.ty(cx.tcx, impl_trait_substs);
+                            if let field_ty = field.ty(cx.tcx, impl_trait_args);
                             if !ty_allowed_in_send(cx, field_ty, send_trait);
                             if let Node::Field(field_def) = hir_map.get(field_hir_id);
                             then {
@@ -206,10 +206,10 @@ fn ty_allowed_with_raw_pointer_heuristic<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'t
             .iter()
             .all(|ty| ty_allowed_with_raw_pointer_heuristic(cx, ty, send_trait)),
         ty::Array(ty, _) | ty::Slice(ty) => ty_allowed_with_raw_pointer_heuristic(cx, *ty, send_trait),
-        ty::Adt(_, substs) => {
+        ty::Adt(_, args) => {
             if contains_pointer_like(cx, ty) {
                 // descends only if ADT contains any raw pointers
-                substs.iter().all(|generic_arg| match generic_arg.unpack() {
+                args.iter().all(|generic_arg| match generic_arg.unpack() {
                     GenericArgKind::Type(ty) => ty_allowed_with_raw_pointer_heuristic(cx, ty, send_trait),
                     // Lifetimes and const generics are not solid part of ADT and ignored
                     GenericArgKind::Lifetime(_) | GenericArgKind::Const(_) => true,
@@ -224,7 +224,7 @@ fn ty_allowed_with_raw_pointer_heuristic<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'t
     }
 }
 
-/// Checks if the type contains any pointer-like types in substs (including nested ones)
+/// Checks if the type contains any pointer-like types in args (including nested ones)
 fn contains_pointer_like<'tcx>(cx: &LateContext<'tcx>, target_ty: Ty<'tcx>) -> bool {
     for ty_node in target_ty.walk() {
         if let GenericArgKind::Type(inner_ty) = ty_node.unpack() {
diff --git a/src/tools/clippy/clippy_lints/src/only_used_in_recursion.rs b/src/tools/clippy/clippy_lints/src/only_used_in_recursion.rs
index 8b77a5c99f767..3615c7ec9bff0 100644
--- a/src/tools/clippy/clippy_lints/src/only_used_in_recursion.rs
+++ b/src/tools/clippy/clippy_lints/src/only_used_in_recursion.rs
@@ -7,7 +7,7 @@ use rustc_hir::def_id::DefId;
 use rustc_hir::hir_id::HirIdMap;
 use rustc_hir::{Body, Expr, ExprKind, HirId, ImplItem, ImplItemKind, Node, PatKind, TraitItem, TraitItemKind};
 use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::ty::subst::{EarlyBinder, GenericArgKind, SubstsRef};
+use rustc_middle::ty::{EarlyBinder, GenericArgKind, GenericArgsRef};
 use rustc_middle::ty::{self, ConstKind};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::symbol::{kw, Ident};
@@ -90,7 +90,7 @@ impl_lint_pass!(OnlyUsedInRecursion => [ONLY_USED_IN_RECURSION]);
 enum FnKind {
     Fn,
     TraitFn,
-    // This is a hack. Ideally we would store a `SubstsRef<'tcx>` type here, but a lint pass must be `'static`.
+    // This is a hack. Ideally we would store a `GenericArgsRef<'tcx>` type here, but a lint pass must be `'static`.
     // Substitutions are, however, interned. This allows us to store the pointer as a `usize` when comparing for
     // equality.
     ImplTraitFn(usize),
@@ -244,12 +244,12 @@ impl<'tcx> LateLintPass<'tcx> for OnlyUsedInRecursion {
             })) => {
                 #[allow(trivial_casts)]
                 if let Some(Node::Item(item)) = get_parent_node(cx.tcx, owner_id.into())
-                    && let Some(trait_ref) = cx.tcx.impl_trait_ref(item.owner_id).map(EarlyBinder::subst_identity)
+                    && let Some(trait_ref) = cx.tcx.impl_trait_ref(item.owner_id).map(EarlyBinder::instantiate_identity)
                     && let Some(trait_item_id) = cx.tcx.associated_item(owner_id).trait_item_def_id
                 {
                     (
                         trait_item_id,
-                        FnKind::ImplTraitFn(cx.tcx.erase_regions(trait_ref.substs) as *const _ as usize),
+                        FnKind::ImplTraitFn(cx.tcx.erase_regions(trait_ref.args) as *const _ as usize),
                         usize::from(sig.decl.implicit_self.has_implicit_self()),
                     )
                 } else {
@@ -289,7 +289,7 @@ impl<'tcx> LateLintPass<'tcx> for OnlyUsedInRecursion {
                         ExprKind::Call(callee, args)
                             if path_def_id(cx, callee).map_or(false, |id| {
                                 id == param.fn_id
-                                    && has_matching_substs(param.fn_kind, typeck.node_substs(callee.hir_id))
+                                    && has_matching_args(param.fn_kind, typeck.node_args(callee.hir_id))
                             }) =>
                         {
                             if let Some(idx) = args.iter().position(|arg| arg.hir_id == child_id) {
@@ -300,7 +300,7 @@ impl<'tcx> LateLintPass<'tcx> for OnlyUsedInRecursion {
                         ExprKind::MethodCall(_, receiver, args, _)
                             if typeck.type_dependent_def_id(parent.hir_id).map_or(false, |id| {
                                 id == param.fn_id
-                                    && has_matching_substs(param.fn_kind, typeck.node_substs(parent.hir_id))
+                                    && has_matching_args(param.fn_kind, typeck.node_args(parent.hir_id))
                             }) =>
                         {
                             if let Some(idx) = iter::once(receiver).chain(args).position(|arg| arg.hir_id == child_id) {
@@ -381,15 +381,15 @@ impl<'tcx> LateLintPass<'tcx> for OnlyUsedInRecursion {
     }
 }
 
-fn has_matching_substs(kind: FnKind, substs: SubstsRef<'_>) -> bool {
+fn has_matching_args(kind: FnKind, args: GenericArgsRef<'_>) -> bool {
     match kind {
         FnKind::Fn => true,
-        FnKind::TraitFn => substs.iter().enumerate().all(|(idx, subst)| match subst.unpack() {
+        FnKind::TraitFn => args.iter().enumerate().all(|(idx, subst)| match subst.unpack() {
             GenericArgKind::Lifetime(_) => true,
             GenericArgKind::Type(ty) => matches!(*ty.kind(), ty::Param(ty) if ty.index as usize == idx),
             GenericArgKind::Const(c) => matches!(c.kind(), ConstKind::Param(c) if c.index as usize == idx),
         }),
         #[allow(trivial_casts)]
-        FnKind::ImplTraitFn(expected_substs) => substs as *const _ as usize == expected_substs,
+        FnKind::ImplTraitFn(expected_args) => args as *const _ as usize == expected_args,
     }
 }
diff --git a/src/tools/clippy/clippy_lints/src/pass_by_ref_or_value.rs b/src/tools/clippy/clippy_lints/src/pass_by_ref_or_value.rs
index eab725de17f68..7b4812e98d8a7 100644
--- a/src/tools/clippy/clippy_lints/src/pass_by_ref_or_value.rs
+++ b/src/tools/clippy/clippy_lints/src/pass_by_ref_or_value.rs
@@ -143,7 +143,7 @@ impl<'tcx> PassByRefOrValue {
             return;
         }
 
-        let fn_sig = cx.tcx.fn_sig(def_id).subst_identity();
+        let fn_sig = cx.tcx.fn_sig(def_id).instantiate_identity();
         let fn_body = cx.enclosing_body.map(|id| cx.tcx.hir().body(id));
 
         // Gather all the lifetimes found in the output type which may affect whether
diff --git a/src/tools/clippy/clippy_lints/src/ptr.rs b/src/tools/clippy/clippy_lints/src/ptr.rs
index 32213718b270d..eb7c008c7a4d2 100644
--- a/src/tools/clippy/clippy_lints/src/ptr.rs
+++ b/src/tools/clippy/clippy_lints/src/ptr.rs
@@ -166,7 +166,7 @@ impl<'tcx> LateLintPass<'tcx> for Ptr {
             check_mut_from_ref(cx, sig, None);
             for arg in check_fn_args(
                 cx,
-                cx.tcx.fn_sig(item.owner_id).subst_identity().skip_binder().inputs(),
+                cx.tcx.fn_sig(item.owner_id).instantiate_identity().skip_binder().inputs(),
                 sig.decl.inputs,
                 &sig.decl.output,
                 &[],
@@ -220,7 +220,7 @@ impl<'tcx> LateLintPass<'tcx> for Ptr {
 
         check_mut_from_ref(cx, sig, Some(body));
         let decl = sig.decl;
-        let sig = cx.tcx.fn_sig(item_id).subst_identity().skip_binder();
+        let sig = cx.tcx.fn_sig(item_id).instantiate_identity().skip_binder();
         let lint_args: Vec<_> = check_fn_args(cx, sig.inputs(), decl.inputs, &decl.output, body.params)
             .filter(|arg| !is_trait_item || arg.mutability() == Mutability::Not)
             .collect();
@@ -423,7 +423,7 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
         .enumerate()
         .filter_map(move |(i, (ty, hir_ty))| {
             if let ty::Ref(_, ty, mutability) = *ty.kind()
-                && let  ty::Adt(adt, substs) = *ty.kind()
+                && let  ty::Adt(adt, args) = *ty.kind()
                 && let TyKind::Ref(lt, ref ty) = hir_ty.kind
                 && let TyKind::Path(QPath::Resolved(None, path)) = ty.ty.kind
                 // Check that the name as typed matches the actual name of the type.
@@ -443,7 +443,7 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
                                     } else {
                                         None
                                     }),
-                                substs.type_at(0),
+                                args.type_at(0),
                             ),
                         ),
                         _ if Some(adt.did()) == cx.tcx.lang_items().string() => (
@@ -496,7 +496,7 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
                                 }
 
                                 let ty_name =
-                                    snippet_opt(cx, ty.span()).unwrap_or_else(|| substs.type_at(1).to_string());
+                                    snippet_opt(cx, ty.span()).unwrap_or_else(|| args.type_at(1).to_string());
 
                                 span_lint_hir_and_then(
                                     cx,
@@ -659,7 +659,7 @@ fn check_ptr_arg_usage<'tcx>(cx: &LateContext<'tcx>, body: &'tcx Body<'_>, args:
                             return;
                         };
 
-                        match *self.cx.tcx.fn_sig(id).subst_identity().skip_binder().inputs()[i]
+                        match *self.cx.tcx.fn_sig(id).instantiate_identity().skip_binder().inputs()[i]
                             .peel_refs()
                             .kind()
                         {
@@ -725,7 +725,7 @@ fn matches_preds<'tcx>(
     let infcx = cx.tcx.infer_ctxt().build();
     preds.iter().all(|&p| match cx.tcx.erase_late_bound_regions(p) {
         ExistentialPredicate::Trait(p) => infcx
-            .type_implements_trait(p.def_id, [ty.into()].into_iter().chain(p.substs.iter()), cx.param_env)
+            .type_implements_trait(p.def_id, [ty.into()].into_iter().chain(p.args.iter()), cx.param_env)
             .must_apply_modulo_regions(),
         ExistentialPredicate::Projection(p) => infcx.predicate_must_hold_modulo_regions(&Obligation::new(
             cx.tcx,
diff --git a/src/tools/clippy/clippy_lints/src/redundant_slicing.rs b/src/tools/clippy/clippy_lints/src/redundant_slicing.rs
index c70ce83a9c45d..2b65c08d25d1d 100644
--- a/src/tools/clippy/clippy_lints/src/redundant_slicing.rs
+++ b/src/tools/clippy/clippy_lints/src/redundant_slicing.rs
@@ -9,7 +9,7 @@ use rustc_hir::{BorrowKind, Expr, ExprKind, LangItem, Mutability};
 use rustc_lint::{LateContext, LateLintPass, Lint};
 use rustc_middle::ty::Ty;
 use rustc_middle::ty::adjustment::{Adjust, AutoBorrow, AutoBorrowMutability};
-use rustc_middle::ty::subst::GenericArg;
+use rustc_middle::ty::GenericArg;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
@@ -135,7 +135,7 @@ impl<'tcx> LateLintPass<'tcx> for RedundantSlicing {
                 } else if let Some(target_id) = cx.tcx.lang_items().deref_target() {
                     if let Ok(deref_ty) = cx.tcx.try_normalize_erasing_regions(
                         cx.param_env,
-                        Ty::new_projection(cx.tcx,target_id, cx.tcx.mk_substs(&[GenericArg::from(indexed_ty)])),
+                        Ty::new_projection(cx.tcx,target_id, cx.tcx.mk_args(&[GenericArg::from(indexed_ty)])),
                     ) {
                         if deref_ty == expr_ty {
                             let snip = snippet_with_context(cx, indexed.span, ctxt, "..", &mut app).0;
diff --git a/src/tools/clippy/clippy_lints/src/returns.rs b/src/tools/clippy/clippy_lints/src/returns.rs
index 958351ad81bb7..4977df6c83f31 100644
--- a/src/tools/clippy/clippy_lints/src/returns.rs
+++ b/src/tools/clippy/clippy_lints/src/returns.rs
@@ -9,7 +9,7 @@ use rustc_hir::intravisit::FnKind;
 use rustc_hir::{Block, Body, Expr, ExprKind, FnDecl, LangItem, MatchSource, PatKind, QPath, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, subst::GenericArgKind, Ty};
+use rustc_middle::ty::{self, GenericArgKind, Ty};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::def_id::LocalDefId;
 use rustc_span::source_map::Span;
@@ -333,7 +333,7 @@ fn last_statement_borrows<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>)
             && cx
                 .tcx
                 .fn_sig(def_id)
-                .subst_identity()
+                .instantiate_identity()
                 .skip_binder()
                 .output()
                 .walk()
diff --git a/src/tools/clippy/clippy_lints/src/self_named_constructors.rs b/src/tools/clippy/clippy_lints/src/self_named_constructors.rs
index beca203c868d8..b92014f68b396 100644
--- a/src/tools/clippy/clippy_lints/src/self_named_constructors.rs
+++ b/src/tools/clippy/clippy_lints/src/self_named_constructors.rs
@@ -53,7 +53,7 @@ impl<'tcx> LateLintPass<'tcx> for SelfNamedConstructors {
 
         let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id()).def_id;
         let item = cx.tcx.hir().expect_item(parent);
-        let self_ty = cx.tcx.type_of(item.owner_id).subst_identity();
+        let self_ty = cx.tcx.type_of(item.owner_id).instantiate_identity();
         let ret_ty = return_ty(cx, impl_item.owner_id);
 
         // Do not check trait impls
diff --git a/src/tools/clippy/clippy_lints/src/significant_drop_tightening.rs b/src/tools/clippy/clippy_lints/src/significant_drop_tightening.rs
index fffa8a380c2f8..1493ad44ee555 100644
--- a/src/tools/clippy/clippy_lints/src/significant_drop_tightening.rs
+++ b/src/tools/clippy/clippy_lints/src/significant_drop_tightening.rs
@@ -10,7 +10,7 @@ use rustc_hir::{
     intravisit::{walk_expr, Visitor},
 };
 use rustc_lint::{LateContext, LateLintPass, LintContext};
-use rustc_middle::ty::{subst::GenericArgKind, Ty, TypeAndMut};
+use rustc_middle::ty::{GenericArgKind, Ty, TypeAndMut};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::{symbol::Ident, Span, DUMMY_SP};
 use std::borrow::Cow;
diff --git a/src/tools/clippy/clippy_lints/src/size_of_in_element_count.rs b/src/tools/clippy/clippy_lints/src/size_of_in_element_count.rs
index ac4e29e9dfdfa..80c834066bbc5 100644
--- a/src/tools/clippy/clippy_lints/src/size_of_in_element_count.rs
+++ b/src/tools/clippy/clippy_lints/src/size_of_in_element_count.rs
@@ -47,7 +47,7 @@ fn get_size_of_ty<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, inverted:
                 if let Some(def_id) = cx.qpath_res(count_func_qpath, count_func.hir_id).opt_def_id();
                 if matches!(cx.tcx.get_diagnostic_name(def_id), Some(sym::mem_size_of | sym::mem_size_of_val));
                 then {
-                    cx.typeck_results().node_substs(count_func.hir_id).types().next()
+                    cx.typeck_results().node_args(count_func.hir_id).types().next()
                 } else {
                     None
                 }
@@ -101,7 +101,7 @@ fn get_pointee_ty_and_count_expr<'tcx>(
         if FUNCTIONS.iter().any(|func_path| match_def_path(cx, def_id, func_path));
 
         // Get the pointee type
-        if let Some(pointee_ty) = cx.typeck_results().node_substs(func.hir_id).types().next();
+        if let Some(pointee_ty) = cx.typeck_results().node_args(func.hir_id).types().next();
         then {
             return Some((pointee_ty, count));
         }
diff --git a/src/tools/clippy/clippy_lints/src/transmute/transmute_undefined_repr.rs b/src/tools/clippy/clippy_lints/src/transmute/transmute_undefined_repr.rs
index 5e24213d07fd2..9e5d766242647 100644
--- a/src/tools/clippy/clippy_lints/src/transmute/transmute_undefined_repr.rs
+++ b/src/tools/clippy/clippy_lints/src/transmute/transmute_undefined_repr.rs
@@ -3,7 +3,7 @@ use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::is_c_void;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
-use rustc_middle::ty::SubstsRef;
+use rustc_middle::ty::GenericArgsRef;
 use rustc_middle::ty::{self, IntTy, Ty, TypeAndMut, UintTy};
 
 #[expect(clippy::too_many_lines)]
@@ -268,12 +268,12 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
                 }
                 ReducedTy::UnorderedFields(ty)
             },
-            ty::Adt(def, substs) if def.is_struct() => {
+            ty::Adt(def, args) if def.is_struct() => {
                 let mut iter = def
                     .non_enum_variant()
                     .fields
                     .iter()
-                    .map(|f| cx.tcx.type_of(f.did).subst(cx.tcx, substs));
+                    .map(|f| cx.tcx.type_of(f.did).instantiate(cx.tcx, args));
                 let Some(sized_ty) = iter.find(|&ty| !is_zero_sized_ty(cx, ty)) else {
                     return ReducedTy::TypeErasure { raw_ptr_only: false };
                 };
@@ -322,7 +322,7 @@ fn is_size_pair(ty: Ty<'_>) -> bool {
     }
 }
 
-fn same_except_params<'tcx>(subs1: SubstsRef<'tcx>, subs2: SubstsRef<'tcx>) -> bool {
+fn same_except_params<'tcx>(subs1: GenericArgsRef<'tcx>, subs2: GenericArgsRef<'tcx>) -> bool {
     // TODO: check const parameters as well. Currently this will consider `Array<5>` the same as
     // `Array<6>`
     for (ty1, ty2) in subs1.types().zip(subs2.types()).filter(|(ty1, ty2)| ty1 != ty2) {
diff --git a/src/tools/clippy/clippy_lints/src/transmute/unsound_collection_transmute.rs b/src/tools/clippy/clippy_lints/src/transmute/unsound_collection_transmute.rs
index b1445311b7112..891fefc17a64b 100644
--- a/src/tools/clippy/clippy_lints/src/transmute/unsound_collection_transmute.rs
+++ b/src/tools/clippy/clippy_lints/src/transmute/unsound_collection_transmute.rs
@@ -10,7 +10,7 @@ use rustc_span::symbol::sym;
 /// Returns `true` if it's triggered, otherwise returns `false`.
 pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> bool {
     match (&from_ty.kind(), &to_ty.kind()) {
-        (ty::Adt(from_adt, from_substs), ty::Adt(to_adt, to_substs)) => {
+        (ty::Adt(from_adt, from_args), ty::Adt(to_adt, to_args)) => {
             if from_adt.did() != to_adt.did() {
                 return false;
             }
@@ -28,9 +28,9 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty
             ) {
                 return false;
             }
-            if from_substs
+            if from_args
                 .types()
-                .zip(to_substs.types())
+                .zip(to_args.types())
                 .any(|(from_ty, to_ty)| is_layout_incompatible(cx, from_ty, to_ty))
             {
                 span_lint(
diff --git a/src/tools/clippy/clippy_lints/src/uninit_vec.rs b/src/tools/clippy/clippy_lints/src/uninit_vec.rs
index 1ab0162a88134..6756df8e716ca 100644
--- a/src/tools/clippy/clippy_lints/src/uninit_vec.rs
+++ b/src/tools/clippy/clippy_lints/src/uninit_vec.rs
@@ -88,7 +88,7 @@ fn handle_uninit_vec_pair<'tcx>(
         if let Some((set_len_self, call_span)) = extract_set_len_self(cx, maybe_set_len);
         if vec.location.eq_expr(cx, set_len_self);
         if let ty::Ref(_, vec_ty, _) = cx.typeck_results().expr_ty_adjusted(set_len_self).kind();
-        if let ty::Adt(_, substs) = vec_ty.kind();
+        if let ty::Adt(_, args) = vec_ty.kind();
         // `#[allow(...)]` attribute can be set on enclosing unsafe block of `set_len()`
         if !is_lint_allowed(cx, UNINIT_VEC, maybe_set_len.hir_id);
         then {
@@ -96,7 +96,7 @@ fn handle_uninit_vec_pair<'tcx>(
                 // with_capacity / reserve -> set_len
 
                 // Check T of Vec<T>
-                if !is_uninit_value_valid_for_ty(cx, substs.type_at(0)) {
+                if !is_uninit_value_valid_for_ty(cx, args.type_at(0)) {
                     // FIXME: #7698, false positive of the internal lints
                     #[expect(clippy::collapsible_span_lint_calls)]
                     span_lint_and_then(
diff --git a/src/tools/clippy/clippy_lints/src/unit_return_expecting_ord.rs b/src/tools/clippy/clippy_lints/src/unit_return_expecting_ord.rs
index 99a1d197678bb..dd829ded0d0d6 100644
--- a/src/tools/clippy/clippy_lints/src/unit_return_expecting_ord.rs
+++ b/src/tools/clippy/clippy_lints/src/unit_return_expecting_ord.rs
@@ -65,7 +65,7 @@ fn get_projection_pred<'tcx>(
     generics.predicates.iter().find_map(|(proj_pred, _)| {
         if let ClauseKind::Projection(pred) = proj_pred.kind().skip_binder() {
             let projection_pred = cx.tcx.erase_late_bound_regions(proj_pred.kind().rebind(pred));
-            if projection_pred.projection_ty.substs == trait_pred.trait_ref.substs {
+            if projection_pred.projection_ty.args == trait_pred.trait_ref.args {
                 return Some(projection_pred);
             }
         }
@@ -76,7 +76,7 @@ fn get_projection_pred<'tcx>(
 fn get_args_to_check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Vec<(usize, String)> {
     let mut args_to_check = Vec::new();
     if let Some(def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id) {
-        let fn_sig = cx.tcx.fn_sig(def_id).subst_identity();
+        let fn_sig = cx.tcx.fn_sig(def_id).instantiate_identity();
         let generics = cx.tcx.predicates_of(def_id);
         let fn_mut_preds = get_trait_predicates_for_trait_id(cx, generics, cx.tcx.lang_items().fn_mut_trait());
         let ord_preds = get_trait_predicates_for_trait_id(cx, generics, cx.tcx.get_diagnostic_item(sym::Ord));
@@ -120,8 +120,8 @@ fn get_args_to_check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) -> Ve
 fn check_arg<'tcx>(cx: &LateContext<'tcx>, arg: &'tcx Expr<'tcx>) -> Option<(Span, Option<Span>)> {
     if_chain! {
         if let ExprKind::Closure(&Closure { body, fn_decl_span, .. }) = arg.kind;
-        if let ty::Closure(_def_id, substs) = &cx.typeck_results().node_type(arg.hir_id).kind();
-        let ret_ty = substs.as_closure().sig().output();
+        if let ty::Closure(_def_id, args) = &cx.typeck_results().node_type(arg.hir_id).kind();
+        let ret_ty = args.as_closure().sig().output();
         let ty = cx.tcx.erase_late_bound_regions(ret_ty);
         if ty.is_unit();
         then {
diff --git a/src/tools/clippy/clippy_lints/src/unit_types/let_unit_value.rs b/src/tools/clippy/clippy_lints/src/unit_types/let_unit_value.rs
index cc7c2b039f2d7..704d7abd7e55a 100644
--- a/src/tools/clippy/clippy_lints/src/unit_types/let_unit_value.rs
+++ b/src/tools/clippy/clippy_lints/src/unit_types/let_unit_value.rs
@@ -161,7 +161,7 @@ fn needs_inferred_result_ty(
         },
         _ => return false,
     };
-    let sig = cx.tcx.fn_sig(id).subst_identity().skip_binder();
+    let sig = cx.tcx.fn_sig(id).instantiate_identity().skip_binder();
     if let ty::Param(output_ty) = *sig.output().kind() {
         let args: Vec<&Expr<'_>> = if let Some(receiver) = receiver {
             std::iter::once(receiver).chain(args.iter()).collect()
diff --git a/src/tools/clippy/clippy_lints/src/unnamed_address.rs b/src/tools/clippy/clippy_lints/src/unnamed_address.rs
index 0f5cdb6aaea17..dea8a1e35bbba 100644
--- a/src/tools/clippy/clippy_lints/src/unnamed_address.rs
+++ b/src/tools/clippy/clippy_lints/src/unnamed_address.rs
@@ -97,7 +97,7 @@ impl LateLintPass<'_> for UnnamedAddress {
             if let ExprKind::Path(ref func_qpath) = func.kind;
             if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id();
             if match_def_path(cx, def_id, &paths::PTR_EQ);
-            let ty_param = cx.typeck_results().node_substs(func.hir_id).type_at(0);
+            let ty_param = cx.typeck_results().node_args(func.hir_id).type_at(0);
             if ty_param.is_trait();
             then {
                 span_lint_and_help(
diff --git a/src/tools/clippy/clippy_lints/src/use_self.rs b/src/tools/clippy/clippy_lints/src/use_self.rs
index 5a02987453c41..81dc426b38991 100644
--- a/src/tools/clippy/clippy_lints/src/use_self.rs
+++ b/src/tools/clippy/clippy_lints/src/use_self.rs
@@ -145,7 +145,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
             then {
                 // `self_ty` is the semantic self type of `impl <trait> for <type>`. This cannot be
                 // `Self`.
-                let self_ty = impl_trait_ref.subst_identity().self_ty();
+                let self_ty = impl_trait_ref.instantiate_identity().self_ty();
 
                 // `trait_method_sig` is the signature of the function, how it is declared in the
                 // trait, not in the impl of the trait.
@@ -154,7 +154,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
                     .associated_item(impl_item.owner_id)
                     .trait_item_def_id
                     .expect("impl method matches a trait method");
-                let trait_method_sig = cx.tcx.fn_sig(trait_method).subst_identity();
+                let trait_method_sig = cx.tcx.fn_sig(trait_method).instantiate_identity();
                 let trait_method_sig = cx.tcx.erase_late_bound_regions(trait_method_sig);
 
                 // `impl_inputs_outputs` is an iterator over the types (`hir::Ty`) declared in the
@@ -226,7 +226,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
             } else {
                 hir_ty_to_ty(cx.tcx, hir_ty)
             };
-            if same_type_and_consts(ty, cx.tcx.type_of(impl_id).subst_identity());
+            if same_type_and_consts(ty, cx.tcx.type_of(impl_id).instantiate_identity());
             then {
                 span_lint(cx, hir_ty.span);
             }
@@ -238,7 +238,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
             if !expr.span.from_expansion();
             if self.msrv.meets(msrvs::TYPE_ALIAS_ENUM_VARIANTS);
             if let Some(&StackItem::Check { impl_id, .. }) = self.stack.last();
-            if cx.typeck_results().expr_ty(expr) == cx.tcx.type_of(impl_id).subst_identity();
+            if cx.typeck_results().expr_ty(expr) == cx.tcx.type_of(impl_id).instantiate_identity();
             then {} else { return; }
         }
         match expr.kind {
@@ -262,7 +262,7 @@ impl<'tcx> LateLintPass<'tcx> for UseSelf {
             if let PatKind::Path(QPath::Resolved(_, path))
                  | PatKind::TupleStruct(QPath::Resolved(_, path), _, _)
                  | PatKind::Struct(QPath::Resolved(_, path), _, _) = pat.kind;
-            if cx.typeck_results().pat_ty(pat) == cx.tcx.type_of(impl_id).subst_identity();
+            if cx.typeck_results().pat_ty(pat) == cx.tcx.type_of(impl_id).instantiate_identity();
             then {
                 check_path(cx, path);
             }
diff --git a/src/tools/clippy/clippy_lints/src/useless_conversion.rs b/src/tools/clippy/clippy_lints/src/useless_conversion.rs
index b6c11cfb35568..98f7bfb4ba15a 100644
--- a/src/tools/clippy/clippy_lints/src/useless_conversion.rs
+++ b/src/tools/clippy/clippy_lints/src/useless_conversion.rs
@@ -227,8 +227,8 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
                     let a = cx.typeck_results().expr_ty(e);
                     let b = cx.typeck_results().expr_ty(recv);
                     if is_type_diagnostic_item(cx, a, sym::Result);
-                    if let ty::Adt(_, substs) = a.kind();
-                    if let Some(a_type) = substs.types().next();
+                    if let ty::Adt(_, args) = a.kind();
+                    if let Some(a_type) = args.types().next();
                     if same_type_and_consts(a_type, b);
 
                     then {
@@ -255,8 +255,8 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
                         if_chain! {
                             if match_def_path(cx, def_id, &paths::TRY_FROM);
                             if is_type_diagnostic_item(cx, a, sym::Result);
-                            if let ty::Adt(_, substs) = a.kind();
-                            if let Some(a_type) = substs.types().next();
+                            if let ty::Adt(_, args) = a.kind();
+                            if let Some(a_type) = args.types().next();
                             if same_type_and_consts(a_type, b);
 
                             then {
diff --git a/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs b/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs
index dced9fcf9abd3..da8654d9388d3 100644
--- a/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs
@@ -78,7 +78,7 @@ impl<'tcx> LateLintPass<'tcx> for InterningDefinedSymbol {
                 for item in cx.tcx.module_children(def_id) {
                     if_chain! {
                         if let Res::Def(DefKind::Const, item_def_id) = item.res;
-                        let ty = cx.tcx.type_of(item_def_id).subst_identity();
+                        let ty = cx.tcx.type_of(item_def_id).instantiate_identity();
                         if match_type(cx, ty, &paths::SYMBOL);
                         if let Ok(ConstValue::Scalar(value)) = cx.tcx.const_eval_poly(item_def_id);
                         if let Ok(value) = value.to_u32();
diff --git a/src/tools/clippy/clippy_lints/src/utils/internal_lints/msrv_attr_impl.rs b/src/tools/clippy/clippy_lints/src/utils/internal_lints/msrv_attr_impl.rs
index 09f0f0d0adb6f..bf835f89cfc7f 100644
--- a/src/tools/clippy/clippy_lints/src/utils/internal_lints/msrv_attr_impl.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/internal_lints/msrv_attr_impl.rs
@@ -7,7 +7,7 @@ use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_hir_analysis::hir_ty_to_ty;
 use rustc_lint::{LateContext, LateLintPass, LintContext};
-use rustc_middle::ty::{self, subst::GenericArgKind};
+use rustc_middle::ty::{self, GenericArgKind};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
@@ -39,7 +39,7 @@ impl LateLintPass<'_> for MsrvAttrImpl {
             if self_ty_def.all_fields().any(|f| {
                 cx.tcx
                     .type_of(f.did)
-                    .subst_identity()
+                    .instantiate_identity()
                     .walk()
                     .filter(|t| matches!(t.unpack(), GenericArgKind::Type(_)))
                     .any(|t| match_type(cx, t.expect_ty(), &paths::MSRV))
diff --git a/src/tools/clippy/clippy_lints/src/utils/internal_lints/unnecessary_def_path.rs b/src/tools/clippy/clippy_lints/src/utils/internal_lints/unnecessary_def_path.rs
index 00842376628cc..f66f33fee1669 100644
--- a/src/tools/clippy/clippy_lints/src/utils/internal_lints/unnecessary_def_path.rs
+++ b/src/tools/clippy/clippy_lints/src/utils/internal_lints/unnecessary_def_path.rs
@@ -229,11 +229,11 @@ fn path_to_matched_type(cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> Option<Ve
             Res::Def(DefKind::Static(_), def_id) => read_mir_alloc_def_path(
                 cx,
                 cx.tcx.eval_static_initializer(def_id).ok()?.inner(),
-                cx.tcx.type_of(def_id).subst_identity(),
+                cx.tcx.type_of(def_id).instantiate_identity(),
             ),
             Res::Def(DefKind::Const, def_id) => match cx.tcx.const_eval_poly(def_id).ok()? {
                 ConstValue::ByRef { alloc, offset } if offset.bytes() == 0 => {
-                    read_mir_alloc_def_path(cx, alloc.inner(), cx.tcx.type_of(def_id).subst_identity())
+                    read_mir_alloc_def_path(cx, alloc.inner(), cx.tcx.type_of(def_id).instantiate_identity())
                 },
                 _ => None,
             },
diff --git a/src/tools/clippy/clippy_lints/src/vec.rs b/src/tools/clippy/clippy_lints/src/vec.rs
index 2a594e750b9b2..d1bf292d71123 100644
--- a/src/tools/clippy/clippy_lints/src/vec.rs
+++ b/src/tools/clippy/clippy_lints/src/vec.rs
@@ -230,8 +230,8 @@ fn size_of(cx: &LateContext<'_>, expr: &Expr<'_>) -> u64 {
 
 /// Returns the item type of the vector (i.e., the `T` in `Vec<T>`).
 fn vec_type(ty: Ty<'_>) -> Ty<'_> {
-    if let ty::Adt(_, substs) = ty.kind() {
-        substs.type_at(0)
+    if let ty::Adt(_, args) = ty.kind() {
+        args.type_at(0)
     } else {
         panic!("The type of `vec!` is a not a struct?");
     }
diff --git a/src/tools/clippy/clippy_lints/src/zero_sized_map_values.rs b/src/tools/clippy/clippy_lints/src/zero_sized_map_values.rs
index 93e4b023c5c79..002304f8840bd 100644
--- a/src/tools/clippy/clippy_lints/src/zero_sized_map_values.rs
+++ b/src/tools/clippy/clippy_lints/src/zero_sized_map_values.rs
@@ -51,8 +51,8 @@ impl LateLintPass<'_> for ZeroSizedMapValues {
             if !in_trait_impl(cx, hir_ty.hir_id);
             let ty = ty_from_hir_ty(cx, hir_ty);
             if is_type_diagnostic_item(cx, ty, sym::HashMap) || is_type_diagnostic_item(cx, ty, sym::BTreeMap);
-            if let Adt(_, substs) = ty.kind();
-            let ty = substs.type_at(1);
+            if let Adt(_, args) = ty.kind();
+            let ty = args.type_at(1);
             // Fixes https://github.com/rust-lang/rust-clippy/issues/7447 because of
             // https://github.com/rust-lang/rust/blob/master/compiler/rustc_middle/src/ty/sty.rs#L968
             if !ty.has_escaping_bound_vars();
diff --git a/src/tools/clippy/clippy_utils/src/consts.rs b/src/tools/clippy/clippy_utils/src/consts.rs
index d1cfdc49658d7..4832a38ecebf6 100644
--- a/src/tools/clippy/clippy_utils/src/consts.rs
+++ b/src/tools/clippy/clippy_utils/src/consts.rs
@@ -12,7 +12,7 @@ use rustc_lint::LateContext;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::ty::{self, EarlyBinder, FloatTy, ScalarInt, Ty, TyCtxt};
-use rustc_middle::ty::{List, SubstsRef};
+use rustc_middle::ty::{List, GenericArgsRef};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::{Ident, Symbol};
 use rustc_span::SyntaxContext;
@@ -327,7 +327,7 @@ pub struct ConstEvalLateContext<'a, 'tcx> {
     typeck_results: &'a ty::TypeckResults<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     source: ConstantSource,
-    substs: SubstsRef<'tcx>,
+    args: GenericArgsRef<'tcx>,
 }
 
 impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
@@ -337,7 +337,7 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
             typeck_results,
             param_env: lcx.param_env,
             source: ConstantSource::Local,
-            substs: List::empty(),
+            args: List::empty(),
         }
     }
 
@@ -473,16 +473,16 @@ impl<'a, 'tcx> ConstEvalLateContext<'a, 'tcx> {
                     return None;
                 }
 
-                let substs = self.typeck_results.node_substs(id);
-                let substs = if self.substs.is_empty() {
-                    substs
+                let args = self.typeck_results.node_args(id);
+                let args = if self.args.is_empty() {
+                    args
                 } else {
-                    EarlyBinder::bind(substs).subst(self.lcx.tcx, self.substs)
+                    EarlyBinder::bind(args).instantiate(self.lcx.tcx, self.args)
                 };
                 let result = self
                     .lcx
                     .tcx
-                    .const_eval_resolve(self.param_env, mir::UnevaluatedConst::new(def_id, substs), None)
+                    .const_eval_resolve(self.param_env, mir::UnevaluatedConst::new(def_id, args), None)
                     .ok()
                     .map(|val| rustc_middle::mir::ConstantKind::from_value(val, ty))?;
                 let result = miri_to_const(self.lcx, result)?;
diff --git a/src/tools/clippy/clippy_utils/src/eager_or_lazy.rs b/src/tools/clippy/clippy_utils/src/eager_or_lazy.rs
index 4a845ca63b49f..94b9006ed5061 100644
--- a/src/tools/clippy/clippy_utils/src/eager_or_lazy.rs
+++ b/src/tools/clippy/clippy_utils/src/eager_or_lazy.rs
@@ -51,7 +51,7 @@ fn fn_eagerness(cx: &LateContext<'_>, fn_id: DefId, name: Symbol, have_one_arg:
     let name = name.as_str();
 
     let ty = match cx.tcx.impl_of_method(fn_id) {
-        Some(id) => cx.tcx.type_of(id).subst_identity(),
+        Some(id) => cx.tcx.type_of(id).instantiate_identity(),
         None => return Lazy,
     };
 
@@ -72,7 +72,7 @@ fn fn_eagerness(cx: &LateContext<'_>, fn_id: DefId, name: Symbol, have_one_arg:
             .variants()
             .iter()
             .flat_map(|v| v.fields.iter())
-            .any(|x| matches!(cx.tcx.type_of(x.did).subst_identity().peel_refs().kind(), ty::Param(_)))
+            .any(|x| matches!(cx.tcx.type_of(x.did).instantiate_identity().peel_refs().kind(), ty::Param(_)))
             && all_predicates_of(cx.tcx, fn_id).all(|(pred, _)| match pred.kind().skip_binder() {
                 ty::ClauseKind::Trait(pred) => cx.tcx.trait_def(pred.trait_ref.def_id).is_marker,
                 _ => true,
@@ -80,7 +80,7 @@ fn fn_eagerness(cx: &LateContext<'_>, fn_id: DefId, name: Symbol, have_one_arg:
             && subs.types().all(|x| matches!(x.peel_refs().kind(), ty::Param(_)))
         {
             // Limit the function to either `(self) -> bool` or `(&self) -> bool`
-            match &**cx.tcx.fn_sig(fn_id).subst_identity().skip_binder().inputs_and_output {
+            match &**cx.tcx.fn_sig(fn_id).instantiate_identity().skip_binder().inputs_and_output {
                 [arg, res] if !arg.is_mutable_ptr() && arg.peel_refs() == ty && res.is_bool() => NoChange,
                 _ => Lazy,
             }
diff --git a/src/tools/clippy/clippy_utils/src/lib.rs b/src/tools/clippy/clippy_utils/src/lib.rs
index 727b59f1f432a..5eed5ddf9e31f 100644
--- a/src/tools/clippy/clippy_utils/src/lib.rs
+++ b/src/tools/clippy/clippy_utils/src/lib.rs
@@ -305,7 +305,7 @@ pub fn match_trait_method(cx: &LateContext<'_>, expr: &Expr<'_>, path: &[&str])
 /// Checks if a method is defined in an impl of a diagnostic item
 pub fn is_diag_item_method(cx: &LateContext<'_>, def_id: DefId, diag_item: Symbol) -> bool {
     if let Some(impl_did) = cx.tcx.impl_of_method(def_id) {
-        if let Some(adt) = cx.tcx.type_of(impl_did).subst_identity().ty_adt_def() {
+        if let Some(adt) = cx.tcx.type_of(impl_did).instantiate_identity().ty_adt_def() {
             return cx.tcx.is_diagnostic_item(diag_item, adt.did());
         }
     }
@@ -812,7 +812,7 @@ fn is_default_equivalent_ctor(cx: &LateContext<'_>, def_id: DefId, path: &QPath<
     if let QPath::TypeRelative(_, method) = path {
         if method.ident.name == sym::new {
             if let Some(impl_did) = cx.tcx.impl_of_method(def_id) {
-                if let Some(adt) = cx.tcx.type_of(impl_did).subst_identity().ty_adt_def() {
+                if let Some(adt) = cx.tcx.type_of(impl_did).instantiate_identity().ty_adt_def() {
                     return std_types_symbols.iter().any(|&symbol| {
                         cx.tcx.is_diagnostic_item(symbol, adt.did()) || Some(adt.did()) == cx.tcx.lang_items().string()
                     });
@@ -1377,7 +1377,7 @@ pub fn get_enclosing_loop_or_multi_call_closure<'tcx>(
                                     .chain(args.iter())
                                     .position(|arg| arg.hir_id == id)?;
                                 let id = cx.typeck_results().type_dependent_def_id(e.hir_id)?;
-                                let ty = cx.tcx.fn_sig(id).subst_identity().skip_binder().inputs()[i];
+                                let ty = cx.tcx.fn_sig(id).instantiate_identity().skip_binder().inputs()[i];
                                 ty_is_fn_once_param(cx.tcx, ty, cx.tcx.param_env(id).caller_bounds()).then_some(())
                             },
                             _ => None,
@@ -1639,13 +1639,13 @@ pub fn is_direct_expn_of(span: Span, name: &str) -> Option<Span> {
 
 /// Convenience function to get the return type of a function.
 pub fn return_ty<'tcx>(cx: &LateContext<'tcx>, fn_def_id: hir::OwnerId) -> Ty<'tcx> {
-    let ret_ty = cx.tcx.fn_sig(fn_def_id).subst_identity().output();
+    let ret_ty = cx.tcx.fn_sig(fn_def_id).instantiate_identity().output();
     cx.tcx.erase_late_bound_regions(ret_ty)
 }
 
 /// Convenience function to get the nth argument type of a function.
 pub fn nth_arg<'tcx>(cx: &LateContext<'tcx>, fn_def_id: hir::OwnerId, nth: usize) -> Ty<'tcx> {
-    let arg = cx.tcx.fn_sig(fn_def_id).subst_identity().input(nth);
+    let arg = cx.tcx.fn_sig(fn_def_id).instantiate_identity().input(nth);
     cx.tcx.erase_late_bound_regions(arg)
 }
 
diff --git a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
index fbf4ab2722e60..515f80e0edfbf 100644
--- a/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
+++ b/src/tools/clippy/clippy_utils/src/qualify_min_const_fn.rs
@@ -15,7 +15,7 @@ use rustc_middle::mir::{
     Terminator, TerminatorKind,
 };
 use rustc_middle::traits::{ImplSource, ObligationCause};
-use rustc_middle::ty::subst::GenericArgKind;
+use rustc_middle::ty::GenericArgKind;
 use rustc_middle::ty::{self, adjustment::PointerCoercion, Ty, TyCtxt};
 use rustc_middle::ty::{BoundConstness, TraitRef};
 use rustc_semver::RustcVersion;
@@ -35,7 +35,7 @@ pub fn is_min_const_fn<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, msrv: &Msrv)
     // impl trait is gone in MIR, so check the return type manually
     check_ty(
         tcx,
-        tcx.fn_sig(def_id).subst_identity().output().skip_binder(),
+        tcx.fn_sig(def_id).instantiate_identity().output().skip_binder(),
         body.local_decls.iter().next().unwrap().source_info.span,
     )?;
 
diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs
index cf781e18cd66e..3953a7d8fa7ee 100644
--- a/src/tools/clippy/clippy_utils/src/sugg.rs
+++ b/src/tools/clippy/clippy_utils/src/sugg.rs
@@ -877,7 +877,7 @@ impl<'tcx> DerefDelegate<'_, 'tcx> {
                     .cx
                     .typeck_results()
                     .type_dependent_def_id(parent_expr.hir_id)
-                    .map(|did| self.cx.tcx.fn_sig(did).subst_identity().skip_binder())
+                    .map(|did| self.cx.tcx.fn_sig(did).instantiate_identity().skip_binder())
                 {
                     std::iter::once(receiver)
                         .chain(call_args.iter())
diff --git a/src/tools/clippy/clippy_utils/src/ty.rs b/src/tools/clippy/clippy_utils/src/ty.rs
index d650cbe0b1329..7687d361923c5 100644
--- a/src/tools/clippy/clippy_utils/src/ty.rs
+++ b/src/tools/clippy/clippy_utils/src/ty.rs
@@ -17,7 +17,7 @@ use rustc_lint::LateContext;
 use rustc_middle::mir::interpret::{ConstValue, Scalar};
 use rustc_middle::ty::{
     self, layout::ValidityRequirement, AdtDef, AliasTy, AssocKind, Binder, BoundRegion, FnSig, IntTy, List, ParamEnv,
-    Region, RegionKind, SubstsRef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
+    Region, RegionKind, GenericArgsRef, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor,
     UintTy, VariantDef, VariantDiscr,
 };
 use rustc_middle::ty::{GenericArg, GenericArgKind};
@@ -90,14 +90,14 @@ pub fn contains_ty_adt_constructor_opaque<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'
                         return false;
                     }
 
-                    for (predicate, _span) in cx.tcx.explicit_item_bounds(def_id).subst_identity_iter_copied() {
+                    for (predicate, _span) in cx.tcx.explicit_item_bounds(def_id).instantiate_identity_iter_copied() {
                         match predicate.kind().skip_binder() {
                             // For `impl Trait<U>`, it will register a predicate of `T: Trait<U>`, so we go through
                             // and check substitutions to find `U`.
                             ty::ClauseKind::Trait(trait_predicate) => {
                                 if trait_predicate
                                     .trait_ref
-                                    .substs
+                                    .args
                                     .types()
                                     .skip(1) // Skip the implicit `Self` generic parameter
                                     .any(|ty| contains_ty_adt_constructor_opaque_inner(cx, ty, needle, seen))
@@ -237,7 +237,7 @@ pub fn implements_trait_with_env<'tcx>(
         kind: TypeVariableOriginKind::MiscVariable,
         span: DUMMY_SP,
     };
-    let ty_params = tcx.mk_substs_from_iter(
+    let ty_params = tcx.mk_args_from_iter(
         ty_params
             .into_iter()
             .map(|arg| arg.unwrap_or_else(|| infcx.next_ty_var(orig).into())),
@@ -265,7 +265,7 @@ pub fn is_must_use_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
             // because we don't want to lint functions returning empty arrays
             is_must_use_ty(cx, *ty)
         },
-        ty::Tuple(substs) => substs.iter().any(|ty| is_must_use_ty(cx, ty)),
+        ty::Tuple(args) => args.iter().any(|ty| is_must_use_ty(cx, ty)),
         ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) => {
             for (predicate, _) in cx.tcx.explicit_item_bounds(def_id).skip_binder() {
                 if let ty::ClauseKind::Trait(trait_predicate) = predicate.kind().skip_binder() {
@@ -314,11 +314,11 @@ fn is_normalizable_helper<'tcx>(
     let cause = rustc_middle::traits::ObligationCause::dummy();
     let result = if infcx.at(&cause, param_env).query_normalize(ty).is_ok() {
         match ty.kind() {
-            ty::Adt(def, substs) => def.variants().iter().all(|variant| {
+            ty::Adt(def, args) => def.variants().iter().all(|variant| {
                 variant
                     .fields
                     .iter()
-                    .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, substs), cache))
+                    .all(|field| is_normalizable_helper(cx, param_env, field.ty(cx.tcx, args), cache))
             }),
             _ => ty.walk().all(|generic_arg| match generic_arg.unpack() {
                 GenericArgKind::Type(inner_ty) if inner_ty != ty => {
@@ -517,14 +517,14 @@ pub fn walk_ptrs_ty_depth(ty: Ty<'_>) -> (Ty<'_>, usize) {
 /// otherwise returns `false`
 pub fn same_type_and_consts<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
     match (&a.kind(), &b.kind()) {
-        (&ty::Adt(did_a, substs_a), &ty::Adt(did_b, substs_b)) => {
+        (&ty::Adt(did_a, args_a), &ty::Adt(did_b, args_b)) => {
             if did_a != did_b {
                 return false;
             }
 
-            substs_a
+            args_a
                 .iter()
-                .zip(substs_b.iter())
+                .zip(args_b.iter())
                 .all(|(arg_a, arg_b)| match (arg_a.unpack(), arg_b.unpack()) {
                     (GenericArgKind::Const(inner_a), GenericArgKind::Const(inner_b)) => inner_a == inner_b,
                     (GenericArgKind::Type(type_a), GenericArgKind::Type(type_b)) => {
@@ -643,7 +643,7 @@ impl<'tcx> ExprFnSig<'tcx> {
 /// If the expression is function like, get the signature for it.
 pub fn expr_sig<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>) -> Option<ExprFnSig<'tcx>> {
     if let Res::Def(DefKind::Fn | DefKind::Ctor(_, CtorKind::Fn) | DefKind::AssocFn, id) = path_res(cx, expr) {
-        Some(ExprFnSig::Sig(cx.tcx.fn_sig(id).subst_identity(), Some(id)))
+        Some(ExprFnSig::Sig(cx.tcx.fn_sig(id).instantiate_identity(), Some(id)))
     } else {
         ty_sig(cx, cx.typeck_results().expr_ty_adjusted(expr).peel_refs())
     }
@@ -661,11 +661,11 @@ pub fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'t
                 .and_then(|id| cx.tcx.hir().fn_decl_by_hir_id(cx.tcx.hir().local_def_id_to_hir_id(id)));
             Some(ExprFnSig::Closure(decl, subs.as_closure().sig()))
         },
-        ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.fn_sig(id).subst(cx.tcx, subs), Some(id))),
-        ty::Alias(ty::Opaque, ty::AliasTy { def_id, substs, .. }) => sig_from_bounds(
+        ty::FnDef(id, subs) => Some(ExprFnSig::Sig(cx.tcx.fn_sig(id).instantiate(cx.tcx, subs), Some(id))),
+        ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => sig_from_bounds(
             cx,
             ty,
-            cx.tcx.item_bounds(def_id).subst_iter(cx.tcx, substs),
+            cx.tcx.item_bounds(def_id).arg_iter(cx.tcx, args),
             cx.tcx.opt_parent(def_id),
         ),
         ty::FnPtr(sig) => Some(ExprFnSig::Sig(sig, None)),
@@ -681,7 +681,7 @@ pub fn ty_sig<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> Option<ExprFnSig<'t
                         .projection_bounds()
                         .find(|p| lang_items.fn_once_output().map_or(false, |id| id == p.item_def_id()))
                         .map(|p| p.map_bound(|p| p.term.ty().unwrap()));
-                    Some(ExprFnSig::Trait(bound.map_bound(|b| b.substs.type_at(0)), output, None))
+                    Some(ExprFnSig::Trait(bound.map_bound(|b| b.args.type_at(0)), output, None))
                 },
                 _ => None,
             }
@@ -713,7 +713,7 @@ fn sig_from_bounds<'tcx>(
                     || lang_items.fn_once_trait() == Some(p.def_id()))
                     && p.self_ty() == ty =>
             {
-                let i = pred.kind().rebind(p.trait_ref.substs.type_at(1));
+                let i = pred.kind().rebind(p.trait_ref.args.type_at(1));
                 if inputs.map_or(false, |inputs| i != inputs) {
                     // Multiple different fn trait impls. Is this even allowed?
                     return None;
@@ -744,7 +744,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: AliasTy<'tcx>) -> Option
     for (pred, _) in cx
         .tcx
         .explicit_item_bounds(ty.def_id)
-        .subst_iter_copied(cx.tcx, ty.substs)
+        .arg_iter_copied(cx.tcx, ty.args)
     {
         match pred.kind().skip_binder() {
             ty::ClauseKind::Trait(p)
@@ -752,7 +752,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: AliasTy<'tcx>) -> Option
                     || lang_items.fn_mut_trait() == Some(p.def_id())
                     || lang_items.fn_once_trait() == Some(p.def_id())) =>
             {
-                let i = pred.kind().rebind(p.trait_ref.substs.type_at(1));
+                let i = pred.kind().rebind(p.trait_ref.args.type_at(1));
 
                 if inputs.map_or(false, |inputs| inputs != i) {
                     // Multiple different fn trait impls. Is this even allowed?
@@ -793,7 +793,7 @@ impl core::ops::Add<u32> for EnumValue {
 #[expect(clippy::cast_possible_truncation, clippy::cast_possible_wrap)]
 pub fn read_explicit_enum_value(tcx: TyCtxt<'_>, id: DefId) -> Option<EnumValue> {
     if let Ok(ConstValue::Scalar(Scalar::Int(value))) = tcx.const_eval_poly(id) {
-        match tcx.type_of(id).subst_identity().kind() {
+        match tcx.type_of(id).instantiate_identity().kind() {
             ty::Int(_) => Some(EnumValue::Signed(match value.size().bytes() {
                 1 => i128::from(value.assert_bits(Size::from_bytes(1)) as u8 as i8),
                 2 => i128::from(value.assert_bits(Size::from_bytes(2)) as u16 as i16),
@@ -927,7 +927,7 @@ pub fn adt_and_variant_of_res<'tcx>(cx: &LateContext<'tcx>, res: Res) -> Option<
             Some((adt, adt.variant_with_id(var_id)))
         },
         Res::SelfCtor(id) => {
-            let adt = cx.tcx.type_of(id).subst_identity().ty_adt_def().unwrap();
+            let adt = cx.tcx.type_of(id).instantiate_identity().ty_adt_def().unwrap();
             Some((adt, adt.non_enum_variant()))
         },
         _ => None,
@@ -1025,13 +1025,13 @@ pub fn make_projection<'tcx>(
     tcx: TyCtxt<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
 ) -> Option<AliasTy<'tcx>> {
     fn helper<'tcx>(
         tcx: TyCtxt<'tcx>,
         container_id: DefId,
         assoc_ty: Symbol,
-        substs: SubstsRef<'tcx>,
+        args: GenericArgsRef<'tcx>,
     ) -> Option<AliasTy<'tcx>> {
         let Some(assoc_item) = tcx
             .associated_items(container_id)
@@ -1052,18 +1052,18 @@ pub fn make_projection<'tcx>(
                 .map(|x| &x.kind);
 
             debug_assert!(
-                generic_count == substs.len(),
-                "wrong number of substs for `{:?}`: found `{}` expected `{generic_count}`.\n\
+                generic_count == args.len(),
+                "wrong number of args for `{:?}`: found `{}` expected `{generic_count}`.\n\
                     note: the expected parameters are: {:#?}\n\
-                    the given arguments are: `{substs:#?}`",
+                    the given arguments are: `{args:#?}`",
                 assoc_item.def_id,
-                substs.len(),
+                args.len(),
                 params.map(ty::GenericParamDefKind::descr).collect::<Vec<_>>(),
             );
 
             if let Some((idx, (param, arg))) = params
                 .clone()
-                .zip(substs.iter().map(GenericArg::unpack))
+                .zip(args.iter().map(GenericArg::unpack))
                 .enumerate()
                 .find(|(_, (param, arg))| {
                     !matches!(
@@ -1078,20 +1078,20 @@ pub fn make_projection<'tcx>(
                     false,
                     "mismatched subst type at index {idx}: expected a {}, found `{arg:?}`\n\
                         note: the expected parameters are {:#?}\n\
-                        the given arguments are {substs:#?}",
+                        the given arguments are {args:#?}",
                     param.descr(),
                     params.map(ty::GenericParamDefKind::descr).collect::<Vec<_>>()
                 );
             }
         }
 
-        Some(tcx.mk_alias_ty(assoc_item.def_id, substs))
+        Some(tcx.mk_alias_ty(assoc_item.def_id, args))
     }
     helper(
         tcx,
         container_id,
         assoc_ty,
-        tcx.mk_substs_from_iter(substs.into_iter().map(Into::into)),
+        tcx.mk_args_from_iter(args.into_iter().map(Into::into)),
     )
 }
 
@@ -1106,25 +1106,25 @@ pub fn make_normalized_projection<'tcx>(
     param_env: ParamEnv<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
 ) -> Option<Ty<'tcx>> {
     fn helper<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: AliasTy<'tcx>) -> Option<Ty<'tcx>> {
         #[cfg(debug_assertions)]
         if let Some((i, subst)) = ty
-            .substs
+            .args
             .iter()
             .enumerate()
             .find(|(_, subst)| subst.has_late_bound_regions())
         {
             debug_assert!(
                 false,
-                "substs contain late-bound region at index `{i}` which can't be normalized.\n\
+                "args contain late-bound region at index `{i}` which can't be normalized.\n\
                     use `TyCtxt::erase_late_bound_regions`\n\
                     note: subst is `{subst:#?}`",
             );
             return None;
         }
-        match tcx.try_normalize_erasing_regions(param_env, Ty::new_projection(tcx,ty.def_id, ty.substs)) {
+        match tcx.try_normalize_erasing_regions(param_env, Ty::new_projection(tcx,ty.def_id, ty.args)) {
             Ok(ty) => Some(ty),
             Err(e) => {
                 debug_assert!(false, "failed to normalize type `{ty}`: {e:#?}");
@@ -1132,7 +1132,7 @@ pub fn make_normalized_projection<'tcx>(
             },
         }
     }
-    helper(tcx, param_env, make_projection(tcx, container_id, assoc_ty, substs)?)
+    helper(tcx, param_env, make_projection(tcx, container_id, assoc_ty, args)?)
 }
 
 /// Check if given type has inner mutability such as [`std::cell::Cell`] or [`std::cell::RefCell`]
@@ -1147,7 +1147,7 @@ pub fn is_interior_mut_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
                 && is_interior_mut_ty(cx, inner_ty)
         },
         ty::Tuple(fields) => fields.iter().any(|ty| is_interior_mut_ty(cx, ty)),
-        ty::Adt(def, substs) => {
+        ty::Adt(def, args) => {
             // Special case for collections in `std` who's impl of `Hash` or `Ord` delegates to
             // that of their type parameters.  Note: we don't include `HashSet` and `HashMap`
             // because they have no impl for `Hash` or `Ord`.
@@ -1168,7 +1168,7 @@ pub fn is_interior_mut_ty<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
             let is_box = Some(def_id) == cx.tcx.lang_items().owned_box();
             if is_std_collection || is_box {
                 // The type is mutable if any of its type parameters are
-                substs.types().any(|ty| is_interior_mut_ty(cx, ty))
+                args.types().any(|ty| is_interior_mut_ty(cx, ty))
             } else {
                 !ty.has_escaping_bound_vars()
                     && cx.tcx.layout_of(cx.param_env.and(ty)).is_ok()
@@ -1184,19 +1184,19 @@ pub fn make_normalized_projection_with_regions<'tcx>(
     param_env: ParamEnv<'tcx>,
     container_id: DefId,
     assoc_ty: Symbol,
-    substs: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
+    args: impl IntoIterator<Item = impl Into<GenericArg<'tcx>>>,
 ) -> Option<Ty<'tcx>> {
     fn helper<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: AliasTy<'tcx>) -> Option<Ty<'tcx>> {
         #[cfg(debug_assertions)]
         if let Some((i, subst)) = ty
-            .substs
+            .args
             .iter()
             .enumerate()
             .find(|(_, subst)| subst.has_late_bound_regions())
         {
             debug_assert!(
                 false,
-                "substs contain late-bound region at index `{i}` which can't be normalized.\n\
+                "args contain late-bound region at index `{i}` which can't be normalized.\n\
                     use `TyCtxt::erase_late_bound_regions`\n\
                     note: subst is `{subst:#?}`",
             );
@@ -1207,7 +1207,7 @@ pub fn make_normalized_projection_with_regions<'tcx>(
             .infer_ctxt()
             .build()
             .at(&cause, param_env)
-            .query_normalize(Ty::new_projection(tcx,ty.def_id, ty.substs))
+            .query_normalize(Ty::new_projection(tcx,ty.def_id, ty.args))
         {
             Ok(ty) => Some(ty.value),
             Err(e) => {
@@ -1216,7 +1216,7 @@ pub fn make_normalized_projection_with_regions<'tcx>(
             },
         }
     }
-    helper(tcx, param_env, make_projection(tcx, container_id, assoc_ty, substs)?)
+    helper(tcx, param_env, make_projection(tcx, container_id, assoc_ty, args)?)
 }
 
 pub fn normalize_with_regions<'tcx>(tcx: TyCtxt<'tcx>, param_env: ParamEnv<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
diff --git a/src/tools/clippy/tests/ui/crashes/ice-6256.rs b/src/tools/clippy/tests/ui/crashes/ice-6256.rs
index 1d336b3cdc0c8..bb488c2dcb35a 100644
--- a/src/tools/clippy/tests/ui/crashes/ice-6256.rs
+++ b/src/tools/clippy/tests/ui/crashes/ice-6256.rs
@@ -1,5 +1,5 @@
 // originally from rustc ./tests/ui/regions/issue-78262.rs
-// ICE: to get the signature of a closure, use substs.as_closure().sig() not fn_sig()
+// ICE: to get the signature of a closure, use args.as_closure().sig() not fn_sig()
 #![allow(clippy::upper_case_acronyms)]
 
 trait TT {}
diff --git a/src/tools/clippy/tests/ui/eta.fixed b/src/tools/clippy/tests/ui/eta.fixed
index bf44bcb564ecc..db7bd99e0ae6c 100644
--- a/src/tools/clippy/tests/ui/eta.fixed
+++ b/src/tools/clippy/tests/ui/eta.fixed
@@ -331,7 +331,7 @@ impl dyn TestTrait + '_ {
 }
 
 // https://github.com/rust-lang/rust-clippy/issues/7746
-fn angle_brackets_and_substs() {
+fn angle_brackets_and_args() {
     let array_opt: Option<&[u8; 3]> = Some(&[4, 8, 7]);
     array_opt.map(<[u8; 3]>::as_slice);
 
diff --git a/src/tools/clippy/tests/ui/eta.rs b/src/tools/clippy/tests/ui/eta.rs
index b2af4bf095373..52fc17686fdfc 100644
--- a/src/tools/clippy/tests/ui/eta.rs
+++ b/src/tools/clippy/tests/ui/eta.rs
@@ -331,7 +331,7 @@ impl dyn TestTrait + '_ {
 }
 
 // https://github.com/rust-lang/rust-clippy/issues/7746
-fn angle_brackets_and_substs() {
+fn angle_brackets_and_args() {
     let array_opt: Option<&[u8; 3]> = Some(&[4, 8, 7]);
     array_opt.map(|a| a.as_slice());
 
diff --git a/src/tools/miri/src/eval.rs b/src/tools/miri/src/eval.rs
index aba7dd5a9fee0..ed3d741db1cbb 100644
--- a/src/tools/miri/src/eval.rs
+++ b/src/tools/miri/src/eval.rs
@@ -380,7 +380,7 @@ pub fn create_ecx<'mir, 'tcx: 'mir>(
                 tcx,
                 ty::ParamEnv::reveal_all(),
                 start_id,
-                tcx.mk_substs(&[ty::subst::GenericArg::from(main_ret_ty)]),
+                tcx.mk_args(&[ty::GenericArg::from(main_ret_ty)]),
             )
             .unwrap()
             .unwrap();
diff --git a/src/tools/miri/src/machine.rs b/src/tools/miri/src/machine.rs
index 5510e3f94b75a..5ebd1fae49259 100644
--- a/src/tools/miri/src/machine.rs
+++ b/src/tools/miri/src/machine.rs
@@ -972,7 +972,7 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for MiriMachine<'mir, 'tcx> {
                 panic!("extern_statics cannot contain wildcards")
             };
             let (shim_size, shim_align, _kind) = ecx.get_alloc_info(alloc_id);
-            let def_ty = ecx.tcx.type_of(def_id).subst_identity();
+            let def_ty = ecx.tcx.type_of(def_id).instantiate_identity();
             let extern_decl_layout = ecx.tcx.layout_of(ty::ParamEnv::empty().and(def_ty)).unwrap();
             if extern_decl_layout.size != shim_size || extern_decl_layout.align.abi != shim_align {
                 throw_unsup_format!(
diff --git a/tests/mir-opt/issue_99325.main.built.after.mir b/tests/mir-opt/issue_99325.main.built.after.mir
index 0fe66d3fb7021..aef89c7f9f742 100644
--- a/tests/mir-opt/issue_99325.main.built.after.mir
+++ b/tests/mir-opt/issue_99325.main.built.after.mir
@@ -1,8 +1,8 @@
 // MIR for `main` after built
 
 | User Type Annotations
-| 0: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserSubsts { substs: [Const { ty: &'static [u8; 4], kind: Branch([Leaf(0x41), Leaf(0x41), Leaf(0x41), Leaf(0x41)]) }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:10:16: 10:46, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
-| 1: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserSubsts { substs: [Const { ty: &'static [u8; 4], kind: UnevaluatedConst { def: DefId(0:8 ~ issue_99325[22bb]::main::{constant#1}), substs: [] } }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:11:16: 11:68, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
+| 0: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &'static [u8; 4], kind: Branch([Leaf(0x41), Leaf(0x41), Leaf(0x41), Leaf(0x41)]) }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:10:16: 10:46, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
+| 1: user_ty: Canonical { value: TypeOf(DefId(0:3 ~ issue_99325[22bb]::function_with_bytes), UserArgs { args: [Const { ty: &'static [u8; 4], kind: UnevaluatedConst { def: DefId(0:8 ~ issue_99325[22bb]::main::{constant#1}), args: [] } }], user_self_ty: None }), max_universe: U0, variables: [] }, span: $DIR/issue_99325.rs:11:16: 11:68, inferred_ty: fn() -> &'static [u8] {function_with_bytes::<&*b"AAAA">}
 |
 fn main() -> () {
     let mut _0: ();
diff --git a/tests/run-coverage/partial_eq.coverage b/tests/run-coverage/partial_eq.coverage
index a77175af66360..be4f23ec0bad7 100644
--- a/tests/run-coverage/partial_eq.coverage
+++ b/tests/run-coverage/partial_eq.coverage
@@ -36,7 +36,7 @@
    35|       |            did: DefId(0:101 ~ autocfg[c44a]::version::{impl#2}::partial_cmp),
    36|       |            const_param_did: None
    37|       |        }),
-   38|       |        substs: []
+   38|       |        args: []
    39|       |    }'
    40|       |The `PartialOrd` derived by `Version` happened to generate a MIR that generated coverage
    41|       |without a code region associated with any `Counter`. Code regions were associated with at least
diff --git a/tests/run-coverage/partial_eq.rs b/tests/run-coverage/partial_eq.rs
index 4ceaba9b111e9..dd8b42c18cea9 100644
--- a/tests/run-coverage/partial_eq.rs
+++ b/tests/run-coverage/partial_eq.rs
@@ -35,7 +35,7 @@ thread 'rustc' panicked at 'No counters provided the source_hash for function:
             did: DefId(0:101 ~ autocfg[c44a]::version::{impl#2}::partial_cmp),
             const_param_did: None
         }),
-        substs: []
+        args: []
     }'
 The `PartialOrd` derived by `Version` happened to generate a MIR that generated coverage
 without a code region associated with any `Counter`. Code regions were associated with at least
diff --git a/tests/ui/closures/binder/nested-closures-regions.stderr b/tests/ui/closures/binder/nested-closures-regions.stderr
index 381aadb1564cc..a30339ac67b1c 100644
--- a/tests/ui/closures/binder/nested-closures-regions.stderr
+++ b/tests/ui/closures/binder/nested-closures-regions.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     for<'a> || -> () { for<'c> |_: &'a ()| -> () {}; };
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: main::{closure#0}::{closure#0} with closure substs [
+   = note: defining type: main::{closure#0}::{closure#0} with closure args [
                i8,
                extern "rust-call" fn((&(),)),
                (),
@@ -21,7 +21,7 @@ note: no external requirements
 LL |     for<'a> || -> () { for<'c> |_: &'a ()| -> () {}; };
    |     ^^^^^^^^^^^^^^^^
    |
-   = note: defining type: main::{closure#0} with closure substs [
+   = note: defining type: main::{closure#0} with closure args [
                i8,
                extern "rust-call" fn(()),
                (),
diff --git a/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr b/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
index 381bb0c084a22..49453b0538b3d 100644
--- a/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
+++ b/tests/ui/closures/print/closure-print-generic-trim-off-verbose-2.stderr
@@ -9,7 +9,7 @@ LL |         let c1 : () = c;
    |                  expected due to this
    |
    = note: expected unit type `()`
-                found closure `[mod1::f<T>::{closure#0} closure_substs=(unavailable) substs=[T, ?16t, extern "rust-call" fn(()), ?15t]]`
+                found closure `[mod1::f<T>::{closure#0} closure_args=(unavailable) args=[T, ?16t, extern "rust-call" fn(()), ?15t]]`
 help: use parentheses to call this closure
    |
 LL |         let c1 : () = c();
diff --git a/tests/ui/closures/print/closure-print-generic-verbose-2.stderr b/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
index 2a4d16c48dc2e..d2deba3dd84fb 100644
--- a/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
+++ b/tests/ui/closures/print/closure-print-generic-verbose-2.stderr
@@ -9,7 +9,7 @@ LL |         let c1 : () = c;
    |                  expected due to this
    |
    = note: expected unit type `()`
-                found closure `[f<T>::{closure#0} closure_substs=(unavailable) substs=[T, ?16t, extern "rust-call" fn(()), ?15t]]`
+                found closure `[f<T>::{closure#0} closure_args=(unavailable) args=[T, ?16t, extern "rust-call" fn(()), ?15t]]`
 help: use parentheses to call this closure
    |
 LL |         let c1 : () = c();
diff --git a/tests/ui/closures/print/closure-print-verbose.stderr b/tests/ui/closures/print/closure-print-verbose.stderr
index 9e219435e5ce0..acc81f5e466f1 100644
--- a/tests/ui/closures/print/closure-print-verbose.stderr
+++ b/tests/ui/closures/print/closure-print-verbose.stderr
@@ -7,7 +7,7 @@ LL |     let foo: fn(u8) -> u8 = |v: u8| { a += v; a };
    |              expected due to this
    |
    = note: expected fn pointer `fn(u8) -> u8`
-                 found closure `[main::{closure#0} closure_substs=(unavailable) substs=[i8, extern "rust-call" fn((u8,)) -> u8, ?6t]]`
+                 found closure `[main::{closure#0} closure_args=(unavailable) args=[i8, extern "rust-call" fn((u8,)) -> u8, ?6t]]`
 note: closures can only be coerced to `fn` types if they do not capture any variables
   --> $DIR/closure-print-verbose.rs:10:39
    |
diff --git a/tests/ui/nll/closure-requirements/escape-argument-callee.stderr b/tests/ui/nll/closure-requirements/escape-argument-callee.stderr
index 61233fd84077c..1e3a5328d3d35 100644
--- a/tests/ui/nll/closure-requirements/escape-argument-callee.stderr
+++ b/tests/ui/nll/closure-requirements/escape-argument-callee.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |         let mut closure = expect_sig(|p, y| *p = y);
    |                                      ^^^^^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) i32)),
                (),
diff --git a/tests/ui/nll/closure-requirements/escape-argument.stderr b/tests/ui/nll/closure-requirements/escape-argument.stderr
index 61e2a1ea6f019..bc4ba93f88499 100644
--- a/tests/ui/nll/closure-requirements/escape-argument.stderr
+++ b/tests/ui/nll/closure-requirements/escape-argument.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |         let mut closure = expect_sig(|p, y| *p = y);
    |                                      ^^^^^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) mut &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32)),
                (),
diff --git a/tests/ui/nll/closure-requirements/escape-upvar-nested.stderr b/tests/ui/nll/closure-requirements/escape-upvar-nested.stderr
index c00a31ef8e15a..727df1cf890c7 100644
--- a/tests/ui/nll/closure-requirements/escape-upvar-nested.stderr
+++ b/tests/ui/nll/closure-requirements/escape-upvar-nested.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |             let mut closure1 = || p = &y;
    |                                ^^
    |
-   = note: defining type: test::{closure#0}::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0}::{closure#0} with closure args [
                i16,
                extern "rust-call" fn(()),
                (&'?1 mut &'?2 i32, &'?3 i32),
@@ -18,7 +18,7 @@ note: external requirements
 LL |         let mut closure = || {
    |                           ^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                extern "rust-call" fn(()),
                (&'?1 mut &'?2 i32, &'?3 i32),
diff --git a/tests/ui/nll/closure-requirements/escape-upvar-ref.stderr b/tests/ui/nll/closure-requirements/escape-upvar-ref.stderr
index 2d67e6e7d722a..ff638f2a1eca8 100644
--- a/tests/ui/nll/closure-requirements/escape-upvar-ref.stderr
+++ b/tests/ui/nll/closure-requirements/escape-upvar-ref.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |         let mut closure = || p = &y;
    |                           ^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                extern "rust-call" fn(()),
                (&'?1 mut &'?2 i32, &'?3 i32),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr
index ba42576d40346..f8383cc42a205 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-fail-no-postdom.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |         |_outlives1, _outlives2, _outlives3, x, y| {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&'?2 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'?3 u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-ref.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-ref.stderr
index 9dd6e02081faf..113173d8f764c 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-ref.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-ref.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) &'?2 u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
index e2f5576d3953f..ba15199ab5a11 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-comparing-against-free.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |     foo(cell, |cell_a, cell_x| {
    |               ^^^^^^^^^^^^^^^^
    |
-   = note: defining type: case1::{closure#0} with closure substs [
+   = note: defining type: case1::{closure#0} with closure args [
                i32,
                for<Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'?1 u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>)),
                (),
@@ -34,7 +34,7 @@ note: external requirements
 LL |     foo(cell, |cell_a, cell_x| {
    |               ^^^^^^^^^^^^^^^^
    |
-   = note: defining type: case2::{closure#0} with closure substs [
+   = note: defining type: case2::{closure#0} with closure args [
                i32,
                for<Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'?1 u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
index 383fb471ad3af..f2bf83c6c59e4 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-no-bound.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
    |                                               ^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
index ac346c0b110ae..2734326ed6471 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-shorter-to-static-wrong-bound.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&'?2 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-approximated-val.stderr b/tests/ui/nll/closure-requirements/propagate-approximated-val.stderr
index b217ae19773ab..5ab321eb666de 100644
--- a/tests/ui/nll/closure-requirements/propagate-approximated-val.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-approximated-val.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     establish_relationships(cell_a, cell_b, |outlives1, outlives2, x, y| {
    |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'?2 u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr b/tests/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr
index f31478b6d1cfb..595fd5ff565cb 100644
--- a/tests/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-despite-same-free-region.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |         |_outlives1, _outlives2, x, y| {
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'?2 u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) u32>, std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr b/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr
index 1509ade87fa09..62b0e3eed85b5 100644
--- a/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-no-bounds.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives, x, y| {
    |                                               ^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'?1 u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr b/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr
index c85a9872e212d..6f2044d621eb3 100644
--- a/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-fail-to-approximate-longer-wrong-bounds.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |     establish_relationships(&cell_a, &cell_b, |_outlives1, _outlives2, x, y| {
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: defining type: supply::{closure#0} with closure substs [
+   = note: defining type: supply::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) &'?1 u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 2, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) &'?2 u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 4, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) u32>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 5, kind: BrAnon(None) }) std::cell::Cell<&ReLateBound(DebruijnIndex(0), BoundRegion { var: 3, kind: BrAnon(None) }) u32>)),
                (),
diff --git a/tests/ui/nll/closure-requirements/propagate-from-trait-match.stderr b/tests/ui/nll/closure-requirements/propagate-from-trait-match.stderr
index 05e274ab22032..1aa7de1e13703 100644
--- a/tests/ui/nll/closure-requirements/propagate-from-trait-match.stderr
+++ b/tests/ui/nll/closure-requirements/propagate-from-trait-match.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     establish_relationships(value, |value| {
    |                                    ^^^^^^^
    |
-   = note: defining type: supply::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: supply::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((T,)),
                (),
diff --git a/tests/ui/nll/closure-requirements/return-wrong-bound-region.stderr b/tests/ui/nll/closure-requirements/return-wrong-bound-region.stderr
index 4e34ba5165958..7635f2ede0a31 100644
--- a/tests/ui/nll/closure-requirements/return-wrong-bound-region.stderr
+++ b/tests/ui/nll/closure-requirements/return-wrong-bound-region.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |     expect_sig(|a, b| b); // ought to return `a`
    |                ^^^^^^
    |
-   = note: defining type: test::{closure#0} with closure substs [
+   = note: defining type: test::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((&ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) i32, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) i32)) -> &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) i32,
                (),
diff --git a/tests/ui/nll/ty-outlives/projection-no-regions-closure.stderr b/tests/ui/nll/ty-outlives/projection-no-regions-closure.stderr
index 4eefb180ee506..433024c30bbcf 100644
--- a/tests/ui/nll/ty-outlives/projection-no-regions-closure.stderr
+++ b/tests/ui/nll/ty-outlives/projection-no-regions-closure.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(x, |mut y| Box::new(y.next()))
    |                       ^^^^^^^
    |
-   = note: defining type: no_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: no_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::boxed::Box<T>,)) -> std::boxed::Box<(dyn Anything + '?2)>,
                (),
@@ -37,7 +37,7 @@ note: external requirements
 LL |     with_signature(x, |mut y| Box::new(y.next()))
    |                       ^^^^^^^
    |
-   = note: defining type: correct_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: correct_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::boxed::Box<T>,)) -> std::boxed::Box<(dyn Anything + '?2)>,
                (),
@@ -61,7 +61,7 @@ note: external requirements
 LL |     with_signature(x, |mut y| Box::new(y.next()))
    |                       ^^^^^^^
    |
-   = note: defining type: wrong_region::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: wrong_region::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::boxed::Box<T>,)) -> std::boxed::Box<(dyn Anything + '?3)>,
                (),
@@ -94,7 +94,7 @@ note: external requirements
 LL |     with_signature(x, |mut y| Box::new(y.next()))
    |                       ^^^^^^^
    |
-   = note: defining type: outlives_region::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: outlives_region::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::boxed::Box<T>,)) -> std::boxed::Box<(dyn Anything + '?3)>,
                (),
diff --git a/tests/ui/nll/ty-outlives/projection-one-region-closure.stderr b/tests/ui/nll/ty-outlives/projection-one-region-closure.stderr
index 986c2bd2182b4..ebdce7bc10832 100644
--- a/tests/ui/nll/ty-outlives/projection-one-region-closure.stderr
+++ b/tests/ui/nll/ty-outlives/projection-one-region-closure.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -54,7 +54,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -104,7 +104,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -129,7 +129,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
diff --git a/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-closure.stderr b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-closure.stderr
index 25cc60d814159..52040663e005c 100644
--- a/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-closure.stderr
+++ b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-closure.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -42,7 +42,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -80,7 +80,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -105,7 +105,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -130,7 +130,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: one_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: one_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
diff --git a/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.stderr b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.stderr
index 5a092d7b8497a..97be61b77a87f 100644
--- a/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.stderr
+++ b/tests/ui/nll/ty-outlives/projection-one-region-trait-bound-static-closure.stderr
@@ -4,7 +4,7 @@ note: no external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_late::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -27,7 +27,7 @@ note: no external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_early::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -50,7 +50,7 @@ note: no external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: projection_outlives::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -73,7 +73,7 @@ note: no external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: elements_outlive::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -96,7 +96,7 @@ note: no external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: one_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: one_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
diff --git a/tests/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr b/tests/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr
index 51283aa88289f..dbad8e478463c 100644
--- a/tests/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr
+++ b/tests/ui/nll/ty-outlives/projection-two-region-trait-bound-closure.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_late::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_late::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -38,7 +38,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: no_relationships_early::<'?1, '?2, '?3, T>::{closure#0} with closure substs [
+   = note: defining type: no_relationships_early::<'?1, '?2, '?3, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?4 ()>, T)),
                (),
@@ -72,7 +72,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: projection_outlives::<'?1, '?2, '?3, T>::{closure#0} with closure substs [
+   = note: defining type: projection_outlives::<'?1, '?2, '?3, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?4 ()>, T)),
                (),
@@ -97,7 +97,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: elements_outlive1::<'?1, '?2, '?3, T>::{closure#0} with closure substs [
+   = note: defining type: elements_outlive1::<'?1, '?2, '?3, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?4 ()>, T)),
                (),
@@ -122,7 +122,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: elements_outlive2::<'?1, '?2, '?3, T>::{closure#0} with closure substs [
+   = note: defining type: elements_outlive2::<'?1, '?2, '?3, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?4 ()>, T)),
                (),
@@ -147,7 +147,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: two_regions::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: two_regions::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -188,7 +188,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: two_regions_outlive::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: two_regions_outlive::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
@@ -213,7 +213,7 @@ note: external requirements
 LL |     with_signature(cell, t, |cell, t| require(cell, t));
    |                             ^^^^^^^^^
    |
-   = note: defining type: one_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: one_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
diff --git a/tests/ui/nll/ty-outlives/ty-param-closure-approximate-lower-bound.stderr b/tests/ui/nll/ty-outlives/ty-param-closure-approximate-lower-bound.stderr
index 04616f9b7028b..660211fe21ad0 100644
--- a/tests/ui/nll/ty-outlives/ty-param-closure-approximate-lower-bound.stderr
+++ b/tests/ui/nll/ty-outlives/ty-param-closure-approximate-lower-bound.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     twice(cell, value, |a, b| invoke(a, b));
    |                        ^^^^^^
    |
-   = note: defining type: generic::<T>::{closure#0} with closure substs [
+   = note: defining type: generic::<T>::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) T)),
                (),
@@ -26,7 +26,7 @@ note: external requirements
 LL |     twice(cell, value, |a, b| invoke(a, b));
    |                        ^^^^^^
    |
-   = note: defining type: generic_fail::<T>::{closure#0} with closure substs [
+   = note: defining type: generic_fail::<T>::{closure#0} with closure args [
                i16,
                for<Region(BrAnon(None)), Region(BrAnon(None))> extern "rust-call" fn((std::option::Option<std::cell::Cell<&'?1 &ReLateBound(DebruijnIndex(0), BoundRegion { var: 0, kind: BrAnon(None) }) ()>>, &ReLateBound(DebruijnIndex(0), BoundRegion { var: 1, kind: BrAnon(None) }) T)),
                (),
diff --git a/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-return-type.stderr b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-return-type.stderr
index d580774ff8cbf..ddad1d205e761 100644
--- a/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-return-type.stderr
+++ b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-return-type.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(x, |y| y)
    |                       ^^^
    |
-   = note: defining type: no_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: no_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::boxed::Box<T>,)) -> std::boxed::Box<(dyn std::fmt::Debug + '?2)>,
                (),
diff --git a/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.stderr b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.stderr
index 3d4c11a3c547a..bb455e9aed090 100644
--- a/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.stderr
+++ b/tests/ui/nll/ty-outlives/ty-param-closure-outlives-from-where-clause.stderr
@@ -4,7 +4,7 @@ note: external requirements
 LL |     with_signature(a, b, |x, y| {
    |                          ^^^^^^
    |
-   = note: defining type: no_region::<T>::{closure#0} with closure substs [
+   = note: defining type: no_region::<T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?1 ()>, T)),
                (),
@@ -38,7 +38,7 @@ note: external requirements
 LL |     with_signature(a, b, |x, y| {
    |                          ^^^^^^
    |
-   = note: defining type: correct_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: correct_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -62,7 +62,7 @@ note: external requirements
 LL |     with_signature(a, b, |x, y| {
    |                          ^^^^^^
    |
-   = note: defining type: wrong_region::<'?1, T>::{closure#0} with closure substs [
+   = note: defining type: wrong_region::<'?1, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?2 ()>, T)),
                (),
@@ -98,7 +98,7 @@ note: external requirements
 LL |     with_signature(a, b, |x, y| {
    |                          ^^^^^^
    |
-   = note: defining type: outlives_region::<'?1, '?2, T>::{closure#0} with closure substs [
+   = note: defining type: outlives_region::<'?1, '?2, T>::{closure#0} with closure args [
                i32,
                extern "rust-call" fn((std::cell::Cell<&'?3 ()>, T)),
                (),
diff --git a/tests/ui/nll/user-annotations/dump-adt-brace-struct.rs b/tests/ui/nll/user-annotations/dump-adt-brace-struct.rs
index ccda9129dabae..1d0b0d55af6c8 100644
--- a/tests/ui/nll/user-annotations/dump-adt-brace-struct.rs
+++ b/tests/ui/nll/user-annotations/dump-adt-brace-struct.rs
@@ -8,7 +8,7 @@
 
 struct SomeStruct<T> { t: T }
 
-#[rustc_dump_user_substs]
+#[rustc_dump_user_args]
 fn main() {
     SomeStruct { t: 22 }; // Nothing given, no annotation.
 
diff --git a/tests/ui/nll/user-annotations/dump-adt-brace-struct.stderr b/tests/ui/nll/user-annotations/dump-adt-brace-struct.stderr
index 5860621909ce4..7809b2470fedc 100644
--- a/tests/ui/nll/user-annotations/dump-adt-brace-struct.stderr
+++ b/tests/ui/nll/user-annotations/dump-adt-brace-struct.stderr
@@ -1,4 +1,4 @@
-error: user substs: UserSubsts { substs: [&ReStatic u32], user_self_ty: None }
+error: user args: UserArgs { args: [&ReStatic u32], user_self_ty: None }
   --> $DIR/dump-adt-brace-struct.rs:19:5
    |
 LL |     SomeStruct::<&'static u32> { t: &22 };
diff --git a/tests/ui/nll/user-annotations/dump-fn-method.rs b/tests/ui/nll/user-annotations/dump-fn-method.rs
index 148d63d848f80..9bdbbc37caad6 100644
--- a/tests/ui/nll/user-annotations/dump-fn-method.rs
+++ b/tests/ui/nll/user-annotations/dump-fn-method.rs
@@ -15,7 +15,7 @@ impl<S, T> Bazoom<T> for S {
 
 fn foo<'a, T>(_: T) { }
 
-#[rustc_dump_user_substs]
+#[rustc_dump_user_args]
 fn main() {
     // Here: nothing is given, so we don't have any annotation.
     let x = foo;
diff --git a/tests/ui/nll/user-annotations/dump-fn-method.stderr b/tests/ui/nll/user-annotations/dump-fn-method.stderr
index d139efa888ff7..1daf49825116b 100644
--- a/tests/ui/nll/user-annotations/dump-fn-method.stderr
+++ b/tests/ui/nll/user-annotations/dump-fn-method.stderr
@@ -1,22 +1,22 @@
-error: user substs: UserSubsts { substs: [&ReStatic u32], user_self_ty: None }
+error: user args: UserArgs { args: [&ReStatic u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:29:13
    |
 LL |     let x = foo::<&'static u32>;
    |             ^^^^^^^^^^^^^^^^^^^
 
-error: user substs: UserSubsts { substs: [^0, u32, ^1], user_self_ty: None }
+error: user args: UserArgs { args: [^0, u32, ^1], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:35:13
    |
 LL |     let x = <_ as Bazoom<u32>>::method::<_>;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: user substs: UserSubsts { substs: [u8, &ReStatic u16, u32], user_self_ty: None }
+error: user args: UserArgs { args: [u8, &ReStatic u16, u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:44:13
    |
 LL |     let x = <u8 as Bazoom<&'static u16>>::method::<u32>;
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: user substs: UserSubsts { substs: [^0, ^1, u32], user_self_ty: None }
+error: user args: UserArgs { args: [^0, ^1, u32], user_self_ty: None }
   --> $DIR/dump-fn-method.rs:52:5
    |
 LL |     y.method::<u32>(44, 66);
diff --git a/tests/ui/thir-print/thir-flat-const-variant.stdout b/tests/ui/thir-print/thir-flat-const-variant.stdout
index 1b76f07c31889..7bddc92599613 100644
--- a/tests/ui/thir-print/thir-flat-const-variant.stdout
+++ b/tests/ui/thir-print/thir-flat-const-variant.stdout
@@ -35,7 +35,7 @@ Thir {
                 AdtExpr {
                     adt_def: Foo,
                     variant_index: 0,
-                    substs: [],
+                    args: [],
                     user_ty: None,
                     fields: [
                         FieldExpr {
@@ -120,7 +120,7 @@ Thir {
                 AdtExpr {
                     adt_def: Foo,
                     variant_index: 0,
-                    substs: [],
+                    args: [],
                     user_ty: None,
                     fields: [
                         FieldExpr {
@@ -205,7 +205,7 @@ Thir {
                 AdtExpr {
                     adt_def: Foo,
                     variant_index: 0,
-                    substs: [],
+                    args: [],
                     user_ty: None,
                     fields: [
                         FieldExpr {
@@ -290,7 +290,7 @@ Thir {
                 AdtExpr {
                     adt_def: Foo,
                     variant_index: 0,
-                    substs: [],
+                    args: [],
                     user_ty: None,
                     fields: [
                         FieldExpr {
diff --git a/tests/ui/thir-print/thir-tree-match.stdout b/tests/ui/thir-print/thir-tree-match.stdout
index eea04c0951d39..3fc130f01765a 100644
--- a/tests/ui/thir-print/thir-tree-match.stdout
+++ b/tests/ui/thir-print/thir-tree-match.stdout
@@ -106,7 +106,7 @@ body:
                                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])) }], flags: NO_VARIANT_FLAGS }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], flags: NO_VARIANT_FLAGS }]
                                                                                                                 flags: IS_ENUM
                                                                                                                 repr: ReprOptions { int: None, align: None, pack: None, flags: (empty), field_shuffle_seed: 3477539199540094892 }
-                                                                                                        substs: []
+                                                                                                        args: []
                                                                                                         variant_index: 0
                                                                                                         subpatterns: [
                                                                                                             Pat: {
@@ -120,7 +120,7 @@ body:
                                                                                                                                 variants: [VariantDef { def_id: DefId(0:4 ~ thir_tree_match[fcf8]::Bar::First), ctor: Some((Const, DefId(0:5 ~ thir_tree_match[fcf8]::Bar::First::{constructor#0}))), name: "First", discr: Relative(0), fields: [], flags: NO_VARIANT_FLAGS }, VariantDef { def_id: DefId(0:6 ~ thir_tree_match[fcf8]::Bar::Second), ctor: Some((Const, DefId(0:7 ~ thir_tree_match[fcf8]::Bar::Second::{constructor#0}))), name: "Second", discr: Relative(1), fields: [], flags: NO_VARIANT_FLAGS }, VariantDef { def_id: DefId(0:8 ~ thir_tree_match[fcf8]::Bar::Third), ctor: Some((Const, DefId(0:9 ~ thir_tree_match[fcf8]::Bar::Third::{constructor#0}))), name: "Third", discr: Relative(2), fields: [], flags: NO_VARIANT_FLAGS }]
                                                                                                                                 flags: IS_ENUM
                                                                                                                                 repr: ReprOptions { int: None, align: None, pack: None, flags: (empty), field_shuffle_seed: 10333377570083945360 }
-                                                                                                                        substs: []
+                                                                                                                        args: []
                                                                                                                         variant_index: 0
                                                                                                                         subpatterns: []
                                                                                                                     }
@@ -179,7 +179,7 @@ body:
                                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])) }], flags: NO_VARIANT_FLAGS }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], flags: NO_VARIANT_FLAGS }]
                                                                                                                 flags: IS_ENUM
                                                                                                                 repr: ReprOptions { int: None, align: None, pack: None, flags: (empty), field_shuffle_seed: 3477539199540094892 }
-                                                                                                        substs: []
+                                                                                                        args: []
                                                                                                         variant_index: 0
                                                                                                         subpatterns: [
                                                                                                             Pat: {
@@ -242,7 +242,7 @@ body:
                                                                                                                 variants: [VariantDef { def_id: DefId(0:11 ~ thir_tree_match[fcf8]::Foo::FooOne), ctor: Some((Fn, DefId(0:12 ~ thir_tree_match[fcf8]::Foo::FooOne::{constructor#0}))), name: "FooOne", discr: Relative(0), fields: [FieldDef { did: DefId(0:13 ~ thir_tree_match[fcf8]::Foo::FooOne::0), name: "0", vis: Restricted(DefId(0:0 ~ thir_tree_match[fcf8])) }], flags: NO_VARIANT_FLAGS }, VariantDef { def_id: DefId(0:14 ~ thir_tree_match[fcf8]::Foo::FooTwo), ctor: Some((Const, DefId(0:15 ~ thir_tree_match[fcf8]::Foo::FooTwo::{constructor#0}))), name: "FooTwo", discr: Relative(1), fields: [], flags: NO_VARIANT_FLAGS }]
                                                                                                                 flags: IS_ENUM
                                                                                                                 repr: ReprOptions { int: None, align: None, pack: None, flags: (empty), field_shuffle_seed: 3477539199540094892 }
-                                                                                                        substs: []
+                                                                                                        args: []
                                                                                                         variant_index: 1
                                                                                                         subpatterns: []
                                                                                                     }