Auto merge of #92805 - BoxyUwU:revert-lazy-anon-const-substs, r=lcnr

partially revertish `lazily "compute" anon const default substs`

reverts #87280 except for some of the changes around `ty::Unevaluated` having a visitor and a generic for promoted
why revert: <#92805 (comment)>

r? `@lcnr`

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -171,7 +171,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
         for (local, location) in drop_used {
             if !live_locals.contains(&local) {
                 let local_ty = self.cx.body.local_decls[local].ty;
-                if local_ty.has_free_regions(self.cx.typeck.tcx()) {
+                if local_ty.has_free_regions() {
                     self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
                 }
             }

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -426,7 +426,7 @@ impl<'a, 'b, 'tcx> Visitor<'tcx> for TypeVerifier<'a, 'b, 'tcx> {
                         self.cx.param_env.and(type_op::ascribe_user_type::AscribeUserType::new(
                             constant.literal.ty(),
                             uv.def.did,
-                            UserSubsts { substs: uv.substs(self.tcx()), user_self_ty: None },
+                            UserSubsts { substs: uv.substs, user_self_ty: None },
                         )),
                     ) {
                         span_mirbug!(
@@ -1970,7 +1970,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                         let predicates = self.prove_closure_bounds(
                             tcx,
                             def_id.expect_local(),
-                            uv.substs(tcx),
+                            uv.substs,
                             location,
                         );
                         self.normalize_and_prove_instantiated_predicates(

compiler/rustc_codegen_cranelift/src/constant.rs

@@ -129,11 +129,13 @@ pub(crate) fn codegen_constant<'tcx>(
     };
     let const_val = match const_.val {
         ConstKind::Value(const_val) => const_val,
-        ConstKind::Unevaluated(uv) if fx.tcx.is_static(uv.def.did) => {
-            assert!(uv.substs(fx.tcx).is_empty());
-            assert!(uv.promoted.is_none());
+        ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
+            if fx.tcx.is_static(def.did) =>
+        {
+            assert!(substs.is_empty());
+            assert!(promoted.is_none());
 
-            return codegen_static_ref(fx, uv.def.did, fx.layout_of(const_.ty)).to_cvalue(fx);
+            return codegen_static_ref(fx, def.did, fx.layout_of(const_.ty)).to_cvalue(fx);
         }
         ConstKind::Unevaluated(unevaluated) => {
             match fx.tcx.const_eval_resolve(ParamEnv::reveal_all(), unevaluated, None) {

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -507,7 +507,7 @@ impl<'ll, 'tcx> DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
                         ty::Adt(def, ..) if !def.is_box() => {
                             // Again, only create type information if full debuginfo is enabled
                             if cx.sess().opts.debuginfo == DebugInfo::Full
-                                && !impl_self_ty.definitely_needs_subst(cx.tcx)
+                                && !impl_self_ty.needs_subst()
                             {
                                 Some(type_metadata(cx, impl_self_ty, rustc_span::DUMMY_SP))
                             } else {

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -1477,7 +1477,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 LocalRef::UnsizedPlace(_) => bug!("transmute must not involve unsized locals"),
                 LocalRef::Operand(None) => {
                     let dst_layout = bx.layout_of(self.monomorphized_place_ty(dst.as_ref()));
-                    assert!(!dst_layout.ty.has_erasable_regions(self.cx.tcx()));
+                    assert!(!dst_layout.ty.has_erasable_regions());
                     let place = PlaceRef::alloca(bx, dst_layout);
                     place.storage_live(bx);
                     self.codegen_transmute_into(bx, src, place);

compiler/rustc_codegen_ssa/src/mir/mod.rs

@@ -209,7 +209,7 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         let mut allocate_local = |local| {
             let decl = &mir.local_decls[local];
             let layout = bx.layout_of(fx.monomorphize(decl.ty));
-            assert!(!layout.ty.has_erasable_regions(cx.tcx()));
+            assert!(!layout.ty.has_erasable_regions());
 
             if local == mir::RETURN_PLACE && fx.fn_abi.ret.is_indirect() {
                 debug!("alloc: {:?} (return place) -> place", local);

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -568,7 +568,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             ty::ConstKind::Param(_) | ty::ConstKind::Bound(..) => throw_inval!(TooGeneric),
             ty::ConstKind::Error(_) => throw_inval!(AlreadyReported(ErrorReported)),
             ty::ConstKind::Unevaluated(uv) => {
-                let instance = self.resolve(uv.def, uv.substs(*self.tcx))?;
+                let instance = self.resolve(uv.def, uv.substs)?;
                 Ok(self.eval_to_allocation(GlobalId { instance, promoted: uv.promoted })?.into())
             }
             ty::ConstKind::Infer(..) | ty::ConstKind::Placeholder(..) => {

compiler/rustc_const_eval/src/interpret/util.rs

@@ -9,7 +9,7 @@ where
     T: TypeFoldable<'tcx>,
 {
     debug!("ensure_monomorphic_enough: ty={:?}", ty);
-    if !ty.potentially_needs_subst() {
+    if !ty.needs_subst() {
         return Ok(());
     }
 
@@ -21,12 +21,8 @@ where
     impl<'tcx> TypeVisitor<'tcx> for UsedParamsNeedSubstVisitor<'tcx> {
         type BreakTy = FoundParam;
 
-        fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-            Some(self.tcx)
-        }
-
         fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-            if !ty.potentially_needs_subst() {
+            if !ty.needs_subst() {
                 return ControlFlow::CONTINUE;
             }
 
@@ -44,7 +40,7 @@ where
                         let is_used = unused_params.contains(index).map_or(true, |unused| !unused);
                         // Only recurse when generic parameters in fns, closures and generators
                         // are used and require substitution.
-                        match (is_used, subst.definitely_needs_subst(self.tcx)) {
+                        match (is_used, subst.needs_subst()) {
                             // Just in case there are closures or generators within this subst,
                             // recurse.
                             (true, true) => return subst.super_visit_with(self),

compiler/rustc_const_eval/src/transform/check_consts/check.rs

@@ -347,7 +347,7 @@ impl<'mir, 'tcx> Checker<'mir, 'tcx> {
     fn check_local_or_return_ty(&mut self, ty: Ty<'tcx>, local: Local) {
         let kind = self.body.local_kind(local);
 
-        for ty in ty.walk(self.tcx) {
+        for ty in ty.walk() {
             let ty = match ty.unpack() {
                 GenericArgKind::Type(ty) => ty,
 

compiler/rustc_const_eval/src/transform/check_consts/qualifs.rs

@@ -337,7 +337,7 @@ where
 
     // Check the qualifs of the value of `const` items.
     if let Some(ct) = constant.literal.const_for_ty() {
-        if let ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs_: _, promoted }) = ct.val {
+        if let ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs: _, promoted }) = ct.val {
             // 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.

compiler/rustc_const_eval/src/transform/promote_consts.rs

@@ -843,17 +843,13 @@ impl<'a, 'tcx> Promoter<'a, 'tcx> {
                             ty,
                             val: ty::ConstKind::Unevaluated(ty::Unevaluated {
                                 def,
-                                substs_: Some(InternalSubsts::for_item(
-                                    tcx,
-                                    def.did,
-                                    |param, _| {
-                                        if let ty::GenericParamDefKind::Lifetime = param.kind {
-                                            tcx.lifetimes.re_erased.into()
-                                        } else {
-                                            tcx.mk_param_from_def(param)
-                                        }
-                                    },
-                                )),
+                                substs: InternalSubsts::for_item(tcx, def.did, |param, _| {
+                                    if let ty::GenericParamDefKind::Lifetime = param.kind {
+                                        tcx.lifetimes.re_erased.into()
+                                    } else {
+                                        tcx.mk_param_from_def(param)
+                                    }
+                                }),
                                 promoted: Some(promoted_id),
                             }),
                         })
@@ -969,7 +965,6 @@ pub fn promote_candidates<'tcx>(
         scope.parent_scope = None;
 
         let promoted = Body::new(
-            tcx,
             body.source, // `promoted` gets filled in below
             IndexVec::new(),
             IndexVec::from_elem_n(scope, 1),

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -470,7 +470,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
     {
         let needs_canonical_flags = if canonicalize_region_mode.any() {
             TypeFlags::NEEDS_INFER |
-            TypeFlags::HAS_POTENTIAL_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_POTENTIAL_FREE_REGIONS`
+            TypeFlags::HAS_FREE_REGIONS | // `HAS_RE_PLACEHOLDER` implies `HAS_FREE_REGIONS`
             TypeFlags::HAS_TY_PLACEHOLDER |
             TypeFlags::HAS_CT_PLACEHOLDER
         } else {

compiler/rustc_infer/src/infer/combine.rs

@@ -129,8 +129,6 @@ impl<'infcx, 'tcx> InferCtxt<'infcx, 'tcx> {
     where
         R: ConstEquateRelation<'tcx>,
     {
-        let a = self.tcx.expose_default_const_substs(a);
-        let b = self.tcx.expose_default_const_substs(b);
         debug!("{}.consts({:?}, {:?})", relation.tag(), a, b);
         if a == b {
             return Ok(a);
@@ -746,9 +744,10 @@ impl<'tcx> TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                     }
                 }
             }
-            ty::ConstKind::Unevaluated(uv) if self.tcx().lazy_normalization() => {
-                assert_eq!(uv.promoted, None);
-                let substs = uv.substs(self.tcx());
+            ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
+                if self.tcx().lazy_normalization() =>
+            {
+                assert_eq!(promoted, None);
                 let substs = self.relate_with_variance(
                     ty::Variance::Invariant,
                     ty::VarianceDiagInfo::default(),
@@ -757,7 +756,7 @@ impl<'tcx> TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                 )?;
                 Ok(self.tcx().mk_const(ty::Const {
                     ty: c.ty,
-                    val: ty::ConstKind::Unevaluated(ty::Unevaluated::new(uv.def, substs)),
+                    val: ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted }),
                 }))
             }
             _ => relate::super_relate_consts(self, c, c),
@@ -991,9 +990,10 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
                     }
                 }
             }
-            ty::ConstKind::Unevaluated(uv) if self.tcx().lazy_normalization() => {
-                assert_eq!(uv.promoted, None);
-                let substs = uv.substs(self.tcx());
+            ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted })
+                if self.tcx().lazy_normalization() =>
+            {
+                assert_eq!(promoted, None);
                 let substs = self.relate_with_variance(
                     ty::Variance::Invariant,
                     ty::VarianceDiagInfo::default(),
@@ -1002,7 +1002,7 @@ impl<'tcx> TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
                 )?;
                 Ok(self.tcx().mk_const(ty::Const {
                     ty: c.ty,
-                    val: ty::ConstKind::Unevaluated(ty::Unevaluated::new(uv.def, substs)),
+                    val: ty::ConstKind::Unevaluated(ty::Unevaluated { def, substs, promoted }),
                 }))
             }
             _ => relate::super_relate_consts(self, c, c),

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1549,10 +1549,6 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         }
 
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for OpaqueTypesVisitor<'tcx> {
-            fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-                Some(self.tcx)
-            }
-
             fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
                 if let Some((kind, def_id)) = TyCategory::from_ty(self.tcx, t) {
                     let span = self.tcx.def_span(def_id);

compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -52,7 +52,7 @@ impl<'a, 'tcx> FindHirNodeVisitor<'a, 'tcx> {
 
     fn node_ty_contains_target(&self, hir_id: HirId) -> Option<Ty<'tcx>> {
         self.node_type_opt(hir_id).map(|ty| self.infcx.resolve_vars_if_possible(ty)).filter(|ty| {
-            ty.walk(self.infcx.tcx).any(|inner| {
+            ty.walk().any(|inner| {
                 inner == self.target
                     || match (inner.unpack(), self.target.unpack()) {
                         (GenericArgKind::Type(inner_ty), GenericArgKind::Type(target_ty)) => {
@@ -445,9 +445,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                             parent: None,
                         }
                     }
-                    ty::ConstKind::Unevaluated(ty::Unevaluated {
-                        substs_: Some(substs), ..
-                    }) => {
+                    ty::ConstKind::Unevaluated(ty::Unevaluated { substs, .. }) => {
                         assert!(substs.has_infer_types_or_consts());
 
                         // FIXME: We only use the first inference variable we encounter in

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -558,12 +558,6 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 pub(super) struct TraitObjectVisitor(pub(super) FxHashSet<DefId>);
 
 impl<'tcx> TypeVisitor<'tcx> for TraitObjectVisitor {
-    fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-        // The default anon const substs cannot include
-        // trait objects, so we don't have to bother looking.
-        None
-    }
-
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match t.kind() {
             ty::Dynamic(preds, RegionKind::ReStatic) => {

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/trait_impl_difference.rs

@@ -80,26 +80,21 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 
         // Mark all unnamed regions in the type with a number.
         // This diagnostic is called in response to lifetime errors, so be informative.
-        struct HighlightBuilder<'tcx> {
+        struct HighlightBuilder {
             highlight: RegionHighlightMode,
-            tcx: TyCtxt<'tcx>,
             counter: usize,
         }
 
-        impl<'tcx> HighlightBuilder<'tcx> {
-            fn build(tcx: TyCtxt<'tcx>, ty: Ty<'tcx>) -> RegionHighlightMode {
+        impl HighlightBuilder {
+            fn build(ty: Ty<'_>) -> RegionHighlightMode {
                 let mut builder =
-                    HighlightBuilder { highlight: RegionHighlightMode::default(), counter: 1, tcx };
+                    HighlightBuilder { highlight: RegionHighlightMode::default(), counter: 1 };
                 builder.visit_ty(ty);
                 builder.highlight
             }
         }
 
-        impl<'tcx> ty::fold::TypeVisitor<'tcx> for HighlightBuilder<'tcx> {
-            fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-                Some(self.tcx)
-            }
-
+        impl<'tcx> ty::fold::TypeVisitor<'tcx> for HighlightBuilder {
             fn visit_region(&mut self, r: ty::Region<'tcx>) -> ControlFlow<Self::BreakTy> {
                 if !r.has_name() && self.counter <= 3 {
                     self.highlight.highlighting_region(r, self.counter);
@@ -109,12 +104,12 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
             }
         }
 
-        let expected_highlight = HighlightBuilder::build(self.tcx(), expected);
+        let expected_highlight = HighlightBuilder::build(expected);
         let expected = self
             .infcx
             .extract_inference_diagnostics_data(expected.into(), Some(expected_highlight))
             .name;
-        let found_highlight = HighlightBuilder::build(self.tcx(), found);
+        let found_highlight = HighlightBuilder::build(found);
         let found =
             self.infcx.extract_inference_diagnostics_data(found.into(), Some(found_highlight)).name;
 

compiler/rustc_infer/src/infer/freshen.rs

@@ -146,7 +146,7 @@ impl<'a, 'tcx> TypeFolder<'tcx> for TypeFreshener<'a, 'tcx> {
     }
 
     fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
-        if !t.needs_infer() && !t.has_erasable_regions(self.tcx()) {
+        if !t.needs_infer() && !t.has_erasable_regions() {
             return t;
         }
 

compiler/rustc_infer/src/infer/mod.rs

@@ -1585,8 +1585,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         unevaluated: ty::Unevaluated<'tcx>,
         span: Option<Span>,
     ) -> EvalToConstValueResult<'tcx> {
-        let mut substs = unevaluated.substs(self.tcx);
-        substs = self.resolve_vars_if_possible(substs);
+        let substs = self.resolve_vars_if_possible(unevaluated.substs);
 
         // Postpone the evaluation of constants whose substs depend on inference
         // variables
@@ -1599,7 +1598,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
 
         let unevaluated = ty::Unevaluated {
             def: unevaluated.def,
-            substs_: Some(substs_erased),
+            substs: substs_erased,
             promoted: unevaluated.promoted,
         };
 

compiler/rustc_infer/src/infer/nll_relate/mod.rs

@@ -201,7 +201,6 @@ where
         };
 
         value.skip_binder().visit_with(&mut ScopeInstantiator {
-            tcx: self.infcx.tcx,
             next_region: &mut next_region,
             target_index: ty::INNERMOST,
             bound_region_scope: &mut scope,
@@ -759,18 +758,13 @@ where
 /// `for<..`>.  For each of those, it creates an entry in
 /// `bound_region_scope`.
 struct ScopeInstantiator<'me, 'tcx> {
-    tcx: TyCtxt<'tcx>,
     next_region: &'me mut dyn FnMut(ty::BoundRegion) -> ty::Region<'tcx>,
     // The debruijn index of the scope we are instantiating.
     target_index: ty::DebruijnIndex,
     bound_region_scope: &'me mut BoundRegionScope<'tcx>,
 }
 
 impl<'me, 'tcx> TypeVisitor<'tcx> for ScopeInstantiator<'me, 'tcx> {
-    fn tcx_for_anon_const_substs(&self) -> Option<TyCtxt<'tcx>> {
-        Some(self.tcx)
-    }
-
     fn visit_binder<T: TypeFoldable<'tcx>>(
         &mut self,
         t: &ty::Binder<'tcx, T>,