Auto merge of #139271 - compiler-errors:super-visit, r=<try>

Rely on type flags to avoid visiting types/consts/preds

Not sure if this is actually that useful, but let's see.

r? `@ghost`

Author: bors

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

@@ -515,6 +515,10 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
             ct
         }
     }
+
+    fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+        if p.flags().intersects(self.needs_canonical_flags) { p.super_fold_with(self) } else { p }
+    }
 }
 
 impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {

compiler/rustc_infer/src/infer/resolve.rs

@@ -56,6 +56,10 @@ impl<'a, 'tcx> TypeFolder<TyCtxt<'tcx>> for OpportunisticVarResolver<'a, 'tcx> {
             ct.super_fold_with(self)
         }
     }
+
+    fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+        if !p.has_non_region_infer() { p } else { p.super_fold_with(self) }
+    }
 }
 
 /// The opportunistic region resolver opportunistically resolves regions

compiler/rustc_middle/src/ty/abstract_const.rs

@@ -63,7 +63,12 @@ impl<'tcx> TyCtxt<'tcx> {
                     },
                     _ => c,
                 };
-                ct.super_fold_with(self)
+
+                if ct.has_type_flags(ty::TypeFlags::HAS_CT_PROJECTION) {
+                    ct.super_fold_with(self)
+                } else {
+                    ct
+                }
             }
         }
         ac.fold_with(&mut Expander { tcx: self })

compiler/rustc_middle/src/ty/erase_regions.rs

@@ -64,4 +64,20 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
             _ => self.tcx.lifetimes.re_erased,
         }
     }
+
+    fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
+        if ct.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
+            ct.super_fold_with(self)
+        } else {
+            ct
+        }
+    }
+
+    fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+        if p.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
+            p.super_fold_with(self)
+        } else {
+            p
+        }
+    }
 }

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -376,6 +376,22 @@ pub fn normalize_param_env_or_error<'tcx>(
 
                     c
                 }
+
+                fn fold_ty(&mut self, t: Ty<'tcx>) -> Ty<'tcx> {
+                    if t.has_type_flags(ty::TypeFlags::HAS_CT_PROJECTION) {
+                        t.super_fold_with(self)
+                    } else {
+                        t
+                    }
+                }
+
+                fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
+                    if p.has_type_flags(ty::TypeFlags::HAS_CT_PROJECTION) {
+                        p.super_fold_with(self)
+                    } else {
+                        p
+                    }
+                }
             }
 
             // This whole normalization step is a hack to work around the fact that

compiler/rustc_type_ir/src/binder.rs

@@ -697,12 +697,24 @@ impl<'a, I: Interner> TypeFolder<I> for ArgFolder<'a, I> {
     }
 
     fn fold_const(&mut self, c: I::Const) -> I::Const {
+        if !c.has_param() {
+            return c;
+        }
+
         if let ty::ConstKind::Param(p) = c.kind() {
             self.const_for_param(p, c)
         } else {
             c.super_fold_with(self)
         }
     }
+
+    fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate {
+        if !p.has_param() {
+            return p;
+        }
+
+        p.super_fold_with(self)
+    }
 }
 
 impl<'a, I: Interner> ArgFolder<'a, I> {

compiler/rustc_type_ir/src/fold.rs

@@ -54,7 +54,7 @@ use tracing::{debug, instrument};
 
 use crate::inherent::*;
 use crate::visit::{TypeVisitable, TypeVisitableExt as _};
-use crate::{self as ty, Interner};
+use crate::{self as ty, Interner, TypeFlags};
 
 #[cfg(feature = "nightly")]
 type Never = !;
@@ -502,4 +502,34 @@ impl<'a, I: Interner> TypeFolder<I> for RegionFolder<'a, I> {
             }
         }
     }
+
+    fn fold_ty(&mut self, t: I::Ty) -> I::Ty {
+        if t.has_type_flags(
+            TypeFlags::HAS_FREE_REGIONS | TypeFlags::HAS_RE_BOUND | TypeFlags::HAS_RE_ERASED,
+        ) {
+            t.super_fold_with(self)
+        } else {
+            t
+        }
+    }
+
+    fn fold_const(&mut self, ct: I::Const) -> I::Const {
+        if ct.has_type_flags(
+            TypeFlags::HAS_FREE_REGIONS | TypeFlags::HAS_RE_BOUND | TypeFlags::HAS_RE_ERASED,
+        ) {
+            ct.super_fold_with(self)
+        } else {
+            ct
+        }
+    }
+
+    fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate {
+        if p.has_type_flags(
+            TypeFlags::HAS_FREE_REGIONS | TypeFlags::HAS_RE_BOUND | TypeFlags::HAS_RE_ERASED,
+        ) {
+            p.super_fold_with(self)
+        } else {
+            p
+        }
+    }
 }