Auto merge of #141581 - lcnr:fold-clauses, r=compiler-errors

add additional `TypeFlags` fast paths

Some crates, e.g. `diesel`, have items with a lot of where-clauses (more than 150). In these cases checking the `TypeFlags` of the whole `param_env` can be very beneficial.

This adds `fn fold_clauses` to mirror the existing `fn visit_clauses` and then uses this in folders which fold `ParamEnv`s.

Split out from rust-lang/rust#141451, depends on rust-lang/rust#141442.

r? `@compiler-errors`

4 files changed, 40 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/ty/erase_regions.rs b/compiler/rustc_middle/src/ty/erase_regions.rs
index 45a0b1288db..f4fead7e952 100644
--- a/compiler/rustc_middle/src/ty/erase_regions.rs
+++ b/compiler/rustc_middle/src/ty/erase_regions.rs
@@ -86,4 +86,12 @@ impl<'tcx> TypeFolder<TyCtxt<'tcx>> for RegionEraserVisitor<'tcx> {
             p
         }
     }
+
+    fn fold_clauses(&mut self, c: ty::Clauses<'tcx>) -> ty::Clauses<'tcx> {
+        if c.has_type_flags(TypeFlags::HAS_BINDER_VARS | TypeFlags::HAS_FREE_REGIONS) {
+            c.super_fold_with(self)
+        } else {
+            c
+        }
+    }
 }
diff --git a/compiler/rustc_middle/src/ty/fold.rs b/compiler/rustc_middle/src/ty/fold.rs
index 8d6871d2f1f..b2057fa36d7 100644
--- a/compiler/rustc_middle/src/ty/fold.rs
+++ b/compiler/rustc_middle/src/ty/fold.rs
@@ -177,6 +177,10 @@ where
     fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
         if p.has_vars_bound_at_or_above(self.current_index) { p.super_fold_with(self) } else { p }
     }
+
+    fn fold_clauses(&mut self, c: ty::Clauses<'tcx>) -> ty::Clauses<'tcx> {
+        if c.has_vars_bound_at_or_above(self.current_index) { c.super_fold_with(self) } else { c }
+    }
 }
 
 impl<'tcx> TyCtxt<'tcx> {
diff --git a/compiler/rustc_middle/src/ty/predicate.rs b/compiler/rustc_middle/src/ty/predicate.rs
index 551d816941b..bc2ac42b6b1 100644
--- a/compiler/rustc_middle/src/ty/predicate.rs
+++ b/compiler/rustc_middle/src/ty/predicate.rs
@@ -238,6 +238,8 @@ impl<'tcx> Clause<'tcx> {
     }
 }
 
+impl<'tcx> rustc_type_ir::inherent::Clauses<TyCtxt<'tcx>> for ty::Clauses<'tcx> {}
+
 #[extension(pub trait ExistentialPredicateStableCmpExt<'tcx>)]
 impl<'tcx> ExistentialPredicate<'tcx> {
     /// Compares via an ordering that will not change if modules are reordered or other changes are
diff --git a/compiler/rustc_middle/src/ty/structural_impls.rs b/compiler/rustc_middle/src/ty/structural_impls.rs
index 7a7c33fb34d..000ba7b6fa7 100644
--- a/compiler/rustc_middle/src/ty/structural_impls.rs
+++ b/compiler/rustc_middle/src/ty/structural_impls.rs
@@ -570,6 +570,19 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Clause<'tcx> {
     }
 }
 
+impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Clauses<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        folder.try_fold_clauses(self)
+    }
+
+    fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
+        folder.fold_clauses(self)
+    }
+}
+
 impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ty::Predicate<'tcx> {
     fn visit_with<V: TypeVisitor<TyCtxt<'tcx>>>(&self, visitor: &mut V) -> V::Result {
         visitor.visit_predicate(*self)
@@ -615,6 +628,19 @@ impl<'tcx> TypeSuperVisitable<TyCtxt<'tcx>> for ty::Clauses<'tcx> {
     }
 }
 
+impl<'tcx> TypeSuperFoldable<TyCtxt<'tcx>> for ty::Clauses<'tcx> {
+    fn try_super_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        ty::util::try_fold_list(self, folder, |tcx, v| tcx.mk_clauses(v))
+    }
+
+    fn super_fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
+        ty::util::fold_list(self, folder, |tcx, v| tcx.mk_clauses(v))
+    }
+}
+
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ty::Const<'tcx> {
     fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
         self,
@@ -775,7 +801,6 @@ macro_rules! list_fold {
 }
 
 list_fold! {
-    ty::Clauses<'tcx> : mk_clauses,
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> : mk_poly_existential_predicates,
     &'tcx ty::List<PlaceElem<'tcx>> : mk_place_elems,
     &'tcx ty::List<ty::Pattern<'tcx>> : mk_patterns,