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`

2 files changed, 12 insertions, 0 deletions

diff --git a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
index 0b543f091f7..060447ba720 100644
--- a/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
+++ b/compiler/rustc_infer/src/infer/canonical/canonicalizer.rs
@@ -497,6 +497,10 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
     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 }
     }
+
+    fn fold_clauses(&mut self, c: ty::Clauses<'tcx>) -> ty::Clauses<'tcx> {
+        if c.flags().intersects(self.needs_canonical_flags) { c.super_fold_with(self) } else { c }
+    }
 }
 
 impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
diff --git a/compiler/rustc_infer/src/infer/resolve.rs b/compiler/rustc_infer/src/infer/resolve.rs
index 4b0ace8c554..a95f24b5b95 100644
--- a/compiler/rustc_infer/src/infer/resolve.rs
+++ b/compiler/rustc_infer/src/infer/resolve.rs
@@ -55,6 +55,14 @@ 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) }
+    }
+
+    fn fold_clauses(&mut self, c: ty::Clauses<'tcx>) -> ty::Clauses<'tcx> {
+        if !c.has_non_region_infer() { c } else { c.super_fold_with(self) }
+    }
 }
 
 /// The opportunistic region resolver opportunistically resolves regions