Actually visit/fold the types inside CanonicalVarInfos

Author: oli-obk

compiler/rustc_middle/src/infer/canonical.rs

@@ -29,7 +29,7 @@ use rustc_index::vec::IndexVec;
 use rustc_macros::HashStable;
 use smallvec::SmallVec;
 use std::iter;
-use std::ops::Index;
+use std::ops::{ControlFlow, Index};
 
 /// A "canonicalized" type `V` is one where all free inference
 /// variables have been rewritten to "canonical vars". These are
@@ -44,6 +44,21 @@ pub struct Canonical<'tcx, V> {
 
 pub type CanonicalVarInfos<'tcx> = &'tcx List<CanonicalVarInfo<'tcx>>;
 
+impl<'tcx> ty::TypeFoldable<'tcx> for CanonicalVarInfos<'tcx> {
+    fn try_fold_with<F: ty::FallibleTypeFolder<'tcx>>(
+        self,
+        folder: &mut F,
+    ) -> Result<Self, F::Error> {
+        ty::util::fold_list(self, folder, |tcx, v| tcx.intern_canonical_var_infos(v))
+    }
+}
+
+impl<'tcx> ty::TypeVisitable<'tcx> for CanonicalVarInfos<'tcx> {
+    fn visit_with<V: ty::TypeVisitor<'tcx>>(&self, visitor: &mut V) -> ControlFlow<V::BreakTy> {
+        self.iter().try_for_each(|t| t.visit_with(visitor))
+    }
+}
+
 /// A set of values corresponding to the canonical variables from some
 /// `Canonical`. You can give these values to
 /// `canonical_value.substitute` to substitute them into the canonical
@@ -305,12 +320,6 @@ TrivialTypeTraversalAndLiftImpls! {
     }
 }
 
-TrivialTypeTraversalImpls! {
-    for <'tcx> {
-        crate::infer::canonical::CanonicalVarInfos<'tcx>,
-    }
-}
-
 impl<'tcx> CanonicalVarValues<'tcx> {
     #[inline]
     pub fn len(&self) -> usize {