instantiate_own doesn't need to return a pair of vectors

2 files changed, 18 insertions, 9 deletions

diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 8a5e765b9a3..801ca600445 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -341,15 +341,9 @@ impl<'tcx> GenericPredicates<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         substs: SubstsRef<'tcx>,
-    ) -> InstantiatedPredicates<'tcx> {
-        InstantiatedPredicates {
-            predicates: self
-                .predicates
-                .iter()
-                .map(|(p, _)| EarlyBinder(*p).subst(tcx, substs))
-                .collect(),
-            spans: self.predicates.iter().map(|(_, sp)| *sp).collect(),
-        }
+    ) -> impl Iterator<Item = (Predicate<'tcx>, Span)> + DoubleEndedIterator + ExactSizeIterator
+    {
+        EarlyBinder(self.predicates).subst_iter_copied(tcx, substs)
     }
 
     #[instrument(level = "debug", skip(self, tcx))]
diff --git a/compiler/rustc_middle/src/ty/subst.rs b/compiler/rustc_middle/src/ty/subst.rs
index 8f764011d0a..5dc9e311bf6 100644
--- a/compiler/rustc_middle/src/ty/subst.rs
+++ b/compiler/rustc_middle/src/ty/subst.rs
@@ -639,6 +639,13 @@ where
     }
 }
 
+impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIter<'_, 'tcx, I>
+where
+    I::IntoIter: ExactSizeIterator,
+    I::Item: TypeFoldable<'tcx>,
+{
+}
+
 impl<'tcx, 's, I: IntoIterator> EarlyBinder<I>
 where
     I::Item: Deref,
@@ -686,6 +693,14 @@ where
     }
 }
 
+impl<'tcx, I: IntoIterator> ExactSizeIterator for SubstIterCopied<'_, 'tcx, I>
+where
+    I::IntoIter: ExactSizeIterator,
+    I::Item: Deref,
+    <I::Item as Deref>::Target: Copy + TypeFoldable<'tcx>,
+{
+}
+
 pub struct EarlyBinderIter<T> {
     t: T,
 }