New upstream version 1.63.0+dfsg1

[rustc.git] / compiler / rustc_infer / src / infer / glb.rs

diff --git a/compiler/rustc_infer/src/infer/glb.rs b/compiler/rustc_infer/src/infer/glb.rs
index 0d38b94965afe2d61f401d3771b43ef5a5600195..1570a08f3ca8bdb0aa11a3e4bbbe9131fc673a64 100644 (file)
--- a/compiler/rustc_infer/src/infer/glb.rs
+++ b/compiler/rustc_infer/src/infer/glb.rs
@@ -95,12 +95,20 @@ impl<'tcx> TypeRelation<'tcx> for Glb<'_, '_, 'tcx> {
         T: Relate<'tcx>,
     {
         debug!("binders(a={:?}, b={:?})", a, b);
-
-        // When higher-ranked types are involved, computing the LUB is
-        // very challenging, switch to invariance. This is obviously
-        // overly conservative but works ok in practice.
-        self.relate_with_variance(ty::Variance::Invariant, ty::VarianceDiagInfo::default(), a, b)?;
-        Ok(a)
+        if a.skip_binder().has_escaping_bound_vars() || b.skip_binder().has_escaping_bound_vars() {
+            // When higher-ranked types are involved, computing the GLB is
+            // very challenging, switch to invariance. This is obviously
+            // overly conservative but works ok in practice.
+            self.relate_with_variance(
+                ty::Variance::Invariant,
+                ty::VarianceDiagInfo::default(),
+                a,
+                b,
+            )?;
+            Ok(a)
+        } else {
+            Ok(ty::Binder::dummy(self.relate(a.skip_binder(), b.skip_binder())?))
+        }
     }
 }