1 files changed, 10 insertions, 1 deletions
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index f8fc2cc8303..ad26383df6a 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -1522,10 +1522,17 @@ impl UniverseIndex {
 
     /// True if `self` can name a name from `other` -- in other words,
     /// if the set of names in `self` is a superset of those in
-    /// `other`.
+    /// `other` (`self >= other`).
     pub fn can_name(self, other: UniverseIndex) -> bool {
         self.private >= other.private
     }
+
+    /// True if `self` cannot name some names from `other` -- in other
+    /// words, if the set of names in `self` is a strict subset of
+    /// those in `other` (`self < other`).
+    pub fn cannot_name(self, other: UniverseIndex) -> bool {
+        self.private < other.private
+    }
 }
 
 /// The "placeholder index" fully defines a placeholder region.
@@ -1540,6 +1547,8 @@ pub struct Placeholder {
     pub name: BoundRegion,
 }
 
+impl_stable_hash_for!(struct Placeholder { universe, name });
+
 /// When type checking, we use the `ParamEnv` to track
 /// details about the set of where-clauses that are in scope at this
 /// particular point.