1 files changed, 9 insertions, 5 deletions
diff --git a/compiler/rustc_middle/src/infer/canonical.rs b/compiler/rustc_middle/src/infer/canonical.rs
index 2bbc48b633c..4fe4c2dadee 100644
--- a/compiler/rustc_middle/src/infer/canonical.rs
+++ b/compiler/rustc_middle/src/infer/canonical.rs
@@ -81,13 +81,18 @@ pub struct QueryResponse<'tcx, R> {
 #[derive(HashStable, TypeFoldable, TypeVisitable)]
 pub struct QueryRegionConstraints<'tcx> {
     pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
+    pub assumptions: Vec<ty::ArgOutlivesPredicate<'tcx>>,
 }
 
 impl QueryRegionConstraints<'_> {
-    /// Represents an empty (trivially true) set of region
-    /// constraints.
+    /// Represents an empty (trivially true) set of region constraints.
+    ///
+    /// FIXME(higher_ranked_auto): This could still just be true if there are only assumptions?
+    /// Because I don't expect for us to get cases where an assumption from one query would
+    /// discharge a requirement from another query, which is a potential problem if we did throw
+    /// away these assumptions because there were no constraints.
     pub fn is_empty(&self) -> bool {
-        self.outlives.is_empty()
+        self.outlives.is_empty() && self.assumptions.is_empty()
     }
 }
 
@@ -130,8 +135,7 @@ impl<'tcx, R> QueryResponse<'tcx, R> {
     }
 }
 
-pub type QueryOutlivesConstraint<'tcx> =
-    (ty::OutlivesPredicate<'tcx, GenericArg<'tcx>>, ConstraintCategory<'tcx>);
+pub type QueryOutlivesConstraint<'tcx> = (ty::ArgOutlivesPredicate<'tcx>, ConstraintCategory<'tcx>);
 
 #[derive(Default)]
 pub struct CanonicalParamEnvCache<'tcx> {