Fix propagation of the HAS_PROJECTION flag in object types. Fixes #20831 some more.

1 files changed, 15 insertions, 1 deletions

diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index cf30969ebef..fb216a5e99d 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -2604,12 +2604,17 @@ impl FlagComputation {
 
             &ty_projection(ref data) => {
                 self.add_flags(HAS_PROJECTION);
-                self.add_substs(data.trait_ref.substs);
+                self.add_projection_ty(data);
             }
 
             &ty_trait(box TyTrait { ref principal, ref bounds }) => {
                 let mut computation = FlagComputation::new();
                 computation.add_substs(principal.0.substs);
+                for projection_bound in bounds.projection_bounds.iter() {
+                    let mut proj_computation = FlagComputation::new();
+                    proj_computation.add_projection_predicate(&projection_bound.0);
+                    computation.add_bound_computation(&proj_computation);
+                }
                 self.add_bound_computation(&computation);
 
                 self.add_bounds(bounds);
@@ -2673,6 +2678,15 @@ impl FlagComputation {
         }
     }
 
+    fn add_projection_predicate(&mut self, projection_predicate: &ProjectionPredicate) {
+        self.add_projection_ty(&projection_predicate.projection_ty);
+        self.add_ty(projection_predicate.ty);
+    }
+
+    fn add_projection_ty(&mut self, projection_ty: &ProjectionTy) {
+        self.add_substs(projection_ty.trait_ref.substs);
+    }
+
     fn add_substs(&mut self, substs: &Substs) {
         self.add_tys(substs.types.as_slice());
         match substs.regions {