Normalize types in supertraits when checking that impls are valid during wf.

Fixes #20559.

src/librustc/middle/traits/project.rs

@@ -244,12 +244,11 @@ pub struct Normalized<'tcx,T> {
 pub type NormalizedTy<'tcx> = Normalized<'tcx, Ty<'tcx>>;
 
 impl<'tcx,T> Normalized<'tcx,T> {
-    fn with<U>(self, value: U) -> Normalized<'tcx,U> {
+    pub fn with<U>(self, value: U) -> Normalized<'tcx,U> {
         Normalized { value: value, obligations: self.obligations }
     }
 }
 
-
 pub fn normalize_projection_type<'a,'b,'tcx>(
     selcx: &'a mut SelectionContext<'b,'tcx>,
     projection_ty: ty::ProjectionTy<'tcx>,

src/librustc_typeck/check/wf.rs

@@ -235,9 +235,16 @@ impl<'ccx, 'tcx> CheckTypeWellFormedVisitor<'ccx, 'tcx> {
             // Find the supertrait bounds. This will add `int:Bar`.
             let poly_trait_ref = ty::Binder(trait_ref);
             let predicates = ty::predicates_for_trait_ref(fcx.tcx(), &poly_trait_ref);
-            for predicate in predicates.into_iter() {
+            let predicates = {
+                let selcx = &mut traits::SelectionContext::new(fcx.infcx(), fcx);
+                traits::normalize(selcx, cause.clone(), &predicates)
+            };
+            for predicate in predicates.value.into_iter() {
                 fcx.register_predicate(traits::Obligation::new(cause.clone(), predicate));
             }
+            for obligation in predicates.obligations.into_iter() {
+                fcx.register_predicate(obligation);
+            }
         });
     }
 }

src/test/run-pass/associated-types-projection-in-supertrait.rs

@@ -0,0 +1,50 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test that we are handle to correctly handle a projection type
+// that appears in a supertrait bound. Issue #20559.
+
+trait A
+{
+    type TA;
+}
+
+trait B<TB>
+{
+    fn foo (&self, t : TB) -> String;
+}
+
+trait C<TC : A> : B<<TC as A>::TA> { }
+
+struct X;
+
+impl A for X
+{
+    type TA = i32;
+}
+
+struct Y;
+
+impl C<X> for Y { }
+
+// Both of these impls are required for successful compilation
+impl B<i32> for Y
+{
+    fn foo (&self, t : i32) -> String
+    {
+        format!("First {}", t)
+    }
+}
+
+fn main ()
+{
+    let y = Y;
+    assert_eq!(y.foo(5), format!("First 5"));
+}