---

yaml
---
r: 232402
b: refs/heads/try
c: ab450ef
h: refs/heads/master
v: v3

Author: bors

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: edeb4f1c86cbf6af8ef9874d4b3af50f721ea1b8
 refs/heads/snap-stage3: 1af31d4974e33027a68126fa5a5a3c2c6491824f
-refs/heads/try: 45bf1ed1a1123122ded05ae2eedaf0f190e52726
+refs/heads/try: ab450ef22b08241513734f73952a4a1315738b03
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try/src/librustc_typeck/diagnostics.rs

@@ -2229,6 +2229,42 @@ type Foo = Trait<Bar=i32>; // ok!
 ```
 "##,
 
+E0221: r##"
+An attempt was made to retrieve an associated type, but the type was ambiguous.
+For example:
+
+```
+trait T1 {}
+trait T2 {}
+
+trait Foo {
+    type A: T1;
+}
+
+trait Bar : Foo {
+    type A: T2;
+    fn do_something() {
+        let _: Self::A;
+    }
+}
+```
+
+In this example, `Foo` defines an associated type `A`. `Bar` inherits that type
+from `Foo`, and defines another associated type of the same name. As a result,
+when we attempt to use `Self::A`, it's ambiguous whether we mean the `A` defined
+by `Foo` or the one defined by `Bar`.
+
+There are two options to work around this issue. The first is simply to rename
+one of the types. Alternatively, one can specify the intended type using the
+following syntax:
+
+```
+fn do_something() {
+    let _: <Self as Bar>::A;
+}
+```
+"##,
+
 E0223: r##"
 An attempt was made to retrieve an associated type, but the type was ambiguous.
 For example:
@@ -2698,7 +2734,6 @@ register_diagnostics! {
     E0217, // ambiguous associated type, defined in multiple supertraits
     E0218, // no associated type defined
     E0219, // associated type defined in higher-ranked supertrait
-    E0221, // ambiguous associated type in bounds
 //  E0222, // Error code E0045 (variadic function must have C calling
            // convention) duplicate
     E0224, // at least one non-builtin train is required for an object type