Add a test for issue #18865. Fixes #18865.

src/test/compile-fail/associated-types-invalid-trait-ref-issue-18865.rs

@@ -0,0 +1,26 @@
+// Copyright 2014 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 report an error if the trait ref in an qualified type
+// uses invalid type arguments.
+
+#![feature(associated_types)]
+
+trait Foo<T> {
+    type Bar;
+    fn get_bar(&self) -> Self::Bar;
+}
+
+fn f<T:Foo<int>>(t: &T) {
+    let u: <T as Foo<uint>>::Bar = t.get_bar();
+    //~^ ERROR the trait `Foo<uint>` is not implemented for the type `T`
+}
+
+fn main() { }