test: Add regression test for "source trait is private"

src/test/compile-fail/privacy-ufcs.rs

@@ -0,0 +1,24 @@
+// 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 to ensure private traits are inaccessible with UFCS angle-bracket syntax.
+
+mod foo {
+    trait Bar {
+        fn baz() {}
+    }
+
+    impl Bar for i32 {}
+}
+
+fn main() {
+    <i32 as ::foo::Bar>::baz(); //~ERROR method `baz` is inaccessible
+                                //~^NOTE: trait `Bar` is private
+}

src/test/compile-fail/trait-not-accessible.rs

@@ -0,0 +1,28 @@
+// 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.
+
+mod m {
+    trait Priv {
+        fn f(&self) {}
+    }
+    impl Priv for super::S {}
+    pub trait Pub: Priv {}
+}
+
+struct S;
+impl m::Pub for S {}
+
+fn g<T: m::Pub>(arg: T) {
+    arg.f(); //~ ERROR: source trait is private
+}
+
+fn main() {
+    g(S);
+}