Add a test that causes an ICE currently

src/test/compile-fail/unconstrained-ref.rs

@@ -0,0 +1,17 @@
+// Copyright 2012 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.
+
+struct S<'self, T> {
+    o: &'self Option<T>
+}
+
+fn main() {
+    S { o: &None }; //~ ERROR cannot determine a type for this expression: unconstrained type
+}