Add a test case for #12187, which appears to have been fixed

Closes #12187.

src/test/compile-fail/issue-12187-1.rs

@@ -0,0 +1,18 @@
+// 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.
+
+fn new<T>() -> &'static T {
+    fail!()
+}
+
+fn main() {
+    let &v = new();
+    //~^ ERROR cannot determine a type for this local variable: unconstrained type
+}

src/test/compile-fail/issue-12187-2.rs

@@ -0,0 +1,18 @@
+// 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.
+
+fn new<'r, T>() -> &'r T {
+    fail!()
+}
+
+fn main() {
+    let &v = new();
+    //~^ ERROR cannot determine a type for this local variable: unconstrained type
+}