Added test for module_path! fix

Author: murarth

src/test/run-pass/issue-18859.rs

@@ -0,0 +1,24 @@
+// 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.
+
+mod foo {
+    pub mod bar {
+        pub mod baz {
+            pub fn name() -> &'static str {
+                module_path!()
+            }
+        }
+    }
+}
+
+fn main() {
+    assert_eq!(module_path!(), "issue-18859");
+    assert_eq!(foo::bar::baz::name(), "issue-18859::foo::bar::baz");
+}