Add regression test.

Author: jseyfried

src/test/compile-fail/imports/unused.rs

@@ -0,0 +1,38 @@
+// Copyright 2016 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.
+
+#![feature(pub_restricted, item_like_imports)]
+#![deny(unused)]
+
+mod foo {
+    fn f() {}
+
+    mod m1 {
+        pub(super) use super::f; //~ ERROR unused
+    }
+
+    mod m2 {
+        #[allow(unused)]
+        use super::m1::*; // (despite this glob import)
+    }
+
+    mod m3 {
+        pub(super) use super::f; // Check that this is counted as used (c.f. #36249).
+    }
+
+    pub mod m4 {
+        use super::m3::*;
+        pub fn g() { f(); }
+    }
+}
+
+fn main() {
+    foo::m4::g();
+}