Add test for #44128.

Author: jseyfried

src/test/run-pass/hygiene/issue-44128.rs

@@ -0,0 +1,25 @@
+// Copyright 2017 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(decl_macro)]
+
+pub macro create_struct($a:ident) {
+    struct $a;
+    impl Clone for $a {
+        fn clone(&self) -> Self {
+            $a
+        }
+    }
+}
+
+fn main() {
+    create_struct!(Test);
+    Test.clone();
+}