Add regression test for #22463

Closes #22463.

src/test/run-pass/issue-22463.rs

@@ -0,0 +1,29 @@
+// Copyright 2015 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.
+
+macro_rules! items {
+    () => {
+        type A = ();
+        fn a() {}
+    }
+}
+
+trait Foo {
+    type A;
+    fn a();
+}
+
+impl Foo for () {
+    items!();
+}
+
+fn main() {
+
+}