Add test for passing keywords through macros

Author: Manishearth

src/test/compile-fail/auxiliary/edition-kw-macro-2015.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 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.
+
+// compile-flags: -Zedition=2015 -Zunstable-options
+
+#[macro_export]
+macro_rules! consumes_async {
+    (async) => (1)
+}
+

src/test/compile-fail/edition-keywords-2018.rs

@@ -0,0 +1,22 @@
+// Copyright 2018 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.
+
+// compile-flags: -Zedition=2018 -Zunstable-options
+// aux-build:edition-kw-macro-2015.rs
+
+#![feature(raw_identifiers)]
+
+#[macro_use]
+extern crate edition_kw_macro_2015;
+
+pub fn main() {
+    let _ = consumes_async!(async);
+    //~^ ERROR no rules expected the token `async`
+}