syntax: allow macros to expand to items with attributes.

Fixes #4471.

src/test/run-pass/macro-attributes.rs

@@ -0,0 +1,35 @@
+// Copyright 2013 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.
+
+// xfail-pretty - token trees can't pretty print
+
+#[feature(macro_rules)];
+
+macro_rules! compiles_fine {
+    ($at:attr) => {
+        // test that the different types of attributes work
+        #[attribute]
+        /// Documentation!
+        $at
+
+        // check that the attributes are recognised by requiring this
+        // to be removed to avoid a compile error
+        #[cfg(always_remove)]
+        static MISTYPED: () = "foo";
+    }
+}
+
+// item
+compiles_fine!(#[foo])
+
+pub fn main() {
+    // statement
+    compiles_fine!(#[bar]);
+}