Rollup merge of #29004 - frewsxcv:regression-test-22814, r=alexcrichton

Closes #22814

src/test/run-pass/issue-22814.rs

@@ -0,0 +1,22 @@
+// 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.
+
+trait Test {}
+
+macro_rules! test {
+( $($name:ident)+) => (
+    impl<$($name: Test),*> Test for ($($name,)*) {
+    }
+)
+}
+
+test!(A B C);
+
+fn main() {}