Rollup merge of #50416 - rleungx:non-lifetime, r=estebank

check if the token is a lifetime before parsing

Fixes #50381.

src/test/compile-fail/macro-non-lifetime.rs

@@ -0,0 +1,20 @@
+// 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.
+
+// Test for issue #50381: non-lifetime passed to :lifetime.
+
+#![feature(macro_lifetime_matcher)]
+
+macro_rules! m { ($x:lifetime) => { } }
+
+fn main() {
+    m!(a);
+    //~^ ERROR expected a lifetime, found `a`
+}