add edition to regression test

nikomatsakis · nikomatsakis · commit a02a171e6a8e · 2019-08-12T18:33:53.000-04:00
diff --git a/src/test/ui/async-await/async-fn-elided-impl-lifetime-parameter.rs b/src/test/ui/async-await/async-fn-elided-impl-lifetime-parameter.rs
@@ -4,6 +4,7 @@
 // Regression test for #63500.
 //
 // check-pass
+// edition:2018
 
 #![feature(async_await)]
 
