Error on using `yield` without also using `#[coroutine]` on the closure

And suggest adding the `#[coroutine]` to the closure

1 files changed, 3 insertions, 2 deletions

diff --git a/example/polymorphize_coroutine.rs b/example/polymorphize_coroutine.rs
index c965b34e13b..407da94c0f0 100644
--- a/example/polymorphize_coroutine.rs
+++ b/example/polymorphize_coroutine.rs
@@ -1,4 +1,4 @@
-#![feature(coroutines, coroutine_trait)]
+#![feature(coroutines, coroutine_trait, stmt_expr_attributes)]
 
 use std::ops::Coroutine;
 use std::pin::Pin;
@@ -8,7 +8,8 @@ fn main() {
 }
 
 fn run_coroutine<T>() {
-    let mut coroutine = || {
+    let mut coroutine = #[coroutine]
+    || {
         yield;
         return;
     };