auto merge of #15191 : pcwalton/rust/variance-in-trait-matching, r=huonw

I believe that #5781 got fixed by the DST work. It duplicated the
variance inference work in #12828. Therefore, all that is left in #5781
is adding a test.

Closes #5781.

r? @huonw

1 files changed, 5 insertions, 3 deletions

diff --git a/src/libstd/task.rs b/src/libstd/task.rs
index dad241002f8..8ccded6681b 100644
--- a/src/libstd/task.rs
+++ b/src/libstd/task.rs
@@ -630,9 +630,11 @@ mod test {
         let mut reader = ChanReader::new(rx);
         let stdout = ChanWriter::new(tx);
 
-        TaskBuilder::new().stdout(box stdout as Box<Writer + Send>).try(proc() {
-            print!("Hello, world!");
-        }).unwrap();
+        let r = TaskBuilder::new().stdout(box stdout as Box<Writer + Send>)
+                                  .try(proc() {
+                print!("Hello, world!");
+            });
+        assert!(r.is_ok());
 
         let output = reader.read_to_str().unwrap();
         assert_eq!(output, "Hello, world!".to_string());