1 files changed, 21 insertions, 0 deletions
diff --git a/src/test/ui/impl-trait/auto-trait-leak-rpass.rs b/src/test/ui/impl-trait/auto-trait-leak-rpass.rs
new file mode 100644
index 000000000..9976a018b
--- /dev/null
+++ b/src/test/ui/impl-trait/auto-trait-leak-rpass.rs
@@ -0,0 +1,21 @@
+// run-pass
+
+// Fast path, main can see the concrete type returned.
+fn before() -> impl FnMut(i32) {
+    let mut p = Box::new(0);
+    move |x| *p = x
+}
+
+fn send<T: Send>(_: T) {}
+
+fn main() {
+    send(before());
+    send(after());
+}
+
+// Deferred path, main has to wait until typeck finishes,
+// to check if the return type of after is Send.
+fn after() -> impl FnMut(i32) {
+    let mut p = Box::new(0);
+    move |x| *p = x
+}