Import async-trait crate.

Bug: 164106399
Bug: 158290206
Test: mm
Change-Id: I0c4a491b785134e4ac1d5572e5ff94b8699dc0bc
diff --git a/tests/ui/send-not-implemented.rs b/tests/ui/send-not-implemented.rs
new file mode 100644
index 0000000..a3e3856
--- /dev/null
+++ b/tests/ui/send-not-implemented.rs
@@ -0,0 +1,15 @@
+use async_trait::async_trait;
+use std::sync::Mutex;
+
+async fn f() {}
+
+#[async_trait]
+trait Test {
+    async fn test(&self) {
+        let mutex = Mutex::new(());
+        let _guard = mutex.lock().unwrap();
+        f().await;
+    }
+}
+
+fn main() {}