chore: checkpoint before Python removal

vendor/async-trait/tests/ui/must-use.rs

@@ -0,0 +1,21 @@
+#![deny(unused_must_use)]
+
+use async_trait::async_trait;
+
+#[async_trait]
+trait Interface {
+    async fn f(&self);
+}
+
+struct Thing;
+
+#[async_trait]
+impl Interface for Thing {
+    async fn f(&self) {}
+}
+
+pub async fn f() {
+    Thing.f();
+}
+
+fn main() {}