also add an async fn test

tests/run-pass-fullmir/async-fn.rs

@@ -0,0 +1,35 @@
+#![feature(
+    async_await,
+    await_macro,
+    futures_api,
+    pin,
+)]
+
+use std::{future::Future, pin::Pin, task::Poll};
+
+// See if we can run a basic `async fn`
+pub async fn foo(x: &u32, y: u32) -> u32 {
+    let y = &y;
+    let z = 9;
+    let z = &z;
+    let y = await!(async { *y + *z });
+    let a = 10;
+    let a = &a;
+    *x + y + *a
+}
+
+fn main() {
+    use std::{sync::Arc, task::{Wake, local_waker}};
+
+    struct NoWake;
+    impl Wake for NoWake {
+        fn wake(_arc_self: &Arc<Self>) {
+            panic!();
+        }
+    }
+
+    let lw = unsafe { local_waker(Arc::new(NoWake)) };
+    let x = 5;
+    let mut fut = foo(&x, 7);
+    assert_eq!(unsafe { Pin::new_unchecked(&mut fut) }.poll(&lw), Poll::Ready(31));
+}