Rollup merge of rust-lang#61818 - tmandry:issue-60709-test, r=cramertj

Issue rust-lang#60709 test

Adds a test for rust-lang#60709, which was fixed as part of rust-lang#59897.

r? @cramertj

Author: Centril

src/test/run-pass/async-fn-size.rs renamed to src/test/run-pass/async-await/async-fn-size.rs

@@ -1,9 +1,9 @@
 // edition:2018
-// aux-build:arc_wake.rs
 
 #![feature(async_await, await_macro)]
 
-extern crate arc_wake;
+#[path = "../auxiliary/arc_wake.rs"]
+mod arc_wake;
 
 use std::pin::Pin;
 use std::future::Future;

src/test/run-pass/async-await/issue-60709.rs

@@ -0,0 +1,28 @@
+// This used to compile the future down to ud2, due to uninhabited types being
+// handled incorrectly in generators.
+// compile-flags: -Copt-level=z -Cdebuginfo=2 --edition=2018
+
+#![feature(async_await, await_macro)]
+#![allow(unused)]
+
+use std::future::Future;
+use std::task::Poll;
+use std::task::Context;
+use std::pin::Pin;
+use std::rc::Rc;
+
+struct Never();
+impl Future for Never {
+    type Output = ();
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Pending
+    }
+}
+
+fn main() {
+    let fut = async {
+        let _rc = Rc::new(()); // Also crashes with Arc
+        await!(Never());
+    };
+    let _bla = fut; // Moving the future is required.
+}