1 files changed, 105 insertions, 0 deletions
diff --git a/src/test/ui/async-await/async-fn-size.rs b/src/test/ui/async-await/async-fn-size.rs
new file mode 100644
index 000000000..0c1f36364
--- /dev/null
+++ b/src/test/ui/async-await/async-fn-size.rs
@@ -0,0 +1,105 @@
+// run-pass
+// aux-build:arc_wake.rs
+// edition:2018
+
+extern crate arc_wake;
+
+use std::pin::Pin;
+use std::future::Future;
+use std::sync::{
+    Arc,
+    atomic::{self, AtomicUsize},
+};
+use std::task::{Context, Poll};
+use arc_wake::ArcWake;
+
+struct Counter {
+    wakes: AtomicUsize,
+}
+
+impl ArcWake for Counter {
+    fn wake(self: Arc<Self>) {
+        Self::wake_by_ref(&self)
+    }
+    fn wake_by_ref(arc_self: &Arc<Self>) {
+        arc_self.wakes.fetch_add(1, atomic::Ordering::SeqCst);
+    }
+}
+
+struct WakeOnceThenComplete(bool, u8);
+
+impl Future for WakeOnceThenComplete {
+    type Output = u8;
+    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<u8> {
+        if self.0 {
+            Poll::Ready(self.1)
+        } else {
+            cx.waker().wake_by_ref();
+            self.0 = true;
+            Poll::Pending
+        }
+    }
+}
+
+fn wait(fut: impl Future<Output = u8>) -> u8 {
+    let mut fut = Box::pin(fut);
+    let counter = Arc::new(Counter { wakes: AtomicUsize::new(0) });
+    let waker = ArcWake::into_waker(counter.clone());
+    let mut cx = Context::from_waker(&waker);
+    loop {
+        match fut.as_mut().poll(&mut cx) {
+            Poll::Ready(out) => return out,
+            Poll::Pending => (),
+        }
+    }
+}
+
+fn base() -> WakeOnceThenComplete { WakeOnceThenComplete(false, 1) }
+
+async fn await1_level1() -> u8 {
+    base().await
+}
+
+async fn await2_level1() -> u8 {
+    base().await + base().await
+}
+
+async fn await3_level1() -> u8 {
+    base().await + base().await + base().await
+}
+
+async fn await3_level2() -> u8 {
+    await3_level1().await + await3_level1().await + await3_level1().await
+}
+
+async fn await3_level3() -> u8 {
+    await3_level2().await + await3_level2().await + await3_level2().await
+}
+
+async fn await3_level4() -> u8 {
+    await3_level3().await + await3_level3().await + await3_level3().await
+}
+
+async fn await3_level5() -> u8 {
+    await3_level4().await + await3_level4().await + await3_level4().await
+}
+
+fn main() {
+    assert_eq!(2, std::mem::size_of_val(&base()));
+    assert_eq!(3, std::mem::size_of_val(&await1_level1()));
+    assert_eq!(4, std::mem::size_of_val(&await2_level1()));
+    assert_eq!(5, std::mem::size_of_val(&await3_level1()));
+    assert_eq!(8, std::mem::size_of_val(&await3_level2()));
+    assert_eq!(11, std::mem::size_of_val(&await3_level3()));
+    assert_eq!(14, std::mem::size_of_val(&await3_level4()));
+    assert_eq!(17, std::mem::size_of_val(&await3_level5()));
+
+    assert_eq!(1,   wait(base()));
+    assert_eq!(1,   wait(await1_level1()));
+    assert_eq!(2,   wait(await2_level1()));
+    assert_eq!(3,   wait(await3_level1()));
+    assert_eq!(9,   wait(await3_level2()));
+    assert_eq!(27,  wait(await3_level3()));
+    assert_eq!(81,  wait(await3_level4()));
+    assert_eq!(243, wait(await3_level5()));
+}