Add test for Future inflating arg size to 3x

This adds one more test that should track improvements to generator
layout, like #62958 and #62575.

In particular, this test highlights suboptimal layout, as the storage
for the argument future is not being reused across its usage as `upvar`,
`local` and `awaitee` (being polled to completion).

1 files changed, 24 insertions, 0 deletions

diff --git a/tests/ui/async-await/future-sizes/async-awaiting-fut.rs b/tests/ui/async-await/future-sizes/async-awaiting-fut.rs
new file mode 100644
index 00000000000..1816d842d6c
--- /dev/null
+++ b/tests/ui/async-await/future-sizes/async-awaiting-fut.rs
@@ -0,0 +1,24 @@
+// compile-flags: -Z print-type-sizes --crate-type lib
+// edition:2021
+// build-pass
+// ignore-pass
+
+async fn wait() {}
+
+async fn big_fut(arg: [u8; 1024]) {}
+
+async fn calls_fut(fut: impl std::future::Future<Output = ()>) {
+    loop {
+        wait().await;
+        if true {
+            return fut.await;
+        } else {
+            wait().await;
+        }
+    }
+}
+
+pub async fn test() {
+    let fut = big_fut([0u8; 1024]);
+    calls_fut(fut).await;
+}