add test for issue 98634

src/test/ui/async-await/issue-98634.rs

@@ -0,0 +1,50 @@
+// edition: 2021
+
+use std::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll, Waker},
+};
+
+pub struct StructAsync<F: Fn() -> Pin<Box<dyn Future<Output = ()>>>> {
+    pub callback: F,
+}
+
+impl<F> Future for StructAsync<F>
+where
+    F: Fn() -> Pin<Box<dyn Future<Output = ()>>>,
+{
+    type Output = ();
+
+    fn poll(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Self::Output> {
+        Poll::Pending
+    }
+}
+
+async fn callback() {}
+
+struct Runtime;
+
+fn waker() -> &'static Waker {
+    todo!()
+}
+
+impl Runtime {
+    #[track_caller]
+    pub fn block_on<F: Future>(&self, mut future: F) -> F::Output {
+        loop {
+            unsafe {
+                Pin::new_unchecked(&mut future).poll(&mut Context::from_waker(waker()));
+            }
+        }
+    }
+}
+
+fn main() {
+    Runtime.block_on(async {
+        StructAsync { callback }.await;
+        //~^ ERROR expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+        //~| ERROR expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+        //~| ERROR expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+    });
+}

src/test/ui/async-await/issue-98634.stderr

@@ -0,0 +1,60 @@
+error[E0271]: expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+  --> $DIR/issue-98634.rs:45:23
+   |
+LL |         StructAsync { callback }.await;
+   |                       ^^^^^^^^ expected struct `Pin`, found opaque type
+   |
+note: while checking the return type of the `async fn`
+  --> $DIR/issue-98634.rs:24:21
+   |
+LL | async fn callback() {}
+   |                     ^ checked the `Output` of this `async fn`, found opaque type
+   = note:   expected struct `Pin<Box<(dyn Future<Output = ()> + 'static)>>`
+           found opaque type `impl Future<Output = ()>`
+note: required by a bound in `StructAsync`
+  --> $DIR/issue-98634.rs:9:35
+   |
+LL | pub struct StructAsync<F: Fn() -> Pin<Box<dyn Future<Output = ()>>>> {
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `StructAsync`
+
+error[E0271]: expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+  --> $DIR/issue-98634.rs:45:9
+   |
+LL |         StructAsync { callback }.await;
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `Pin`, found opaque type
+   |
+note: while checking the return type of the `async fn`
+  --> $DIR/issue-98634.rs:24:21
+   |
+LL | async fn callback() {}
+   |                     ^ checked the `Output` of this `async fn`, found opaque type
+   = note:   expected struct `Pin<Box<(dyn Future<Output = ()> + 'static)>>`
+           found opaque type `impl Future<Output = ()>`
+note: required by a bound in `StructAsync`
+  --> $DIR/issue-98634.rs:9:35
+   |
+LL | pub struct StructAsync<F: Fn() -> Pin<Box<dyn Future<Output = ()>>>> {
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `StructAsync`
+
+error[E0271]: expected `fn() -> impl Future<Output = ()> {callback}` to be a fn item that returns `Pin<Box<(dyn Future<Output = ()> + 'static)>>`, but it returns `impl Future<Output = ()>`
+  --> $DIR/issue-98634.rs:45:33
+   |
+LL |         StructAsync { callback }.await;
+   |                                 ^^^^^^ expected struct `Pin`, found opaque type
+   |
+note: while checking the return type of the `async fn`
+  --> $DIR/issue-98634.rs:24:21
+   |
+LL | async fn callback() {}
+   |                     ^ checked the `Output` of this `async fn`, found opaque type
+   = note:   expected struct `Pin<Box<(dyn Future<Output = ()> + 'static)>>`
+           found opaque type `impl Future<Output = ()>`
+note: required by a bound in `StructAsync`
+  --> $DIR/issue-98634.rs:9:35
+   |
+LL | pub struct StructAsync<F: Fn() -> Pin<Box<dyn Future<Output = ()>>>> {
+   |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `StructAsync`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0271`.