Utility for polling a future from an async function

[Plecra]

struct Check<'a, F: Future + ?Sized>(Pin<&'a mut F>);
impl<F: Future + ?Sized> Future for Check<'_, F> {
    type Output = Poll<F::Output>;
    fn poll(mut self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
        Poll::Ready(self.0.as_mut().poll(cx))
    }
}
async fn checkup(tasks: Vec<Task>) {
    for mut task in tasks {
        if let Poll::Ready(val) = Check(task.fut.as_mut()).await {
            handle(val);
            cleanup(task);
        }
    }
}

I've seen this pattern come up in a few different projects now, and it seems generic enough for the futures crate. It could well be too niche though.

[taiki-e]

This seems similar to use now_or_never on (pinned) reference. (in this case, task.fut.as_mut().now_or_never())

[Plecra]

It does look similar ☺️ The difference is that Check may be used multiple times, due to it being implemented on a pinned reference (now_or_never is implemented for all T: Future).

[taiki-e]

The difference is that Check may be used multiple times, due to it being implemented on a pinned reference (now_or_never is implemented for all T: Future).

Pinned future implements Future, so I don't think this difference is a problem.

The actual difference is the context passed to the future. (now_or_never pass no-op context.)
See also #1747 (comment)