`Shared` `.await` affects polling the unrelated `Future` that is `.await`ed right after it

[toni-rmc]

I'm using Windows 10, futures version 0.3.31 and same behavior is observed when using Tokio or async-std.

The following is simple dummy future implementation:

pub struct Dummy(pub u8);

impl Future for Dummy {
    type Output = ();

    fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        println!("Polling in dummy");
        if self.0 == 0 {
            println!("Dummy is ready");
            Poll::Ready(())
        } else {
            println!("Dummy is not ready");
            self.0 -= 1;
            Poll::Pending
        }
    }
}

Using this in async main e.g. with Tokio of course prints:

Polling in dummy
Dummy is not ready

and blocks.

But if i use Shared before like this:

    let s1 = async {};

    let shared = s1.shared();
    shared.await;

    let dummy = Dummy(1);
    dummy.await;

than dummy is polled twice and completes:

Polling in dummy
Dummy is not ready
Polling in dummy
Dummy is ready

Why is it affected by it?