`FutureExt::remote_handle` causes a silent panic

[Hakuyume]

The following code causes Exited with status 101.

use futures::FutureExt;

fn main() {
    futures::executor::block_on(async {
        let f = std::future::pending::<()>();
        let (remote, remote_handle) = f.remote_handle();
        // poll remote at least once
        futures::future::select(remote, std::future::ready(())).await;
        remote_handle.await
    });
}

https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=d62babe3ab6856b94d7a95fffdb457e4

The expected behavior is pending infinity on remote_handle.await .

[taiki-e]

futures::future::select(remote, std::future::ready(())).await;

I think the panic happened because remote is not cancel-safe and remote_handle was polled after remote was dropped without complete on this line (passing remote by mutable reference works as you expect), but panic without a message is odd anyway.

[Hakuyume]

I think the panic happened because remote is not cancel-safe

Thank you.

I read the source and found that panic::resume_unwind is used when remote is dropped.

futures-rs/futures-util/src/future/future/remote_handle.rs

Lines 66 to 67 in 7211cb7

	// The oneshot sender was dropped.
	Err(e) => panic::resume_unwind(Box::new(e)),