`return` from inside a `async` block

main.rs

use core::pin::pin;
use core::sync::atomic::{AtomicBool, Ordering::Relaxed};
use core::task::Poll;

async fn foo() -> std::io::Result<i32> {
    let no_return = AtomicBool::new(false);
    let mut value = None;
    let mut fut = pin!(async {
        value = Some({
            // begin user code
            if rand::random() {
                std::fs::File::open("non_existent_file")?;
            }
            42
            // end user code
        });
        no_return.store(true, Relaxed);
        core::future::pending().await
    });
    if let Some(ret) = core::future::poll_fn(|cx| {
        let ret = fut.as_mut().poll(cx);
        if no_return.load(Relaxed) {
            Poll::Ready(None)
        } else {
            ret.map(Some)
        }
    })
    .await
    {
        return ret;
    }
    Ok(value.unwrap())
}

#[tokio::main]
async fn main() {
    for _ in 0..10 {
        eprintln!("{:?}", foo().await);
    }
}