1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44

use std::future::Future;
use std::marker::PhantomData;
use std::pin::Pin;

use crate::task::{Context, Poll};

/// Never resolves to a value.

///

/// # Examples

///

/// ```

/// # async_std::task::block_on(async {

/// #

/// use std::time::Duration;

///

/// use async_std::future;

/// use async_std::io;

///

/// let dur = Duration::from_secs(1);

/// let fut = future::pending();

///

/// let res: io::Result<()> = io::timeout(dur, fut).await;

/// assert!(res.is_err());

/// #

/// # })

/// ```

pub async fn pending<T>() -> T {
    let fut = Pending {
        _marker: PhantomData,
    };
    fut.await
}

struct Pending<T> {
    _marker: PhantomData<T>,
}

impl<T> Future for Pending<T> {
    type Output = T;

    fn poll(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<T> {
        Poll::Pending
    }
}