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use super::chain::Chain;
use core::fmt;
use core::pin::Pin;
use futures_core::future::Future;
use futures_core::task::{LocalWaker, Poll};
use pin_utils::unsafe_pinned;
#[must_use = "futures do nothing unless polled"]
pub struct Flatten<Fut>
where Fut: Future,
Fut::Output: Future,
{
state: Chain<Fut, Fut::Output, ()>,
}
impl<Fut> Flatten<Fut>
where Fut: Future,
Fut::Output: Future,
{
unsafe_pinned!(state: Chain<Fut, Fut::Output, ()>);
pub(super) fn new(future: Fut) -> Flatten<Fut> {
Flatten {
state: Chain::new(future, ()),
}
}
}
impl<Fut> fmt::Debug for Flatten<Fut>
where Fut: Future + fmt::Debug,
Fut::Output: Future + fmt::Debug,
{
fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
fmt.debug_struct("Flatten")
.field("state", &self.state)
.finish()
}
}
impl<Fut> Future for Flatten<Fut>
where Fut: Future,
Fut::Output: Future,
{
type Output = <Fut::Output as Future>::Output;
fn poll(mut self: Pin<&mut Self>, lw: &LocalWaker) -> Poll<Self::Output> {
self.state().poll(lw, |a, ()| a)
}
}