blob: ba290d161c1ce249ed2d1c4650d971eeff99d01c [file] [log] [blame]
use core::marker::Unpin;
use core::pin::Pin;
use futures_core::future::{FusedFuture, Future, TryFuture};
use futures_core::task::{LocalWaker, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// Future for the [`unwrap_or_else`](super::TryFutureExt::unwrap_or_else)
/// combinator.
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct UnwrapOrElse<Fut, F> {
future: Fut,
f: Option<F>,
}
impl<Fut, F> UnwrapOrElse<Fut, F> {
unsafe_pinned!(future: Fut);
unsafe_unpinned!(f: Option<F>);
/// Creates a new UnwrapOrElse.
pub(super) fn new(future: Fut, f: F) -> UnwrapOrElse<Fut, F> {
UnwrapOrElse { future, f: Some(f) }
}
}
impl<Fut: Unpin, F> Unpin for UnwrapOrElse<Fut, F> {}
impl<Fut, F> FusedFuture for UnwrapOrElse<Fut, F> {
fn is_terminated(&self) -> bool {
self.f.is_none()
}
}
impl<Fut, F> Future for UnwrapOrElse<Fut, F>
where Fut: TryFuture,
F: FnOnce(Fut::Error) -> Fut::Ok,
{
type Output = Fut::Ok;
fn poll(
mut self: Pin<&mut Self>,
lw: &LocalWaker,
) -> Poll<Self::Output> {
match self.as_mut().future().try_poll(lw) {
Poll::Pending => Poll::Pending,
Poll::Ready(result) => {
let op = self.as_mut().f().take()
.expect("UnwrapOrElse already returned `Poll::Ready` before");
Poll::Ready(result.unwrap_or_else(op))
}
}
}
}