blob: 2c47ff183340207afa962b0e574d28dd7d5e0b57 [file] [log] [blame]
use core::marker::Unpin;
use core::mem::PinMut;
use futures_core::future::{Future, TryFuture};
use futures_core::task::{self, Poll};
use pin_utils::{unsafe_pinned, unsafe_unpinned};
/// Future for the [`map_err`](super::TryFutureExt::map_err) combinator.
#[must_use = "futures do nothing unless polled"]
pub struct MapErr<Fut, F> {
future: Fut,
f: Option<F>,
impl<Fut, F> MapErr<Fut, F> {
unsafe_pinned!(future: Fut);
unsafe_unpinned!(f: Option<F>);
/// Creates a new MapErr.
pub(super) fn new(future: Fut, f: F) -> MapErr<Fut, F> {
MapErr { future, f: Some(f) }
impl<Fut: Unpin, F> Unpin for MapErr<Fut, F> {}
impl<Fut, F, E> Future for MapErr<Fut, F>
where Fut: TryFuture,
F: FnOnce(Fut::Error) -> E,
type Output = Result<Fut::Ok, E>;
fn poll(
mut self: PinMut<Self>,
cx: &mut task::Context,
) -> Poll<Self::Output> {
match self.future().try_poll(cx) {
Poll::Pending => Poll::Pending,
Poll::Ready(result) => {
let f = self.f().take()
.expect("MapErr must not be polled after it returned `Poll::Ready`");