1use std::{
2 pin::Pin,
3 task::{Context, Poll},
4};
5
6use either::Either;
7use futures::{TryFuture, future};
8use pin_project::pin_project;
9
10#[pin_project(project = EitherFutureProj)]
11#[derive(Debug, Copy, Clone)]
12#[must_use = "futures do nothing unless polled"]
13pub enum EitherFuture<A, B> {
14 Left(#[pin] A),
15 Right(#[pin] B),
16}
17
18impl<AFuture, BFuture, AInner, BInner> Future for EitherFuture<AFuture, BFuture>
19where
20 AFuture: TryFuture<Ok = AInner>,
21 BFuture: TryFuture<Ok = BInner>,
22{
23 type Output = Result<future::Either<AInner, BInner>, Either<AFuture::Error, BFuture::Error>>;
24
25 fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
26 match self.project() {
27 EitherFutureProj::Left(a) => a
28 .try_poll(cx)
29 .map_ok(future::Either::Left)
30 .map_err(Either::Left),
31 EitherFutureProj::Right(a) => a
32 .try_poll(cx)
33 .map_ok(future::Either::Right)
34 .map_err(Either::Right),
35 }
36 }
37}