| use core::pin::Pin; |
| use futures_core::future::{FusedFuture, Future, TryFuture}; |
| use futures_core::ready; |
| use futures_core::task::{Context, Poll}; |
| use pin_project_lite::pin_project; |
| |
| pin_project! { |
| #[project = TryFlattenErrProj] |
| #[derive(Debug)] |
| pub enum TryFlattenErr<Fut1, Fut2> { |
| First { #[pin] f: Fut1 }, |
| Second { #[pin] f: Fut2 }, |
| Empty, |
| } |
| } |
| |
| impl<Fut1, Fut2> TryFlattenErr<Fut1, Fut2> { |
| pub(crate) fn new(future: Fut1) -> Self { |
| Self::First { f: future } |
| } |
| } |
| |
| impl<Fut> FusedFuture for TryFlattenErr<Fut, Fut::Error> |
| where |
| Fut: TryFuture, |
| Fut::Error: TryFuture<Ok = Fut::Ok>, |
| { |
| fn is_terminated(&self) -> bool { |
| match self { |
| Self::Empty => true, |
| _ => false, |
| } |
| } |
| } |
| |
| impl<Fut> Future for TryFlattenErr<Fut, Fut::Error> |
| where |
| Fut: TryFuture, |
| Fut::Error: TryFuture<Ok = Fut::Ok>, |
| { |
| type Output = Result<Fut::Ok, <Fut::Error as TryFuture>::Error>; |
| |
| fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> { |
| Poll::Ready(loop { |
| match self.as_mut().project() { |
| TryFlattenErrProj::First { f } => match ready!(f.try_poll(cx)) { |
| Err(f) => self.set(Self::Second { f }), |
| Ok(e) => { |
| self.set(Self::Empty); |
| break Ok(e); |
| } |
| }, |
| TryFlattenErrProj::Second { f } => { |
| let output = ready!(f.try_poll(cx)); |
| self.set(Self::Empty); |
| break output; |
| } |
| TryFlattenErrProj::Empty => panic!("TryFlattenErr polled after completion"), |
| } |
| }) |
| } |
| } |