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    use core::pin::Pin;
    use futures_core::future::{Future, TryFuture};
    use futures_core::task::{Context, Poll};
    use crate::future::{Either, TryFutureExt};

    /// Future for the [`try_select()`] function.
    #[must_use = "futures do nothing unless you `.await` or poll them"]
    #[derive(Debug)]
    pub struct TrySelect<A, B> {
        inner: Option<(A, B)>,
    }

    impl<A: Unpin, B: Unpin> Unpin for TrySelect<A, B> {}

    /// Waits for either one of two differently-typed futures to complete.
    ///
    /// This function will return a new future which awaits for either one of both
    /// futures to complete. The returned future will finish with both the value
    /// resolved and a future representing the completion of the other work.
    ///
    /// Note that this function consumes the receiving futures and returns a
    /// wrapped version of them.
    ///
    /// Also note that if both this and the second future have the same
    /// success/error type you can use the `Either::factor_first` method to
    /// conveniently extract out the value at the end.
    ///
    /// # Examples
    ///
    /// ```
    /// use futures::future::{self, Either, Future, FutureExt, TryFuture, TryFutureExt};
    ///
    /// // A poor-man's try_join implemented on top of select
    ///
    /// fn try_join<A, B, E>(a: A, b: B) -> impl TryFuture<Ok=(A::Ok, B::Ok), Error=E>
    ///      where A: TryFuture<Error = E> + Unpin + 'static,
    ///            B: TryFuture<Error = E> + Unpin + 'static,
    ///            E: 'static,
    /// {
    ///     future::try_select(a, b).then(|res| -> Box<dyn Future<Output = Result<_, _>> + Unpin> {
    ///         match res {
    ///             Ok(Either::Left((x, b))) => Box::new(b.map_ok(move |y| (x, y))),
    ///             Ok(Either::Right((y, a))) => Box::new(a.map_ok(move |x| (x, y))),
    ///             Err(Either::Left((e, _))) => Box::new(future::err(e)),
    ///             Err(Either::Right((e, _))) => Box::new(future::err(e)),
    ///         }
    ///     })
    /// }
    /// ```
    pub fn try_select<A, B>(future1: A, future2: B) -> TrySelect<A, B>
        where A: TryFuture + Unpin, B: TryFuture + Unpin
    {
        super::assert_future::<Result<
            Either<(A::Ok, B), (B::Ok, A)>,
            Either<(A::Error, B), (B::Error, A)>,
        >, _>(TrySelect { inner: Some((future1, future2)) })
    }

    impl<A: Unpin, B: Unpin> Future for TrySelect<A, B>
        where A: TryFuture, B: TryFuture
    {
        #[allow(clippy::type_complexity)]
        type Output = Result<
            Either<(A::Ok, B), (B::Ok, A)>,
            Either<(A::Error, B), (B::Error, A)>,
        >;

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
            let (mut a, mut b) = self.inner.take().expect("cannot poll Select twice");
            match a.try_poll_unpin(cx) {
                Poll::Ready(Err(x)) => Poll::Ready(Err(Either::Left((x, b)))),
                Poll::Ready(Ok(x)) => Poll::Ready(Ok(Either::Left((x, b)))),
                Poll::Pending => match b.try_poll_unpin(cx) {
                    Poll::Ready(Err(x)) => Poll::Ready(Err(Either::Right((x, a)))),
                    Poll::Ready(Ok(x)) => Poll::Ready(Ok(Either::Right((x, a)))),
                    Poll::Pending => {
                        self.inner = Some((a, b));
                        Poll::Pending
                    }
                }
            }
        }
    }