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//! Futures.

use crate::task::{self, Poll};
use core::mem::PinMut;

pub use core::future::{Future, FutureObj, LocalFutureObj, UnsafeFutureObj};

/// A convenience for futures that return `Result` values that includes
/// a variety of adapters tailored to such futures.
pub trait TryFuture {
    /// The type of successful values yielded by this future
    type Ok;

    /// The type of failures yielded by this future
    type Error;

    /// Poll this `TryFuture` as if it were a `Future`.
    ///
    /// This method is a stopgap for a compiler limitation that prevents us from
    /// directly inheriting from the `Future` trait; in the future it won't be
    /// needed.
    fn try_poll(
        self: PinMut<Self>,
        cx: &mut task::Context,
    ) -> Poll<Result<Self::Ok, Self::Error>>;
}

impl<F, T, E> TryFuture for F
    where F: Future<Output = Result<T, E>>
{
    type Ok = T;
    type Error = E;

    #[inline]
    fn try_poll(self: PinMut<Self>, cx: &mut task::Context) -> Poll<F::Output> {
        self.poll(cx)
    }
}