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use std::{
    future::Future,
    marker::Unpin,
    pin::Pin,
    task::{Context, Poll},
};

/// Unstabilized [`Ready`](https://doc.rust-lang.org/nightly/std/future/struct.Ready.html) future.
pub struct Ready<T>(Option<T>);

impl<T> Unpin for Ready<T> {}

impl<T> Future for Ready<T> {
    type Output = T;

    #[inline]
    fn poll(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<T> {
        Poll::Ready(self.0.take().expect("Ready polled after completion"))
    }
}

/// Unstabilized [`ready`](https://doc.rust-lang.org/nightly/std/future/fn.ready.html) function.
pub fn ready<T>(t: T) -> Ready<T> {
    Ready(Some(t))
}