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    #![allow(dead_code)]

    //! Definition of the `PollFn` adapter combinator

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

    /// Future for the [`poll_fn`] function.
    pub struct PollFn<F> {
        f: F,
    }

    impl<F> Unpin for PollFn<F> {}

    /// Creates a new future wrapping around a function returning [`Poll`].
    pub fn poll_fn<T, F>(f: F) -> PollFn<F>
    where
        F: FnMut(&mut Context<'_>) -> Poll<T>,
    {
        PollFn { f }
    }

    impl<F> fmt::Debug for PollFn<F> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("PollFn").finish()
        }
    }

    impl<T, F> Future for PollFn<F>
    where
        F: FnMut(&mut Context<'_>) -> Poll<T>,
    {
        type Output = T;

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<T> {
            (&mut self.f)(cx)
        }
    }