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    //! Definition of the `SelectAll`, finding the first future in a list that
    //! finishes.

    use std::mem;
    use std::prelude::v1::*;

    use {Future, IntoFuture, Poll, Async};

    /// Future for the `select_all` combinator, waiting for one of any of a list of
    /// futures to complete.
    ///
    /// This is created by the `select_all` function.
    #[derive(Debug)]
    #[must_use = "futures do nothing unless polled"]
    pub struct SelectAll<A> where A: Future {
        inner: Vec<A>,
    }

    #[doc(hidden)]
    pub type SelectAllNext<A> = A;

    /// Creates a new future which will select over a list of futures.
    ///
    /// The returned future will wait for any future within `iter` to be ready. Upon
    /// completion or failure the item resolved will be returned, along with the
    /// index of the future that was ready and the list of all the remaining
    /// futures.
    ///
    /// # Panics
    ///
    /// This function will panic if the iterator specified contains no items.
    pub fn select_all<I>(iter: I) -> SelectAll<<I::Item as IntoFuture>::Future>
        where I: IntoIterator,
              I::Item: IntoFuture,
    {
        let ret = SelectAll {
            inner: iter.into_iter()
                       .map(|a| a.into_future())
                       .collect(),
        };
        assert!(ret.inner.len() > 0);
        ret
    }

    impl<A> Future for SelectAll<A>
        where A: Future,
    {
        type Item = (A::Item, usize, Vec<A>);
        type Error = (A::Error, usize, Vec<A>);

        fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
            let item = self.inner.iter_mut().enumerate().filter_map(|(i, f)| {
                match f.poll() {
                    Ok(Async::NotReady) => None,
                    Ok(Async::Ready(e)) => Some((i, Ok(e))),
                    Err(e) => Some((i, Err(e))),
                }
            }).next();
            match item {
                Some((idx, res)) => {
                    self.inner.remove(idx);
                    let rest = mem::replace(&mut self.inner, Vec::new());
                    match res {
                        Ok(e) => Ok(Async::Ready((e, idx, rest))),
                        Err(e) => Err((e, idx, rest)),
                    }
                }
                None => Ok(Async::NotReady),
            }
        }
    }

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