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futures 0.3.13

An implementation of futures and streams featuring zero allocations, composability, and iterator-like interfaces.
Documentation 
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mod util {
    use std::future::Future;
    use std::fmt::Debug;

    pub fn assert_done<T, F>(actual_fut: F, expected: T)
    where
        T: PartialEq + Debug,
        F: FnOnce() -> Box<dyn Future<Output = T> + Unpin>,
    {
        use futures::executor::block_on;

        let output = block_on(actual_fut());
        assert_eq!(output, expected);
    }
}

#[test]
fn collect_collects() {
    use futures_util::future::{join_all,ready};

    util::assert_done(|| Box::new(join_all(vec![ready(1), ready(2)])), vec![1, 2]);
    util::assert_done(|| Box::new(join_all(vec![ready(1)])), vec![1]);
    // REVIEW: should this be implemented?
    // assert_done(|| Box::new(join_all(Vec::<i32>::new())), vec![]);

    // TODO: needs more tests
}

#[test]
fn join_all_iter_lifetime() {
    use futures_util::future::{join_all,ready};
    use std::future::Future;
    // In futures-rs version 0.1, this function would fail to typecheck due to an overly
    // conservative type parameterization of `JoinAll`.
    fn sizes(bufs: Vec<&[u8]>) -> Box<dyn Future<Output = Vec<usize>> + Unpin> {
        let iter = bufs.into_iter().map(|b| ready::<usize>(b.len()));
        Box::new(join_all(iter))
    }

    util::assert_done(|| sizes(vec![&[1,2,3], &[], &[0]]), vec![3_usize, 0, 1]);
}

#[test]
fn join_all_from_iter() {
    use futures_util::future::{JoinAll,ready};

    util::assert_done(
        || Box::new(vec![ready(1), ready(2)].into_iter().collect::<JoinAll<_>>()),
        vec![1, 2],
    )
}