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    use super::assert_stream;
    use core::pin::Pin;
    use futures_core::stream::Stream;
    use futures_core::task::{Context, Poll};

    /// Stream for the [`iter`] function.
    #[derive(Debug, Clone)]
    #[must_use = "streams do nothing unless polled"]
    pub struct Iter<I> {
        iter: I,
    }

    impl<I> Unpin for Iter<I> {}

    /// Converts an `Iterator` into a `Stream` which is always ready
    /// to yield the next value.
    ///
    /// Iterators in Rust don't express the ability to block, so this adapter
    /// simply always calls `iter.next()` and returns that.
    ///
    /// ```
    /// # futures::executor::block_on(async {
    /// use futures::stream::{self, StreamExt};
    ///
    /// let stream = stream::iter(vec![17, 19]);
    /// assert_eq!(vec![17, 19], stream.collect::<Vec<i32>>().await);
    /// # });
    /// ```
    pub fn iter<I>(i: I) -> Iter<I::IntoIter>
        where I: IntoIterator,
    {
        assert_stream::<I::Item, _>(Iter {
            iter: i.into_iter(),
        })
    }

    impl<I> Stream for Iter<I>
        where I: Iterator,
    {
        type Item = I::Item;

        fn poll_next(mut self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<I::Item>> {
            Poll::Ready(self.iter.next())
        }

        fn size_hint(&self) -> (usize, Option<usize>) {
            self.iter.size_hint()
        }
    }