Function ordered_stream::join

pub fn join<A, B>(stream_a: A, stream_b: B) -> Join<A, B> where
    A: OrderedStream,
    B: OrderedStream<Data = A::Data, Ordering = A::Ordering>, 

Join two streams while preserving the overall ordering of elements.

You can think of this as implementing the “merge” step of a merge sort on the two streams, producing a single stream that is sorted given two sorted streams. If the streams return PollResult::NoneBefore as intended, then the joined stream will be able to produce items when only one of the sources has unblocked.