next() function is called it is expected to return a value asynchronusly for an async
If the values are not created in response to calling this function these values will have to be provided
somehow. This channel supports sending values which the
next() can return.
In the unit tests, a channel is created which is also a sequence. The
AyncIterator is a nested type.
When the iterator is created it is given the same channel. Calling
send on the channel will make new
values available. When the
next function is called it creates a
continuation which will be matched
to a value so it can be returned. Calling
terminate will use a
continuation to send
nil which tells
for loop it is done.
All of the work done by the channel is done as an actor type so that it is thread-safe. Since it only uses features from the Swift Standard Library it should be usable on every platform which has Swift support.