Channel not unblocking during some iteration situations

General Usage
3

Further discussion where @jakobnissen points to a “best practices” implementation of the interface as:

function Base.iterate(node::AbstractNode)
    state = Channel(c -> traverse(node, c))
    iterate(node, state)
end

function Base.iterate(node::AbstractNode, state::Channel)
    # This iterate call on the channel will block if there are no more elements,
    # and will return `nothing` if there are no more elements AND the channel
    # is closed, which happens when `traverse` has yielded all its elements.
    y = iterate(state)
    isnothing(y) ? y : (first(y), state)
end

And that the behavior found with my implementation is expected (or at least not unexpected):

Putting in yield in iterate seems to solve the problem, because it allows the scheduler to switch to traverse. But it’s not a real fix, because there is still no guarantee the scheduler will actually switch task.