QueueSignalMixin is a mixin for a Signal that adds reactive methods for Queue.
class MySignal extends Signal<Queue<int>> with QueueSignalMixin<int> { MySignal(Queue<int> value) : super(value);} void main() { final q = Queue<int>(); a.addFirst(1); final signal = MySignal(q); effect(() { print(signal.length); }); signal.addLast(4);}