Thanks for creating this library!

This isn't strictly a bug, but the preserveState=true default for useStream can lead to some confusing/inconsistent behavior. I observed this with an application where you have a parent stream that indicates transitions between application states, along with a child stream to show the underlying status:

class ChildEventType {}
class ChildEventA extends ChildEventType {}
class ChildEventB extends ChildEventType{}

enum AppState { a, b }

class AppEvent {
  AppState state;
  Stream<ChildEventType> childEvent;
}

Stream<AppEvent> appStream();

Expected behavior

I expect that should be impossible for an AppEvent to yield events which are inconsistent with the AppState, but the preserveState behavior on the stream gives this behavior.

You can see this behavior in the DartPad here:
https://dartpad.dev/?id=02aa39ef7799d520d4f6e7c3d332da23

I suspect "I'm holding it wrong", and there's a more correct way to do this, but having this as the default made it hard to track down. (I'm filing this partly in case others run into the same issue).