Enthusiastic support for this proposal, the use cases motivating the proposal are relevant to my team and the features we implement, preview and test.
During the pitch, this comment was made:
Perhaps what follows is reading a bit too much into the above comment. While I can't imagine how else it might work, could there be a way of avoiding the existential (that is, use a concrete type only) whose behaviour can be controlled environmentally, much like how a Task can inherit priority, could it inherit a clock or the clock inherit a way to control the passage of time?