In general I agree that Rc could've been nice to copy instead of cloning explicitly, but on another hand I'm a pretty big opponent of having "lots of Arcs and R

In general I agree that Rc could've been nice to copy instead of cloning explicitly, but on another hand I'm a pretty big opponent of having "lots of Arcs and Rcs" since they usually hide the ownership and data flow, and are rather hard to refactor out once added.