> I would really like to see "newruntime" win, as it is unique and more elegant.
Me too. Ok, here is what I know: Our `async` seems to work with the refcounting GC without its cycle collector with a tiny codegen patch (I don't know whether that patch is always correct). So lets assume (atomic) refcounting is sufficient. B/D is not only a "faster refcounting", it describes the spanning tree of a graph so that it's free of cycles by construction (ignoring some edge cases). This is achieved by making `owned` a "move-only" type but that's too inexpressive for our async. So we need a way to duplicate owned refs that still guarantees cycle freedom, statically. I know that's what you're proposing via a `=deepCopy` for `owned` but I don't know if it can work out.
