Determine generality of Mu's weak reference + finaliser support
Mu already has weak refs and there is an existing finalisation proposal. The question this issue seek an answer to is what language semantics of weak references can these constructs implement? In particular, Java has four levels of strength of pointers, each with specific semantics. Can Mu model that? Likewise, various flavors of Lisp and Scheme offer different weak reference semantics. Which of those can Mu model? A guess going in to this is that Mu can model some, but not all, the flavors of weak references there are out in the wild. So another question is: How much do we care? If we want to cover more cases, what additional semantics would do that, in a language-neutral way? Would we instead support some kind of side interface to the Mu collector that allows clients to directly bolt stuff on? What would that look like? (Maybe that's way beyond reasonable.)