what if return returned subclasses

[Adam D Ruppe]

ok consider this:

Object identity(return Object o) { return o; }


Subclass s = identity(new Subclass());


That is, it is converted to the base class before passed to the 
function, but since it is marked `return` anyway, the compiler 
knows it is the same instance, so the static type passed in is 
retained in the return value. So it is kinda like type erased but 
then repainted back on.

Would this break anything? There's a few OOP patterns that might 
be made a lil nicer if this just worked.