Adding shared mutability, while still maintaining memory safety

[scottmcm]

@izagawd

Cell would be pretty expensive if u have to copy the collection everytime u want to check the contents in it. How would you go about this?

You don't have to copy the collection -- you even can't, since Clone needs a &Vec not a &Cell<Vec> -- but you can swap in something else.

Reusing a recent conversation, one way is this:

Zero-cost interior mutability - proposal

You can couple this with temporaries & deref for a fun way of doing it, too. I tossed together a sketch of it here, for example: