It's what Delphi has been doing with strings since 1995. It really is just copy on write, which normally has an assumption that the thing is shared before you c

It's what Delphi has been doing with strings since 1995. It really is just copy on write, which normally has an assumption that the thing is shared before you copy. It's easily implemented with a refcount. It makes heap allocated types behave a lot like value types.