RFC: scope and borrowing

[via Digitalmars-d]

On Monday, 25 August 2014 at 10:06:12 UTC, Rikki Cattermole wrote:
> Have you considered what happens when you cast away scope?
> I didn't read anything about that, unless I missed something.

Right, this should be specified. But it's fairly obvious what 
would happen: you lose the safety guarantees (=> @system), and 
you're responsible to make sure you don't get dangling 
references. You'd basically get what you have with normal 
pointers. I don't think it has any deeper implications than that, 
but I'm not sure there aren't any obscure optimizations the 
compiler could make based on scope. If there are, it's no 
different from casting away const, in this respect.

>
> I do have to ask this, because what if you wanted to optionally 
> return a scoped reference?

Well, it's part of the return type, so it's either scoped, or it 
isn't. You could return a tuple with a scoped and a non-scoped 
pointer, though.

If it's only about returning a non-scoped pointer from a function 
with a scoped return type, that's fine, because it's adding 
scope, not removing it. (Use case: ScopeBuffer.)