[skrrtww]

Yeah after thinking about it a bit more it does make more sense to me. The primary gap I had was, as you allude here:

> You can use a copyable anywhere you’d use a non-copyable since there is no restriction.

Effectively copyable always conforms to non-copyable, just not the other way around.

And the compiler effectively automatically notates literally everything with Copyable, so you need the explicit (& ~Copyable) in the function definition so you're still able to define functions within a ~Copyable protocol that have Copyable semantics.

It's very in the weeds, and I still don't like it (I would have preferred NotCopyable since the ~, especially next to the &, directly implies something like bitwise operators), but I guess custom ownership is itself very in the weeds and you will have to think about it hard no matter what approach is taken. I would have expected custom ownership to be fundamentally incompatible with Swift, but clearly it's here; I should probably read about it more so I have a more clear understanding.

(I also didn't realize & was extant syntax).

[MBCook]

Yeah, I’ll admit it’s hard to get your head around. I had to think about it a couple of times just writing that explanation.

It took me a couple of minutes to figure out why it was in the function definition. I guess it had to be but that wasn’t obvious to me at all at first.

> And the compiler effectively automatically notates literally everything

Right. Just like how all classes in Java extend Object even though you don’t have to literally write it.

I believe they’re still working on a more Rust-like borrowing system, but I could be wrong. I know this helped them implement parts of the standard library much better because they could make assumptions that you can’t make with copyable objects.

I do get your point about just calling it NotCopyable. I don’t actually know why they settled on the name they did, I didn’t ever try to look that up. Maybe it’s because it’s a special thing that requires compiler machinery and there’s no way for you to make an equivalent?