Vector, a fixed-size array

[ksluder (Kyle Sluder)]

@scanon

Well, that's because it isn't.

The proposed type is conditionally copyable:

extension Vector: Copyable where Element: Copyable {}

Ah, my mistake. But I think this highlights a downside of the chosen ~Copyable syntax, since so many container types’ main declarations are ~Copyable, including ones that are not conditionally copyable.