> > Hmm, is there any need to have zero as an actual static extent?
>
> What is the use case for a zero-capacity static extent?

I was thinking generic code that instantiates span with an
extent that depends on some template parameter (as I mentioned
in the previous reply), but I don't currently have any
concrete examples on top of my head. Otherwise, a span of size
0 would be useless.

- T