On Thu, Jul 6, 2023 at 2:50 AM Andrey Davydov via Std-Proposals
<std-proposals@lists.isocpp.org> wrote:
>
> Hello everyone!
>
> I'd like to propose a support span of elements of incomplete type.
> The draft of the proposal (https://github.com/AndreyG/cpp-papers/blob/main/span-of-incomplete-element-type.md) contains motivation. What do you think about it?

The proposal needs to investigate why the limitation exists at all. I
didn't know about it until you brought it up. You should spend some
time looking into older versions of `span` or asking the people who
made those proposals why the type is required to be complete.

There could be some good-yet-esoteric reason why this limitation is here.