[libcxx-commits] [libcxx] [libcxx] Add span includes to some mdspan tests (PR #142693)

[Nikolas Klauser via libcxx-commits]

philnik777 wrote:

I think the proper fix here is to `#include <__fwd/span.h>` in `<mdspan>`. AFAICT this also requires an LWG issue, since `dynamic_extent` is almost certainly supposed to be provided via `<mdspan>`, but I think it's not specified to be.

https://github.com/llvm/llvm-project/pull/142693