[Bug libstdc++/97869] <version> defines __cpp_lib_span even when <span> doesn't provide an implementation

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97869

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |redi at gcc dot gnu.org

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Oops. JeanHeyd's original <span> worked without concepts, so the definition in
<version> was correct. We modified <span> later to be empty unless concepts are
supported.

I have a script to check the macros, but I only have clang 10.0 installed,
which defines __cpp_concepts.

It looks like we also have a discrepancy for __cpp_lib_coroutine.