[Bug c++/124430] Unexpected error including module-containing header before nlohmann/json.hpp

[nshead at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124430

Nathaniel Shead <nshead at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |nshead at gcc dot gnu.org

--- Comment #1 from Nathaniel Shead <nshead at gcc dot gnu.org> ---
Thanks for the report!

Unfortunately GCC still has issues with includes after imports, see
https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Modules.html

> Textual merging of reachable GM entities
>   Entities may be multiply defined across different header-units.
>   These must be de-duplicated, and this is implemented across imports,
>   or when an import redefines a textually-defined entity.
>   However the reverse is not implemented—textually redefining
>   an entity that has been defined in an imported header-unit.
>   A redefinition error is emitted.

This is quite complex to handle and will not be fixed by GCC16.  I'll mark as a
dup of the main bug for this.

*** This bug has been marked as a duplicate of bug 99000 ***