https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105707
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
That is a bug but in your code only, C++ explicitly says that it is not valid:
https://eel.is/c++draft/requirements#using.headers-3
