[Bug c++/115915] gcc fails to detect invalid friend declaration of classes in different namespaces

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115915

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
The question is does that friend is naming `::extent` or is naming
`std_1::extent` using the `using namespace` statement. I suspect GCC and EDG
think it is `::extent` while clang and MSVC think it is `std_1::extent`.