https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90291
--- Comment #8 from Igor A. Goussarov <igusarov at mail dot ru> --- P.S. It seems that different compilers have different ideas about inline namespaces. If godbolt.org can be trusted, clang-8.0 and msvc 2017 do not merge namespaces in described scenario.
