https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123728
--- Comment #5 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Yes there is an heurstic to try to disable the warning. But that heurstic does not change the fact on there might be an ODR issue involved here. Also the (template) type here is not defined in the main source file, it is defined in the header. The heurstic is just there to try not to warn if LocalEnum is used directly as a field in Test; not if it is used indirectly via Test to a template type defined in a different header file.
