https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71784
--- Comment #12 from Ela <mct_ancs at yahoo dot com> --- Example: When an usual member function is missing (say template class instantiated with extern), the compiler (4.9.3, 6.1) will complain in_clear about the missing function. When a ref-qual'ed one is missing it will show some mangle _Z-etc-etc as missing. If it's just the class templated, then letting the class instantiate its own functions => will work. If the function is nested templated, then it has to be explicitly instantiated and again ICE.
