https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106223
--- Comment #2 from Nimrod <nimrodcowboy at gmail dot com> --- Quoted from https://timsong-cpp.github.io/cppwp/n4659/namespace.std#2 "A program may explicitly instantiate a template defined in the standard library only if the declaration depends on the name of a user-defined type and the instantiation meets the standard library requirements for the original template." If I understand correctly, at least in C++17, this is allowed. I don't see any special rules for the specialization of std::forward
