Function call_wrapper_variable

extlibs/sol3/include/sol/sol.hpp:16873–16878

	namespace function_detail {
		template <typename F, F fx>
		inline int call_wrapper_variable(std::false_type, lua_State* L) {
			typedef meta::bind_traits<meta::unqualified_t<F>> traits_type;
			typedef typename traits_type::args_list args_list;
			typedef meta::tuple_types<typename traits_type::return_type> return_type;
			return stack::call_into_lua(return_type(), args_list(), L, 1, fx);
		}

		template <typename R, typename V, V, typename T>
		inline int call_set_assignable(std::false_type, T&&, lua_State* L) {