Function select_member_variable

Libs/sol/sol.hpp:18320–18367

		template <bool is_yielding, typename Fx, typename... Args>
		void select_member_variable(lua_State* L, Fx&& fx, Args&&... args) {
			using uFx = meta::unqualified_t<Fx>;
			if constexpr (sizeof...(Args) < 1) {
				using C = typename meta::bind_traits<uFx>::object_type;
				lua_CFunction freefunc = &function_detail::upvalue_this_member_variable<C, Fx, is_yielding>::call;

				int upvalues = 0;
				upvalues += stack::push(L, nullptr);
				upvalues += stack::stack_detail::push_as_upvalues(L, fx);
				stack::push(L, c_closure(freefunc, upvalues));
			}
			else if constexpr (sizeof...(Args) < 2) {
				using Tu = typename meta::meta_detail::unqualified_non_alias<Args...>::type;
				constexpr bool is_reference = meta::is_specialization_of_v<Tu, std::reference_wrapper> || std::is_pointer_v<Tu>;
				if constexpr (meta::is_specialization_of_v<Tu, function_detail::class_indicator>) {
					lua_CFunction freefunc = &function_detail::upvalue_this_member_variable<typename Tu::type, Fx, is_yielding>::call;

					int upvalues = 0;
					upvalues += stack::push(L, nullptr);
					upvalues += stack::stack_detail::push_as_upvalues(L, fx);
					stack::push(L, c_closure(freefunc, upvalues));
				}
				else if constexpr (is_reference) {
					typedef std::decay_t<Fx> dFx;
					dFx memfxptr(std::forward<Fx>(fx));
					auto userptr = detail::ptr(std::forward<Args>(args)...);
					lua_CFunction freefunc
					     = &function_detail::upvalue_member_variable<std::decay_t<decltype(*userptr)>, meta::unqualified_t<Fx>, is_yielding>::call;

					int upvalues = 0;
					upvalues += stack::push(L, nullptr);
					upvalues += stack::stack_detail::push_as_upvalues(L, memfxptr);
					upvalues += stack::push(L, static_cast<void const*>(userptr));
					stack::push(L, c_closure(freefunc, upvalues));
				}
				else {
					using clean_fx = std::remove_pointer_t<std::decay_t<Fx>>;
					using F = function_detail::member_variable<Tu, clean_fx, is_yielding>;
					select_set_fx<false, false, F>(L, std::forward<Fx>(fx), std::forward<Args>(args)...);
				}
			}
			else {
				using C = typename meta::bind_traits<uFx>::object_type;
				using clean_fx = std::remove_pointer_t<std::decay_t<Fx>>;
				using F = function_detail::member_variable<C, clean_fx, is_yielding>;
				select_set_fx<false, false, F>(L, std::forward<Fx>(fx), std::forward<Args>(args)...);
			}
		}

		template <bool is_yielding, typename Fx, typename T, typename... Args>
		void select_member_function_with(lua_State* L, Fx&& fx, T&& obj, Args&&... args) {