19 template<
typename Default,
typename Placeholder,
template<
typename...>
class Op,
typename... Args>
26 template<
typename Default,
template<
typename...>
class Op,
typename... Args>
27 struct IsDetected<Default, std::void_t<Op<Args...>>, Op, Args...>
34 template<
template<
typename...>
class Op,
typename... Args>
37 template<
typename Type,
template<
typename...>
class Op,
typename... Args>
constexpr bool IsDetected_v
typename detail::IsDetected< Type, void, Op, Args... >::type IsDetected_t