// PR c++/91923 - failure-to-SFINAE with class type NTTP in C++17.
// { dg-do compile { target c++11 } }

template<typename T>
constexpr bool is_integral_(...) {
    return false;
}
template<typename T, T = 1>
constexpr bool is_integral_(long) {
    return true;
}

static_assert(is_integral_<int>(42), "");
static_assert(!is_integral_<void>(42), "");

struct S {};
static_assert(!is_integral_<S>(42), "");