constexpr_if_not_lazy.cpp

template <int v>
struct int_c { static constexpr int value = v; };

struct a_tag { };
struct b_tag { };
template <bool cond>
struct c_tag
{
  static_assert(cond);
};

template <typename T>
constexpr auto get(T)
{
  if constexpr(T::value > 9)
    return c_tag<false>{};
  else if constexpr(T::value > 4)
    return b_tag{};
  else
    return a_tag{};
}

int main()
{
  constexpr a_tag a = get(int_c<0>{});
  constexpr b_tag b = get(int_c<5>{});
  //constexpr c_tag<false> c = get(int_c<10>{});
}