Contribute to gcc-mirror/gcc development by creating an account on GitHub.

struct IntMember {
   const int value = 1;
};

struct NonConstexprThing
{
   NonConstexprThing()
   {
       new int;
   }
};

struct ArrayMember {
   NonConstexprThing thing;
   //const std::vector<int> array{10};
};

template <bool IsArray>
struct Poly final : public std::conditional_t<IsArray, ArrayMember, IntMember>
{
   static constexpr bool isArray() noexcept { return IsArray; };
};

template <class T>
constexpr int some_func(T callback)
{
   Poly<true> a;
   Poly<false> i;
   return callback(a, i);
}

constexpr auto process = [](const auto first, const auto second)
{
   if constexpr (first.isArray() && second.isArray())
       return 1000;
   else if constexpr (!first.isArray() && !second.isArray())
       return -1000;
   else
       return -1;
};

int main()
{
   return some_func(process);
}