a.cpp

#include <iostream>

template <int x> struct C {};

template<>
struct C<0> { using type = void; };

struct D : C<1>, C<0> {};

template <typename A = C<0>, typename = typename A::type>
void f (const C<0> &y)  { std::cout << 0 << "\n"; }

template <typename A = C<1>, typename = typename A::type, typename = void>
void f (const C<1> &y)  { std::cout << 1 << "\n"; }


int main ()
{
  f (D ());
}