How to make Clang changle the rules of two-phase lookup?

Question

I want this to compile without an error. Just want it to wait until the instantiation

template<class T>
struct A : public T{
   void f(){ foo(); }
};

int main() {}

Answer 1

You might change your code to:

template<class T>
struct A : public T{
   void f(){ this->foo(); } // or T::foo();
};

int main() {}

making foo type dependent to fix your code.

Answer 2

Two-phase lookup rules is defined by the c++ standard and/or by compiler. Changing rules aren't possible like you can't change laws. You need to tell us what the real problem is.