#include <iostream>

class type_one
{
};

class type_two
{
};

class i_one
{
public:
  virtual void set (const type_one & val, int id) = 0;
};

class i_two
{
public:
  virtual void set (const type_two & val) = 0;
};



class i_one_two:public i_one, public i_two
{
};


class OneTwo:public i_one_two
{
public:
  void set (const type_one & val, int id)
  {
    std::cout << "type_one value, id = " << id;
  }

  void set (const type_two & val)
  {
    std::cout << "type_two value\n";
  }
};


int
main ()
{
  OneTwo ot;

  i_one_two *i12 = &ot;

  i12->set(type_one (), 111); // error: request for member ‘set’ is ambiguous
  i12->set(type_two ());      // error: request for member ‘set’ is ambiguous
  return 0;
}

//==============================
main.cpp: In function ‘int main()’:
main.cpp:52:8: error: request for member ‘set’ is ambiguous
   i12->set(type_one (), 111);
        ^~~
main.cpp:20:16: note: candidates are: virtual void i_two::set(const type_two&)
   virtual void set (const type_two & val) = 0;
                ^~~
main.cpp:14:16: note:                 virtual void i_one::set(const type_one&, int)
   virtual void set (const type_one & val, int id) = 0;
                ^~~
main.cpp:53:8: error: request for member ‘set’ is ambiguous
   i12->set(type_two ());
        ^~~
main.cpp:20:16: note: candidates are: virtual void i_two::set(const type_two&)
   virtual void set (const type_two & val) = 0;
                ^~~
main.cpp:14:16: note:                 virtual void i_one::set(const type_one&, int)
   virtual void set (const type_one & val, int id) = 0;
                ^~~