template <class T>
class A
{
public:

    virtual void FunThings ( const A<T> &orig, A<T>* new_one ) = 0;

    T thing{};
};


template <class T>
class C: public A < T >
{
public:

    virtual void FunThings ( const C<T> &orig, C<T>* new_one ) {}

};


template <class T>
class PrimaryClass
{
public:

    virtual void DoFunThings ( A<T>* d ) = 0;
};



template<class T>
class DerivedClass: public PrimaryClass<T>
{
public:
    virtual void DoFunThings ( C<T>* d ) {}
};


int main ()
{
    DerivedClass<int> derived;

    return 0;
}