Implements.cpp, C++ (vc++)

Implements.cpp

//Microsoft (R) C/C++ Optimizing Compiler Version 19.00.23506 for x86

#include <iostream>
#include <string>
#include <vector>
#include <memory>
#include <type_traits>
#include <functional>

struct query_interface
{
	template <class T>
	static decltype(std::declval<T>().queryInterface()) execute(T* pImpl_)
	{
        std::cout << "query_interface\n";
		return pImpl_->queryInterface();
	}
};

template<class T>
class interface
{
public:
    inline void * query_interface() 
    {
        std::cout << "interface\n";
        return query_interface::execute(pImpl_);
    }
    
    interface(T * smth) : pImpl_(smth)
    {
    
    }
private:
    T * pImpl_;
};

class Itest 
{

};

class Itest2
{

};

class Itest3
{

};

template<typename T, typename... Args>
class Implements : public T, public virtual Implements<Args...>
{
public:
    inline void * queryInterface() 
    {
        std::cout << "implements all " << typeid(T).name() << "\n";
        return Implements<Args...>::queryInterface();
    }
};

template<typename T>
class Implements<T> : public T
{
public:
    inline void * queryInterface() 
    {
        std::cout << "implements base " << typeid(T).name() << '\n';
        return nullptr;
    }
};

class test : public Implements<Itest,Itest2,Itest3> 
{
public:
    
};

int main() 
{
    test t;
    interface<test> i(&t);
    i.query_interface();
}


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