fork download

#include <iostream>
 
struct A {
	virtual void run() const = 0;
};
 
struct B : public A {
    // uncomment the following line to make the code work
    // using A::run;
	virtual void run(int) const = 0;
};
 
struct C : public B {
	void run() const override {
		std::cout << "implementation of A::run\n";
	}
};
 
struct D : public C {
	void run(int) const override {
		std::cout << "implementation of B::run\n";
	}
};
 
struct E : public D {};
 
int main() {
	const B& obj = E{};
	obj.run(); // not visible to the compiler in the overload set
    obj.run(5);
	return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:29:10: error: no matching function for call to ‘B::run() const’
  obj.run(); // not visible to the compiler in the overload set
          ^
prog.cpp:10:15: note: candidate: ‘virtual void B::run(int) const’
  virtual void run(int) const = 0;
               ^~~
prog.cpp:10:15: note:   candidate expects 1 argument, 0 provided

Standard output is empty