gistfile1.cpp

#include <iostream>
#include <typeinfo>

class B {
};

class A {
  public:
    virtual ~A() = default;
};

class C : public A {
  public:
    operator B() const { return B(); }
};

int main() {
  A *c = new C();
  try {
    B b = dynamic_cast<const B &>(*c);
  } catch (const std::bad_cast &) {
    std::cout << "Why?!" << std::endl;
  }
}