employee_promotion.cpp

struct Manager;

struct Employee
{
   Manager * promote_to_manager();
};

struct Manager : Employee
{
   Manager() {}
   
   /* converting constructor */
   Manager(const Employee &employee)
   {
      *(Employee *)this = employee;
   }
};

Manager * Employee::promote_to_manager()
{
   Employee *manager = new Manager;
   *manager = *this;
   delete this;
   return (Manager *)manager;
}

int main()
{
   Employee *employee = new Employee;
   Manager *manager = employee->promote_to_manager();
   return 0;
}