#include <iostream>

struct C {
  const int i;
  void f() const {
     std::cout << i << "\n";
  }
  C(int i) : i(i) {}
  C& operator=( const C& );
};

C& C::operator=( const C& other) {
  if ( this != &other ) {
    this->~C();                 // lifetime of *this ends
    new (this) C(other);        // new object of type C created
    f();                        // well-defined
  }
  return *this;
}

int main(){
    C c1(1);
    C c2(2);
    c1 = c2;                        // well-defined
    c1.f();
}