template <class I>
class B {
public:
  I b;
};

template <class T> class C;

template <class I>
class A {
  I a;
public:
  A(const B<I> &b) : a(b.b) {}
  template <class T> A &operator << (const C<T> &);
};

template <class T>
class C {
public:
  T c;
  C(const T &n) : c(n) {}
};

template <class I>
template <class T>
inline A<I> &A<I>::operator << (const C<T> &c) { a = (I)c.c; return *this; }

template <class I, class T>
inline A<I> &operator << (B<I> &b, const C<T> &c) { return A<I>(b) << c; }

int main() {
  B<int> b;
  b << C<double>(1.2);
  return 0;
}