class foo {
  foo(foo f) : x(f.x) { }
  foo(int y) : x(y) { }
  int x;
};

class bar {
  bar(bar b) : x(b.x) { }
  bar(int y) : x(y) { }
  int x;
};

fun operator+(foo a, foo b) -> foo@ {
  return @foo(a.x + b.x);
}

fun operator+(bar a, bar b) -> bar@ {
  return @bar(a.x + b.x);
}

fun main() -> int@ {
  let f = @foo(2);
  let g = @foo(4);
  let h = @bar(2);
  let k = @bar(4);
  return (f + g).x - (h + k).x + 1 - 1;
}