anchor.diff:  
   void indexSet(var a, var index, var value) {
     if (isJsArray(a)) {
  -    if (!(index is int)) {
  +    if (index is !int) {
         throw new IllegalArgumentException(index);
       }
       if (index < 0 || index >= a.length) {
  
positive.code: shl(var a, var b) {
    // TODO(floitsch): inputs must be integers.
    if (checkNumbers(a, b)) {
      if (b < 0) throw new IllegalArgumentException(b);
      // JavaScript only looks at the last 5 bits of the shift-amount. Shifting
      // by 33 is hence equivalent to a shift by 1.
  
negative.code:     int result = JS('num', @'# % #', a, b);
      if (result == 0) return 0;  // Make sure we don't return -0.0.
      if (result > 0) return result;
      // TODO(floitsch): Find cleaner way of forcing the type.
      b = JS('num', '#', b);
      if (b < 0) {
        return result - b;
      } else {
  