anchor.diff:  
     int operator[](int index) {
       _checkIndex(index, length);
  -    return JS("JSUInt32", "#[#]", this, index);
  -  }
  -
  -  void operator[]=(int index, int value) {
  -    _checkIndex(index, length);
  -    JS("void", "#[#] = #", this, index, value);
  +    return JS('JSUInt32', '#[#]', this, index);
     }
   
     List<int> sublist(int start, [int end]) {
  
positive.code:   }
  }
  
  // TODO(sra): Move to private library, like [NativeTypedArray].
  abstract class NativeTypedArrayOfDouble
      extends NativeTypedArray
          with ListMixin<double>, FixedLengthListMixin<double>
      implements List<double> {
  
    void setRange(int start, int end, Iterable<double> iterable,
                  [int skipCount = 0]) {
  
negative.code: 
    int operator[](int index) {
      _checkIndex(index, length);
      return JS('int', '#[#]', this, index);
    }
  
    List<int> sublist(int start, [int end]) {
  