anchor.diff:      return false;
     }
   
  -  int firstWhere(bool test(int element), {int orElse()}) {
  +  int firstWhere(bool test(int element), {int orElse()?}) {
       var len = this.length;
       for (var i = 0; i < len; ++i) {
         var element = this[i];
  
positive.code:     throw IterableElementError.noElement();
    }
  
    Int32x4 singleWhere(bool test(Int32x4 element), {Int32x4 orElse()}) {
      var result = null;
      bool foundMatching = false;
      var len = this.length;
  
negative.code:         offsetInBytes + (index * Int16List.bytesPerElement), _toInt16(value));
    }
  
    void setRange(int start, int end, Iterable<int> iterable,
        [int skipCount = 0]) {
      if (iterable is CodeUnits) {
        end = RangeError.checkValidRange(start, end, this.length);
        int length = end - start;
  