anchor.diff:  
   /** Specialized alternative to [MappedIterable] for mapped [List]s. */
   class MappedListIterable<S, T> extends Iterable<T> {
  -  final Iterable<S> _list;
  +  final List<S> _list;
     /**
      * Start index of the part of the list to map.
      *
  
positive.code:     int start = _startIndex;
      int end = _endIndex;
      if (start == end) return null;
      int value = _f(_list[start]);
      if (_list.length != length) {
        throw new ConcurrentModificationError(_list);
      }
      for (int i = start + 1; i < end; i++) {
        int nextValue = _f(_list[i]);
        if (compare(value, nextValue) > 0) {
          value = nextValue;
        }
  
negative.code:     return value;
    }
  
    T max([int compare(T a, T b)]) {
      if (compare == null) {
        var defaultCompare = Comparable.compare;
        compare = defaultCompare;
  