anchor.diff:    // allocations...
     var base = new CompoundSelector([new PlaceholderSelector('<temp>')]);
     return complexIsSuperselector(
  -      complex1..toList().add(base), complex2..toList().add(base));
  +      complex1.toList()..add(base), complex2.toList()..add(base));
   }
   
   /// Returns whether [complex1] is a superselector of [complex2].
  
positive.code:   var groups1 = _groupSelectors(queue1);
    var groups2 = _groupSelectors(queue2);
    var lcs = longestCommonSubsequence/*<List<ComplexSelectorComponent>>*/(
        groups1, groups2, select: (group1, group2) {
      if (listEquals(group1, group2)) return group1;
      if (group1.first is! CompoundSelector ||
          group2.first is! CompoundSelector) {
  
negative.code:     var compound1 = complex1[i1] as CompoundSelector;
  
      if (remaining1 == 1) {
        return compoundIsSuperselector(
            compound1, complex2.last as CompoundSelector,
            parents: complex2.skip(i2 + 1));
      }
  
  