anchor.diff:    void addConstant(ConstantValue constant, ImportSet importSet) {
       var item = pendingConstants[constant];
       if (item == null) {
  -      item = new ConstantWorkItem(constant, importSet);
  +      item = ConstantWorkItem(constant, importSet);
         pendingConstants[constant] = item;
         queue.add(item);
       } else {
  
positive.code:       // Continue recursively updating from [oldSet] to [newSet].
        _memberToSet[element] = newSet;
  
        Dependencies dependencies = new Dependencies();
        _collectAllElementsAndConstantsResolvedFromMember(
            closedWorld, element, dependencies);
  
  
negative.code:       bool isMainOutput = source.readBool();
        String name = source.readString();
        Set<ImportEntity> importSet = source.readImports().toSet();
        return OutputUnit(isMainOutput, name, importSet);
      });
      OutputUnit mainOutputUnit = outputUnits[source.readInt()];
  
  