anchor.diff:    void discardListChanges() => delegate.discardListChages();
     
     void notifyChange(ChangeRecord record) => delegate.notifyChange(record);
  -  notifyPropertyChange(Symbol field, Object oldValue, Object newValue) => delegate.notifyPropertyChange(oldValue, newValue);
  +  notifyPropertyChange(Symbol field, Object oldValue, Object newValue) =>
  +      delegate.notifyPropertyChange(oldValue, newValue);
     void observed() => delegate.observed();
     void unobserved() => delegate.unobserved();
     
  
positive.code:     delegate[index] = value;
    }
    
    // Manually delegating [add] and [addAll] as per [ListBase] performance recommendations.
    void add(E value) => delegate.add(value);
    void addAll(Iterable<E> iterable) => delegate.addAll(iterable);
    
  
negative.code:       // Replace the resolved value in the list.
        delegate[index] = value;
        
        // Make sure the replacement change has been discarded before enabling
        // changes again.
        deliverChanges();
        _changesDisabled = false;
      }
  