anchor.diff:  }
   
   class _ObservableImmutableListView implements ObservableList {
  -  
  +
     ObservableList _delegate;
  -  
  +
     _ObservableImmutableListView(ObservableList this._delegate);
  -  
  +
     Stream<List<ChangeRecord>> get changes => _delegate.changes;
     get first => _delegate.first;
     bool get hasObservers => _delegate.hasObservers;
  
positive.code:   Set toSet() => _delegate.toSet();
    String toString() => _delegate.toString();
    Iterable where(test(element)) => _delegate.where(test);
    
    _throw() => throw new UnsupportedError('List is immutable.');
  }
  
  
negative.code:   bool deliverChanges() => _delegate.deliverChanges();
    elementAt(int index) => _delegate.elementAt(index);
    bool every(bool test(element)) => _delegate.every(test);
    Iterable expand(Iterable f(element)) => _delegate.expand(f);
    void fillRange(_a, _b, [_c]) => _throw();
    firstWhere(bool test(element), {Object orElse()}) => _delegate.firstWhere(test, orElse: orElse);
    fold(initialValue, combine(previousValue, element)) => _delegate.fold(initialValue, combine);
  