anchor.diff:  
       totalIndent = 0;
   
  -    if (_parent != null) {
  -      _parent!.refreshTotalUsedIndent(usedNesting);
  -      totalIndent += _parent!.totalUsedIndent;
  +    if (parent != null) {
  +      parent!.refreshTotalUsedIndent(usedNesting);
  +      totalIndent += parent!.totalUsedIndent;
       }
   
       if (usedNesting.contains(this)) totalIndent += indent;
  
positive.code:   /// Clears the previously calculated total indent of this nesting level.
    void clearTotalUsedIndent() {
      _totalUsedIndent = null;
      _parent?.clearTotalUsedIndent();
    }
  
    /// Calculates the total amount of indentation from this nesting level and
  
negative.code:   int get totalUsedIndent => _totalUsedIndent!;
    int? _totalUsedIndent;
  
    bool get isNested => parent != null;
  
    NestingLevel()
        : parent = null,
          indent = 0;
  
    NestingLevel._(this.parent, this.indent);
  
    /// Creates a new deeper level of nesting indented [spaces] more characters
    /// that the outer level.
  