anchor.diff:    int get totalUsedIndent => _totalUsedIndent!;
     int? _totalUsedIndent;
   
  -  bool get isNested => _parent != null;
  +  bool get isNested => parent != null;
   
     NestingLevel()
  -      : _parent = null,
  +      : parent = null,
           indent = 0;
   
  -  NestingLevel._(this._parent, this.indent);
  +  NestingLevel._(this.parent, this.indent);
   
     /// Creates a new deeper level of nesting indented [spaces] more characters
     /// that the outer level.
  
positive.code: class NestingLevel extends FastHash {
    /// The nesting level surrounding this one, or `null` if this is represents
    /// top level code in a block.
    NestingLevel? get parent => _parent;
    final NestingLevel? _parent;
  
    /// The number of characters that this nesting level is indented relative to
    /// the containing level.
  
negative.code: 
    @override
    String toString() {
      if (parent == null) return indent.toString();
      return '$parent:$indent';
    }
  }
  