anchor.diff:            continue;
           if (!config.isCompatibleWith(fragment.config))
             toBeMarkedExplicit.add(fragment);
  -        for (final _InterestingSemanticsFragment siblingFragment in fragments.sublist(0, fragments.length - 1)) {
  +        final int siblingLength = fragments.length - 1;
  +        for (int i = 0; i < siblingLength; i += 1) {
  +          final _InterestingSemanticsFragment siblingFragment = fragments[i];
             if (!fragment.config!.isCompatibleWith(siblingFragment.config)) {
               toBeMarkedExplicit.add(fragment);
               toBeMarkedExplicit.add(siblingFragment);
  
positive.code:   final List<_InterestingSemanticsFragment> _children = <_InterestingSemanticsFragment>[];
  
    @override
    Iterable<SemanticsNode> compileChildren({ Rect? parentSemanticsClipRect, Rect? parentPaintClipRect, required double elevationAdjustment }) sync* {
      if (!_isExplicit) {
        owner._semantics = null;
        for (final _InterestingSemanticsFragment fragment in _children) {
          assert(_ancestorChain.first == fragment._ancestorChain.last);
          fragment._ancestorChain.addAll(_ancestorChain.sublist(1));
          yield* fragment.compileChildren(
            parentSemanticsClipRect: parentSemanticsClipRect,
            parentPaintClipRect: parentPaintClipRect,
            // The fragment is not explicit, its elevation has been absorbed by
            // the parent config (as thickness). We still need to make sure that
            // its children are placed at the elevation dictated by this config.
            elevationAdjustment: elevationAdjustment + _config.elevation,
          );
        }
        return;
  
negative.code: 
      node.rect = owner.semanticBounds;
  
      final List<SemanticsNode> children = <SemanticsNode>[];
      for (final _InterestingSemanticsFragment fragment in _children) {
        assert(fragment.config == null);
        fragment.compileChildren(
          parentSemanticsClipRect: parentSemanticsClipRect,
          parentPaintClipRect: parentPaintClipRect,
          elevationAdjustment: 0.0,
          result: children,
        );
      }
      node.updateWith(config: null, childrenInInversePaintOrder: children);
  
      // The root node is the only semantics node allowed to be invisible. This
  