anchor.diff:    void debugFillProperties(DiagnosticPropertiesBuilder properties) {
       super.debugFillProperties(properties);
       properties.add(EnumProperty<AxisDirection>('axisDirection', axisDirection));
  -    properties.add(EnumProperty<AxisDirection>('crossAxisDirection', crossAxisDirection, defaultValue: null));
  +    properties.add(EnumProperty<AxisDirection>(
  +        'crossAxisDirection', crossAxisDirection,
  +        defaultValue: null));
       properties.add(DoubleProperty('anchor', anchor));
       properties.add(DiagnosticsProperty<ViewportOffset>('offset', offset));
       if (center != null) {
         properties.add(DiagnosticsProperty<Key>('center', center));
       } else if (children.isNotEmpty && children.first.key != null) {
  -      properties.add(DiagnosticsProperty<Key>('center', children.first.key, tooltip: 'implicit'));
  +      properties.add(DiagnosticsProperty<Key>('center', children.first.key,
  +          tooltip: 'implicit'));
       }
       properties.add(DiagnosticsProperty<double>('cacheExtent', cacheExtent));
  -    properties.add(DiagnosticsProperty<CacheExtentStyle>('cacheExtentStyle', cacheExtentStyle));
  +    properties.add(DiagnosticsProperty<CacheExtentStyle>(
  +        'cacheExtentStyle', cacheExtentStyle));
     }
   }
   
  
positive.code:       case AxisDirection.down:
          assert(debugCheckHasDirectionality(
            context,
            why: 'to determine the cross-axis direction when the viewport has a \'down\' axisDirection',
            alternative: 'Alternatively, consider specifying the \'crossAxisDirection\' argument on the Viewport.',
          ));
          return textDirectionToAxisDirection(Directionality.of(context));
        case AxisDirection.left:
  
negative.code:   /// bar) can tag its [SemanticsNode] with [excludeFromScrolling] to indicate
    /// that it should no longer be considered for semantic actions related to
    /// scrolling.
    static const SemanticsTag excludeFromScrolling =
        SemanticsTag('RenderViewport.excludeFromScrolling');
  
    @override
    void setupParentData(RenderObject child) {
  