anchor.diff:    /// Platforms has special handling for buttons, for example Android's TalkBack
     /// and iOS's VoiceOver provides an additional hint when the focused object is
     /// a button.
  -  static const SemanticsFlags isButton = const SemanticsFlags._(_kIsButton);
  +  static const SemanticsFlags isButton = const SemanticsFlags._(_kIsButtonIndex);
   
     /// The possible semantics flags.
     ///
  
positive.code:   static const int _kHasCheckedStateIndex = 1 << 0;
    static const int _kIsCheckedIndex = 1 << 1;
    static const int _kIsSelectedIndex = 1 << 2;
    static const int _kIsButton = 1 << 3;
  
    const SemanticsFlags._(this.index);
  
  
negative.code:         return 'SemanticsFlags.isChecked';
        case _kIsSelectedIndex:
          return 'SemanticsFlags.isSelected';
        case _kIsButtonIndex:
          return 'SemanticsFlags.isButton';
      }
      return null;
    }
  