anchor.diff:      _kIsCheckedIndex: isChecked,
       _kIsSelectedIndex: isSelected,
       _kIsButtonIndex: isButton,
  +    _kIsLinkIndex: isLink,
       _kIsTextFieldIndex: isTextField,
       _kIsFocusableIndex: isFocusable,
       _kIsFocusedIndex: isFocused,
  
positive.code:         return 'SemanticsFlag.isSelected';
        case _kIsButtonIndex:
          return 'SemanticsFlag.isButton';
        case _kIsTextFieldIndex:
          return 'SemanticsFlag.isTextField';
        case _kIsFocusableIndex:
  
negative.code:   /// and iOS's VoiceOver provides an additional hint when the focused object is
    /// a button.
    static const SemanticsFlag isButton = SemanticsFlag._(_kIsButtonIndex);
  
    /// Whether the semantic node represents a link.
    ///
    /// Platforms have special handling for links, for example, iOS's VoiceOver
    /// provides an additional hint when the focused object is a link.
    static const SemanticsFlag isLink = SemanticsFlag._(_kIsButtonIndex);
  
    /// Whether the semantic node represents a text field.
    ///
  