anchor.diff:      this.onHover,
       this.cursor = MouseCursor.defer,
       this.opaque = true,
  -    this.child,
  +    Widget? child,
     }) : assert(cursor != null),
          assert(opaque != null),
  -       super(key: key);
  +       super(key: key, child: child);
   
     /// Triggered when a mouse pointer has entered this widget.
     ///
  
positive.code: ///
  ///  * [Listener], a similar widget that tracks pointer events when the pointer
  ///    has buttons pressed.
  class MouseRegion extends StatefulWidget {
    /// Creates a widget that forwards mouse events to callbacks.
    ///
    /// By default, all callbacks are empty, [cursor] is [MouseCursor.defer], and
  
negative.code:   /// This defaults to true.
    final bool opaque;
  
    @override
    RenderMouseRegion createRenderObject(BuildContext context) {
      return RenderMouseRegion(
        onEnter: onEnter,
        onHover: onHover,
        onExit: onExit,
        cursor: cursor,
        opaque: opaque,
      );
    }
  
    @override
    void updateRenderObject(BuildContext context, RenderMouseRegion renderObject) {
      renderObject
        ..onEnter = onEnter
        ..onHover = onHover
        ..onExit = onExit
        ..cursor = cursor
        ..opaque = opaque;
    }
  
    @override
    void debugFillProperties(DiagnosticPropertiesBuilder properties) {
  