anchor.diff:  /// A hover card based tooltip.
   class HoverCardTooltip extends StatefulWidget {
     const HoverCardTooltip({
  -    @required this.enabled,
  -    @required this.onHover,
  -    @required this.child,
  +    required this.enabled,
  +    required this.onHover,
  +    required this.child,
       this.disposable,
     });
   
  
positive.code: // Copyright 2021 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  // @dart=2.9
  
  import 'dart:async';
  import 'dart:math' as math;
  
negative.code: /// Note that if a mouse has never entered, it will not remove itself.
  class HoverCard {
    HoverCard({
      required BuildContext context,
      required Widget contents,
      required double width,
      required Offset position,
      String? title,
    }) {
      final overlayState = Overlay.of(context)!;
      final colorScheme = Theme.of(context).colorScheme;
      final focusColor = Theme.of(context).focusColor;
      final hoverHeading = colorScheme.hoverTitleTextStyle;
  