anchor.diff:      BuildContext context,
       ClassHeapDetailStats item, {
       bool isRowSelected = false,
  -    VoidCallback onPressed,
  +    VoidCallback? onPressed,
     }) {
       final controller = Provider.of<MemoryController>(context);
   
       return Checkbox(
         value: item.isStacktraced,
         onChanged: (value) {
  -        controller.toggleAllocationTracking(item, value);
  +        controller.toggleAllocationTracking(item, value!);
         },
       );
     }
  
positive.code: // Copyright 2020 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:math';
  
  
negative.code: 
    @override
    int compare(ClassHeapDetailStats a, ClassHeapDetailStats b) {
      final Comparable valueA = getValue(a)!;
      final Comparable valueB = getValue(b)!;
      return valueA.compareTo(valueB);
    }
  }
  