anchor.diff:  
   class LabeledRadio extends StatelessWidget {
     final String? title;
  -  final Meal? value;
  +  final Meal value;
     final Meal? groupValue;
  -  final Function? onChanged;
  +  final void Function(Meal?)? onChanged;
   
     const LabeledRadio(
  -      {Key? key, this.title, this.value, this.groupValue, this.onChanged})
  +      {Key? key, this.title, required this.value, this.groupValue, this.onChanged})
         : super(key: key);
   
     @override
  
positive.code:           title: 'Breakfast',
            value: Meal.breakfast,
            groupValue: Provider.of<DiningDataProvider>(context).mealTime,
            onChanged: (Meal value) {
              setState(() {
                Provider.of<DiningDataProvider>(context, listen: false).mealTime =
                    value;
              });
            },
          ),
          LabeledRadio(
            title: 'Lunch',
            value: Meal.lunch,
            groupValue: Provider.of<DiningDataProvider>(context).mealTime,
            onChanged: (Meal value) {
              setState(() {
                Provider.of<DiningDataProvider>(context, listen: false).mealTime =
                    value;
              });
            },
          ),
  
negative.code:           title: 'Dinner',
            value: Meal.dinner,
            groupValue: Provider.of<DiningDataProvider>(context).mealTime,
            onChanged: (Meal? value) =>
              setState(() {
                Provider.of<DiningDataProvider>(context, listen: false).mealTime =
                    value!;
            })
          ),
        ],
      );
  