anchor.diff:  ///                 iconSize: 24,
   ///                 elevation: 16,
   ///                 style: TextStyle(color: Colors.deepPurple),
  -///                 onChanged: (String newValue) {
  +///                 onChanged: (String? newValue) {
   ///                   setState(() {
   ///                     _dropdownValue = newValue;
   ///                   });
  
positive.code: ///                 decoration: InputDecoration(
  ///                   hintText: 'This is a regular TextFormField',
  ///                 ),
  ///                 validator: (String value) {
  ///                   if (value.isEmpty) {
  ///                     return 'Can\'t be empty.';
  ///                   }
  ///                   return null;
  
negative.code: /// }
  ///
  /// class AutocompleteCustomTypeExample extends StatelessWidget {
  ///   AutocompleteCustomTypeExample({Key? key}) : super(key: key);
  ///
  ///   static final List<User> _userOptions = <User>[
  ///     User(name: 'Alice', email: 'alice@example.com'),
  