anchor.diff:    useWidget(child: text); // ref
   }
   
  -void useWidget({Widget child}) {}
  +void useWidget({required Widget child}) {}
   ''');
       var expression = findNode.simple('text); // ref');
       expect(_flutter.identifyWidgetExpression(expression), expression);
  
positive.code: 
  @reflectiveTest
  class FlutterTest extends AbstractSingleUnitTest {
    @override
    // TODO(brianwilkerson) Update these tests. I believe that will require
    //  updating the mock flutter package.
    String? get testPackageLanguageVersion => '2.9';
  
    Flutter get _flutter => Flutter.instance;
  
    @override
  
negative.code: 
  abstract class Foo extends Widget {
    Widget bar;
  
    Foo(this.bar);
  }
  
  void f(Foo foo) {
  