anchor.diff:  
     test_initializer_ifNull() async {
       await assertNoErrorsInCode('''
  -var a = 1;
  +int? a = 1;
   var t = a ?? 2;
   ''');
     }
  
positive.code:   defineReflectiveSuite(() {
      defineReflectiveTests(TopLevelInferenceTest);
      defineReflectiveTests(TopLevelInferenceErrorsTest);
      defineReflectiveTests(TopLevelInferenceTestWithSpread);
  //    defineReflectiveTests(ApplyCheckElementTextReplacements);
    });
  }
  
negative.code:   double foo(int x);
  }
  abstract class C implements A, B {
    Never foo/*error: overrideNoCombinedSuperSignature*/(dynamic x);
  }
  ''');
    }
  
    test_method_error_noCombinedSuperSignature2_legacy() async {
      var library = await _encodeDecodeLibrary(r'''
  // @dart = 2.9
  abstract class A {
    int foo(int x);
  }
  
  abstract class B {
    double foo(int x);
  }
  
  abstract class C implements A, B {
    Never foo(x);
  }
  ''');
      checkElementText(library, r'''
  abstract class A {
    int foo(int x);
  }
  abstract class B {
    double foo(int x);
  }
  abstract class C implements A, B {
    Null foo/*error: overrideNoCombinedSuperSignature*/(dynamic x);
  }
  ''');
  