anchor.diff:  
   @reflectiveTest
   class BinaryExpressionResolutionWithNullSafetyTest
  -    extends PubPackageResolutionTest with WithNullSafetyMixin {
  +    extends PubPackageResolutionTest
  +    with WithNullSafetyMixin, BinaryExpressionResolutionTestCases {
     test_ifNull_left_nullableContext() async {
       await assertNoErrorsInCode(r'''
   T f<T>(T t) => t;
  
positive.code:   }
  
    test_ifNull() async {
      await assertNoErrorsInCode(r'''
  f(int a, double b) {
    a ?? b;
  }
  ''');
  
negative.code: }
  
  @reflectiveTest
  class BinaryExpressionResolutionTest extends PubPackageResolutionTest
      with BinaryExpressionResolutionTestCases {}
  
  mixin BinaryExpressionResolutionTestCases on PubPackageResolutionTest {
    test_bangEq() async {
      await assertNoErrorsInCode(r'''
  f(int a, int b) {
  