anchor.diff:  import 'package:analysis_server/src/nullability/transitional_api.dart';
   import 'package:analysis_server/src/nullability/unit_propagation.dart';
   import 'package:analyzer/dart/ast/ast.dart';
  +import 'package:analyzer/src/dart/analysis/experiments.dart';
   import 'package:analyzer/src/generated/resolver.dart';
   import 'package:analyzer/src/generated/source.dart';
   import 'package:analyzer/src/test_utilities/find_node.dart';
  
positive.code:       _variables.decoratedElementType(
            findNode.functionDeclaration(search).declaredElement);
  
    @FailingTest(issue: 'https://github.com/dart-lang/sdk/issues/35909')
    test_interfaceType_nullable() async {
      await analyze('''
  void f(int? x) {}
  
negative.code:   ConstraintVariable possiblyOptionalParameter(String text) {
      return _variables
          .possiblyOptionalParameter(findNode.defaultParameter(text));
    }
  
    @override
    void setUp() {
      createAnalysisOptionsFile(experiments: [EnableString.non_nullable]);
      super.setUp();
    }
  
    /// Gets the [ConditionalDiscard] information associated with the statement
  