anchor.diff:    });
   }
   
  +/// Returns `true` if the language version of [uri] does not support null
  +/// safety.
   Future<bool> uriUsesLegacyLanguageVersion(
       Uri uri, CompilerOptions options) async {
     // This method is here in order to use the opt out hack here for test
     // sources.
     if (SourceLibraryBuilder.isOptOutTest(uri)) return true;
     Version uriVersion = await languageVersionForUri(uri, options);
  -  return (uriVersion < defaultLanguageVersion);
  +  return (uriVersion < experimentReleasedVersion[ExperimentalFlag.nonNullable]);
   }
  
positive.code: import 'package:_fe_analyzer_shared/src/scanner/scanner.dart'
      show LanguageVersionToken, Scanner, ScannerConfiguration, scan;
  
  import 'package:kernel/ast.dart' show Version, defaultLanguageVersion;
  export 'package:kernel/ast.dart' show Version;
  
  import 'package:package_config/package_config.dart'
  
negative.code: 
  import 'compiler_options.dart' show CompilerOptions;
  
  import 'experimental_flags.dart'
      show ExperimentalFlag, experimentReleasedVersion;
  import 'file_system.dart' show FileSystem, FileSystemException;
  
  /// Gets the language version for a specific URI.
  