anchor.diff:    void visitCompilationUnit(CompilationUnit node) {
       enclosingLibrary = node.declaredElement.library;
       typeSystem = enclosingLibrary.typeSystem;
  +    inheritanceManager = InheritanceManager3();
   
       for (var directive in node.directives) {
         _recordTokenType('CompilationUnit (directive)', directive,
  
positive.code:   RelevanceMetricsComputer();
  
    /// Compute the metrics for the file(s) in the [rootPath].
    void compute(String rootPath) async {
      final collection = AnalysisContextCollection(
        includedPaths: [rootPath],
        resourceProvider: PhysicalResourceProvider.INSTANCE,
      );
      final collector = RelevanceDataCollector(data);
  
      for (var context in collection.contexts) {
        for (var filePath in context.contextRoot.analyzedFiles()) {
          if (AnalysisEngine.isDartFileName(filePath)) {
            try {
              ResolvedUnitResult resolvedUnitResult =
                  await context.currentSession.getResolvedUnit(filePath);
              //
              // Check for errors that cause the file to be skipped.
              //
              if (resolvedUnitResult.state != ResultState.VALID) {
                print('File $filePath skipped because it could not be analyzed.');
                print('');
                continue;
              } else if (hasError(resolvedUnitResult)) {
                print('File $filePath skipped due to errors:');
                for (var error in resolvedUnitResult.errors) {
                  print('  ${error.toString()}');
                }
                print('');
                continue;
              }
  
              resolvedUnitResult.unit.accept(collector);
            } catch (exception) {
              print('Exception caught analyzing: "$filePath"');
              print(exception.toString());
            }
          }
        }
  
negative.code:   var computer = RelevanceMetricsComputer();
    var stopwatch = Stopwatch();
    stopwatch.start();
    await computer.compute(rootPath, corpus: corpus);
    stopwatch.stop();
    var duration = Duration(milliseconds: stopwatch.elapsedMilliseconds);
    out.writeln('  Metrics computed in $duration');
  