anchor.diff:      return columnWidths;
     }
   
  +  List<String> _computeRootPaths(String rootPath, bool corpus) {
  +    var roots = <String>[];
  +    if (!corpus) {
  +      roots.add(rootPath);
  +    } else {
  +      for (var child in io.Directory(rootPath).listSync()) {
  +        if (child is io.Directory) {
  +          roots.add(path.join(rootPath, child.path));
  +        }
  +      }
  +    }
  +    return roots;
  +  }
  +
     Iterable<List<String>> _convertColumnsToRows(
         Iterable<List<String>> columns) sync* {
       var maxRowCount = columns.fold<int>(
  
positive.code: 
      typeSystem = null;
      enclosingLibrary = null;
    }
  
    @override
  
negative.code: import 'package:analyzer/file_system/physical_file_system.dart';
  import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
  import 'package:analyzer/src/generated/engine.dart';
  import 'package:path/path.dart' as path;
  
  Future<void> main(List<String> args) async {
    var out = io.stdout;
  