anchor.diff:    final List<ImportDirective> _duplicateImports = <ImportDirective>[];
   
     /**
  -   * This is a map between the set of [LibraryElement]s that the current library imports, and the
  -   * list of [ImportDirective]s that import each [LibraryElement]. In cases where the current
  -   * library imports a library with a single directive (such as `import lib1.dart;`), the library
  -   * element will map to a list of one [ImportDirective], which will then be removed from the
  -   * [unusedImports] list. In cases where the current library imports a library with multiple
  -   * directives (such as `import lib1.dart; import lib1.dart show C;`), the [LibraryElement] will
  -   * be mapped to a list of the import directives, and the namespace will need to be used to
  -   * compute the correct [ImportDirective] being used; see [_namespaceMap].
  -   */
  -  final HashMap<LibraryElement, List<ImportDirective>> _libraryMap =
  -      new HashMap<LibraryElement, List<ImportDirective>>();
  -
  -  /**
  -   * In cases where there is more than one import directive per library element, this mapping is
  -   * used to determine which of the multiple import directives are used by generating a
  -   * [Namespace] for each of the imports to do lookups in the same way that they are done from
  -   * the [ElementResolver].
  +   * The cache of [Namespace]s for [ImportDirective]s.
      */
     final HashMap<ImportDirective, Namespace> _namespaceMap =
         new HashMap<ImportDirective, Namespace>();
  
positive.code:  */
  class ImportsVerifier {
    /**
     * A list of [ImportDirective]s that the current library imports, but does not use.
     *
     * As identifiers are visited by this visitor and an import has been identified as being used
  
negative.code:             // TODO (jwren) Can the element ever not be a PrefixElement?
            }
          }
          _addShownNames(directive);
        }
      }
  