anchor.diff:          _variables =
               compilationUnit.topLevelVariables.where(_isNotSynthetic).toList();
   
  -  /**
  -   * Creates an [ElementWalker] which walks the child elements of a compilation
  -   * unit element.
  -   */
  +  /// Creates an [ElementWalker] which walks the child elements of a compilation
  +  /// unit element.
     ElementWalker.forExecutable(
         ExecutableElement element, CompilationUnitElement compilationUnit)
         : this._forExecutable(element, compilationUnit, new ElementHolder());
   
  -  /**
  -   * Creates an [ElementWalker] which walks the child elements of a typedef
  -   * element.
  -   */
  +  /// Creates an [ElementWalker] which walks the child elements of a typedef
  +  /// element.
     ElementWalker.forGenericFunctionType(GenericFunctionTypeElement element)
         : element = element,
           _parameters = element.parameters,
           _typeParameters = element.typeParameters;
   
  -  /**
  -   * Creates an [ElementWalker] which walks the child elements of a typedef
  -   * element defined using a generic function type.
  -   */
  +  /// Creates an [ElementWalker] which walks the child elements of a typedef
  +  /// element defined using a generic function type.
     ElementWalker.forGenericTypeAlias(FunctionTypeAliasElement element)
         : element = element,
           _typeParameters = element.typeParameters;
   
  -  /**
  -   * Creates an [ElementWalker] which walks the child elements of a parameter
  -   * element.
  -   */
  +  /// Creates an [ElementWalker] which walks the child elements of a parameter
  +  /// element.
     ElementWalker.forParameter(ParameterElement element, bool functionTyped)
         : element = element,
           _parameters = element.parameters,
  
positive.code:     }
    }
  
    /**
     * Recurses through the element model and AST, verifying that all elements are
     * matched.
     *
     * Executes [callback] with [_walker] pointing to the given [walker] (which
     * should be a new instance of [ElementWalker]).  Once [callback] returns,
     * uses [ElementWalker.validate] to verify that all expected elements have
     * been matched.
     */
    void _walk(ElementWalker walker, void callback()) {
      ElementWalker outerWalker = _walker;
      _walker = walker;
  
negative.code: }
  
  class _ElementMismatchException extends AnalysisException {
    /// Creates an exception to refer to the given [compilationUnit], [element],
    /// and [cause].
    _ElementMismatchException(
        CompilationUnitElement compilationUnit, Element element,
        [CaughtException cause = null])
  