anchor.diff:    }
   
     void _registerDartErrorsForSource(RegisterExtension registerExtension) {
  -    String id = DART_ERRORS_FOR_SOURCE_EXTENSION_POINT_ID;
  -    registerExtension(id, PARSE_ERRORS);
  -    registerExtension(id, SCAN_ERRORS);
  +    registerExtension(DART_ERRORS_FOR_SOURCE_EXTENSION_POINT_ID, PARSE_ERRORS);
  +    registerExtension(DART_ERRORS_FOR_SOURCE_EXTENSION_POINT_ID, SCAN_ERRORS);
     }
   
     void _registerDartErrorsForUnit(RegisterExtension registerExtension) {
  -    String id = DART_ERRORS_FOR_UNIT_EXTENSION_POINT_ID;
  -    registerExtension(id, LIBRARY_UNIT_ERRORS);
  +    registerExtension(
  +        DART_ERRORS_FOR_UNIT_EXTENSION_POINT_ID, LIBRARY_UNIT_ERRORS);
     }
   
     void _registerHtmlErrors(RegisterExtension registerExtension) {
  -    String id = HTML_ERRORS_EXTENSION_POINT_ID;
  -    registerExtension(id, HTML_DOCUMENT_ERRORS);
  +    registerExtension(HTML_ERRORS_EXTENSION_POINT_ID, HTML_DOCUMENT_ERRORS);
     }
   
     void _registerTaskExtensions(RegisterExtension registerExtension) {
  
positive.code:    * Return a list containing all of the contributed analysis error result
     * descriptors for Dart library specific units.
     */
    List<TaskDescriptor> get dartErrorsForUnit =>
        dartErrorsForUnitExtensionPoint.extensions;
  
  
negative.code:    * Return a list containing all of the contributed analysis error result
     * descriptors for HTML sources.
     */
    @ExtensionPointId('HTML_ERRORS_EXTENSION_POINT_ID')
    List<TaskDescriptor> get htmlErrors => htmlErrorsExtensionPoint.extensions;
  
    /**
  