anchor.diff:  
   interfaceMember
   	: const_
  -	| attributeOrOperationOrIterator
  +	| operation
  +	| serializer
  +	| stringifier
  +	| staticMember
  +	| iterable
  +	| readonlyMember
  +	| readWriteAttribute
  +	| readWriteMaplike
  +	| readWriteSetlike
   ;
   
   dictionary
  
positive.code: 	| 'legacycaller'
  ;
  
  operationOrIteratorRest
  	: iteratorRest
  	| operationRest
  ;
  
  iteratorRest
  	: 'iterator' optionalIteratorInterfaceOrObject ';'
  ;
  
  optionalIteratorInterfaceOrObject
  	: optionalIteratorInterface
  	| 'object'
  ;
  
  optionalIteratorInterface
  	: '=' IDENTIFIER_WEBIDL
  	| /* empty */
  ;
  
  operationRest
  	: optionalIdentifier '(' argumentList ')' ';'
  ;
  
negative.code: 	: callbackOrInterface
  	| partial
  	| dictionary
  	| enum_
  	| typedef
  	| implementsStatement
  