anchor.diff:      INTERFACE_BODY;
       MEMBER_NAME;
       MEMBER_TYPE;
  +    METHOD_DECL;
       METATYPE_LIST;
       NAMED_ARG;
       SEQ_ARG;
  
positive.code:     ;
  
  memberDeclaration
      : memberHeader memberDefinition
      ;
  
  memberHeader
      : memberType memberName
      -> ^(MEMBER_TYPE memberType) memberName
      | 'assign' memberName
      -> ^(ATTRIBUTE_SETTER memberName)
      ;
  
  memberType
  
negative.code:     
  primary
      : base selector*
      -> ^(PRIMARY base selector*)
      ;
  
  postfixOperator
  