anchor.diff:      ;
   
   attr_expression_cond
  -    :   NAME_COND ATTR_EQ ATTR_VALUE_START expression ATTR_VALUE_END
  -        -> expression
  +    :   NAME_COND! ATTR_EQ! ATTR_VALUE_START! expression ATTR_VALUE_END!
       ;
   
   attr_expression_default
  
positive.code:     	doc=SHORTDOC*
          struct_add*
          TAG_END_STRUCT SHORTDOC*
          -> ^(CLASSDEF ^(DOC $doc) $name struct_add*);
  
  // for the time being, bitflags are converted to enums
  // TODO: implement bitstructs in the FFI grammar and use them here
  
negative.code:     	doc=SHORTDOC*
          enum_option+
          TAG_END_BITFLAGS SHORTDOC*
          -> ^(ENUMDEF ^(DOC $doc) $name $type enum_option+)
      ;
  
  struct_add
  @init {
  