anchor.diff:      ;
   
   dpackage
  -    : PACKAGE k=IDENTIFIER LCURLY definition* RCURLY -> ^(PACKAGE $k definition*) 
  +    : PACKAGE k=IDENTIFIER LCURLY definition* RCURLY list_separator? -> ^(PACKAGE $k definition*) 
       ;
   
   namespace
  
positive.code:     ;
  
  enum_rule
      : ENUM IDENTIFIER LCURLY enum_field* RCURLY -> ^(ENUM IDENTIFIER enum_field*)
      ;
  
  enum_field
  
negative.code:     ;
  
  struct
      : STRUCT IDENTIFIER LCURLY field* RCURLY type_annotations? list_separator? -> ^(STRUCT IDENTIFIER field* type_annotations?)
      ;
  
  union
  