anchor.diff:              | LPAREN Type_nitem RPAREN
               )
               [ TOKENABLE
  -            | struct_arg_list
  +            | Type_nitem
  +#VAR
  +#struct_arg_list
               ]
               SEMICOLON
           | TOKENUM LBRACE enum_element ( COMMA enum_element )* RBRACE VAR
  
positive.code:         )
  
      rule instance_statement:
          TOKINSTANCE TYPEVAR LPAREN instance_arg ( COMMA instance_arg )* RPAREN
          [ provisos_clause ] SEMICOLON
          ( function_declaration
          | module_declaration
  
negative.code:         )*  {{ return v }}
  
      rule nterm<<V>>:
          [ (TOKEXCLAIM | TOKTILDE | TOKMINUS | TOKBAR) ] term<<V>> {{ return term }}
  
      rule call_pitem:
          [ TOKCLOCKED_BY | TOKRESET_BY ] assign_value
  