看 none 對應的 C code

# define Qnull 0

  case 782: /* none: %empty  */
#line 6127 "../parse.y"
                    {
			(yyval.node) = Qnull;
		    }
#line 15761 "parse.c"
    break;

parse 的結果記在 yyval.node，回頭找 yyval 是什麼

union YYSTYPE
{

    VALUE val;
    NODE *node;
    ID id;
    int num;
    st_table *tbl;
    const struct vtable *vars;
    struct rb_strterm_struct *strterm;
    struct lex_context ctxt;


};


  /* The variables used to return semantic value and location from the
     action routines.  */
  YYSTYPE yyval;
  YYLTYPE yyloc;