Temporary MERGE table with temporary underlying is broken by ALTER

[Igor Babaev]

The bug #57657 from bugs.mysql.com is reproducible in MariaDB 5.5

MariaDB [test]> create temporary table t1_temp(i int);
Query OK, 0 rows affected (0.02 sec)

MariaDB [test]> create temporary table tm_temp_temp (i int) engine=merge union=(t1_temp) insert_method=last;
Query OK, 0 rows affected (0.00 sec)

MariaDB [test]> alter table tm_temp_temp insert_method=first;
ERROR 1168 (HY000): Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist
MariaDB [test]> check table tm_temp_temp;
+-------------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-------------------+-------+----------+-----------------------------------------------------------------------------------------------------+
| test.tm_temp_temp | check | Error | Table 'test.t1_temp' is differently defined or of non-MyISAM type or doesn't exist |
| test.tm_temp_temp | check | Error | Unable to open underlying table which is differently defined or of non-MyISAM type or doesn't exist |
| test.tm_temp_temp | check | error | Corrupt |
+-------------------+-------+----------+-----------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)