Xmltype default values inconsistency is not checked

MariaDB [test]> select b + 1 from t1;

ERROR 4078 (HY000): Illegal parameter data types xmltype and int for operation '+'

MariaDB [test]> CREATE or replace TABLE t2 (a INT, b xmltype as (a+1));

ERROR 4078 (HY000): Cannot cast 'bigint' as 'xmltype' in assignment of `test`.`t2`.`b`

MariaDB [test]> CREATE or replace TABLE t2 (a INT, b xmltype default (a+1));

Query OK, 0 rows affected (0,039 sec)

MariaDB [test]> insert into t2(a) select 5;

Query OK, 1 row affected (0,016 sec)

Records: 1  Duplicates: 0  Warnings: 0

MariaDB [test]> select * from t2;

+------+------+

| a    | b    |

+------+------+

|    5 | 6    |

+------+------+

1 row in set (0,003 sec)

MariaDB [test]> create sequence s;

Query OK, 0 rows affected (0,043 sec)

MariaDB [test]> create table t ( a xmltype default nextval(s));

Query OK, 0 rows affected (0,038 sec)

MariaDB [test]> insert into t select nextval(s);

ERROR 4078 (HY000): Cannot cast 'bigint' as 'xmltype' in assignment of `test`.`t`.`a`

MariaDB [test]> insert into t values ();

Query OK, 1 row affected (0,015 sec)