AUTO_INCREMENT is silently dropped on a pluggable data type column

INSTALL SONAME 'type_test';

CREATE TABLE t1 (i TEST_INT8 NOT NULL AUTO_INCREMENT, a INT, KEY(i));

INSERT INTO t1 (a) VALUES (1),(2),(3);

SELECT i, a FROM t1 ORDER BY a;

13.1.0-opt>    INSTALL SONAME 'type_test';

Query OK, 0 rows affected (0.008 sec)

13.1.0-opt>    CREATE TABLE t1 (i TEST_INT8 NOT NULL AUTO_INCREMENT, a INT, KEY(i));

Query OK, 0 rows affected (0.011 sec)

13.1.0-opt>    INSERT INTO t1 (a) VALUES (1),(2),(3);

Query OK, 3 rows affected (0.001 sec)

Records: 3  Duplicates: 0  Warnings: 0

13.1.0-opt>    SELECT i, a FROM t1 ORDER BY a;

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

| i | a    |

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

| 0 |    1 |

| 0 |    2 |

| 0 |    3 |

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

3 rows in set (0.000 sec)

13.1.0-opt>

13.1.0-opt>show create table t1\G

*************************** 1. row ***************************

       Table: t1

Create Table: CREATE TABLE `t1` (

  `i` test_int8(20) NOT NULL DEFAULT 0,

  `a` int(11) DEFAULT NULL,

  KEY `i` (`i`)

) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_uca1400_ai_ci

1 row in set (0.000 sec)

13.1.0-opt>