Rounding functions return a wrong data type for a BIT, ENUM, SET argument

CREATE OR REPLACE TABLE t1 (a BIT(64));

INSERT INTO t1 VALUES (0xFFFFFFFFFFFFFFFF);

CREATE OR REPLACE TABLE t2 AS

  SELECT a, FLOOR(a), CEILING(a), TRUNCATE(a,0), ROUND(a) FROM t1;

SHOW CREATE TABLE t2;

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

| Table | Create Table                                                                                                                                                                                                                                                                    |

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

| t2    | CREATE TABLE `t2` (

  `a` bit(64) DEFAULT NULL,

  `FLOOR(a)` decimal(64,0) DEFAULT NULL,

  `CEILING(a)` decimal(64,0) DEFAULT NULL,

  `TRUNCATE(a,0)` bigint(64) unsigned DEFAULT NULL,

  `ROUND(a)` decimal(64,0) unsigned DEFAULT NULL

) ENGINE=InnoDB DEFAULT CHARSET=latin1 |

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