TIMEDIFF with fraction doesn't function in TiDB

[espresso98]

Bug Report

TIMEDIFF(expr1,expr2) returns expr1 − expr2 expressed as a time value.
TiDB returns NULL values in time data with fraction in default sql mode.

1. Minimal reproduce step

DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a TIME(6));
INSERT INTO t1 VALUES ('-01:00:00.000001');
INSERT INTO t1 VALUES ('-01:00:00.000000');
INSERT INTO t1 VALUES ('-00:00:00.000001');
INSERT INTO t1 VALUES ('00:00:00.000000');
INSERT INTO t1 VALUES ('00:00:00.000001');
INSERT INTO t1 VALUES ('01:00:00.000000');
INSERT INTO t1 VALUES ('01:00:00.000001');

SELECT a, TIMEDIFF(a, '00:00:00.000001') FROM t1;
SELECT a, TIMEDIFF('00:00:00.000001', a) FROM t1;
DROP TABLE t1;

2. What did you expect to see?

mysql> SELECT a, TIMEDIFF(a, '00:00:00.000001') FROM t1;
+------------------+--------------------------------+
| a                | TIMEDIFF(a, '00:00:00.000001') |
+------------------+--------------------------------+
| -01:00:00.000001 | -01:00:00.000002               |
| -01:00:00.000000 | -01:00:00.000001               |
| -00:00:00.000001 | -00:00:00.000002               |
| 00:00:00.000000  | -00:00:00.000001               |
| 00:00:00.000001  | 00:00:00.000000                |
| 01:00:00.000000  | 00:59:59.999999                |
| 01:00:00.000001  | 01:00:00.000000                |
+------------------+--------------------------------+

mysql> SELECT a, TIMEDIFF('00:00:00.000001', a) FROM t1;
+------------------+--------------------------------+
| a                | TIMEDIFF('00:00:00.000001', a) |
+------------------+--------------------------------+
| -01:00:00.000001 | 01:00:00.000002                |
| -01:00:00.000000 | 01:00:00.000001                |
| -00:00:00.000001 | 00:00:00.000002                |
| 00:00:00.000000  | 00:00:00.000001                |
| 00:00:00.000001  | 00:00:00.000000                |
| 01:00:00.000000  | -00:59:59.999999               |
| 01:00:00.000001  | -01:00:00.000000               |
+------------------+--------------------------------+

3. What did you see instead

tidb> SELECT a, TIMEDIFF(a, '00:00:00.000001') FROM t1;
+------------------+--------------------------------+
| a                | TIMEDIFF(a, '00:00:00.000001') |
+------------------+--------------------------------+
| -01:00:00.000001 | NULL                           |
| -01:00:00.000000 | NULL                           |
| -00:00:00.000001 | NULL                           |
| 00:00:00.000000  | NULL                           |
| 00:00:00.000001  | NULL                           |
| 01:00:00.000000  | NULL                           |
| 01:00:00.000001  | NULL                           |
+------------------+--------------------------------+

tidb> SELECT a, TIMEDIFF('00:00:00.000001', a) FROM t1;
+------------------+--------------------------------+
| a                | TIMEDIFF('00:00:00.000001', a) |
+------------------+--------------------------------+
| -01:00:00.000001 | NULL                           |
| -01:00:00.000000 | NULL                           |
| -00:00:00.000001 | NULL                           |
| 00:00:00.000000  | NULL                           |
| 00:00:00.000001  | NULL                           |
| 01:00:00.000000  | NULL                           |
| 01:00:00.000001  | NULL                           |
+------------------+--------------------------------+

4. What is your TiDB version?

tidb_version(): Release Version: v5.5.0-alpha-105-gaabd4e04d
Edition: Community
Git Commit Hash: aabd4e04d994eb91663abaa80865daec4cf970a6
Git Branch: master
UTC Build Time: 2022-01-13 05:36:36
GoVersion: go1.17.2
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false

[Defined2014]

/assign