Builtin func convert() can't deal with GBK charset correctly

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

start tidb-server with

./bin/tidb-server --config=cmd/explaintest/config.tom

drop table if exists t;
create table t(a binary(10));
insert into t values (0xe240), (0x01e240);
select convert(a using gbk) from t;

2. What did you expect to see? (Required)

mysql> select convert(a using gbk) from t;
+----------------------+
| convert(a using gbk) |
+----------------------+
| 釦                   |
| 釦                  |
+----------------------+
2 rows in set (0.00 sec)

3. What did you see instead (Required)

mysql> select convert(a using gbk) from t;
ERROR 1105 (HY000): encoding: rune not supported by encoding.

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                                                                           |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v5.4.0-alpha-97-g5bece67a9
Edition: Community
Git Commit Hash: 5bece67a9bae979020186b9819b1d3e90cff6678
Git Branch: master
UTC Build Time: 2021-11-12 11:19:21
GoVersion: go1.16.6
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false |
+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

[Defined2014]

/assign

[github-actions]

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