Cast from utf8mb4 to latin1 is not compatible with MySQL

[YangKeao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

Run SQL SELECT CAST('中文' AS CHAR CHARACTER SET latin1);

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

mysql> SELECT CAST('中文' AS CHAR CHARACTER SET latin1);
+---------------------------------------------+
| CAST('中文' AS CHAR CHARACTER SET latin1)   |
+---------------------------------------------+
| ??                                          |
+---------------------------------------------+
1 row in set (0.01 sec)

3. What did you see instead (Required)

mysql> SELECT CAST('中文' AS CHAR CHARACTER SET latin1);
+---------------------------------------------+
| CAST('中文' AS CHAR CHARACTER SET latin1)   |
+---------------------------------------------+
| 中文                                        |
+---------------------------------------------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

[zanmato1984]

This seems to be charset/collation related. Handing over to sig/infra.