TiDB returns error instead of warning for some truncated error

[YangKeao]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

SELECT FOUND_ROWS() - 3;

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

mysql> SELECT FOUND_ROWS() - 3;
+------------------+
| FOUND_ROWS() - 3 |
+------------------+
|               -2 |
+------------------+
1 row in set, 1 warning (0.02 sec)

3. What did you see instead (Required)

mysql> SELECT FOUND_ROWS() - 3;
ERROR 1690 (22003): BIGINT UNSIGNED value is out of range in '(found_rows() - 3)'

4. What is your TiDB version? (Required)