Wrong unusable key column on char_col BETWEEN 'a' AND 3

SET @@note_verbosity='all';

CREATE OR REPLACE TABLE t1 (f char(8), KEY(f));

INSERT INTO t1 VALUES (''),('');

SELECT * FROM t1 WHERE f BETWEEN 'a' AND 3;

SHOW WARNINGS;

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

| Level   | Code | Message                                                                                                                    |

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

| Note    | 1105 | Cannot use key `f` part[0] for lookup: `test`.`t1`.`f` of collation `utf8mb4_uca1400_ai_ci` >= "'a'" of collation `binary` |

| Warning | 1292 | Truncated incorrect DECIMAL value: ''                                                                                      |

| Warning | 1292 | Truncated incorrect DECIMAL value: 'a'                                                                                     |

| Warning | 1292 | Truncated incorrect DECIMAL value: ''                                                                                      |

| Warning | 1292 | Truncated incorrect DECIMAL value: 'a'                                                                                     |

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

SELECT * FROM t1 WHERE f BETWEEN 3  AND 'a';

SHOW WARNINGS;

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

| Level   | Code | Message                                                                                    |

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

| Note    | 1105 | Cannot use key `f` part[0] for lookup: `test`.`t1`.`f` of type `char` >= "3" of type `int` |

| Warning | 1292 | Truncated incorrect DOUBLE value: ''                                                       |

| Warning | 1292 | Truncated incorrect DOUBLE value: 'a'                                                      |

| Warning | 1292 | Truncated incorrect DOUBLE value: ''                                                       |

| Warning | 1292 | Truncated incorrect DOUBLE value: 'a'                                                      |

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