Copying from DECIMAL to YEAR is not consistent about warnings

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a YEAR);

INSERT INTO t1 VALUES (-0.1);

SHOW WARNINGS;

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

| Level   | Code | Message                                    |

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

| Warning | 1264 | Out of range value for column 'a' at row 1 |

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

DROP TABLE IF EXISTS t1,t2;

CREATE TABLE t1 (a YEAR);

CREATE TABLE t2 (a DECIMAL(10,1));

INSERT INTO t2 VALUES (-0.1);

INSERT INTO t1 SELECT * FROM t2;

SHOW WARNINGS;

DROP TABLE IF EXISTS t1;

CREATE TABLE t1 (a DECIMAL(10,1));

INSERT INTO t1 VALUES (-0.1);

ALTER TABLE t1 MODIFY a YEAR;

SHOW WARNINGS;