A BOOLEAN != NOT NOT INT predicate evaluates false in projection but true in filtering

For the only row `(t2.c0, t2.c1) = (TRUE, 1500534146)`, `NOT (NOT t2.c1)` is `1`, so `t2.c0 != (NOT (NOT t2.c1))` is `1 != 1`, i.e. false. MariaDB's own projection evaluation reports that value as false, so the `WHERE` clause that builds `join_temp_2` should reject the row. Instead, MariaDB keeps the row and the subsequent join returns `1500534146 | 1500534146`.

How to repeat:

CREATE TABLE t1(c0 INT);
CREATE TABLE t2(c0 BOOLEAN, c1 INT);

INSERT INTO t1 VALUES (0);
INSERT INTO t2 VALUES (TRUE, 1500534146);

CREATE TEMPORARY TABLE join_temp_2 (c0 TINYINT(1) NOT NULL, c1 INT NOT NULL);
INSERT INTO join_temp_2 SELECT * FROM t2 WHERE (t2.c0 != (NOT (NOT t2.c1)));

SELECT t2.c1, t2.c1
FROM t1 STRAIGHT_JOIN join_temp_2 AS t2
ON (t1.c0 < t2.c1); – Expected correct result: <empty> – actual Wrong result: 1500534146 | 1500534146