Not sure if this is a bug, but when selecting from a table using a unique index (and implicit casting of type), multiple rows are returned, one of which is obviously wrong.

DROP TABLE IF EXISTS index_test;

CREATE TABLE index_test (
    string VARCHAR(40),
    number BIGINT,
    
    UNIQUE INDEX uq_string(string),
    UNIQUE INDEX uq_number(number)
) ENGINE = INNODB;

INSERT INTO index_test
(string, number)
VALUES
("42356411000001102", 42356411000001102),
("42356411000001104", 42356411000001104);

SELECT * FROM index_test WHERE number = 42356411000001102;      -- 1 Row        NATIVE BIGINT
SELECT * FROM index_test WHERE string = "42356411000001102";    -- 1 Row        NATIVE VARCHAR
SELECT * FROM index_test WHERE number = "42356411000001102";    -- 1 Row        CASTING
SELECT * FROM index_test WHERE string = 42356411000001102;      -- 2 ROWS!!!    CASTING