Bug #120003 column name unexpectedly change because of '1' as a column

Description:
the first column's value should be c2, but it's c2_1 because of the second column and the '1' as a column

mysql> SELECT DISTINCT subq.c2 AS c2, subq.c2 AS c2_1 FROM (SELECT 1 AS c2 FROM t2 AS s467) AS subq;
+------+------+
| c2_1 | c2_1 |
+------+------+
|    1 |    1 |
+------+------+
1 row in set (0.00 sec)

How to repeat:
DROP DATABASE IF EXISTS test;
CREATE DATABASE IF NOT EXISTS test;
SET GLOBAL sort_buffer_size = 64 * 1024 * 1024;
SET GLOBAL read_rnd_buffer_size = 8 * 1024 * 1024;
USE test;

CREATE TABLE t2 (
    c1 INT NOT NULL AUTO_INCREMENT,
    PRIMARY KEY (c1)
);

INSERT INTO t2 (c1) VALUES (9921);

SELECT DISTINCT subq.c2 AS c2, subq.c2 AS c2_1 FROM (SELECT 1 AS c2 FROM t2 AS s467) AS subq;

Thank you for the bug report.
Verified as described.