Partition pruning with column list causes syntax error in 10.4

--source include/have_partition.inc

create table t (a int) partition by hash(a);

insert into t partition (p0) (a) values (1);

select * from t;

drop table t;

insert into t partition (p0) (a) values (1);

bug.t2                                   [ fail ]

        Test ended at 2019-03-20 19:44:18

CURRENT_TEST: bug.t2

mysqltest: At line 3: query 'insert into t partition (p0) (a) values (1)' failed: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'a) values (1)' at line 1

--source include/have_partition.inc

create table t (a int) partition by hash(a);

insert into t partition (p0) (a) select 1;

select * from t;

drop table t;

mysqltest: At line 3: query 'insert into t partition (p0) (a) select 1' failed: 1064: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near 'a) select 1' at line 1