add a test case

MDEV-20330 Combination of "," (comma), cross join and left join fails to parse

mysql-test/r/join.result

@@ -3308,3 +3308,6 @@ SELECT STRAIGHT_JOIN * FROM t1, t2 AS t2_1, t2 AS t2_2
 WHERE t2_2.c = t2_1.c AND t2_2.b = t2_1.b AND ( a IS NULL OR t2_1.c = a );
 a	b	c	b	c
 DROP TABLE t1,t2;
+select a.a from (select 1 as a) a, (select 2 as b) b cross join (select 3 as c) c left join (select 4 as d) d on 1;
+a
+1

mysql-test/t/join.test

@@ -1718,3 +1718,8 @@ SELECT STRAIGHT_JOIN * FROM t1, t2 AS t2_1, t2 AS t2_2
   WHERE t2_2.c = t2_1.c AND t2_2.b = t2_1.b AND ( a IS NULL OR t2_1.c = a );                  
 
 DROP TABLE t1,t2;
+
+#
+# MDEV-20330 Combination of "," (comma), cross join and left join fails to parse
+#
+select a.a from (select 1 as a) a, (select 2 as b) b cross join (select 3 as c) c left join (select 4 as d) d on 1;