MDEV-5012 Server crashes in Item_ref::real_item on EXPLAIN with select...

MDEV-5012 Server crashes in Item_ref::real_item on EXPLAIN with select subqueries or views, constant table, derived_merge+derived_with_keys

revert incorrect change, merged from mysql-5.5

mysql-test/r/derived.result

@@ -476,4 +476,18 @@ n	d1	d2	result
 2085	2012-01-01 00:00:00	2013-01-01 00:00:00	0
 2084	2012-02-01 00:00:00	2013-01-01 00:00:00	0
 drop table t1;
+SET optimizer_switch = 'derived_merge=on,derived_with_keys=on,in_to_exists=on';
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (8);
+CREATE TABLE t2 (b INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(7);
+EXPLAIN SELECT * FROM (SELECT * FROM t1) AS table1,
+(SELECT DISTINCT * FROM t2) AS table2 WHERE b = a AND a <> ANY (SELECT 9);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	system	NULL	NULL	NULL	NULL	1	
+1	PRIMARY	<derived3>	ref	key0	key0	5	const	0	
+3	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	2	Using temporary
+Warnings:
+Note	1249	Select 4 was reduced during optimization
+DROP TABLE t1, t2;
 set optimizer_switch=@save_derived_optimizer_switch;

mysql-test/t/derived.test

@@ -389,4 +389,16 @@ select * from (
 ) as calculated_result;
 drop table t1;
 
+#
+# MDEV-5012 Server crashes in Item_ref::real_item on EXPLAIN with select subqueries or views, constant table, derived_merge+derived_with_keys
+#
+SET optimizer_switch = 'derived_merge=on,derived_with_keys=on,in_to_exists=on';
+CREATE TABLE t1 (a INT) ENGINE=MyISAM;
+INSERT INTO t1 VALUES (8);
+CREATE TABLE t2 (b INT) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (1),(7);
+EXPLAIN SELECT * FROM (SELECT * FROM t1) AS table1,
+  (SELECT DISTINCT * FROM t2) AS table2 WHERE b = a AND a <> ANY (SELECT 9);
+DROP TABLE t1, t2;
+
 set optimizer_switch=@save_derived_optimizer_switch;

sql/item_subselect.cc

@@ -1746,7 +1746,7 @@ Item_in_subselect::single_value_transformer(JOIN *join)
       of the statement. Thus one of 'substitution' arguments
       can be broken in case of PS.
     */ 
-    substitution= func->create(left_expr->real_item(), where_item);
+    substitution= func->create(left_expr, where_item);
     have_to_be_excluded= 1;
     if (thd->lex->describe)
     {