Bug#21547779 Assertion failed: select_lex->leaf_table_count == 0

The problem here is that we try to evaluate a subquery from the
resolver. Item_is_not_null_test::update_used_tables() attempts
to call is_null() on its argument because with_subselect is
erroneously false. This field is wrongly updated because
Item_func_make_set::update_used_tables() has a bad propagation of
with_subselect: It first calls Item_func::update_used_tables() to update
data for each arguments, then it calls item->update_used_tables().
But instead of accumulating data for with_subselect and
with_stored_program, it assigns directly to those fields.

The fix is to convert the assignments into OR assignments.

Author: roylyseng

mysql-test/r/func_set.result

@@ -247,3 +247,9 @@ from( make_set( ( extract( minute_second from
 Warnings:
 Warning	1292	Truncated incorrect date value: '1.01'
 Warning	1411	Incorrect datetime value: '1.01' for function str_to_date
+# Bug#21547779 Assertion failed: select_lex->leaf_table_count == 0
+CREATE TABLE t(a INTEGER) engine=innodb;
+SELECT 1 IN (SELECT MAKE_SET(-1, 1, (SELECT 1 FROM t)) FROM t);
+1 IN (SELECT MAKE_SET(-1, 1, (SELECT 1 FROM t)) FROM t)
+0
+DROP TABLE t;

mysql-test/t/func_set.test

@@ -162,3 +162,9 @@ trim( both(-8388607)
           )
     )
 ;
+
+--echo # Bug#21547779 Assertion failed: select_lex->leaf_table_count == 0
+
+CREATE TABLE t(a INTEGER) engine=innodb;
+SELECT 1 IN (SELECT MAKE_SET(-1, 1, (SELECT 1 FROM t)) FROM t);
+DROP TABLE t;

sql/item_strfunc.cc

@@ -3352,8 +3352,8 @@ void Item_func_make_set::update_used_tables()
   item->update_used_tables();
   used_tables_cache|=item->used_tables();
   const_item_cache&=item->const_item();
-  with_subselect= item->has_subquery();
-  with_stored_program= item->has_stored_program();
+  with_subselect|= item->has_subquery();
+  with_stored_program|= item->has_stored_program();
 }