MDEV-14629: failing assertion when a user-defined variable is defined by the recursive CTE

During the user-defined variable defined by the recursive CTE handling procedure
check_dependencies_in_with_clauses that checks dependencies between the tables
that are defined in the CTE and find recursive definitions wasn't called.

mysql-test/r/cte_recursive.result

@@ -2897,3 +2897,50 @@ n
 1
 2
 3
+#
+# mdev-14629: a user-defined variable is defined by the recursive CTE
+#
+set @var=
+(
+with recursive cte_tab(a) as (
+select 1
+union
+select a+1 from cte_tab
+where a<3)
+select count(*) from cte_tab
+);
+select @var;
+@var
+3
+create table t1(a int, b int);
+insert into t1 values (3,8),(1,5),(5,7),(7,4),(4,3);
+set @var=
+(
+with recursive summ(a,s) as (
+select 1, 0 union
+select t1.b, t1.b+summ.s from summ, t1
+where summ.a=t1.a)
+select s from summ
+order by a desc
+limit 1
+);
+select @var;
+@var
+27
+set @var=
+(
+with recursive
+cte_1 as (
+select 1
+union
+select * from cte_2),
+cte_2 as (
+select * from cte_1
+union
+select a from t1, cte_2
+where t1.a=cte_2.a)
+select * from cte_2
+limit 1
+);
+ERROR HY000: Unacceptable mutual recursion with anchored table 'cte_1'
+drop table t1;

mysql-test/t/cte_recursive.test

@@ -1947,3 +1947,54 @@ cte2 as (
 )
 SELECT *
 FROM cte1;
+
+--echo #
+--echo # mdev-14629: a user-defined variable is defined by the recursive CTE
+--echo #
+
+set @var=
+(
+  with recursive cte_tab(a) as (
+    select 1
+    union
+    select a+1 from cte_tab
+    where a<3)
+  select count(*) from cte_tab
+);
+
+select @var;
+
+create table t1(a int, b int);
+insert into t1 values (3,8),(1,5),(5,7),(7,4),(4,3);
+
+set @var=
+(
+  with recursive summ(a,s) as (
+    select 1, 0 union
+    select t1.b, t1.b+summ.s from summ, t1
+    where summ.a=t1.a)
+  select s from summ
+    order by a desc
+    limit 1
+);
+
+select @var;
+
+--ERROR ER_UNACCEPTABLE_MUTUAL_RECURSION
+set @var=
+(
+  with recursive
+  cte_1 as (
+    select 1
+    union
+    select * from cte_2),
+  cte_2 as (
+    select * from cte_1
+    union
+    select a from t1, cte_2
+    where t1.a=cte_2.a)
+  select * from cte_2
+  limit 1
+);
+
+drop table t1;

sql/sql_parse.cc

@@ -4818,6 +4818,9 @@ mysql_execute_command(THD *thd)
   {
     List<set_var_base> *lex_var_list= &lex->var_list;
 
+    if (check_dependencies_in_with_clauses(thd->lex->with_clauses_list))
+      goto error;
+
     if ((check_table_access(thd, SELECT_ACL, all_tables, FALSE, UINT_MAX, FALSE)
          || open_and_lock_tables(thd, all_tables, TRUE, 0)))
       goto error;