Fix for bug #16829 "Firing trigger with RETURN crashes the server"

We should disallow usage of RETURN statement in triggers and emit
error at parsing time (instead of crashing when trigger is fired).

mysql-test/r/trigger.result

@@ -785,3 +785,8 @@ create trigger test.t1_bi before insert on t1 for each row set @a:=0;
 ERROR 3D000: No database selected
 drop trigger t1_bi;
 ERROR 3D000: No database selected
+create table t1 (i int);
+create trigger t1_bi before insert on t1 for each row return 0;
+ERROR 42000: RETURN is only allowed in a FUNCTION
+insert into t1 values (1);
+drop table t1;

mysql-test/t/trigger.test

@@ -958,3 +958,12 @@ create trigger test.t1_bi before insert on t1 for each row set @a:=0;
 --error ER_NO_DB_ERROR
 drop trigger t1_bi;
 connection default;
+
+# Test for bug #16829 "Firing trigger with RETURN crashes the server"
+# RETURN is not supposed to be used anywhere except functions, so error
+# should be returned when one attempts to create trigger with RETURN.
+create table t1 (i int);
+--error ER_SP_BADRETURN
+create trigger t1_bi before insert on t1 for each row return 0;
+insert into t1 values (1);
+drop table t1;

sql/sql_yacc.yy

@@ -1981,7 +1981,7 @@ sp_proc_stmt:
 	    LEX *lex= Lex;
 	    sp_head *sp= lex->sphead;
 
-	    if (sp->m_type == TYPE_ENUM_PROCEDURE)
+	    if (sp->m_type != TYPE_ENUM_FUNCTION)
 	    {
 	      my_message(ER_SP_BADRETURN, ER(ER_SP_BADRETURN), MYF(0));
 	      YYABORT;