Don't allow adding AS ROW START column to a not versioned table

mysql-test/suite/versioning/r/alter.result

@@ -71,6 +71,8 @@ Table	Create Table
 t	CREATE TABLE `t` (
   `a` int(11) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
+alter table t add column trx_start timestamp(6) as row start;
+ERROR HY000: Table `t` is not system-versioned
 alter table t add system versioning;
 show create table t;
 Table	Create Table

mysql-test/suite/versioning/t/alter.test

@@ -57,6 +57,9 @@ alter table t drop column trx_start, drop column trx_end;
 alter table t drop system versioning;
 show create table t;
 
+--error ER_VERS_NOT_VERSIONED
+alter table t add column trx_start timestamp(6) as row start;
+
 alter table t add system versioning;
 show create table t;
 

sql/sql_table.cc

@@ -3090,7 +3090,7 @@ void promote_first_timestamp_column(List<Create_field> *column_definitions)
           column_definition->default_value == NULL &&   // no constant default,
           column_definition->unireg_check == Field::NONE && // no function default
           column_definition->vcol_info == NULL &&
-          !(column_definition->flags & (VERS_SYS_START_FLAG | VERS_SYS_END_FLAG))) // column isn't generated
+          !(column_definition->flags & VERS_SYSTEM_FIELD)) // column isn't generated
       {
         DBUG_PRINT("info", ("First TIMESTAMP column '%s' was promoted to "
                             "DEFAULT CURRENT_TIMESTAMP ON UPDATE "
@@ -8079,6 +8079,12 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
         alter_ctx->datetime_field= def;
         alter_ctx->error_if_not_empty= TRUE;
     }
+    if (def->flags & VERS_SYSTEM_FIELD &&
+        !(alter_info->flags & Alter_info::ALTER_ADD_SYSTEM_VERSIONING))
+    {
+      my_error(ER_VERS_NOT_VERSIONED, MYF(0), table->s->table_name.str);
+      goto err;
+    }
     if (!def->after.str)
       new_create_list.push_back(def, thd->mem_root);
     else