MDEV-25942: Assertion failure in trx_t::drop_table()

trx_t::drop_table(): Relax also another assertion that would fail
due to an AUTO_INCREMENT lock that is being held by the current
test case. This should have been part of
commit 63e9a054.

mysql-test/suite/innodb/r/lock_insert_into_empty.result

@@ -37,3 +37,18 @@ REPLACE INTO t1 VALUES (1,12);
 ERROR 23000: Cannot add or update a child row: a foreign key constraint fails (`test`.`t1`, CONSTRAINT `t1_ibfk_1` FOREIGN KEY (`f`) REFERENCES `nonexistent` (`x`))
 COMMIT;
 DROP TABLE t1;
+#
+# MDEV-25942 Assertion failed in trx_t::drop_table()
+#
+CREATE TABLE t1 (k INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 SET k=1;
+START TRANSACTION;
+INSERT INTO t1 SET k=2;
+connect  con1,localhost,root,,test;
+SET innodb_lock_wait_timeout= 1;
+CREATE TABLE t2 (pk INT AUTO_INCREMENT PRIMARY KEY) ENGINE=InnoDB
+AS SELECT k FROM t1;
+ERROR HY000: Lock wait timeout exceeded; try restarting transaction
+disconnect con1;
+connection default;
+DROP TABLE t1;

mysql-test/suite/innodb/t/lock_insert_into_empty.test

@@ -39,3 +39,22 @@ REPLACE INTO t1 VALUES (1,12);
 COMMIT;
 
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-25942 Assertion failed in trx_t::drop_table()
+--echo #
+
+CREATE TABLE t1 (k INT PRIMARY KEY) ENGINE=InnoDB;
+INSERT INTO t1 SET k=1;
+START TRANSACTION;
+INSERT INTO t1 SET k=2;
+
+--connect (con1,localhost,root,,test)
+SET innodb_lock_wait_timeout= 1;
+--error ER_LOCK_WAIT_TIMEOUT
+CREATE TABLE t2 (pk INT AUTO_INCREMENT PRIMARY KEY) ENGINE=InnoDB
+AS SELECT k FROM t1;
+--disconnect con1
+--connection default
+
+DROP TABLE t1;

storage/innobase/dict/drop.cc

@@ -159,10 +159,16 @@ dberr_t trx_t::drop_table(const dict_table_t &table)
        lock= UT_LIST_GET_NEXT(un_member.tab_lock.locks, lock))
   {
     ut_ad(lock->trx == this);
-    if (lock->type_mode == (LOCK_X | LOCK_TABLE))
+    switch (lock->type_mode) {
+    case LOCK_TABLE | LOCK_X:
       found_x= true;
-    else
-      ut_ad(lock->type_mode == (LOCK_IX | LOCK_TABLE));
+      break;
+    case LOCK_TABLE | LOCK_IX:
+    case LOCK_TABLE | LOCK_AUTO_INC:
+      break;
+    default:
+      ut_ad("unexpected lock type" == 0);
+    }
   }
   ut_ad(found_x);
 #endif