Alter table with RenameIndex and ModifyColumn are not changed related columns

[Defined2014]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

create table a (a int, b double, index i(a, b));
alter table a rename index i to i1, change column b c int;
show create table a;

2. What did you expect to see? (Required)

mysql> show create table a;
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
| a     | CREATE TABLE `a` (
  `a` int(11) DEFAULT NULL,
  `c` int(11) DEFAULT NULL,
  KEY `i1` (`a`,`c`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

3. What did you see instead (Required)

mysql> show create table a;
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
| a     | CREATE TABLE `a` (
  `a` int(11) DEFAULT NULL,
  `c` int(11) DEFAULT NULL,
  KEY `i1` (`a`,`b`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+-------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

4. What is your TiDB version? (Required)

found by schrddl test #63