Bug #61146 "Incorrect index name" error when using InnoDB fast add/drop index

Description:
The following fails with InnoDB plugin in both 5.1 and 5.5, but passes with built-in InnoDB in 5.1:

mysql> create table t1(a int, b int, primary key (a), key b (b)) engine=innodb;
Query OK, 0 rows affected (0.02 sec)

mysql> alter table t1 drop key b, add key (b, a);
ERROR 1280 (42000): Incorrect index name 'b'

Specifying the index name explicitly does work:

mysql> alter table t1 drop key b, add key b (b, a);
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

How to repeat:
create table t1(a int, b int, primary key (a), key b (b)) engine=innodb;
alter table t1 drop key b, add key (b, a);

Thank you for the bug report. Verified just as described:

C:\Program Files\MySQL\MySQL Server 5.5\bin>mysql -uroot -proot -P3312 test
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 24
Server version: 5.5.11 MySQL Community Server (GPL)

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Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> create table t1(a int, b int, primary key (a), key b (b)) engine=innodb;
Query OK, 0 rows affected (0.11 sec)

mysql> alter table t1 drop key b, add key (b, a);
ERROR 1280 (42000): Incorrect index name 'b'

This bug s a duplicate of bug#54927 that is fixed in an upcoming release - the fix will not be back ported as a good workaround (split the drop and add to two separate commands exists.