CREATE INDEX fails to heal a FOREIGN KEY constraint

--source include/have_innodb.inc

set foreign_key_checks=0;

create or replace table t2 (b int, foreign key (b) references t1(a)) engine=InnoDB;

create or replace table t1 (pk int primary key, a int) engine=InnoDB;

set foreign_key_checks=1;

check table t2 extended;

alter table t1 add key(a);

check table t2 extended;

create or replace table t2 (b int, foreign key (b) references t1(a)) engine=InnoDB;

check table t2 extended;

drop table t2, t1;

check table t2 extended;

Table	Op	Msg_type	Msg_text

test.t2	check	Warning	No suitable key found for foreign key t2_ibfk_1 in table test.t1

test.t2	check	error	Corrupt

alter table t1 add key(a);

check table t2 extended;

Table	Op	Msg_type	Msg_text

test.t2	check	Warning	No suitable key found for foreign key t2_ibfk_1 in table test.t1

test.t2	check	error	Corrupt

create or replace table t2 (b int, foreign key (b) references t1(a)) engine=InnoDB;

check table t2 extended;

Table	Op	Msg_type	Msg_text

test.t2	check	status	OK