How are the "Associative Arrays" and "Indexed Arrays" declared in bash?

Issue

• In this version of bash, the associative arrays are not working :

[root@rhel7u3-1 ~]# rpm -qa | grep bash 
bash-4.2.46-20.el7_2.x86_64 
bash-completion-2.1-6.el7.noarch 

[root@rhel7u3-1 ~]# declare -a B 
[root@rhel7u3-1 ~]# B[ddd]=aa 
[root@rhel7u3-1 ~]# B[AB]=cc
[root@rhel7u3-1 ~]# echo ${B["AB"]}
 cc
[root@rhel7u3-1 ~]# echo ${B["ddd"]}
 cc 

• This is not correct for Bash Associative Arrays on my system with Red Hat Enterprise Linux 7.3

[root@test ~]# rpm -q bash 
bash-4.2.46-21.el7_3.x86_64

[root@test ~]# declare -a test 
[root@test ~]# test[a]=what
[root@test ~]# echo ${test[a]} 
what 
[root@test ~]# test[b]=that
[root@test ~]# echo ${test[a]} 
that 
[root@test ~]# echo ${test[b]} 
that