Array not defined when being set inline

[shawn wilson]

I guess that's the right way to describe what I'm seeing:

[swilson@localhost ~]$ unset f; f=(aaa bbb ccc) declare -p f
declare -x f="(aaa bbb ccc)"
[swilson@localhost ~]$ unset f; f=("aaa" "bbb" "ccc") declare -p f
declare -x f="(aaa bbb ccc)"
[swilson@localhost ~]$ unset f; f=(aaa bbb ccc)
[swilson@localhost ~]$ declare -p f
declare -a f='([0]="aaa" [1]="bbb" [2]="ccc")'

Is this known? What exactly is going on / what does this mean?