COMPREPLY as a nameref to a readonly associative array

[Grisha Levit]

It's possible to change any readonly associative array to the indexed
array (''):

$ declare -rA var=([foo]=bar)
$ f() { declare -ng COMPREPLY=var; }
$ compgen -F f .
bash: compgen: warning: -F option may not work as you expect

$ declare -p var
declare -ar var=([0]="")