Effects of readonly on associative arrays

["Bart Schaefer" <schaefer@brasslantern.com>]

This is probably my fault somehow, but:

% typeset -a arr
% typeset -r arr
% arr=(a 1)
zsh: read-only variable: arr
% arr[1]=a
zsh: read-only variable: arr
% typeset -A hash
% typeset -r hash
% hash=(a 1)
zsh: read-only variable: hash
% hash[a]=1
% typeset hash
hash=(a 1 )

I have a potential use for this quirk, but it seems like something not
really to be relied upon.

This is probably related to:

% typeset -r hash[a]
typeset: hash[a]: can't create readonly array elements

Furthermore, continuing the above example:

% typeset -a hash
% typeset hash
hash=()
% hash=(a 1)
zsh: readonly variable: hash

As it happens, what I really have use for is a variable whose values
can be changed but whose type cannot.  Here we have a situation where
I can effectively erase a read-only variable by changing its type --
which "works" for any non-special readonly variable.

Contrast this with what happens when the readonly variable is a
special parameter:

% userdirs[xxxx]=yyyy
zsh: read-only variable: xxxx
% typeset -a userdirs
zsh: userdirs: can't change type of a special parameter

Aside -- this is a bit strange:

% noglob typeset userdirs[xxxx]
zsh: read-only variable: xxxx