a few question about named reference

[Jun T <takimoto-j@xxxxxxxxxxxxxxxxx>]

[1] what does 'typeset -n ref' do when a variable 'ref' already exists?

(1a) removing a named reference

In the section NAMED REFERENCE in zshparam(1), 

       ... so  to  remove  a
       named reference, use either `unset -n pname' or one of:
              typeset -n pname
              typeset +n pname
       followed by
              unset pname

But:
% i=10
% typeset -n pname=i
% typeset -p pname
typeset -n pname=i
# now try to remove pname
% typeset -n pname     # this does nothing
% typeset -p pname
typeset -n pname=i     # still points to i
% unset pname
% typeset -p i pname
typeset: no such variable: i
typeset -n pname=i

The following works:
% typeset -n pname=    # reset to empty
% unset pname
% typeset -p pname
typeset: no such variable: pname

Just fix the document?

(1b) converting a scalar into named reference

In the first post by Bart about the named reference (worker/51360⁩):

> One difference from ksh93 is that you can't convert scalars into
> namerefs

But it seems we can convert a scalar into nameref:
% i=10
% ref=i
% typeset -n ref
% echo $ref
10

I have no idea whether the conversion needs be prohibited or not.


[2] readonly named reference

% typeset -nr ref=i
% typeset -n +r ref
typeset: no other attributes allowed with -n
% typeset +n ref
typeset: ref: read-only reference
% unset -n ref
zsh: read-only variable: ref

So we can't remove the readonly attribute (and will not be able
to remove/unset it). Is this intentional?


[3] can named reference be in 'unset' state?

If typeset_to_unset is on, creating namerefs with and without =''
have some difference:

% setopt typesettounset
% typeset -n r1 r2=
% typeset -p r1 r2
typeset -n r1
typeset -n r2=''
% echo ${(\!)r1-unset}
unset

So it seems r1 is 'unset'. But:

% echo ${+r1}        # or just "echo $r1"
1
% typeset -p r1
typeset -n r1=''     # now it is set to ''

It seems resolve_nameref() in params.c resets the PM_UNSET bit.
I feel it would be simpler to ignore typesettounset when creating
a nameref.