bug#59956: 29.0.60: Failure when completing arguments in Eshell after variable interpolation

[Gregory Heytings <gregory@heytings.org>]

>>>> Starting from "emacs -Q -f -eshell", type "echo $exec-path " (note 
>>>> the trailing space), and then hit TAB. The result is this error:
>>>>
>>>>    pcomplete-match: Wrong type argument: stringp, ("/usr/bin" ...)
>>>>
>>>> This is a regression from Emacs 28, and it looks like it's due to 
>>>> 'pcomplete-here-using-help' assuming that all the pcomplete args are 
>>>> strings. However, 'exec-path' is a list (and Eshell reports it this 
>>>> way to pcomplete), so the completion fails. I think all that's 
>>>> necessary is checking that the pcomplete args are strings in 
>>>> 'pcomplete-here-using-help', but I know next to nothing about 
>>>> pcomplete...
>>>
>>> Adding Stefan, who should know more about pcomplete.
>>>
>>> Stefan, any suggestions?
>>
>> I'm still not Stefan, but this bug is fixed by the attached patch.
>
> This is not a fix to the problem, in my opinion.  Just take any other 
> command with a pcomplete rule, say "cvs $exec-path SPC TAB" and you will 
> see the same problem.
>

Agreed, it's not a proper fix for that bug.