Re: `M-.' can't skip to the corresponding DEFUN from within the Apropos buffer.

[Emanuel Berg]

Hongyi Zhao wrote:

>>> (add-hook 'apropos-mode-hook
>>>    (lambda ()
>>>       (add-hook 'xref-backend-functions
>>>          #'elisp--xref-backend 0 t)))
>>
>> Based on my tries, passing nil or 0 as the third argument
>> is equivalent. Thank you again.
>
> For this case, according to my understanding, the 3rd
> argument used here is just as a placeholder.

C-h f add-hook RET

  DEPTH defaults to 0.

That means, it is better to send nil than 0 if you want the
default value. If you pass 0 is sounds like that's the value
you have computed for your purposes. Well, if it IS, only then
you should pass it.

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