bug#55038: 29.0.50; Does macroexp-file-name return nil unnecessarily?

[Lars Ingebrigtsen <larsi@gnus.org>]

Philip Kaludercic <philipk@posteo.net> writes:

> Consider a macro like
>
>         (defmacro foo ()
>           `(message "Defined in %s" ,(macroexp-file-name)))
>
> Why does this expand to
>
>         (message "Defined in %s" nil)
>
> when evaluated directly in a file (say using `eval-buffer' or
> `eval-last-sexp`).  Shouldn't it be fair to return the file name of the
> buffer, if nothing else can be used:

[...]

> Or is there something that would go wrong in that case?

Such a change sounds like a good one to me, but perhaps there's a good
reason it works the way it does today.  Perhaps Stefan has a comment;
added to the CCs.

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