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

[Philip Kaludercic]

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:

diff --git a/lisp/emacs-lisp/macroexp.el b/lisp/emacs-lisp/macroexp.el
index e4bc2df280..5df9d4b221 100644
--- a/lisp/emacs-lisp/macroexp.el
+++ b/lisp/emacs-lisp/macroexp.el
@@ -143,7 +143,8 @@ macroexp-file-name
   ;; so prefer using it over using `load-file-name'.
   (let ((file (car (last current-load-list))))
     (or (if (stringp file) file)
-        (bound-and-true-p byte-compile-current-file))))
+        (bound-and-true-p byte-compile-current-file)
+        (buffer-file-name))))
 
 (defvar macroexp--warned (make-hash-table :test #'equal :weakness 'key))
 

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


In GNU Emacs 29.0.50 (build 6, x86_64-pc-linux-gnu, GTK+ Version 3.24.30, cairo 
version 1.16.0)
 of 2022-04-19 built on viero
Repository revision: d168decab4a03cd48b8b96257c36ffa575c720e6
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Guix System

Configured using:
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PKG_CONFIG_PATH=/home/philip/.guix-profile/lib/pkgconfig:/home/philip/.guix-profile/share/pkgconfig'

Configured features:
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GTK3 ZLIB

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/home/philip/Source/sp-tutor/waffel hides 
/home/philip/.config/emacs/site-lisp/sp-tutor/waffel
/home/philip/.config/emacs/site-lisp/modus-themes/modus-vivendi-theme hides 
/home/philip/.config/emacs/elpa/modus-themes-2.3.0/modus-vivendi-theme
/home/philip/.config/emacs/site-lisp/modus-themes/modus-operandi-theme hides 
/home/philip/.config/emacs/elpa/modus-themes-2.3.0/modus-operandi-theme
/home/philip/.config/emacs/site-lisp/modus-themes/modus-themes hides 
/home/philip/.config/emacs/elpa/modus-themes-2.3.0/modus-themes
/home/philip/.config/emacs/elpa/transient-0.3.7/transient hides 
/home/philip/Source/emacs/lisp/transient
~/.config/emacs/site-lisp/autoload hides 
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Memory information:
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-- 
        Philip Kaludercic