Subject: bug#64232: 28.2; Incorrect(?) byte compilation warning about ‘ansi-color-apply-on-region’

From: Stefan Monnier <[email-masked]>
Date: Thu, 29 Jun 2023 00:51:08 -0400

> The warning is the same as when one did just
>
> #+begin_src emacs-lisp
> (eval-when-compile
>   (require 'ansi-color))
> #+end_src
>
> When removing that `eval-when-compile' the warning message goes away.
> So the compiler warns stricter when something is required inside
> `eval-when-compile', even if there would be no warning at all without
> it.

Indeed, it's a vaguely known problem which we haven't tried to
fix seriously.

The usual workaround is to shuffle things around (e.g. move the

    (eval-when-compile
      (check-declare-file byte-compile-current-file))

earlier or later in the file) ... until the warnings disappear :-(

Someone™ should sit down and figure out how to make `bytecomp.el` keep
track of those things more reliably/predictably.
In the mean time, maybe we can simply tweak `byte-compile-eval` so it
never adds to `byte-compile-noruntime-functions` functions which have
already been seen/declared during the current compilation?

        Stefan

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 99202185d8d..cfec4b3be06 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -1128,7 +1128,8 @@ byte-compile-eval
 		     ;; we arguably should add it to b-c-noruntime-functions,
                      ;; but it's not clear it's worth the trouble
 		     ;; trying to recognize that case.
-		     (unless (get f 'function-history)
+		     (unless (or (get f 'function-history)
+                                 (assq f byte-compile-function-environment))
                        (push f byte-compile-noruntime-functions)))))))))))))
 
 (defun byte-compile-eval-before-compile (form)