bug#24863: Functions declared as side-effect-free do not generate warnings in the same file

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severity 24863 minor
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Wilfred Hughes <me@wilfred.me.uk> writes:

>
> However, ideally this wouldn't be required. I think it's just a matter
> of changing defun-declarations-alist to:
>
>    (list 'side-effect-free
>          #'(lambda (f _args val)
>              `(eval-and-compile (function-put ',f 'side-effect-free ',val)))
>          "If non-nil, calls can be ignored if their value is unused.
> If `error-free', drop calls even if `byte-compile-delete-errors' is nil.")

Note the comment above:

   ;; We can only use backquotes inside the lambdas and not for those
   ;; properties that are used by functions loaded before backquote.el.

Since the side-effect-free lambda wasn't using backquotes, I presume it
has to stay that way.

On StackExchange you commented

    changing defun-declarations-alist in my current Emacs instance
    doesn't fix the issue

But doing

    (setf (nth 1 (assq 'side-effect-free defun-declarations-alist))
          (lambda (f _args val)
            `(eval-and-compile (function-put ',f 'side-effect-free ',val))))

in a running Emacs works for me.  By "changing" did you mean just
changing the source?  In that case, you would have to redump Emacs
before the change would take effect.