bug#49877: [Emacs 28.0.50 Trunk] *ERROR*: No applicable method: frame-creation-function

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

merge 49877 49866
thanks

> I'm still not able to reproduce the problem, but a different user
> reported exactly the same problem...  which then went away.  So
> something's definitely going on here.
>
> So I've added Stefan to the CCs -- could you take a look at this?  It
> looks like a possible problem with the recent eql changes, but is
> weirdly difficult to reproduce.  
>
> diff --git a/lisp/frame.el b/lisp/frame.el
> index 9b3d120598..8c05ad2fe5 100644
> --- a/lisp/frame.el
> +++ b/lisp/frame.el
> @@ -36,7 +36,11 @@ as its argument.")
> (cl-generic-define-context-rewriter window-system (value)
> ;; If `value' is a `consp', it's probably an old-style specializer,
> ;; so just use it, and anyway `eql' isn't very useful on cons cells.
> - `(window-system ,(if (consp value) value `(eql ,value))))
> + `(window-system ,(if (consp value) value
> + ;; WARNING: unsure whether this eql expression
> + ;; is actually an eql specializer.
> + ;; Bug #47327
> + `(eql ',value))))

I hope this is the same as bug#49866.


        Stefan