bug#62417: 30.0.50; Regression: 59ecf25fc860 is the first bad commit

[João Távora]

This was originally reported in
https://github.com/joaotavora/sly/issues/534.  I had forgotten about it
high time I reported it, since it seems to be breaking the SLY Common
Lisp package in more places than I expected.

Before this commit:

   5ecf25fc86081c9df05b84194c36414c225c265 is the first bad commit
   commit 59ecf25fc86081c9df05b84194c36414c225c265
   Author: Philip Kaludercic <philipk@posteo.net>
   Date:   Thu Mar 10 10:59:52 2022 +0100
    
       * window.el (display-buffer-assq-regexp): Use buffer-match
    
    lisp/window.el | 15 ++++-----------
    1 file changed, 4 insertions(+), 11 deletions(-)

SLY, as can be downloaded from https://github.com/joaotavora/sly
operates normally in the following minimal invocation

   src/emacs -Q -nw -L ~/Source/Emacs/sly -l sly --eval '(setq 
tab-always-indent (quote complete))' -f sly
   ;; type (def, following by TAB

(This is the command I used for bisecting the error.)

After this commit, an error comes up about

   (wrong-type-argument stringp #<buffer *sly-completions*>)

I haven't yet investigated the reason.  There are other use cases inside
SLY that are also failing with similar errors, but they are not as easy
to trigger.

SLY in it its current state has worked for every version of Emacs 25
onwards, probably also 24. I just tested this case with Emacs 26 and it
works fine.

João