bug#32351: assq_no_quit: circular loop (default, line-number, line-number-current-line)

[Keith David Bershatsky]

The preceding post to issue #32351 contains a proposed solution, which appears 
to resolve the issue.

Here is the Emacs -Q recipe (to create the infinite redisplay loop) for both 
Emacs master branch and also Emacs 26.  Tested on Emacs GUI versions built 
--with-ns.

(let ((buffer-one (get-buffer-create "*ONE*"))
      (buffer-two (get-buffer-create "*TWO*"))
      (alist (list (cons 'window-width (- (window-width) 5))))
      (window (split-window (selected-window) nil 'right)))
    (with-current-buffer buffer-one
      (set (make-local-variable 'truncate-partial-width-windows) nil)
      (dotimes (i 200)
        (insert-char 9786 10)
        (insert-char 10 1))
      (setq display-line-numbers t))
    (with-current-buffer buffer-two
      (dotimes (i 200)
        (insert-char 9786 80)
        (insert-char 10 1)))
    (set-window-buffer (selected-window) buffer-one)
    (window--display-buffer buffer-two window 'window alist nil))