Subject: bug#60048: 30.0.50; Freeze when next-line on details in Completions list

From: Gabriel <[email-masked]>
Date: Tue, 13 Dec 2022 17:43:15 -0300

Description:

Emacs freeze when the command `previous-line-completion' or
`next-line-completion' are executed in Completions list and the cursor
is positioned at some details (the prefix and suffix annotations).  The
steps below `describe-face', but I could reproduce with other details in
Completions list, for example, using `completions-detailed` set to t and
`describe-function'.

Steps:

1) emacs -Q (master "85108d541217f0333860c4f86c3b16b4349f85a4")

2) M-x describe-face

3) Switch to Completions list: M-v (`switch-to-completions')

4) Scroll up: C-v (`scroll-up-command')

5) Go to next completion line: <down> (`next-line-completion')

Result: Emacs freeze (user have to C-g to unfreeze).

The problem is caused by the cursor position, the freeze only happens
when cursor in on SAMPLE.  Can also be reproduced with M-b, which will
move the cursor from the completion line to SAMPLE.  The freeze does not
happen with <left> or <right> commands (`previous-completion' and
`next-completion').

---
Gabriel