>>>>> On Tue, 2 Aug 2022 10:09:43 +0000, Stefan Kangas <stefan@marxist.se> said:

    Stefan> Robert Pluim <rpluim@gmail.com> writes:
    Stefan> (defvar-keymap foo
    Stefan> "a" #'next-line
    Stefan> "a" #'previous-line)
    >> 
    >> Is that a common occurence?

    Stefan> I don't know.  I've only seen such a mistake once, but flagging it might
    Stefan> help us find more.

There are in fact 4 instances in Emacsʼ sources.

    Stefan> Your patch looks fine to me, but I agree with Lars that it should be an
    Stefan> error instead of a warning.  (And putting it in `define-keymap' is
    Stefan> indeed better.)

I put it in both, and it turns out we have errors in both, which I
propose to fix like this (this preserves current behaviour, due to the
'last definition wins' nature of define-keymap). I decided that for
coherence, the gnus-summary-up-thread binding should go as well (itʼs
available on "T-u" anyway).