On Sun, 29 Jan 2023 15:35:22 +0100 Stephen Berman <stephen.berman@gmx.net> wrote:

> On Sun, 29 Jan 2023 15:44:44 +0200 Eli Zaretskii <eliz@gnu.org> wrote:
>
>> To reproduce:
>>
>>   emacs -Q
>>   M-x keymap-local-set
>>   C-c .
>>   forward-line RET
>>
>> Observe the error message:
>>
>>   [3 46] is not a valid key definition; see ‘key-valid-p’
>>
>> (The error message comes from keymap--check.)
>>
>> To type the key sequence, I actually pressed Ctrl and typed 'c', then
>> released Ctrl and typed '.'.  Isn't that what one is supposed to use?
>>
>> So the above basically makes keymap-local-set useless, or am I missing
>> something?  The following does work:
>>
>>   M-: (keymap-local-set "C-c ." 'forward-line) RET
>>
>> However, I could find no way of typing the string "C-c ." at the
>> prompt of keymap-local-set.
>
> This patch seems to DTRT:
>
> diff --git a/lisp/keymap.el b/lisp/keymap.el
> index 791221f2459..9643dce5f9c 100644
> --- a/lisp/keymap.el
> +++ b/lisp/keymap.el
> @@ -95,7 +95,8 @@ keymap-local-set
>  cases is shared with all other buffers in the same major mode."
>    (declare (compiler-macro (lambda (form) (keymap--compile-check key) form)))
>    (interactive "KSet key locally: \nCSet key %s locally to command: ")
> -  (let ((map (current-local-map)))
> +  (let ((map (current-local-map))
> +	(key (key-description key)))
>      (unless map
>        (use-local-map (setq map (make-sparse-keymap))))
>      (keymap-set map key command)))

... but not in your non-interactive case; so maybe this instead: