bug#73849: 31.0.50; Binding ESC does not throw an error, but binding any M- combination afterwards does

[Eli Zaretskii]

> Date: Thu, 17 Oct 2024 10:18:18 +0000
> From:  Alexander Prähauser via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> If I eval the following
> 
> (progn (defvar-keymap test-map)
>        (define-key test-map (kbd "ESC") #'test)
>        (define-key test-map (kbd "M-i") #'test))
> 
> I get an error
> 
> (error "Key sequence M-i starts with non-prefix key ESC")
> 
> And I get the same error if I try to bind any other key combination
> containing a Meta modifier, including ones which also contain other modifiers.
> Crucially, I do not get an error while binding ESC itself, which I guess
> is what should happen. The error only appears while trying to bind Meta
> keys in the map containing ESC. It also doesn't seem to happen if I bind
> M-i using a vector instead of kbd.
> 
> This was tried while starting Emacs without an
> init.

I don't think this is a bug, this is how Emacs handling of Meta always
worked.

Stefan, any comments or suggestions?