bug#64927: 30.0.50; kill-ring with no X

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

> This also affects Emacs 29, and is a regression from Emacs 28, which
> is related to the use of the new key-* functions.  Specifically, the
> error is signaled by the call to key-valid-p issued by
> possibly_translate_key_sequence, which is a subroutine of lookup-key.
> The argument KEY of possibly_translate_key_sequence in this case is a
> vector whose only element is a string with text properties:
>
>   [#("create a file" 0 13 (face font-lock-comment-face fontified t))]
>
> key-valid-p doesn't support such strings, it expects strings that
> describe key sequences.
>
> Significantly, possibly_translate_key_sequence calls key-parse after
> it calls key-valid-p, and key-parse copes with this string quite well.

No, `key-parse` doesn't handle this correctly either.

The ["create a file"] above is an "internal" key-sequence of length
1 that happens to use a string as the sole key.

`possibly_translate_key_sequence` instead is trying to handle the new
"external" key-sequence format [<KBDSTRING>] where <KBDSTRING> is using
the `kbd` syntax, i.e. the string is not itself a key but represents
a key-sequence.

IOW, this is a fundamental incompatibility introduced by the support for
this new [<KBDSTRING>] format in `define-key`: keys cannot be arbitrary
objects any more (among other things they can't be strings any more).


        Stefan