Re: `aset` on strings, changing the size in bytes

[Stefan Monnier <monnier@IRO.UMontreal.CA>]

>> According to the documentation, that is already an error...
>> (info "(elisp) Modifying Strings")
> Cool! That means we can do Stefan's request simply by reverting Kenichi
> Handa's patch that introduced the ability to change the byte length
> of a string (commit 3c9de1afcde82a99137721436c822059cce79b5b dated
> 2000-07-21 06:45:30 UTC), since that patch made the code explicitly disagree
> with the documentation.

It's very easy to accidentally use that feature, so just because it was
in some doc somewhere doesn't mean no code makes use of it, or that any
code that does deserves to get an error.

So we can't just revert that patch.  We should first announce the
reversal of stance (if not compared to the doc, at least compared to
the code), and then introduce some test&warning.

> Though this leaves open the question of why Handa made that change in
> the first place.

I remember being disappointed by the change, but I can't remember
exactly what was the original justification.  I think the stance was
simply that it was reasonably easy to implement (because of the
pre-existing string-compaction code) and it would satisfy
a user request.


        Stefan