bug#64536: 30.0.50; Make cl-print put buttons on ellipses

[Ihor Radchenko <yantar92@posteo.net>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> I am not sure if this can be done on byte compiler level.
>
> Not sure either.  A compiler-macro placed on `make-text-button` and
> `make-button` could look for a `:type` arg and check its obsolescence,
> but I don't know how effective it would be.

Maybe not that bad.
Of course, it will miss :type values not known at compile time, but it
is the same issue even with ordinary obsolete variables/functions that
are used not by their literal name.

>> For runtime, after skimming through button.el, it looks like
>> `button-category-symbol' might be used to throw a warning when obsolete
>> button type is being used.
>
> Runtime check are easier and more reliable, indeed, but also more
> annoying and directed at the wrong person :-(

Makes sense. Although, they can be useful for maintainers if such checks
can be enabled explicitly, by flipping a variable.
We used such approach for org-element--cache-self-verify.

-- 
Ihor Radchenko // yantar92,
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