RE: On obsoleting defcustoms

[Drew Adams]

> > Would it make sense to change ignored options such as this into
> > defvars instead?
> 
> What problem would that solve?  Not all obsolete defcustoms have no
> effect, do they?
> 
> > 2. Finding out that an option is obsolete
> >
> > The obsolete options use a different face.  However, it's not obvious
> > that this is the meaning of that face.
> 
> IMO, we shouldn't show obsolete options at all in a Custom buffer, for
> the same reason why we remove them from the manuals.

Just because something is declared obsolete, that doesn't
(normally) mean that it's not supported or that it doesn't
still work.

Dunno whether that's true (always? sometimes? never?) for Emacs.

But if it is, then why would it make any more sense to remove
customization of an obsolete option that it would to remove
advising an obsolete function or setting an obsolete defvar?

If people are concerned about someone continuing to use
something that's obsolete, why not just have Customize give
a warning/message saying that the option is obsolete, and 
that the effect of changing its value is undefined?

That's assuming that Emacs takes the (unusual, IME) point of
view that, once declared obsolete, something should no longer
be usable.  And in that case, the right way to handle it would
be to raise an error when it's used.  We don't, thankfully, do
that.