bug#21391: 24.5; `thing-at-point' should return a string

[Dmitry Gutov]

On 09.11.2016 17:45, Eli Zaretskii wrote:

> I don't think I understand what you are suggesting.  Can you show a
> proposed patch, so I could see the light?

See the attached patch.

Or to take a step further, we might want to deprecate the 
`thing-at-point' property, and recommend to only use the 
`bounds-of-thing-at-point' property. This way, we get the string-ness 
guarantee automatically, and the bounds-of-thing-at-point function will 
work for all things (it currently fails for `number').

> > > If
> > > there is such code, why would we want to break it?  To what end?  And
> > > if no code uses this loophole, why do we care that it exists?
> >
> > To make thing-at-point behavior more consistent.
>
> It is consistent now.

Put point on a number. Number is a sexp. Not all sexps are strings.

(thing-at-point 'number) => 123
(thing-at-point 'sexp) => "123"

That doesn't looks consistent to me. And there's no way to guess the 
return value type in advance without knowing which exact function is the 
thing's `thing-at-point' property.

> The only way to make it inconsistent is to have
> a 'thing-at-point' property that violates that, but we never do that
> in Emacs proper, so if someone else does that, it would be their bug.

number's `thing-at-point' property is not like the others.

thingatpt-number.diff
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