bug#18059: 24.3.92; defvar and special variables

[Noam Postavsky <npostavs@gmail.com>]

On Wed, Feb 21, 2018 at 12:15 PM, Drew Adams <drew.adams@oracle.com> wrote:
>> Also, to clarify, I meant specifically non-toplevel (defvar foo), not
>> (defvar foo <value>).
>
> Too bad I didn't get your reply until after I spent time
> digging out the latter, not the former.

Yeah, I broke my rule about not sending a reply immediately. If I had
waited with the draft a bit more, I probably would have included the
clarification in the first message.

> Not to mention lots of vacuous defvars to quiet the byte-compiler:
>
> (unless (> emacs-major-version 22)
>   (defvar display-buffer-reuse-frames))

So here, what is the use of putting it below the toplevel? Why don't
you just write

(defvar display-buffer-reuse-frames) ; For Emacs 22 and earlier.

> I have FAR MORE examples of the former (vacuous defvars)
> if you really need them.

I'd like to see more examples only if they would come with different
answers to my question above (why not write it at toplevel).
Otherwise, no need to repeat yourself.

Do you have any examples of the form (let (...) (defvar foo) ...)?
That's really where the troublesome behaviour that I'm hesitating to
document comes in.