bug#27016: possible bug in `defsetf'

[npostavs]

reopen 27016
tag 27016 - wontfix
quit

Stefan Monnier <monnier@IRO.UMontreal.CA> writes:

>> (unless t
>>   (defalias 'foobar 'cons)
>>   (defsetf foobar setcar))           ; nil 
>> (foobar pair)                                ; same as above
>> (setf (foobar pair) 0)                       ; 0       !
>
> I can confirm that it's a bug.  It's perfectly correct for the defsetf
> to be macroexpanded, but not to be evaluated.
> Not sure how best to get that behavior.  The naive/straightforward way
> might be to introduce some sort of eval-and-compile-when-at-toplevel,
> but there's probably a better way.  The first thing to do is to look at
> how it was done in Emacs-23.

Is the difference in Emacs-23 not just eager macroexpansion?

Both the Emacs-23 and the current code seem to expand to (put 'foobar
...).