On 3/9/2016 10:55 PM, Nelson, Clark wrote:
>> I'd like to see a feature-test for LWG2296, "std::addressof should
>> be
>> constexpr"
>> (http://wiki.edg.com/pub/Wg21jacksonville/StrawPolls/P0304R0.html).
>
> Would it not be possible to test for that using SFINAE, or some other
> template trick?

Possibly, I can imagine a thing or two that might actually work with
non-type template parameters. If it comes to that, however, I'd rather
leave it as is or leave it broken for C++11/14 than to add more SFINAE
magic to that already partially broken SFINAE magic.

>> For P0036, "Unary Folds and Empty Parameter Packs", maybe bump
>> `__cpp_fold_expressions`?
>
> That's a thought.
>
> But if there is really code out there that wants to use the deleted
> identities when they are available, then didn't the committee make a
> mistake in getting rid of them? (Especially without deprecating them
> first.)

I'm not sure what you are saying here. Are you suggesting to keep the
old value of `__cpp_fold_expressions` for the new specification of it?

I don't imagine anyone wants to use the deleted identities when
available, but rather provide those explicitly so that the code works
with both the original and the new wording. Something similar to what
happened with `__cpp_constexpr` and implicit const, except this breaking
change hasn't even been in a published standard yet.

Regards,

-- 
Agustín K-ballo Bergé
http://talesofcpp.fusionfenix.com