Re: [boost] [result_of] now uses decltype on release branch

Subject: Re: [boost] [result_of] now uses decltype on release branch
From: Michel Morin (mimomorin_at_[hidden])
Date: 2012-09-04 12:53:02

Joel de Guzman wrote:
>> I didn't have a closer look at #6915, so I cannot
>> answer about the ticket (sorry!).
>> But the following test case still fails:
>> (Test case attached.)
>
>
> Yes, and I know why. Answer my concerns first (prior post) and I'll
> continue on the whys.
>
> For now, I need a rest :-)

OK.

Joel de Guzman wrote:
> However! This makes the current result_of code not an exact replacement
> to decltype which allows this variation of above:

Right. boost/std::result_of is not an exact replacement to decltype,
since decltype allows SFINAE but boost/std::result_of doesn't.

[...]
> If Fusion's invoke used decltype instead of
> result_of, it would have worked.

I tried to compile my test case for fusion::invoke with SFINAE-enabled
result_of, but it failed to compile. After adding a "fallback type" to
SFINAE-enabled result_of, then the test case runs fine.

Regards,
Michel