Subject: Re: [boost] [result_of] now uses decltype on release branch
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-09-04 22:41:42
On Tue, Sep 4, 2012 at 7:32 PM, Jeffrey Lee Hellrung, Jr. <
> On Tue, Sep 4, 2012 at 7:00 PM, Joel de Guzman <djowel_at_[hidden]> wrote:
>> On 9/5/2012 9:03 AM, Jeffrey Lee Hellrung, Jr. wrote:
>>> On Tue, Sep 4, 2012 at 5:01 PM, Joel de Guzman <djowel_at_[hidden]> wrote:
> The following code (attached) demonstrates the problem of
>>> Fusion::invoke with the current decltype based result_of.
>>>> out the first line for the code to use plain decltype vs. result_of.
>>>> Notice that because result_of does not allow SFINAE, it barfs when
>>>> the compiler tries the first overload of invoke (substitution failure).
>>>> The compiler could have chosen the second overload.
> I see no other way to get around this problem of result_of. I am
>>>> getting inclined to use decltype directly in fusion instead of
>>>> going through result_of. Problems like this kinda defeats the
>>>> purpose of decltype-ifying result_of, but heck.
>>> Is this a recently discovered problem with the use of result_of in
>> How come it didn't come up before?
>> Because BOOST_RESULT_OF_USE_DECLTYPE wasn't there before.
> May we inspect a typical use of result_of that was working before and
> isn't now?
Actually, upon thinking about the larger context, I see where this could
easily happen (sorry for being dense, Joel)...
- I'm surprised it didn't fail TR1-based result_of more often :/
- I don't know how to fix it for TR1-based result_of except using something
like Eric's can_be_called metafunction.
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