[cfe-dev] C++1z invocation_traits

[Richard Smith]

On Mon, Feb 2, 2015 at 5:27 PM, Richard Smith <richard at metafoo.co.uk> wrote:

> On Tue, Jan 27, 2015 at 11:34 AM, Marshall Clow <mclow.lists at gmail.com>
> wrote:
>
>>
>> On Jan 27, 2015, at 12:03 AM, Ben Pope <benpope81 at gmail.com> wrote:
>>
>> On Tuesday, January 27, 2015 03:59 PM, Ben Pope wrote:
>>
>> On Tuesday, January 27, 2015 02:28 PM, Michael Haidl wrote:
>>
>> Hi all,
>>
>> I am curious about the proposed invocation traits
>> (http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n3866.html) and
>> life would be a lot easier if they would make it into the next C++
>> standard (at least for me). However 201z is far away and I was wondering
>> if someone is already working on this in clang. If not can someone
>> direct me to the right spot in clang where such a feature would be in
>> the right place?
>>
>>
>> I'm not sure what happened, they appear to have made it to N3908, then
>> to N4023, then to N4081 but they don't appear in N4270.
>>
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/
>>
>>
>> They're hiding here:
>> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4335.html
>>
>>
>> In other words, they’ll appear in libc++.
>> [ We’re trying to get a full LFTS implementation in there, but it’s not
>> all there yet ]
>>
>
> We should figure out what intrinsics you guys want in order to support
> this. I believe it's straightforward to implement invocation_type in terms
> of raw_invocation_type in the library, so I think providing simply a
> __raw_invocation_type(Fn, Arg1, Arg2, ...) would work?
>

(And it's up to you whether you'd prefer these arguments to be expressions
or types...)


> Looking at N4335 now, I'm a little concerned that we may be standardizing
> a bad interface; we don't support using raw_invocation_type<F(Args...)> if
> F is a function type, because that would create a function type whose
> return type is a function type, which is ill-formed.
>
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