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Re: [SG10] [isocpp-core] No __cpp_concepts in the C++20 draft

From: Casey Carter <cartec69_at_[hidden]>
Date: Mon, 16 Sep 2019 09:34:17 -0700
We haven't had a __cpp_concepts since the TS specified its value as 201507
- which GCC defines. I've been making up values since then for various
compilers which cmcstl2 supports to various degrees:
* clang-concepts defines __cpp_concepts to 201707L - the date of the
Toronto merge - to indicate support for concepts as merged.
* MSVC uses 201811L - the date of the P1084 merge - to indicate that it
supports the above plus P1084's changes to return-type-requirements.
(Unfortunately MSVC does not yet support the changes in P1141 which were
merged at the same meeting.)

I'd appreciate a bump for the changes in Cologne. P1452 seems significant
enough to me, but regardless it would be nice to have a way to discriminate
between what MSVC will support in 16.3 and C++20 concepts' final form.

On Mon, Sep 16, 2019 at 8:26 AM John Spicer <jhs_at_[hidden]> wrote:

> Yes, I think we should have one.
>
> John.
>
> On Sep 14, 2019, at 4:07 PM, Barry Revzin <barry.revzin_at_[hidden]> wrote:
>
> On Sat, Sep 14, 2019, 2:38 PM Jason Merrill via Core <
> core_at_[hidden]> wrote:
>
>> This doesn't seem to have been addressed at Cologne. I don't think
>> any of the changes at Cologne (conditionally trivial, unconstrained
>> TTP, dropping return-type requirements) require a version bump, does
>> anyone else?
>>
>> So I'd stick with the 201811 value.
>>
>> Jason
>>
>
> Wait, do we even have a __cpp_concepts? We have a __cpp_lib_concepts (...
> that def needs to be bumped to 201907), but not one for the language. We
> should add one...
>
> Barry
>
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Received on 2019-09-16 18:34:29