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Date: Thu, 5 Aug 2021 15:40:48 +0100
From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [committed] libstdc++: Move attributes that follow
 requires-clauses [PR101782]
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On 05/08/21 15:19 +0100, Jonathan Wakely wrote:
>On 04/08/21 12:55 +0100, Jonathan Wakely wrote:
>>This adds [[nodiscard]] throughout <iterator>, as proposed by P2377R0
>>(with some minor corrections).
>>
>>The attribute is added for all modes from C++11 up, using
>>[[__nodiscard__]] or _GLIBCXX_NODISCARD where C++17 [[nodiscard]] can't
>>be used directly.
>
>This change causes errors when -fconcepts-ts is used. Fixed like so.
>
>Tested powerpc64le-linux, committed to trunk.
>

>commit 7b1de3eb9ed3f8dde54732d88520292c5ad1157d
>Author: Jonathan Wakely <jwakely@redhat.com>
>Date:   Thu Aug 5 13:34:00 2021
>
>    libstdc++: Move attributes that follow requires-clauses [PR101782]
>    
>    As explained in the PR, the grammar in the Concepts TS means that a [
>    token following a requires-clause is parsed as part of the
>    logical-or-expression rather than the start of an attribute. That makes
>    the following ill-formed when using -fconcepts-ts:
>    
>      template<typename T> requires foo<T> [[nodiscard]] int f(T);
>    
>    This change moves all attributes that follow a requires-clause to the
>    end of the function declarator.


Except that as Jakub pointed out, putting it there doesn't work.

It needs to be:

   template<typename T> requires foo<T> int f [[nodiscard]] (T);

At least the testsuite isn't failing now, but the attributes I moved
have no effect. I'll fix it ... some time.