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    CWG Issue 2428</TITLE>
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<P><EM>This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21
  Core Issues List revision 118b.
  See http://www.open-std.org/jtc1/sc22/wg21/ for the official
  list.</EM></P>
<P>2025-09-28</P>
<HR>
<A NAME="2428"></A><H4>2428.
  
Deprecating a concept
</H4>
<B>Section: </B>13.7.9&#160; [<A href="https://wg21.link/temp.concept">temp.concept</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++23
 &#160;&#160;&#160;

 <B>Submitter: </B>Eric Niebler
 &#160;&#160;&#160;

 <B>Date: </B>2018-12-10<BR>


<P>[Accepted as a DR at the November, 2022 meeting.]</P>



<P>The grammar for a <I>concept-definition</I> does not include an
<I>attribute-specifier-seq<SUB>opt</SUB></I>, making it impossible
to deprecate a concept. This seems like an oversight.</P>

<P><B>CWG telecon 2022-10-07:</B></P>

<P>Agreed.</P>

<P><B>Proposed resolution (approved by CWG 2022-10-21):</B></P>

<OL>
<LI>
<P>Change in 9.13.4 [<A href="https://wg21.link/dcl.attr.deprecated#2">dcl.attr.deprecated</A>] paragraph 2 as follows:</P>

<BLOCKQUOTE>

The attribute may be applied to the declaration of a class,
a <I>typedef-name</I>, a variable, a non-static data member, a
function, a namespace, an enumeration, an enumerator,
<INS>a concept,</INS> or a template specialization.

</BLOCKQUOTE>
</LI>

<LI>
<P>Change in 13.7.9 [<A href="https://wg21.link/temp.concept#1">temp.concept</A>] paragraph 1 as follows:</P>

<BLOCKQUOTE>

A concept is a template that defines constraints on its template
arguments.

<PRE>
<I>concept-definition</I>:
    concept <I>concept-name</I> <INS><I>attribute-specifier-seq</I><SUB>opt</SUB></INS> = <I>constraint-expression</I> ;

<I>concept-name</I>:
    <I>identifier</I>
</PRE>

A <I>concept-definition</I> declares a concept. Its <I>identifier</I>
becomes a <I>concept-name</I> referring to that concept within its
scope. <INS>The optional <I>attribute-specifier-seq</I> appertains to
the concept.</INS>
</BLOCKQUOTE>
</LI>
</OL>

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