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    CWG Issue 1028</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="1028"></A><H4>1028.
  
Dependent names in non-defining declarations
</H4>
<B>Section: </B>13.8.4&#160; [<A href="https://wg21.link/temp.dep.res">temp.dep.res</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD6
 &#160;&#160;&#160;

 <B>Submitter: </B>Sean Hunt
 &#160;&#160;&#160;

 <B>Date: </B>2010-02-03<BR>


<P>[Accepted at the November, 2020 meeting as part of paper P1787R6 and
moved to DR at the February, 2021 meeting.]</P>

<P>The current wording of 13.8.4 [<A href="https://wg21.link/temp.dep.res">temp.dep.res</A>] seems to assume
that dependent names can only appear in the definition of a template:</P>

<BLOCKQUOTE>

<P>In resolving dependent names, names from the following sources
are considered:</P>

<UL>
<LI><P>Declarations that are visible at the point of
definition of the template.</P></LI>

<LI><P>Declarations from namespaces associated with the types of
the function arguments both from the instantiation context
(13.8.4.1 [<A href="https://wg21.link/temp.point">temp.point</A>]) and from the definition context.</P></LI>

</UL>

</BLOCKQUOTE>

<P>However, dependent names can occur in non-defining declarations of
the template as well; for instance,</P>

<PRE>
    template&lt;typename T&gt;
    T foo(T, decltype(bar(T())));
</PRE>

<P>
<TT>bar</TT> needs to be looked up, even though there is no
definition of <TT>foo</TT> in the translation unit.</P>

<P><B>Additional note (February, 2011):</B></P>

<P>The resolution of this issue can't simply replace the word
&#8220;definition&#8221; with the word &#8220;declaration,&#8221;
<I>mutatis mutandis</I>, because there can be multiple declarations
in a translation unit (which isn't true of &#8220;the definition&#8221;).
As a result, the issue was moved back to "open" status for further
consideration.</P>

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