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    CWG Issue 2024</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="2024"></A><H4>2024.
  
Dependent types and unexpanded parameter packs
</H4>
<B>Section: </B>13.8.3.2&#160; [<A href="https://wg21.link/temp.dep.type">temp.dep.type</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD4
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2014-10-17<BR>


<P>[Moved to DR at the October, 2015 meeting.]</P>



<P>Consider an example like:</P>

<PRE>
  template&lt;typename ...Ts&gt; struct X { X(int); };
  template&lt;typename T&gt; using Y = int;
  template&lt;typename ...Ts&gt; void f() {
    X&lt;Y&lt;Ts&gt;...&gt; x;
  }
</PRE>

<P>The presence of the ellipsis should make the reference to
<TT>X</TT> a dependent type, but there is no rule making it so.</P>

<P><B>Proposed resolution (May, 2015):</B></P>

<P>Change 13.8.3.2 [<A href="https://wg21.link/temp.dep.type#9">temp.dep.type</A>] paragraph 9 as follows:</P>

<BLOCKQUOTE>

<P>A type is dependent if it is</P>

<UL>
<LI><P>...</P></LI>

<LI><P>a <I>simple-template-id</I> in which either the
template name is a template parameter or any of the template
arguments is a dependent type or an expression that is
type-dependent or value-dependent <INS>or is a pack
expansion</INS>, or</P></LI>

</UL>

</BLOCKQUOTE>

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