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    CWG Issue 336</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="336"></A><H4>336.
  
Explicit specialization examples are still incorrect
</H4>
<B>Section: </B>13.9.4&#160; [<A href="https://wg21.link/temp.expl.spec">temp.expl.spec</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD1
 &#160;&#160;&#160;

 <B>Submitter: </B>Jason Shirk
 &#160;&#160;&#160;

 <B>Date: </B>29 Jan 2002<BR>


<P>[Voted into WP at April 2003 meeting.]</P>



<P>The examples corrected by <A HREF="24.html">issue 24</A> are still
wrong in one case.</P>

<P>In item #4 (a correction to the example in paragraph 18), the proposed
resolution is:</P>
<PRE>
  template&lt;class T1&gt; class A {
    template&lt;class T2&gt; class B {
      template&lt;class T3&gt; void mf1(T3);
        void mf2();
      };
  };
  template&lt;&gt; template&lt;class X&gt;
    class A&lt;int&gt;::B { };
  template&lt;&gt; template&lt;&gt; template&lt;class T&gt;
    void A&lt;int&gt;::B&lt;double&gt;::mf1(T t) { }
  template&lt;class Y&gt; template&lt;&gt;
    void A&lt;Y&gt;::B&lt;double&gt;::mf2() { } // ill-formed; B&lt;double&gt; is specialized but
                                    // its enclosing class template A is not
</PRE>

<P>The explicit specialization of member <TT>A&lt;int&gt;::B&lt;double&gt;::mf1</TT>
is ill-formed.  The class template <TT>A&lt;int&gt;::B</TT>
is explicitly specialized and
contains no members, so any implicit specialization (such as
<TT>A&lt;int&gt;::B&lt;double&gt;</TT>) would also contain no members.</P>

<P><B>Proposed Resolution (4/02):</B></P>

<P>
Fix the example in 13.9.4 [<A href="https://wg21.link/temp.expl.spec#18">temp.expl.spec</A>] paragraph 18 to read:</P>
<PRE>
  template&lt;class T1&gt; class A {
    template&lt;class T2&gt; class B {
      template&lt;class T3&gt; void mf1(T3);
      void mf2();
    };
  };
  template&lt;&gt; template&lt;class X&gt;
    class A&lt;int&gt;::B {
      template&lt;class T&gt; void mf1(T);
    };
  template&lt;&gt; template&lt;&gt; template&lt;class T&gt;
    void A&lt;int&gt;::B&lt;double&gt;::mf1(T t) { }
  template&lt;class Y&gt; template&lt;&gt;
    void A&lt;Y&gt;::B&lt;double&gt;::mf2() { } // ill-formed; B&lt;double&gt; is specialized but
                                    // its enclosing class template A is not
</PRE>

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