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    CWG Issue 1184</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="1184"></A><H4>1184.
  
Argument conversions to nondeduced parameter types
</H4>
<B>Section: </B>13.10.3.2&#160; [<A href="https://wg21.link/temp.deduct.call">temp.deduct.call</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++11
 &#160;&#160;&#160;

 <B>Submitter: </B>Daniel Kr&#252;gler
 &#160;&#160;&#160;

 <B>Date: </B>2010-08-29<BR>


<P>[Voted into the WP at the March, 2011 meeting as part of paper N3262.]</P>

<P>It is not clear whether the following example is well-formed or not:</P>

<PRE>
    template&lt;class T&gt; struct identity { typedef T type; };

    template&lt;class T, class C&gt;
    void f(T C::*, typename identity&lt;T&gt;::type*){}

    struct X { void f() {}; };

    int main() { f(&amp;X::f, 0); }
</PRE>

<P>The null pointer conversion required for the second parameter of
<TT>f</TT> is not one of the ones permitted by
13.10.3.2 [<A href="https://wg21.link/temp.deduct.call#4">temp.deduct.call</A>] paragraph 4, but it's unclear whether
that list should apply to parameters with nondeduced types or not.
13.10.2 [<A href="https://wg21.link/temp.arg.explicit#6">temp.arg.explicit</A>] paragraph 6 is explicit that</P>

<BLOCKQUOTE>

Implicit conversions (7.3 [<A href="https://wg21.link/conv">conv</A>]) will be performed
on a function argument to convert it to the type of the corresponding
function parameter if the parameter type contains no
<I>template-parameter</I>s that participate in template argument
deduction.

</BLOCKQUOTE>

<P>However, this statement appears in a section dealing with
explicitly-specified template arguments, so its applicability to
nondeduced contexts in general is not clear.</P>

<P>Implementations disagree on the handling of this example.</P>

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