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    CWG Issue 1087</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="1087"></A><H4>1087.
  
Additional applications of issue 899
</H4>
<B>Section: </B>12.2.2.5&#160; [<A href="https://wg21.link/over.match.copy">over.match.copy</A>]
 &#160;&#160;&#160;

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

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

 <B>Date: </B>2010-06-25<BR>


<P>[Voted into the WP at the November, 2010 meeting.]</P>



<P>The resolution of <A HREF="899.html">issue 899</A> needs to be
extended to cover move constructors and template constructors as well.
</P>

<P><B>Proposed resolution (August, 2010):</B></P>

<UL><LI><P>When the type of the initializer expression is a class type
&#8220;<I>cv</I> <TT>S</TT>&#8221;, the non-explicit conversion
functions of <TT>S</TT> and its base classes are considered. When
initializing a temporary to be bound to the first parameter of a
<DEL>copy</DEL> constructor <DEL>(11.4.5.3 [<A href="https://wg21.link/class.copy.ctor">class.copy.ctor</A>])</DEL>
<INS>that takes a reference to possibly cv-qualified <TT>T</TT> as its
first argument,</INS> called with a single argument in the context of
direct-initialization, explicit conversion functions are also
considered.  Those that are not hidden within <TT>S</TT> and yield a
type whose cv-unqualified version is the same type as <TT>T</TT> or is
a derived class thereof are candidate functions.  Conversion functions
that return &#8220;reference to <TT>X</TT>&#8221; return lvalues or
xvalues, depending on the type of reference, of type <TT>X</TT> and
are therefore considered to yield <TT>X</TT> for this process of
selecting candidate functions.</P></LI></UL>

<P>For example</P>

<PRE>
    struct C {
       template &lt;class T = int&gt; C(C&amp;, T = 0);
    };

    struct A {
       explicit operator C&amp;() const;
    };

    int main() {
       A a;
       C c (a); //<SPAN CLASS="cmnt"> should use template constructor</SPAN>
    }
</PRE>

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