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    CWG Issue 847</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="847"></A><H4>847.
  
Error in rvalue reference deduction example
</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>CD2
 &#160;&#160;&#160;

 <B>Submitter: </B>Steve Adamczyk
 &#160;&#160;&#160;

 <B>Date: </B>27 March, 2009<BR>


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

<P>The adoption of paper N2844 made it ill-formed to attempt to bind an
rvalue reference to an lvalue.  However, the example in
13.10.3.2 [<A href="https://wg21.link/temp.deduct.call#3">temp.deduct.call</A>] paragraph 3 still reflects the previous
specification:</P>

<PRE>
    template &lt;typename T&gt; int f(T&amp;&amp;);
    int i;
    int j = f(i);        //<SPAN CLASS="cmnt"> calls </SPAN>f&lt;int&amp;&gt;(i)
    template &lt;typename T&gt; int g(const T&amp;&amp;);
    int k;
    int n = g(k);        //<SPAN CLASS="cmnt"> calls </SPAN>g&lt;int&gt;(k)
</PRE>

<P>The last line of that example is now ill-formed, attempting to bind
the <TT>const int&amp;&amp;</TT> parameter of <TT>g</TT> to the lvalue
<TT>k</TT>.</P>

<P><B>Proposed resolution (July, 2009):</B></P>

<P>Replace the example in 13.10.3.2 [<A href="https://wg21.link/temp.deduct.call#3">temp.deduct.call</A>] paragraph 3 with:</P>

<PRE>
    template&lt;typename T&gt; int f(T&amp;&amp;);
    template&lt;typename T&gt; int g(const T&amp;&amp;);
    int i;
    int n1 = f(i);    //<SPAN CLASS="cmnt"> calls </SPAN>f&lt;int&amp;&gt;(int&amp;)
    int n2 = f(0);    //<SPAN CLASS="cmnt"> calls </SPAN>f&lt;int&gt;(int&amp;&amp;)
    int n3 = g(i);    //<SPAN CLASS="cmnt"> error: would call </SPAN>g&lt;int&gt;(const int&amp;&amp;)<SPAN CLASS="cmnt">, which would</SPAN>
                      //<SPAN CLASS="cmnt"> bind an rvalue reference to an lvalue</SPAN>
</PRE>

<P>(See also <A HREF="858.html">issue 858</A>.)</P>

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