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    CWG Issue 1212</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="1212"></A><H4>1212.
  
Non-function-call xvalues and <TT>decltype</TT>
</H4>
<B>Section: </B>9.2.9.3&#160; [<A href="https://wg21.link/dcl.type.simple">dcl.type.simple</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>2010-10-21<BR>


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



<P>Given</P>

<PRE>
    int&amp;&amp; f();
    int i;
</PRE>

<P>it is surprising that <TT>decltype(f())</TT> and
<TT>decltype(static_cast&lt;int&amp;&amp;&gt;(i))</TT> are not the
same type.</P>

<P><B>Proposed resolution (November, 2010) [SUPERSEDED]:</B></P>

<P>Change 9.2.9.3 [<A href="https://wg21.link/dcl.type.simple#4">dcl.type.simple</A>] paragraph 4 as follows:</P>

<BLOCKQUOTE>

<P>The type denoted by <TT>decltype(e)</TT> is defined as follows:</P>

<UL>
<LI><P>if <TT>e</TT> is an unparenthesized <I>id-expression</I> or
a class member access (7.6.1.5 [<A href="https://wg21.link/expr.ref">expr.ref</A>]),
<TT>decltype(e)</TT> is the type of the entity named by <TT>e</TT>.
If there is no such entity, or if <TT>e</TT> names a set of overloaded
functions, the program is ill-formed;</P></LI>

<LI><P>otherwise, if <TT>e</TT> is <DEL>a function call (7.6.1.3 [<A href="https://wg21.link/expr.call">expr.call</A>]) or an invocation of an overloaded operator (parentheses
around <TT>e</TT> are ignored), <TT>decltype(e)</TT> is the return
type of the statically chosen function</DEL> <INS>an xvalue,
<TT>decltype(e)</TT> is <TT>T&amp;&amp;</TT>, where <TT>T</TT> is the
type of <TT>e</TT></INS>;</P></LI>

<LI><P>otherwise, if <TT>e</TT> is an lvalue, <TT>decltype(e)</TT> is
<TT>T&amp;</TT>, where <TT>T</TT> is the type of <TT>e</TT>;</P></LI>

<LI><P>otherwise, <TT>decltype(e)</TT> is the type of
<TT>e</TT>.</P></LI>

</UL>

</BLOCKQUOTE>

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