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    CWG Issue 1535</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="1535"></A><H4>1535.
  
<TT>typeid</TT> in core constant expressions
</H4>
<B>Section: </B>7.7&#160; [<A href="https://wg21.link/expr.const">expr.const</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD3
 &#160;&#160;&#160;

 <B>Submitter: </B>Richard Smith
 &#160;&#160;&#160;

 <B>Date: </B>2012-08-10<BR>


<P>[Moved to DR at the April, 2013 meeting.]</P>



<P>One of the criteria in 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2 for
disqualifying an expression from being a constant expression is:</P>

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<LI><P>

<BLOCKQUOTE>

a typeid expression (7.6.1.8 [<A href="https://wg21.link/expr.typeid">expr.typeid</A>]) whose operand is of a
polymorphic class type;

</BLOCKQUOTE>
</P></LI>
</UL>

<P>on the basis that a runtime test for the dynamic type is inconsistent
with a constant expression.  However, it is only glvalues of polymorphic
type that require a runtime test; <I>type-id</I>s and prvalues with a
polymorphic type could (and should) be permitted in constant
expressions.</P>

<P><B>Proposed resolution (October, 2012):</B></P>

<P>Change 7.7 [<A href="https://wg21.link/expr.const#2">expr.const</A>] paragraph 2 as follows:</P>

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<LI><P>...</P></LI>

<LI><P>a typeid expression (7.6.1.8 [<A href="https://wg21.link/expr.typeid">expr.typeid</A>]) whose operand
is <INS>a glvalue</INS> of a polymorphic class type;</P></LI>

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