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    CWG Issue 536</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="536"></A><H4>536.
  
Problems in the description of <I>id-expression</I>s
</H4>
<B>Section: </B>_N4567_.5.1.1&#160; [<A href="https://wg21.link/expr.prim.general">expr.prim.general</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD6
 &#160;&#160;&#160;

 <B>Submitter: </B>Mike Miller
 &#160;&#160;&#160;

 <B>Date: </B>13 October 2005<BR>


<P>[Accepted at the November, 2020 meeting as part of paper P1787R6 and
moved to DR at the February, 2021 meeting.]</P>

<P>There are at least a couple of problems in the description of
the various <I>id-expression</I>s in _N4567_.5.1.1 [<A href="https://wg21.link/expr.prim.general">expr.prim.general</A>]:</P>

<OL>
<LI>
<P>Paragraph 4 embodies an incorrect assumption about the
syntax of <I>qualified-id</I>s:</P>

<BLOCKQUOTE>

The operator <TT>::</TT> followed by an <I>identifier</I>, a
<I>qualified-id</I>, or an <I>operator-function-id</I> is a
<I>primary-expression</I>.

</BLOCKQUOTE>

<P>The problem here is that the <TT>::</TT> is actually part of the
syntax of <I>qualified-id</I>; consequently, &#8220;<TT>::</TT> followed by...
a <I>qualified-id</I>&#8221; could be something like
&#8220;<TT>:: ::i</TT>,&#8221; which is ill-formed.  Presumably
this should say something like, &#8220;A <I>qualified-id</I> with
no <I>nested-name-specifier</I> is a <I>primary-expression</I>.&#8221;</P>
</LI>

<LI>
<P>More importantly, some kinds of <I>id-expression</I>s are not
described by _N4567_.5.1.1 [<A href="https://wg21.link/expr.prim.general">expr.prim.general</A>].  The structure of this
section is that the result, type, and lvalue-ness are specified for
each of the cases it covers:</P>

<UL>
<LI><P>paragraph 4 deals with <I>qualified-id</I>s that have no
<I>nested-name-specifier</I>
</P></LI>

<LI><P>paragraph 7 deals with bare <I>identifier</I>s and with
<I>qualified-id</I>s containing a <I>nested-name-specifier</I>
that names a class</P></LI>

<LI><P>paragraph 8 deals with <I>qualified-id</I>s containing a
<I>nested-name-specifier</I> that names a namespace</P></LI>

</UL>

<P>This treatment leaves unspecified all the non-<I>identifier</I>
<I>unqualified-id</I>s (<I>operator-function-id</I>,
<I>conversion-function-id</I>, and <I>template-id</I>), as well as
(perhaps) &#8220;<TT>::</TT> <I>template-id</I>&#8221; (it's not clear
whether the &#8220;<TT>::</TT> followed by a <I>qualified-id</I>&#8221; case
is supposed to apply to <I>template-id</I>s or not).  Note also that the
proposed resolution of <A HREF="301.html">issue 301</A> slightly
exacerbates this problem by removing the form
of <I>operator-function-id</I> that contains
a <I>tmeplate-argument-list</I>; as a result, references like
&#8220;<TT>::operator+&lt;X&gt;</TT>&#8221; are no longer covered in
_N4567_.5.1.1 [<A href="https://wg21.link/expr.prim.general">expr.prim.general</A>].</P>
</LI>

</OL>

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