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    CWG Issue 2716</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="2716"></A><H4>2716.
  
Rule about self-or-base conversion is normatively redundant
</H4>
<B>Section: </B>11.4.8.3&#160; [<A href="https://wg21.link/class.conv.fct">class.conv.fct</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD7
 &#160;&#160;&#160;

 <B>Submitter: </B>Brian Bi
 &#160;&#160;&#160;

 <B>Date: </B>2023-04-11<BR>


<P>[Accepted as a DR at the June, 2023 meeting.]</P>

<P>The rule in 11.4.8.3 [<A href="https://wg21.link/class.conv.fct#4">class.conv.fct</A>] paragraph 4 is normatively
redundant explanation:</P>

<BLOCKQUOTE>

A conversion function is never used to convert a (possibly
cv-qualified) object to the (possibly cv-qualified) same object type
(or a reference to it), to a (possibly cv-qualified) base class of
that type (or a reference to it), or to cv void.
[ Footnote:
These conversions are considered as standard conversions for the
purposes of overload resolution (12.2.4.2 [<A href="https://wg21.link/over.best.ics">over.best.ics</A>],
12.2.4.2.5 [<A href="https://wg21.link/over.ics.ref">over.ics.ref</A>]) and therefore initialization
(9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>]) and explicit casts
(7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>]). A conversion to void does not invoke
any conversion function (7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>]).  Even though
never directly called to perform a conversion, such conversion
functions can be declared and can potentially be reached through a
call to a virtual conversion function in a base class.  -- end footnote ]

</BLOCKQUOTE>

<P><B>Proposed resolution (approved by CWG 2023-04-28):</B></P>

<P>Change in 11.4.8.3 [<A href="https://wg21.link/class.conv.fct#4">class.conv.fct</A>] paragraph 4 as follows:</P>

<BLOCKQUOTE>

<INS>[ Note:</INS> A conversion function is never <DEL>used
to convert</DEL> <INS>invoked for implicit or explicit conversions of an</INS>
<DEL>a (possibly cv-qualified)</DEL> object to the <DEL>(possibly
cv-qualified)</DEL> same object type (or a reference to it), to a <DEL>(possibly
cv-qualified)</DEL> base class of that type (or a reference to it), or to cv
void.
<DEL>[ Footnote:</DEL>
<DEL>These conversions are considered as standard conversions for the
purposes of overload resolution (12.2.4.2 [<A href="https://wg21.link/over.best.ics">over.best.ics</A>],
12.2.4.2.5 [<A href="https://wg21.link/over.ics.ref">over.ics.ref</A>]) and therefore initialization
(9.5 [<A href="https://wg21.link/dcl.init">dcl.init</A>]) and explicit casts
(7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>]). A conversion to void does not invoke
any conversion function (7.6.1.9 [<A href="https://wg21.link/expr.static.cast">expr.static.cast</A>]).</DEL>  Even though
never directly called to perform a conversion, such conversion
functions can be declared and can potentially be reached through a
call to a virtual conversion function in a base class.
<DEL>-- end footnote ]</DEL> <INS>-- end note ]</INS>

<P>[ Example: ... ]</P>

</BLOCKQUOTE>

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