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    CWG Issue 1152</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="1152"></A><H4>1152.
  
Rules for determining existence of implicit conversion sequence
</H4>
<B>Section: </B>12.2.3&#160; [<A href="https://wg21.link/over.match.viable">over.match.viable</A>]
 &#160;&#160;&#160;

 <B>Status: </B>C++11
 &#160;&#160;&#160;

 <B>Submitter: </B>US
 &#160;&#160;&#160;

 <B>Date: </B>2010-08-03<BR><BR>


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

<A href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2011/n3296.html#US67">N3092 comment
  US&#160;67<BR></A>

<P>To determine whether there is an implicit conversion
sequence that converts the argument to the corresponding
parameter, 12.2.3 [<A href="https://wg21.link/over.match.viable#3">over.match.viable</A>] paragraph 3 uses
12.2.4.2 [<A href="https://wg21.link/over.best.ics">over.best.ics</A>] instead of just saying
&#8220;there is an ICS if-and-only-if a copy initialization
would be well-formed.&#8221; Apparently this is intended,
but to a casual reader or an implementor reading these rules
for the first time for a new implementation, it's not clear
why that's desirable. A note should be added to explain the
rationale.</P>

<P><B>Proposed resolution (August, 2010):</B></P>

<P>Change 12.2.4.2.5 [<A href="https://wg21.link/over.ics.ref#3">over.ics.ref</A>] paragraph 3 as follows:</P>

<BLOCKQUOTE>

Except for an implicit object parameter, for which see
12.2.2 [<A href="https://wg21.link/over.match.funcs">over.match.funcs</A>], a standard conversion sequence
cannot be formed if it requires binding an lvalue reference
<DEL>to non-const</DEL> <INS>other than a reference to a non-volatile
const type</INS> to an rvalue or binding an rvalue reference to
an lvalue.  [<I>Note:</I>...

</BLOCKQUOTE>

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