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    CWG Issue 1426</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="1426"></A><H4>1426.
  
Allowing additional parameter types in defaulted functions
</H4>
<B>Section: </B>9.6.2&#160; [<A href="https://wg21.link/dcl.fct.def.default">dcl.fct.def.default</A>]
 &#160;&#160;&#160;

 <B>Status: </B>CD5
 &#160;&#160;&#160;

 <B>Submitter: </B>Nikolay Ivchenkov
 &#160;&#160;&#160;

 <B>Date: </B>2011-12-08<BR>


<P>[Adopted at the November, 2017 meeting as part of paper P0641R2.]</P>



<P>The current wording of 9.6.2 [<A href="https://wg21.link/dcl.fct.def.default#1">dcl.fct.def.default</A>] paragraph 1
allows copy constructors and copy assignment operators to have a
reference to non-const parameter, even if the implicitly-declared
function would have had a reference to const parameter.  This is
safe because the sub-object copy functions that take a reference to
const parameter can be invoked with a non-const lvalue.</P>

<P>It would also be possible to allow the inverse situation &#8212;
permitting the defaulted function to be defined with a reference to
const parameter, even though the sub-object functions have a
reference to non-const parameter &#8212; by defining the defaulted function
as deleted.</P>

<P>See also <A HREF="1331.html">issue 1331</A>.</P>

<P><B>Rationale (February, 2012):</B></P>

<P>This is a request to extend the language and is thus more appropriately
considered by EWG.</P>

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