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<h1>C++ Standard Library Issues Resolved Directly In Albuquerque</h1>
<table>
<tr>
<td align="left">Doc. no.</td>
<td align="left">P0864R0</td>
</tr>
<tr>
<td align="left">Date:</td>
<td align="left"><p>Revised 2017-11-11 at 01:05:20 UTC</p>
</td>
</tr>
<tr>
<td align="left">Project:</td>
<td align="left">Programming Language C++</td>
</tr>
<tr>
<td align="left">Reply to:</td>
<td align="left">Marshall Clow &lt;<a href="mailto:lwgchair@gmail.com">lwgchair@gmail.com</a>&gt;</td>
</tr>
</table>
<h2>Immediate Issues</h2>
<hr>
<h3><a name="2958" href="#2958">2958</a><sup><a href="https://cplusplus.github.io/LWG/issue2958">(i)</a></sup>. Moves improperly defined as deleted</h3>
<p><b>Section:</b> 23.4.2 <a href="https://wg21.link/pairs.pair">[pairs.pair]</a>, 23.5.3.2 <a href="https://wg21.link/tuple.assign">[tuple.assign]</a> <b>Status:</b> <a href="lwg-active.html#Immediate">Immediate</a>
 <b>Submitter:</b> Casey Carter <b>Opened:</b> 2017-05-05 <b>Last modified:</b> 2017-11-10</p>
<p><b>Priority: </b>2
</p>
<p><b>View other</b> <a href="lwg-index-open.html#pairs.pair">active issues</a> in [pairs.pair].</p>
<p><b>View all other</b> <a href="lwg-index.html#pairs.pair">issues</a> in [pairs.pair].</p>
<p><b>Discussion:</b></p>
<p>
LWG <a href="lwg-defects.html#2729">2729</a> constrained many <tt>pair</tt> &amp; <tt>tuple</tt> assignment operators to "not participate in overload resolution" and "be defined as deleted if." As discussed when LWG reviewed <a href="lwg-defects.html#2756">2756</a>, it is undesirable to require 
that a move constructor or assignment operator be "defined as deleted," since it is unclear whether that operation should be 
<em>implicitly</em> deleted, and therefore not participate in overload resolution, or <em>explicitly</em> deleted and therefore 
impede overload resolution for usages that would otherwise find copies.
</p>

<p><i>[2017-07 Toronto Wed Issue Prioritization]</i></p>

<p>Priority 2</p>

<p><i>[2017-11 Albuquerque Wednesday issue processing]</i></p>

<p>Move to Immediate</p>


<p><b>Proposed resolution:</b></p>
<p>This wording is relative to <a href="http://wg21.link/n4659">N4659</a>.</p>

<ol>
<li><p>Edit 23.4.2 <a href="https://wg21.link/pairs.pair">[pairs.pair]</a> as indicated:</p>

<blockquote>
<pre>
pair&amp; operator=(pair&amp;&amp; p) noexcept(<i>see below</i>);
</pre>
<blockquote>
<p>
-21- <i>Effects:</i> Assigns to <tt>first</tt> with <tt>std::forward&lt;first_type&gt;(p.first)</tt> and to 
<tt>second</tt> with <tt>std::forward&lt;second_type&gt;(p.second)</tt>.
<p/>
-22- <i>Remarks:</i> This operator shall <del>be defined as deleted</del><ins>not participate in overload resolution</ins> 
unless <tt>is_move_assignable_v&lt;first_type&gt;</tt> is <tt>true</tt> and <tt>is_move_assignable_v&lt;second_type&gt;</tt> 
is <tt>true</tt>.
<p/>
[&hellip;]
</p>
</blockquote>
</blockquote>
</li>

<li><p>Edit 23.5.3.2 <a href="https://wg21.link/tuple.assign">[tuple.assign]</a> as indicated:</p>

<blockquote>
<pre>
tuple&amp; operator=(tuple&amp;&amp; u) noexcept(<i>see below</i>);
</pre>
<blockquote>
<p>
-5- <i>Effects:</i> For all <tt><i>i</i></tt>, assigns <tt>std::forward&lt;T<sub><i>i</i></sub>&gt;(get&lt;<i>i</i>&gt;(u))</tt> 
to <tt>get&lt;<i>i</i>&gt;(*this)</tt>.
<p/>
-6- <i>Remarks:</i> This operator shall <del>be defined as deleted</del><ins>not participate in overload resolution</ins> unless 
<tt>is_move_assignable_v&lt;T<sub><i>i</i></sub>&gt;</tt> is <tt>true</tt> for all <tt><i>i</i></tt>.
<p/>
[&hellip;]
</p>
</blockquote>
</blockquote>
</li>
</ol>





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