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<title>Issue 3353: locale's copy assignment operator should return locale&amp;</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#New">New</a> status.</em></p>
<h3 id="3353"><a href="lwg-active.html#3353">3353</a>. <code>locale</code>'s copy assignment operator should return <code>locale&amp;</code></h3>
<p><b>Section:</b> 28.3.3.1 <a href="https://wg21.link/locale">[locale]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Stephan T. Lavavej <b>Opened:</b> 2019-12-06 <b>Last modified:</b> 2019-12-21</p>
<p><b>Priority: </b>3
</p>
<p><b>View all other</b> <a href="lwg-index.html#locale">issues</a> in [locale].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
Curiously, <code>locale</code>'s copy assignment operator currently returns <code>const locale&amp;</code>. As Casey 
Carter noted in <a href="https://github.com/microsoft/STL/issues/268">microsoft/STL#268</a>, this is:
</p>
<ul>
<li><p>Weird!</p></li>
<li><p>The only occurrence in the entire Standard Library.</p></li>
<li><p>Preventing <code>locale</code> from satisfying <code>std::copyable</code>.</p></li>
</ul>
<p>
We aren't aware of any reason for this to be <code>const</code>. (I observe that this hasn't changed since 
<a href="https://wg21.link/n1804">N1804</a> on 2005-04-27 and probably goes back to C++98; I suspect that 
when this was originally specified, copy assignment operators were relatively new, and conventions for 
them weren't rigorously followed.)
</p>

<p><i>[2019-12-21 Issue Prioritization]</i></p>

<p>Priority to 3 after reflector discussion based on the observation that we have implementation
divergence.</p>


<p id="res-3353"><b>Proposed resolution:</b></p>
<p>This wording is relative to <a href="https://wg21.link/n4842">N4842</a>.</p>

<ol>
<li><p>Modify 28.3.3.1 <a href="https://wg21.link/locale">[locale]</a> as indicated:</p>

<blockquote>
<pre>
[&hellip;]
~locale(); <i>// not virtual</i>
<del>const</del> locale&amp; operator=(const locale&amp; other) noexcept;
template&lt;class Facet&gt; locale combine(const locale&amp; other) const;
[&hellip;]
</pre>
</blockquote>
</li>

<li><p>Modify 28.3.3.1.3 <a href="https://wg21.link/locale.cons">[locale.cons]</a> as indicated:</p>

<blockquote>
<pre>
<del>const</del> locale&amp; operator=(const locale&amp; other) noexcept;
</pre>
<blockquote>
<p>
-14- <i>Effects:</i> Creates a copy of <code>other</code>, replacing the current value.
<p/>
-15- <i>Returns:</i> <code>*this</code>.
</p>
</blockquote>
</blockquote>
</li>
</ol>



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