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<title>Issue 3709: LWG-3703 was underly ambitious</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#C++23">C++23</a> status.</em></p>
<h3 id="3709"><a href="lwg-defects.html#3709">3709</a>. LWG-3703 was underly ambitious</h3>
<p><b>Section:</b> 22.5.3.1 <a href="https://wg21.link/optional.optional.general">[optional.optional.general]</a>, 22.6.3.1 <a href="https://wg21.link/variant.variant.general">[variant.variant.general]</a> <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> Casey Carter <b>Opened:</b> 2022-06-08 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#optional.optional.general">issues</a> in [optional.optional.general].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++23">C++23</a> status.</p>
<p><b>Discussion:</b></p>
<p>
LWG <a href="lwg-defects.html#3703" title="Missing requirements for expected&lt;T, E&gt; requires is_void&lt;T&gt; (Status: C++23)">3703</a><sup><a href="https://cplusplus.github.io/LWG/issue3703" title="Latest snapshot">(i)</a></sup> struck redundant language from 22.8.7.1 <a href="https://wg21.link/expected.void.general">[expected.void.general]</a> specifying that 
(1) space allocated for an object is suitably aligned, and (2) a member annotated <code><i>// exposition only</i></code> 
in a class synopsis "is provided for exposition only." 
<p/>
Let's also strike similar occurrences from the wording for <code>optional</code> and <code>variant</code>.
</p>

<p><i>[2022-06-21; Reflector poll]</i></p>

<p>
Set status to Tentatively Ready after nine votes in favour during reflector poll.
</p>

<p><i>[2022-07-15; LWG telecon: move to Ready]</i></p>


<p><i>[2022-07-25 Approved at July 2022 virtual plenary. Status changed: Ready &rarr; WP.]</i></p>



<p id="res-3709"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4910" title=" Working Draft, Standard for Programming Language C++">N4910</a>.
</p>

<ol>
<li><p>Modify 22.5.3.1 <a href="https://wg21.link/optional.optional.general">[optional.optional.general]</a> as indicated:</p>

<blockquote>
<p>
-1- Any instance of <code>optional&lt;T&gt;</code> at any given time either contains a value 
or does not contain a value. When an instance of <code>optional&lt;T&gt;</code> <i>contains a value</i>, 
it means that an object of type <code>T</code>, referred to as the optional object's <i>contained value</i>, 
is allocated within the storage of the optional object. Implementations are not permitted to use 
additional storage, such as dynamic memory, to allocate its contained value. <del>The contained
value shall be allocated in a region of the <code>optional&lt;T&gt;</code> storage suitably aligned 
for the type <code>T</code>.</del> When an object of type <code>optional&lt;T&gt;</code> is contextually 
converted to <code>bool</code>, the conversion returns <code>true</code> if the object contains a value; 
otherwise the conversion returns <code>false</code>.
<p/>
-2- <del>Member <code>val</code> is provided for exposition only.</del> When an <code>optional&lt;T&gt;</code> 
object contains a value, <ins>member</ins> <code>val</code> points to the contained value.
</p>
</blockquote>
</li>

<li><p>Modify 22.6.3.1 <a href="https://wg21.link/variant.variant.general">[variant.variant.general]</a> as indicated:</p>

<blockquote>
<p>
-1- Any instance of <code>variant</code> at any given time either holds a value of one of its alternative 
types or holds no value. When an instance of <code>variant</code> holds a value of alternative type <code>T</code>, 
it means that a value of type <code>T</code>, referred to as the <code>variant</code> object's <i>contained value</i>, 
is allocated within the storage of the <code>variant</code> object. Implementations are not permitted to use 
additional storage, such as dynamic memory, to allocate the contained value. <del>The contained value shall 
be allocated in a region of the variant storage suitably aligned for all types in <code>Types</code>.</del>
</p>
</blockquote>
</li>

</ol>





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