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<title>Issue 3010: [networking.ts] uses_executor says "if a type T::executor_type exists"</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="3010"><a href="lwg-defects.html#3010">3010</a>. [networking.ts] <code>uses_executor</code> says "if a type <code>T::executor_type</code> exists"</h3>
<p><b>Section:</b> 13.11.1 [networking.ts::async.uses.executor.trait] <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> Jonathan Wakely <b>Opened:</b> 2017-08-17 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>0
</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><b>Addresses: networking.ts</b></p>
<p>
[async.uses.executor.trait] p1 says "if a type <code>T::executor_type</code> exists" but we don't want it to be required 
to detect private or ambiguous types.
</p>

<p><i>[
2017-11-01 Moved to Tentatively Ready after 7 positive votes for P0 on c++std-lib.
]</i></p>

<p><i>[2018-3-17 Adopted in Jacksonville]</i></p>



<p id="res-3010"><b>Proposed resolution:</b></p>
<p>This resolution is relative to <a href="https://wg21.link/n4656">N4656</a>.</p>

<ol>
<li><p>Edit 13.11.1 [networking.ts::async.uses.executor.trait] as indicated:</p>

<blockquote>
<p>
-1- Remark: Detects whether <code>T</code> has a nested <code>executor_type</code> that is convertible from
<code>Executor</code>. Meets the <code>BinaryTypeTrait</code> requirements (C++Std [meta.rqmts]). The implementation 
provides a definition that is derived from <code>true_type</code> if <del>a type</del><ins>the <em>qualified-id</em></ins> 
<code>T::executor_type</code> <del>exists</del><ins>is valid and denotes a type</ins> and 
<code>is_convertible&lt;Executor, T::executor_type&gt;::value != false</code>, otherwise it is derived from
<code>false_type</code>. A program may specialize this template [&hellip;].
</p>
</blockquote>
</li>

</ol>




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