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<title>Issue 4338: sender unaware coroutines should be able to co_await a task</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="4338"><a href="lwg-active.html#4338">4338</a>. sender unaware coroutines should be able to <code>co_await</code> a <code>task</code></h3>
<p><b>Section:</b> 33.13.6.2 <a href="https://wg21.link/task.class">[task.class]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Dietmar Kühl <b>Opened:</b> 2025-08-31 <b>Last modified:</b> 2025-09-01</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#task.class">active issues</a> in [task.class].</p>
<p><b>View all other</b> <a href="lwg-index.html#task.class">issues</a> in [task.class].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
The <code>task</code> type doesn't have an <code>operator
co_await()</code>.  Thus, a <code>task</code> can't be
<code>co_await</code>ed directly from a coroutine. Using
<code>as_awaitable</code> on the <code>task</code> object also
doesn't work because this function requires a reference to the
promise as second argument.
</p>
<p>
<code>task</code> could define an <code>operator co_await()</code> that
returns an awaitable object or directly provide an awaiter
interface. There are, however, two complications:
</p> 
<ol>  
<li>For scheduler affinity the <code>task</code> needs to get a
scheduler from the object starting the <code>task</code>. While
the promise can be obtained from the coroutine handle passed to
<code>await_suspend()</code> these normally wouldn't have an
associated environment supporting a <code>get_scheduler</code> query.
</li>
<li>
The approach to reporting cancellation is to call a function
<code>unhandled_stopped()</code> on the promise type which is
generally not available. It could be argued that cancellation isn't
really a problem because the it is unlikely that the environment
associated with the promise supports a <code>get_stop_token</code>
query.
</li>
</ol>  
<p>
It is worth noting that senders in general do not support an
<code>operator co_await()</code>, i.e., other senders are also not
awaitable directly. On the other hand, <code>task</code> could
become the generic adapater to make senders awaitable from
coroutines.
</p>


<p id="res-4338"><b>Proposed resolution:</b></p>
<p>
</p>





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