urn value of a function should not be discarded without examining it.</p><li>
	<a href="../reference/macros/requires.html" ><code>BOOST_OUTCOME_REQUIRES(...)</code></a>
<p>A C++ 20 <code>requires(...)</code>, if available.</p><li>
	<a href="../reference/macros/symbol_visible.html" ><code>BOOST_OUTCOME_SYMBOL_VISIBLE</code></a>
<p>How to mark throwable types as always having default ELF symbol visibility.</p><li>
	<a href="../reference/macros/thread_local.html" ><code>BOOST_OUTCOME_THREAD_LOCAL</code></a>
<p