alue_check.html" ><code>static void narrow_value_check(Impl &amp;&amp;) noexcept</code></a>
<p>Observer policy performing hard UB if no value is present. Constexpr, never throws.</p><li>
	<a href="../reference/policies/base/narrow_error_check.html" ><code>static void narrow_error_check(Impl &amp;&amp;) noexcept</code></a>
<p>Observer policy performing hard UB if no error is present. Constexpr, never throws.</p><li>
	<a href="../reference/policies/base/narrow_exception_check.html" ><code>static void narrow_e