<span class="hljs-keyword">template</span> &lt;<span class="hljs-keyword">class</span> <span class="hljs-title class_">T</span>&gt; <span class="hljs-comment">// comment</span>
<span class="hljs-function"><span class="hljs-keyword">auto</span> <span class="hljs-title">foo</span><span class="hljs-params">(T x)</span> </span>{ ... };

<span class="hljs-keyword">namespace</span> impl {
    <span class="hljs-keyword">template</span>&lt;<span class="hljs-keyword">typename</span> T&gt;
    <span class="hljs-keyword">struct</span> <span class="hljs-title class_">is_streamable</span>&lt;T, std::<span class="hljs-type">void_t</span>&lt;<span class="hljs-keyword">decltype</span>(std::<span class="hljs-built_in">declval</span>&lt;std::wostream &amp;&gt;() &lt;&lt; std::<span class="hljs-built_in">declval</span>&lt;T&gt;())&gt;&gt; : std::true_type { };
}

<span class="hljs-comment">// Disable overload for already valid operands.</span>
<span class="hljs-keyword">template</span>&lt;<span class="hljs-keyword">class</span> <span class="hljs-title class_">T</span>, <span class="hljs-keyword">class</span> = std::<span class="hljs-type">enable_if_t</span>&lt;!impl::is_streamable_v&lt;<span class="hljs-type">const</span> T &amp;&gt; &amp;&amp; std::is_convertible_v&lt;<span class="hljs-type">const</span> T &amp;, std::wstring_view&gt;&gt;&gt;
std::wostream &amp;<span class="hljs-keyword">operator</span> &lt;&lt;(std::wostream &amp;stream, <span class="hljs-type">const</span> T &amp;thing)
{
    <span class="hljs-keyword">return</span> stream &lt;&lt; <span class="hljs-built_in">static_cast</span>&lt;std::wstring_view&gt;(thing);
}

<span class="hljs-keyword">enum struct</span> <span class="hljs-title class_">DataHolder</span> { };
<span class="hljs-keyword">enum class</span> <span class="hljs-title class_">DataThingy</span> { };
<span class="hljs-keyword">enum class</span> <span class="hljs-title class_">Boolean</span> : <span class="hljs-type">char</span> {
    True, False, FileNotFound
};

<span class="hljs-keyword">union</span> <span class="hljs-title class_">Soy</span>
{
};