title: Emplacing vector into map
body: <p>Given this type:</p>
  
  <pre><code>std::map&lt;int, std::vector&lt;T&gt;&gt; map;
  </code></pre>
  
  <p>How to directly emplace elements?</p>
  
  <pre><code>map.emplace(10, /* ? */);
  </code></pre>
  
  <p>I can do it by separately creating the vector first, and then using that identifier in the call to emplace, but that is undesirable in case it's possible to do it directly somehow.</p>