title: Hana: How do I create a tuple of types from a variant?
body: <p>If I have a variant, like so:</p>
  
  <pre><code>using my_variant = boost::variant&lt;int, bool, std::string&gt;;
  </code></pre>
  
  <p>Is there an easy way to extract the types the variant can contain into a Boost.Hana tuple so that the following holds:</p>
  
  <pre><code>using boost::hana::type;
  static_assert(std::is_same&lt;my_tuple, boost::hana::tuple&lt;type&lt;int&gt;, type&lt;bool&gt;, type&lt;std::string&gt;&gt;&gt;{});
  </code></pre>