lass="keyword">typename</span> State<span class="special">,</span> <span class="keyword">typename</span> Data<span class="special">&gt;</span> 
  <span class="keyword">struct</span> <a class="link" href="shift_left_assign/impl.html" title="Struct template impl">impl</a> <span class="special">:</span>
    <span class="keyword"></span> <a class="link" href="pass_through.html" title="Struct template pass_through">proto::pass_through</a>&lt;shift_left_assign&gt;::template impl&lt;Expr, State, Data&gt;
  <span c