digraph {
   rankdir = LR;
   dpi = 300.0;
   
   node [shape = "plaintext";];
   
   pinned_box [label = <<table border="0" cellborder="1" cellspacing="0">
      <tr><td sides="B">Pin</td></tr>
      <tr><td port="source"> </td></tr>
      </table>>;];
   
   subgraph cluster_box {
      label = "";
      peripheries = 0;
      
      subgraph cluster_box_internal {
         peripheries = 1;
         label = "b1";
         shape = box;
         style = solid;
         pin [shape = "point";];
      }
   }
   
   subgraph cluster_deref {
      style = bold;
      label = "pinned";
      
      box [label = <<table border="0" cellborder="1" cellspacing="0">
         <tr><td sides="B">fut</td></tr>
         <tr><td port="target">0</td></tr>
         <tr><td port="source"> </td></tr>
         <tr><td style="dashed">...</td></tr>
         <tr><td port="internal">1</td></tr>
         </table>>;];
   }
   
   edge [tailclip = false;];
   pinned_box -> pin [tailport = "source:c"; arrowhead = "none";];
   pin -> box [headport = "target";];
   box -> box [tailport = "source:c"; headport = "internal";];
}