title: Protobuf RPC Service method without parameters
body: <p>I'm trying to describe an RPC service using Google's Protocol Buffers</p>
  
  <pre><code>service WhoamiService {
    rpc WhoAreYou() returns (Whoami) {}
  }
  
  message Whoami {
    optional bytes request_id = 1;
    optional string hostname = 2;
    optional string message = 3;
  }
  </code></pre>
  
  <p>When I try to compile this definition, I get an error <code>Expected type name</code> pointing to the <code>WhoAreYou()</code> piece.</p>
  
  <p>It works fine if I replace <code>WhoAreYou()</code> with <code>WhoAreYou(Whoami)</code>, but in this case, the method does not need any parameters.. Is there a way to do this or is it simply not supported?</p>