title: Void-returning functions in UML sequence diagrams
body: <p>I have a problem with the sequence model seen in the diagram below, specifically where the System object is creating a new Number. In this case, there is no need for a return message since the function SaveInput(n), both in System and Number, is the end of the line for that portion of the program, but unless I include one, the modeller reshaped my diagram into the other one I've uploaded here, and I can't see how to arrange the messages so that my program will work the way I intend without including the return message (the one without a name) from Number to System, since the functions SaveInput() both return a void.</p>
  
  <p>How should void-returning functions be handled in sequence diagrams so that they behave correctly? I have opened the message properties and explicitly defined it as returning a void, but that hasn't helped.</p>
  
  <p><img src="https://i.stack.imgur.com/W6rWL.png" alt="enter image description here">
  <img src="https://i.stack.imgur.com/DcfBT.png" alt="enter image description here"></p>