title: How to test arguments to a case class constructor?
body: <p>I'd like to test the arguments to my case class constructor and throw an exception if they fail certain tests.  The compiler complained when I tried to write my own apply method (Multiple 'apply' methods.</p>
  
  <p>I suppose I could make it a non-case class, and do the apply/unapply constructor field stuff myself, but I had hoped not to.</p>
  
  <p>Thanks</p>