title: What does "Forward reference extends over definition of value" mean in Scala?
body: <p>I keep getting</p>
  
  <pre><code>Forward reference extends over definition of value a
  </code></pre>
  
  <p>error while trying to compile my application (inside SBT).</p>
  
  <p><code>a</code> is just <code>val a = ""</code>, the error is triggered by accessing a particular parameter (of the function) right before <code>a</code> definition. The parameter is of a simple case class type with all three fields of <code>Option[...]</code> type (2 of <code>Option[org.joda.time.DateTime]</code> and 1 of Option of an enumeration value).</p>
  
  <p>What can "Forward reference extends over definition of value" mean at all and what can be the ways to fight it?</p>