gistfile1.scala

// WHY DOES PATTERN MATCH EXHAUSTIVENESS CHECK ONLY WORK WHEN 
// THE CASE CLASS IS SEALED?
case class Foo(a: Option[String])
sealed case class Bar(a: Option[String])
sealed trait Zed
case class Alpha(a: Option[String]) extends Zed

// This causes a scala matchError at runtime
Foo(None) match {
  case Foo(Some(x)) => x
}

// This causes compile time exhaustive-ness warning
Bar(None) match {
  case Bar(Some(x)) => x
}

// This causes a scala matchError at runtime
Alpha(None) match {
  case Alpha(Some(x)) => x
}