Nil and List as case expressions in Scala

This code compiles:

def wtf(arg: Any) = {  
  arg match {  
    case Nil => "Nil was passed to arg"  
    case List() => "List() was passed to arg"  
    case _ =>"otherwise"  
  }  
}

But this one does not:

def wtf(arg: Any) = {  
  arg match {  
    case List() => "List() was passed to arg"  
    case Nil => "Nil was passed to arg"  
    case _ =>"otherwise"  
  }  
}  

The line case Nil => ... is marked as unreachable code. Why, in the first case, the line case List() => ... is not marked with the same error?