Why are `privateval` and `private final val` different?

Question

I used to think that private val and private final val are same, until I saw section 4.1 in Scala Reference:

A constant valu

Answer 1

I think the confusion here arises from conflating immutability with the semantics of final. vals can be overridden in child classes and therefore can't be treated as final unless marked as such explicitly.

@Brian The REPL provides class scope at the line level. See:

scala> $iw.getClass.getPackage
res0: Package = package $line3

scala> private val x = 5
:5: error: value x cannot be accessed in object $iw
  lazy val $result = `x`

scala> private val x = 5; println(x);
5