Forward References - why does this code compile?

Question

Consider this snippet:

 object A {
     val b = c
     val c = \"foo\"
 }
 println( A.b )   // prints \"null\"

As part of a larger program,

Answer 1

It is because of outdated version of Scala.

With Scala 2.11.5 it compiled with warning or doesn't compiled at all:

C:\Users\Andriy\Projects\com\github\plokhotnyuk>scala
Welcome to Scala version 2.11.5 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_31).
Type in expressions to have them evaluated.
Type :help for more information.

scala> { object A { val b = c; val c = "foo" }; println(A.b) }
:9: warning: Reference to uninitialized value c
              { object A { val b = c; val c = "foo" }; println(A.b) }
                                   ^
null

scala> { val b = c; val c = "foo"; println(A.b) }
:9: error: forward reference extends over definition of value b
              { val b = c; val c = "foo"; println(A.b) }
                        ^