Why can't i define a variable recursively in a code block? scala> { | val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} | } <console>:9: error: forward reference extends over definition of value fibs val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} ^ scala> val fibs: Stream[Int] = 1 #:: fibs.scanLeft(1){_ + _} fibs: Stream[Int] = Stream(1, ?) lazy keyword solves this problem, but i can't understand why it works without a code block but throws a compilation error in a code block.