init - Weird initialisation when override val met DelayedInit in Scala -

following code's output makes me confused.

code

object test1 {   trait {     val s: string = "a"     println(s"s = $s")   }    abstract class b extends delayedinit {      override def delayedinit(body: => unit) = {       println("b " + "1" * 80)       body       println("b " + "2" * 80)     }   }    abstract class c extends delayedinit {      override val s: string = "c"      override def delayedinit(body: => unit) = {       println("c " + "1" * 80)       body       println("c " + "2" * 80)     }   }    def main {     println("-- new b begin")     new b {       println("new b context")     }     println("-- new b end")      println("-- new c begin")     new c {       println("new c context")     }     println("-- new c end")   } }  object test2 {   trait {     def s: string = "a"     println(s"s = $s")   }    abstract class b extends delayedinit {      override def delayedinit(body: => unit) = {       println("b " + "1" * 80)       body       println("b " + "2" * 80)     }   }    abstract class c extends delayedinit {      override def s: string = "c"      override def delayedinit(body: => unit) = {       println("c " + "1" * 80)       body       println("c " + "2" * 80)     }   }    def main {     println("-- new b begin")     new b {       println("new b context")     }     println("-- new b end")      println("-- new c begin")     new c {       println("new c context")     }     println("-- new c end")   } }  println("test1") test1.main println("test2") test2.main 

output

test1 -- new b begin s = b 11111111111111111111111111111111111111111111111111111111111111111111111111111111 new b context b 22222222222222222222222222222222222222222222222222222222222222222222222222222222 -- new b end -- new c begin s = null c 11111111111111111111111111111111111111111111111111111111111111111111111111111111 c 22222222222222222222222222222222222222222222222222222222222222222222222222222222 c 11111111111111111111111111111111111111111111111111111111111111111111111111111111 new c context c 22222222222222222222222222222222222222222222222222222222222222222222222222222222 -- new c end test2 -- new b begin s = b 11111111111111111111111111111111111111111111111111111111111111111111111111111111 new b context b 22222222222222222222222222222222222222222222222222222222222222222222222222222222 -- new b end -- new c begin s = c c 11111111111111111111111111111111111111111111111111111111111111111111111111111111 new c context c 22222222222222222222222222222222222222222222222222222222222222222222222222222222 -- new c end 

tried both scala 2.10.2 & 2.11.0-m3.

in understanding, test1 should same test2. here 2 questions:

• why delayedinit has been called twice in test1.c? there not other class inherits trait in class hierarchy
• why s == null in test1.c?

why delayedinit has been called twice in test1.c? there not other class inherits trait in class hierarchy

this looks bug, try reporting scala jira.

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why s == null in test1.c?

i'd it's because val in

override val s: string = "c" 

is backed internal variable , variable initialized during initializatino of c. , because delayedinit doesn't capture traits, initialization a performed before delayedinit, before c , val s initialized.

(it'd interesting if posted decompiled java code classes.)