conceptual block doest not zero out references, so the following code fails with an OutOfMemoryError.

memtest.scala

#!/bin/sh
exec scala -J-Xms80m -J-Xmx80m -deprecation -nocompdaemon "$0" "$@"
!#

def allocate(szInMb:Int=24) =
 Array.fill[Byte](1024*1024*szInMb)(util.Random.nextInt(256).toByte)

def testit = {
  val showStep = {var s=0 ; () => {s+=1 ; println(s"step$s")}}
  { showStep(); val x= allocate(20) }
  { showStep(); val x= allocate(20) }
  { showStep(); val x= allocate(20) }
  { showStep(); val x= allocate(20) }
}

testit