object Test extends App {
  @annotation.tailrec def test(list: List[Int] = Nil, i: Int = 0): Unit = {
    println(i)
    test(i :: list, i+1)
  }
  test()
}

java -Xmx1G -Xms1G -classpath .:/usr/share/scala/lib/scala-library.jar Test

21269711 // not an OutOfMemoryError, but sooo sloooow


Adding to Vector is incredably slow, use VectorBuilder, you should get the same capacity:

import scala.collection.immutable.VectorBuilder

object TestVectorBuilder extends App {
  val b = new VectorBuilder[Int]
  for { i <- 1 to Int.MaxValue} {
    println(i)
    b += i
  }
}

java -Xmx1G -Xms1G -classpath .:/usr/share/scala/lib/scala-library.jar TestVectorBuilder

47754251 // OutOfMemoryError

This works fine without OutOfMemoryError:

scala -J-Xmx1G -J-Xms1G -e '(1 to 45000000).toVector foreach println'