import collection.generic.{FilterMonadic, CanBuildFrom}

object Test extends dotty.runtime.LegacyApp {
  def mapSucc[Repr, That](s: FilterMonadic[Int, Repr])(implicit cbf: CanBuildFrom[Repr, Int, That]) = s map (_ + 1)
  def flatMapId[T, Repr, That](s: FilterMonadic[T, Repr])(implicit cbf: CanBuildFrom[Repr, T, That]) = s flatMap (Seq(_))

  def testStreamPred(s: Stream[Int])(p: Int => Boolean): Unit = {
    val res1 = s withFilter p
    val res2 = s filter p

    val expected = s.toSeq filter p

    val fMapped1 = flatMapId(res1)
    val fMapped2 = flatMapId(res2)
    assert(fMapped1 == fMapped2)
    assert(fMapped1.toSeq == expected)

    val mapped1 = mapSucc(res1)
    val mapped2 = mapSucc(res2)
    assert(mapped1 == mapped2)
    assert(mapped1.toSeq == (expected map (_ + 1)))

    assert((res1 map identity).toSeq == res2.toSeq)
  }

  def testStream(s: Stream[Int]): Unit = {
    testStreamPred(s)(_ => false)
    testStreamPred(s)(_ => true)
    testStreamPred(s)(_ % 2 == 0)
    testStreamPred(s)(_ % 3 == 0)
  }

  //Reduced version of the test case - either invocation used to cause a stack
  //overflow before commit 80b3f433e5536d086806fa108ccdfacf10719cc2.
  val resFMap = (1 to 10000).toStream withFilter (_ => false) flatMap (Seq(_))
  val resMap = (1 to 10000).toStream withFilter (_ => false) map (_ + 1)

  //Complete test case for withFilter + map/flatMap, as requested by @axel22.
  for (j <- (0 to 3) :+ 10000) {
    val stream = (1 to j).toStream
    assert(stream.toSeq == (1 to j).toSeq)
    testStream(stream)
  }
}