Gen.sequence seems to forget that ScalaCheck is a Scala lib (1.12.1)

Consider the following console session, with ScalaCheck 1.12.1:

scala> import org.scalacheck.Gen
import org.scalacheck.Gen

scala> import org.scalacheck.Arbitrary._
import org.scalacheck.Arbitrary._

scala> val genInts = Gen.nonEmptyListOf(arbitrary[Int])
genInts: org.scalacheck.Gen[List[Int]] = org.scalacheck.Gen$$anon$2@393c86dd

scala> case class Bar(str: String, i: Int)
defined class Bar

scala> def genBarWith(i: Int) = for { str <- arbitrary[String] } yield Bar(str, i)
genBarWith: (i: Int)org.scalacheck.Gen[Bar]

scala> val genBarList = for { ints <- genInts; bars <- Gen.sequence { ints.map(genBarWith) } } yield bars
genBarList: org.scalacheck.Gen[java.util.ArrayList[Bar]] = org.scalacheck.Gen$$anon$6@2d97c1a

scala> val genBarList2 = for { ints <- genInts; bars <- Gen.sequence[List[Bar], Bar] { ints.map(genBarWith) } } yield bars
genBarList2: org.scalacheck.Gen[List[Bar]] = org.scalacheck.Gen$$anon$6@57b19137

Incidentally, the type parameters on genBarList2 cause IntelliJ to refuse to compile, although sbt and the REPL are fine with it.

To get back to Scala-land, I have to import scala.collection.JavaConverters._ and map on the generator with .map(_.asScala.toList).

Happy New Year! 😃

Start by reproducing the ScalaCheck 1.12.1 console session and inspect the Gen.sequence entry point, comparing the inferred result with the explicitly typed List result. Done means sequence preserves the expected Scala collection type without requiring JavaConverters or explicit type parameters.