scala 2.12.4: ParSeq broken in REPL?

[borice]

In REPL:

Welcome to Scala 2.12.4 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_151).
Type in expressions for evaluation. Or try :help.

scala> List("Smith","Jones","Frankenstein","Bach","Jackson","Rodin").par.map(_.toUpperCase)
... waits forever - no result ...

Same machine, now using Scala 2.11.7:

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_151).
Type in expressions to have them evaluated.
Type :help for more information.

scala> List("Smith","Jones","Frankenstein","Bach","Jackson","Rodin").par.map(_.toUpperCase)
res0: scala.collection.parallel.immutable.ParSeq[String] = ParVector(SMITH, JONES, FRANKENSTEIN, BACH, JACKSON, RODIN)

What's going on?

[borice]

Apparently this is only broken in the REPL.
A small compiled test app works fine:

object Main {

  def main(args: Array[String]): Unit = {
    List("Smith","Jones","Frankenstein","Bach","Jackson","Rodin").par.map(_.toUpperCase).foreach(println)
  }

}

[SethTisue]

duplicate of #9076