Is this a known repl bug?

Question
1 
$ scala
Welcome to Scala 2.12.6 (OpenJDK 64-Bit Server VM, Java 11).
Type in expressions for evaluation. Or try :help.


scala> import scala.concurrent._, duration._, ExecutionContext.Implicits._
import scala.concurrent._
import duration._
import ExecutionContext.Implicits._

scala> Await.result(Future(Thread.sleep(10)), 1.second)
java.lang.NoClassDefFoundError: Could not initialize class $line13.$read$$iw$$iw$$iw$$iw$$iw$$iw$$iw$$iw$
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:12)
        at scala.concurrent.Future$.$anonfun$apply$1(Future.scala:654)
        at scala.util.Success.$anonfun$map$1(Try.scala:251)
        at scala.util.Success.map(Try.scala:209)
        at scala.concurrent.Future.$anonfun$map$1(Future.scala:288)
        at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:29)
        at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:29)
        at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:60)
        at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
        at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
        at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
        at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
        at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
        at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:177)
java.util.concurrent.TimeoutException: Futures timed out after [1 second]
  at scala.concurrent.impl.Promise$DefaultPromise.ready(Promise.scala:255)
  at scala.concurrent.impl.Promise$DefaultPromise.result(Promise.scala:259)
  at scala.concurrent.Await$.$anonfun$result$1(package.scala:215)
  at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
  at scala.concurrent.Await$.result(package.scala:142)
  ... 28 elided
2

Yes, there is discussion at the issue, with more links, and the workaround scala -Yrepl-class-based.

There is a skunkworks to eliminate this problem for 2.13. Skunkwork because of the code smells.