Add missing overrides to FutureConvertersImpl.CF

Not sure why I missed those initially...

build.sbt

@@ -112,6 +112,7 @@ val mimaPrereleaseHandlingSettings = Seq(
     ProblemFilters.exclude[Problem]("scala.collection.convert.*"),
     ProblemFilters.exclude[Problem]("scala.collection.StepperShape.*"),
     ProblemFilters.exclude[Problem]("scala.jdk.*"),
+    ProblemFilters.exclude[DirectMissingMethodProblem]("scala.concurrent.impl.FutureConvertersImpl#CF.*"),
   ),
 )
 

src/library/scala/concurrent/impl/FutureConvertersImpl.scala

@@ -12,19 +12,84 @@
 
 package scala.concurrent.impl
 
-import java.util.concurrent.{CompletableFuture, CompletionStage}
-import java.util.function.BiConsumer
+import java.util.concurrent.{CompletableFuture, CompletionStage, TimeUnit}
+import java.util.function.{BiConsumer, BiFunction, Consumer, Function => JFunction}
 
 import scala.concurrent.Future
 import scala.concurrent.impl.Promise.DefaultPromise
 import scala.util.{Failure, Success, Try}
 
-object FutureConvertersImpl {
+private[scala] object FutureConvertersImpl {
   final class CF[T](val wrapped: Future[T]) extends CompletableFuture[T] with (Try[T] => Unit) {
     override def apply(t: Try[T]): Unit = t match {
       case Success(v) => complete(v)
       case Failure(e) => completeExceptionally(e)
     }
+
+    // Ensure that completions of this future cannot hold the Scala Future's completer hostage
+
+    override def thenApply[U](fn: JFunction[_ >: T, _ <: U]): CompletableFuture[U] = thenApplyAsync(fn)
+
+    override def thenAccept(fn: Consumer[_ >: T]): CompletableFuture[Void] = thenAcceptAsync(fn)
+
+    override def thenRun(fn: Runnable): CompletableFuture[Void] = thenRunAsync(fn)
+
+    override def thenCombine[U, V](cs: CompletionStage[_ <: U], fn: BiFunction[_ >: T, _ >: U, _ <: V]): CompletableFuture[V] = thenCombineAsync(cs, fn)
+
+    override def thenAcceptBoth[U](cs: CompletionStage[_ <: U], fn: BiConsumer[_ >: T, _ >: U]): CompletableFuture[Void] = thenAcceptBothAsync(cs, fn)
+
+    override def runAfterBoth(cs: CompletionStage[_], fn: Runnable): CompletableFuture[Void] = runAfterBothAsync(cs, fn)
+
+    override def applyToEither[U](cs: CompletionStage[_ <: T], fn: JFunction[_ >: T, U]): CompletableFuture[U] = applyToEitherAsync(cs, fn)
+
+    override def acceptEither(cs: CompletionStage[_ <: T], fn: Consumer[_ >: T]): CompletableFuture[Void] = acceptEitherAsync(cs, fn)
+
+    override def runAfterEither(cs: CompletionStage[_], fn: Runnable): CompletableFuture[Void] = runAfterEitherAsync(cs, fn)
+
+    override def thenCompose[U](fn: JFunction[_ >: T, _ <: CompletionStage[U]]): CompletableFuture[U] = thenComposeAsync(fn)
+
+    override def whenComplete(fn: BiConsumer[_ >: T, _ >: Throwable]): CompletableFuture[T] = whenCompleteAsync(fn)
+
+    override def handle[U](fn: BiFunction[_ >: T, Throwable, _ <: U]): CompletableFuture[U] = handleAsync(fn)
+
+    override def exceptionally(fn: JFunction[Throwable, _ <: T]): CompletableFuture[T] = {
+      val cf = new CompletableFuture[T]
+      whenCompleteAsync((t: T, e: Throwable) => { // param types for dotty b213f24ff (fixed in current dotty master, 311b8512c)
+          if (e == null) cf.complete(t)
+          else {
+            val n: AnyRef =
+              try {
+                fn(e).asInstanceOf[AnyRef]
+              } catch {
+                case thr: Throwable =>
+                  cf.completeExceptionally(thr)
+                  this
+              }
+            if (n ne this) cf.complete(n.asInstanceOf[T])
+          }
+          () // for dotty b213f24ff (fixed in current dotty master, 311b8512c)
+        }
+      )
+      cf
+    }
+
+    /**
+      * @inheritdoc
+      *
+      * WARNING: completing the result of this method will not complete the underlying
+      *          Scala Future or Promise (ie, the one that that was passed to `toJava`.)
+      */
+    override def toCompletableFuture: CompletableFuture[T] = this
+
+    override def obtrudeValue(value: T): Unit = throw new UnsupportedOperationException("obtrudeValue may not be used on the result of toJava(scalaFuture)")
+
+    override def obtrudeException(ex: Throwable): Unit = throw new UnsupportedOperationException("obtrudeException may not be used on the result of toJava(scalaFuture)")
+
+    override def get(): T = scala.concurrent.blocking(super.get())
+
+    override def get(timeout: Long, unit: TimeUnit): T = scala.concurrent.blocking(super.get(timeout, unit))
+
+    override def toString(): String = super[CompletableFuture].toString
   }
 
   final class P[T](val wrapped: CompletionStage[T]) extends DefaultPromise[T] with BiConsumer[T, Throwable] {

src/library/scala/jdk/FutureConverters.scala

@@ -66,8 +66,7 @@ object FutureConverters {
       case c: CompletionStage[T] => c
       case _ =>
         val cf = new CF[T](f)
-        implicit val ec = ExecutionContext.parasitic
-        f onComplete cf
+        f.onComplete(cf)(ExecutionContext.parasitic)
         cf
     }
   }