Fix misuse of underscores.

It's a language bug, but M[_] <: Foo[_] does not mean what
anyone who writes it believes that it means. You have to give
the type parameter a name, like M[X] <: Foo[X].

1 files changed, 4 insertions, 4 deletions

diff --git a/src/library/scala/concurrent/Future.scala b/src/library/scala/concurrent/Future.scala
index d271c4cdeb..4ed0687334 100644
--- a/src/library/scala/concurrent/Future.scala
+++ b/src/library/scala/concurrent/Future.scala
@@ -494,9 +494,9 @@ object Future {
   /** Simple version of `Future.traverse`. Transforms a `TraversableOnce[Future[A]]` into a `Future[TraversableOnce[A]]`.
    *  Useful for reducing many `Future`s into a single `Future`.
    */
-  def sequence[A, M[_] <: TraversableOnce[_]](in: M[Future[A]])(implicit cbf: CanBuildFrom[M[Future[A]], A, M[A]], executor: ExecutionContext): Future[M[A]] = {
+  def sequence[A, M[X] <: TraversableOnce[X]](in: M[Future[A]])(implicit cbf: CanBuildFrom[M[Future[A]], A, M[A]], executor: ExecutionContext): Future[M[A]] = {
     in.foldLeft(successful(cbf(in))) {
-      (fr, fa) => for (r <- fr; a <- fa.asInstanceOf[Future[A]]) yield (r += a)
+      (fr, fa) => for (r <- fr; a <- fa) yield (r += a)
     } map (_.result())
   }
 
@@ -569,9 +569,9 @@ object Future {
    *    val myFutureList = Future.traverse(myList)(x => Future(myFunc(x)))
    *  }}}
    */
-  def traverse[A, B, M[_] <: TraversableOnce[_]](in: M[A])(fn: A => Future[B])(implicit cbf: CanBuildFrom[M[A], B, M[B]], executor: ExecutionContext): Future[M[B]] =
+  def traverse[A, B, M[X] <: TraversableOnce[X]](in: M[A])(fn: A => Future[B])(implicit cbf: CanBuildFrom[M[A], B, M[B]], executor: ExecutionContext): Future[M[B]] =
     in.foldLeft(successful(cbf(in))) { (fr, a) =>
-      val fb = fn(a.asInstanceOf[A])
+      val fb = fn(a)
       for (r <- fr; b <- fb) yield (r += b)
     }.map(_.result())