=str 20843 Scan failure should flow downstream ASAP

akka-stream-tests/src/test/scala/akka/stream/scaladsl/FlowScanSpec.scala

@@ -71,10 +71,9 @@ class FlowScanSpec extends AkkaSpec {
         .expectNext(0)
         .expectComplete()
     }
-    "fail after emitting first element when upsrteam failed" in {
+    "fail when upstream failed" in {
       Source.failed[Int](TE("")).scan(0) { case (a, b) ⇒ a + b }.runWith(TestSink.probe[Int])
         .request(2)
-        .expectNext(0)
         .expectError(TE(""))
     }
   }

akka-stream/src/main/scala/akka/stream/impl/fusing/Ops.scala

@@ -324,12 +324,6 @@ private[akka] final case class Scan[In, Out](zero: Out, f: (Out, In) ⇒ Out) ex
             completeStage()
           }
         })
-        override def onUpstreamFailure(ex: Throwable): Unit = setHandler(out, new OutHandler {
-          override def onPull(): Unit = {
-            push(out, aggregator)
-            failStage(ex)
-          }
-        })
       })
 
       override def onPull(): Unit = pull(in)