=str Mark as final

Author: He-Pin

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

@@ -150,7 +150,7 @@ private[akka] object FlattenConcat {
     def isClosed: Boolean
   }
 
-  class InflightSingleSource[T](elem: T) extends InflightSource[T] {
+  final class InflightSingleSource[T](elem: T) extends InflightSource[T] {
     private var _hasNext = true
     override def materialize(): Unit =
       new UnsupportedOperationException("Do not need materialization for InflightSingleSource.")
@@ -165,7 +165,7 @@ private[akka] object FlattenConcat {
     override def isClosed: Boolean = !hasNext
   }
 
-  class InflightIterableSource[T](elements: Iterable[T]) extends InflightSource[T] {
+  final class InflightIterableSource[T](elements: Iterable[T]) extends InflightSource[T] {
     private val iterator: Iterator[T] = elements.iterator
     override def materialize(): Unit =
       new UnsupportedOperationException("Do not need materialization for InflightSingleSource.")
@@ -176,7 +176,7 @@ private[akka] object FlattenConcat {
     override def isClosed: Boolean = !hasNext
   }
 
-  object InflightEmptySource extends InflightSource[Any] {
+  final object InflightEmptySource extends InflightSource[Any] {
     override def materialize(): Unit =
       new UnsupportedOperationException("Do not need materialization for InflightSingleSource.")
     override def hasNext: Boolean = false