Make `f(await(completedFuture))` execute `f` synchronously

A worthy optimization, suggested by @danarmak.

Closes #73

1 files changed, 28 insertions, 0 deletions

diff --git a/src/test/scala/scala/async/run/SyncOptimizationSpec.scala b/src/test/scala/scala/async/run/SyncOptimizationSpec.scala
new file mode 100644
index 0000000..dd649f4
--- /dev/null
+++ b/src/test/scala/scala/async/run/SyncOptimizationSpec.scala
@@ -0,0 +1,28 @@
+package scala.async.run
+
+import org.junit.Test
+import scala.async.Async._
+import scala.concurrent._
+import scala.concurrent.duration._
+import ExecutionContext.Implicits._
+
+class SyncOptimizationSpec {
+  @Test
+  def awaitOnCompletedFutureRunsOnSameThread: Unit = {
+
+    def stackDepth = Thread.currentThread().getStackTrace.size
+
+    val future = async {
+      val thread1 = Thread.currentThread
+      val stackDepth1 = stackDepth
+
+      val f = await(Future.successful(1))
+      val thread2 = Thread.currentThread
+      val stackDepth2 = stackDepth
+      assert(thread1 == thread2)
+      assert(stackDepth1 == stackDepth2)
+    }
+    Await.result(future, 10.seconds)
+  }
+
+}