Support await in throws.

Also support AsyncId.async[Nothing], which was triggering a NPE
in the generated `null.asInstanceOf[Nothing]`.

3 files changed, 18 insertions, 2 deletions

diff --git a/src/main/scala/scala/async/internal/AnfTransform.scala b/src/main/scala/scala/async/internal/AnfTransform.scala
index 49cc3c3..7b30590 100644
--- a/src/main/scala/scala/async/internal/AnfTransform.scala
+++ b/src/main/scala/scala/async/internal/AnfTransform.scala
@@ -164,6 +164,10 @@ private[async] trait AnfTransform {
             val stats :+ expr = linearize.transformToList(qual)
             stats :+ treeCopy.Select(tree, expr, sel)
 
+          case Throw(expr) =>
+            val stats :+ expr1 = linearize.transformToList(expr)
+            stats :+ treeCopy.Throw(tree, expr1)
+
           case treeInfo.Applied(fun, targs, argss) if argss.nonEmpty =>
             // we an assume that no await call appears in a by-name argument position,
             // this has already been checked.
diff --git a/src/main/scala/scala/async/internal/AsyncId.scala b/src/main/scala/scala/async/internal/AsyncId.scala
index 394f587..4334088 100644
--- a/src/main/scala/scala/async/internal/AsyncId.scala
+++ b/src/main/scala/scala/async/internal/AsyncId.scala
@@ -23,7 +23,9 @@ object AsyncId extends AsyncBase {
  */
 object IdentityFutureSystem extends FutureSystem {
 
-  class Prom[A](var a: A)
+  class Prom[A] {
+    var a: A = _
+  }
 
   type Fut[A] = A
   type ExecContext = Unit
@@ -39,7 +41,7 @@ object IdentityFutureSystem extends FutureSystem {
     def execContextType: Type = weakTypeOf[Unit]
 
     def createProm[A: WeakTypeTag]: Expr[Prom[A]] = reify {
-      new Prom(null.asInstanceOf[A])
+      new Prom()
     }
 
     def promiseToFuture[A: WeakTypeTag](prom: Expr[Prom[A]]) = reify {
diff --git a/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala b/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
index e389a19..ed9f506 100644
--- a/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
+++ b/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
@@ -348,4 +348,14 @@ class AnfTransformSpec {
       foo(await(0), List(id(1), id(2), id(3)): _*)
     } mustBe (List(1, 2, 3))
   }
+
+  @Test
+  def awaitInThrow() {
+    import _root_.scala.async.internal.AsyncId.{async, await}
+    intercept[Exception](
+      async {
+        throw new Exception("msg: " + await(0))
+      }
+    ).getMessage mustBe "msg: 0"
+  }
 }