Compilation error 'A is not class' when using generic parameters in async/await fututures.

src/main/scala/scala/async/internal/TransformUtils.scala

@@ -331,7 +331,7 @@ private[async] trait TransformUtils {
     (cls.info.decls.find(sym => sym.isMethod && sym.asTerm.isParamAccessor) getOrElse NoSymbol)
 
   def mkZero(tp: Type): Tree = {
-    if (tp.typeSymbol.asClass.isDerivedValueClass) {
+    if (tp.typeSymbol.isClass && tp.typeSymbol.asClass.isDerivedValueClass) {
       val argZero = mkZero(derivedValueClassUnbox(tp.typeSymbol).infoIn(tp).resultType)
       val baseType = tp.baseType(tp.typeSymbol) // use base type here to dealias / strip phantom "tagged types" etc.
 

src/test/scala/scala/async/run/gen0/AsyncSpec.scala

@@ -0,0 +1,46 @@
+package scala.async
+package run
+package gen0
+
+import language.{reflectiveCalls, postfixOps}
+import scala.concurrent.{Future, ExecutionContext, future, Await}
+import scala.concurrent.duration._
+import scala.async.Async.{async, await}
+import org.junit.Test
+
+class TestS[A](a:A)
+{
+
+  def awrite(v:A): Future[A] =
+      Future successful v
+
+  def aread: Future[A] =
+      Future successful a
+
+}
+
+class Test1GenAsyncOp[A] {
+
+  import ExecutionContext.Implicits.global
+
+  def testfun[A](a1:A,a2:A): Future[Boolean] = async {
+       val ts = new TestS(a1)
+       val s1 = await(ts.awrite(a2))
+       val s2 = await(ts.aread)
+       s1 == s2
+  }
+
+}
+
+
+class AsyncSpec {
+
+  @Test
+  def `operation with futures generic`() {
+    val op = new Test1GenAsyncOp[Int]
+    val f = op.testfun(1,2)
+    val res = Await.result(f, 2 seconds)
+    res mustBe (false)
+  }
+
+}