Hooks to customize code generation

Author: retronym

src/main/scala/scala/async/internal/AsyncTransform.scala

@@ -50,7 +50,7 @@ trait AsyncTransform {
       }
 
       val tryToUnit = appliedType(definitions.FunctionClass(1), futureSystemOps.tryType[Any], typeOf[Unit])
-      val template = Template(List(tryToUnit, typeOf[() => Unit]).map(TypeTree(_)), emptyValDef, body)
+      val template = Template((futureSystemOps.stateMachineClassParents ::: List(tryToUnit, typeOf[() => Unit])).map(TypeTree(_)), emptyValDef, body)
 
       val t = ClassDef(NoMods, name.stateMachineT, Nil, template)
       typecheckClassDef(t)

src/main/scala/scala/async/internal/ExprBuilder.scala

@@ -357,8 +357,8 @@ trait ExprBuilder {
         val caseForLastState: CaseDef = {
           val lastState = asyncStates.last
           val lastStateBody = c.Expr[T](lastState.body)
-          val rhs = futureSystemOps.completeProm(
-            c.Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), futureSystemOps.tryySuccess[T](lastStateBody))
+          val rhs = futureSystemOps.completeWithSuccess(
+            c.Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), lastStateBody)
           mkHandlerCase(lastState.state, Block(rhs.tree, Return(literalUnit)))
         }
         asyncStates.toList match {

src/main/scala/scala/async/internal/FutureSystem.scala

@@ -33,6 +33,7 @@ trait FutureSystem {
     def promType[A: WeakTypeTag]: Type
     def tryType[A: WeakTypeTag]: Type
     def execContextType: Type
+    def stateMachineClassParents: List[Type] = Nil
 
     /** Create an empty promise */
     def createProm[A: WeakTypeTag]: Expr[Prom[A]]
@@ -55,6 +56,7 @@ trait FutureSystem {
 
     /** Complete a promise with a value */
     def completeProm[A](prom: Expr[Prom[A]], value: Expr[Tryy[A]]): Expr[Unit]
+    def completeWithSuccess[A: WeakTypeTag](prom: Expr[Prom[A]], value: Expr[A]): Expr[Unit] = completeProm(prom, tryySuccess(value))
 
     def spawn(tree: Tree, execContext: Tree): Tree =
       future(c.Expr[Unit](tree))(c.Expr[ExecContext](execContext)).tree