Hooks for custom async implementations

src/main/scala/scala/async/internal/AsyncId.scala

@@ -50,6 +50,7 @@ object IdentityFutureSystem extends FutureSystem {
 
   type Fut[A] = A
   type ExecContext = Unit
+  type Tryy[A] = scala.util.Try[A]
 
   def mkOps(c: SymbolTable): Ops {val universe: c.type} = new Ops {
     val universe: c.type = c
@@ -59,6 +60,7 @@ object IdentityFutureSystem extends FutureSystem {
     def execContext: Expr[ExecContext] = Expr[Unit](Literal(Constant(())))
 
     def promType[A: WeakTypeTag]: Type = weakTypeOf[Prom[A]]
+    def tryType[A: WeakTypeTag]: Type = weakTypeOf[scala.util.Try[A]]
     def execContextType: Type = weakTypeOf[Unit]
 
     def createProm[A: WeakTypeTag]: Expr[Prom[A]] = reify {
@@ -71,15 +73,29 @@ object IdentityFutureSystem extends FutureSystem {
 
     def future[A: WeakTypeTag](t: Expr[A])(execContext: Expr[ExecContext]) = t
 
-    def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[scala.util.Try[A] => U],
+    def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[Tryy[A] => U],
                          execContext: Expr[ExecContext]): Expr[Unit] = reify {
       fun.splice.apply(util.Success(future.splice))
       Expr[Unit](Literal(Constant(()))).splice
     }
 
-    def completeProm[A](prom: Expr[Prom[A]], value: Expr[scala.util.Try[A]]): Expr[Unit] = reify {
+    def completeProm[A](prom: Expr[Prom[A]], value: Expr[Tryy[A]]): Expr[Unit] = reify {
       prom.splice.a = value.splice.get
       Expr[Unit](Literal(Constant(()))).splice
     }
+
+    def tryyIsFailure[A](tryy: Expr[Tryy[A]]): Expr[Boolean] = reify {
+      tryy.splice.isFailure
+    }
+
+    def tryyGet[A](tryy: Expr[Tryy[A]]): Expr[A] = reify {
+      tryy.splice.get
+    }
+    def tryySuccess[A: WeakTypeTag](a: Expr[A]): Expr[Tryy[A]] = reify {
+      scala.util.Success[A](a.splice)
+    }
+    def tryyFailure[A: WeakTypeTag](a: Expr[Throwable]): Expr[Tryy[A]] = reify {
+      scala.util.Failure[A](a.splice)
+    }
   }
 }

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

@@ -20,12 +20,14 @@ trait AsyncTransform {
     // Transform to A-normal form:
     //  - no await calls in qualifiers or arguments,
     //  - if/match only used in statement position.
-    val anfTree: Block = anfTransform(body)
+    val anfTree0: Block = anfTransform(body)
+
+    val anfTree = futureSystemOps.postAnfTransform(anfTree0)
 
     val resumeFunTreeDummyBody = DefDef(Modifiers(), name.resume, Nil, List(Nil), Ident(definitions.UnitClass), Literal(Constant(())))
 
     val applyDefDefDummyBody: DefDef = {
-      val applyVParamss = List(List(ValDef(Modifiers(Flag.PARAM), name.tr, TypeTree(defn.TryAnyType), EmptyTree)))
+      val applyVParamss = List(List(ValDef(Modifiers(Flag.PARAM), name.tr, TypeTree(futureSystemOps.tryType[Any]), EmptyTree)))
       DefDef(NoMods, name.apply, Nil, applyVParamss, TypeTree(definitions.UnitTpe), Literal(Constant(())))
     }
 

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

@@ -89,7 +89,7 @@ trait ExprBuilder {
       val tryGetTree =
         Assign(
           Ident(awaitable.resultName),
-          TypeApply(Select(Select(Ident(symLookup.applyTrParam), Try_get), newTermName("asInstanceOf")), List(TypeTree(awaitable.resultType)))
+          TypeApply(Select(futureSystemOps.tryyGet[T](Expr[futureSystem.Tryy[T]](Ident(symLookup.applyTrParam))).tree, newTermName("asInstanceOf")), List(TypeTree(awaitable.resultType)))
         )
 
       /* if (tr.isFailure)
@@ -101,12 +101,12 @@ trait ExprBuilder {
        * }
        */
       val ifIsFailureTree =
-        If(Select(Ident(symLookup.applyTrParam), Try_isFailure),
+        If(futureSystemOps.tryyIsFailure(Expr[futureSystem.Tryy[T]](Ident(symLookup.applyTrParam))).tree,
            futureSystemOps.completeProm[T](
              Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)),
-             Expr[scala.util.Try[T]](
+             Expr[futureSystem.Tryy[T]](
                TypeApply(Select(Ident(symLookup.applyTrParam), newTermName("asInstanceOf")),
-                         List(TypeTree(weakTypeOf[scala.util.Try[T]]))))).tree,
+                         List(TypeTree(futureSystemOps.tryType[T]))))).tree,
            Block(List(tryGetTree, mkStateTree(nextState, symLookup)), mkResumeApply(symLookup))
          )
 
@@ -325,7 +325,7 @@ trait ExprBuilder {
           val lastState = asyncStates.last
           val lastStateBody = Expr[T](lastState.body)
           val rhs = futureSystemOps.completeProm(
-            Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), reify(scala.util.Success[T](lastStateBody.splice)))
+            Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), futureSystemOps.tryySuccess[T](lastStateBody))
           mkHandlerCase(lastState.state, rhs.tree)
         }
         asyncStates.toList match {
@@ -368,7 +368,7 @@ trait ExprBuilder {
                 Apply(Ident(defn.NonFatalClass), List(Ident(name.t))), {
                   val t = Expr[Throwable](Ident(name.t))
                   futureSystemOps.completeProm[T](
-                    Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), reify(scala.util.Failure(t.splice))).tree
+                    Expr[futureSystem.Prom[T]](symLookup.memberRef(name.result)), futureSystemOps.tryyFailure[T](t)).tree
                 })), EmptyTree))
 
       /**

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

@@ -23,6 +23,8 @@ trait FutureSystem {
   type Fut[A]
   /** An execution context, required to create or register an on completion callback on a Future. */
   type ExecContext
+  /** Any data type isomorphic to scala.util.Try. */
+  type Tryy[T]
 
   trait Ops {
     val universe: reflect.internal.SymbolTable
@@ -31,6 +33,7 @@ trait FutureSystem {
     def Expr[T: WeakTypeTag](tree: Tree): Expr[T] = universe.Expr[T](rootMirror, universe.FixedMirrorTreeCreator(rootMirror, tree))
 
     def promType[A: WeakTypeTag]: Type
+    def tryType[A: WeakTypeTag]: Type
     def execContextType: Type
 
     /** Create an empty promise */
@@ -43,14 +46,23 @@ trait FutureSystem {
     def future[A: WeakTypeTag](a: Expr[A])(execContext: Expr[ExecContext]): Expr[Fut[A]]
 
     /** Register an call back to run on completion of the given future */
-    def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[scala.util.Try[A] => U],
+    def onComplete[A, U](future: Expr[Fut[A]], fun: Expr[Tryy[A] => U],
                          execContext: Expr[ExecContext]): Expr[Unit]
 
     /** Complete a promise with a value */
-    def completeProm[A](prom: Expr[Prom[A]], value: Expr[scala.util.Try[A]]): Expr[Unit]
+    def completeProm[A](prom: Expr[Prom[A]], value: Expr[Tryy[A]]): Expr[Unit]
 
     def spawn(tree: Tree, execContext: Tree): Tree =
       future(Expr[Unit](tree))(Expr[ExecContext](execContext)).tree
+
+    def tryyIsFailure[A](tryy: Expr[Tryy[A]]): Expr[Boolean]
+
+    def tryyGet[A](tryy: Expr[Tryy[A]]): Expr[A]
+    def tryySuccess[A: WeakTypeTag](a: Expr[A]): Expr[Tryy[A]]
+    def tryyFailure[A: WeakTypeTag](a: Expr[Throwable]): Expr[Tryy[A]]
+
+    /** A hook for custom macros to transform the tree post-ANF transform */
+    def postAnfTransform(tree: Block): Block = tree
   }
 
   def mkOps(c: SymbolTable): Ops { val universe: c.type }
@@ -63,13 +75,15 @@ object ScalaConcurrentFutureSystem extends FutureSystem {
   type Prom[A] = Promise[A]
   type Fut[A] = Future[A]
   type ExecContext = ExecutionContext
+  type Tryy[A] = scala.util.Try[A]
 
   def mkOps(c: SymbolTable): Ops {val universe: c.type} = new Ops {
     val universe: c.type = c
 
     import universe._
 
     def promType[A: WeakTypeTag]: Type = weakTypeOf[Promise[A]]
+    def tryType[A: WeakTypeTag]: Type = weakTypeOf[scala.util.Try[A]]
     def execContextType: Type = weakTypeOf[ExecutionContext]
 
     def createProm[A: WeakTypeTag]: Expr[Prom[A]] = reify {
@@ -93,5 +107,19 @@ object ScalaConcurrentFutureSystem extends FutureSystem {
       prom.splice.complete(value.splice)
       Expr[Unit](Literal(Constant(()))).splice
     }
+
+    def tryyIsFailure[A](tryy: Expr[scala.util.Try[A]]): Expr[Boolean] = reify {
+      tryy.splice.isFailure
+    }
+
+    def tryyGet[A](tryy: Expr[Tryy[A]]): Expr[A] = reify {
+      tryy.splice.get
+    }
+    def tryySuccess[A: WeakTypeTag](a: Expr[A]): Expr[Tryy[A]] = reify {
+      scala.util.Success[A](a.splice)
+    }
+    def tryyFailure[A: WeakTypeTag](a: Expr[Throwable]): Expr[Tryy[A]] = reify {
+      scala.util.Failure[A](a.splice)
+    }
   }
 }