From 4c1c9fcf075d6e1e5975a04c5a2ced674716069a Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Fri, 23 Nov 2012 15:58:13 +0100
Subject: Fix #31, Unfinished ANF transform

Prepend {(); ... } before starting the ANF transform.

Add tracing to the anf/inline transform.

Also enables and addresses SIP-18 warnings.
---
 build.sbt                                          |  4 +--
 src/main/scala/scala/async/AnfTransform.scala      | 35 +++++++++++++++++++---
 src/main/scala/scala/async/Async.scala             |  7 ++---
 src/test/scala/scala/async/TreeInterrogation.scala |  2 +-
 .../scala/async/run/anf/AnfTransformSpec.scala     | 33 ++++++++++++++++++++
 5 files changed, 69 insertions(+), 12 deletions(-)

diff --git a/build.sbt b/build.sbt
index ba0544b..9b0a6bd 100644
--- a/build.sbt
+++ b/build.sbt
@@ -30,9 +30,9 @@ libraryDependencies <<= (scalaVersion, libraryDependencies) {
 
 scalacOptions += "-P:continuations:enable"
 
-scalacOptions ++= Seq("-deprecation", "-unchecked", "-Xlint")
+scalacOptions ++= Seq("-deprecation", "-unchecked", "-Xlint", "-feature")
 
-description := "An asynchronous programminig facility for Scala, in the spirit of C# await/async"
+description := "An asynchronous programming facility for Scala, in the spirit of C# await/async"
 
 homepage := Some(url("http://github.com/phaller/scala-async"))
 
diff --git a/src/main/scala/scala/async/AnfTransform.scala b/src/main/scala/scala/async/AnfTransform.scala
index 6bf6e9a..a69fd4e 100644
--- a/src/main/scala/scala/async/AnfTransform.scala
+++ b/src/main/scala/scala/async/AnfTransform.scala
@@ -3,11 +3,21 @@ package scala.async
 
 import scala.reflect.macros.Context
 
+object AnfTranform {
+  def apply[C <: Context](c: C): AnfTransform[c.type] = new AnfTransform[c.type](c)
+}
+
 class AnfTransform[C <: Context](override val c: C) extends TransformUtils(c) {
 
   import c.universe._
 
-  def uniqueNames(tree: Tree): Tree = {
+  def apply(tree: Tree): List[Tree] = {
+    val unique = uniqueNames(tree)
+    // Must prepend the () for issue #31.
+    anf.transformToList(Block(List(c.literalUnit.tree), unique))
+  }
+
+  private def uniqueNames(tree: Tree): Tree = {
     new UniqueNames(tree).transform(tree)
   }
 
@@ -65,8 +75,25 @@ class AnfTransform[C <: Context](override val c: C) extends TransformUtils(c) {
     }
   }
 
+  final class Indent {
+    private var indent = -1
+    def indentString = "  " * indent
+    def apply[T](prefix: String, args: Any)(t: => T): T = {
+      indent += 1
+      try {
+        //println(s"${indentString}$prefix($args)")
+        val result = t
+        //println(s"${indentString}= $result")
+        result
+      } finally {
+        indent -= 1
+      }
+    }
+  }
+  private val indent = new Indent
+
   object inline {
-    def transformToList(tree: Tree): List[Tree] = {
+    def transformToList(tree: Tree): List[Tree] = indent("inline", tree) {
       val stats :+ expr = anf.transformToList(tree)
       expr match {
         case Apply(fun, args) if isAwait(fun) =>
@@ -133,9 +160,9 @@ class AnfTransform[C <: Context](override val c: C) extends TransformUtils(c) {
       vd
     }
   }
-
   object anf {
-    def transformToList(tree: Tree): List[Tree] = {
+
+    private[AnfTransform] def transformToList(tree: Tree): List[Tree] = indent("anf", tree) {
       def containsAwait = tree exists isAwait
       tree match {
         case Select(qual, sel) if containsAwait =>
diff --git a/src/main/scala/scala/async/Async.scala b/src/main/scala/scala/async/Async.scala
index 0b77c78..ed79d0b 100644
--- a/src/main/scala/scala/async/Async.scala
+++ b/src/main/scala/scala/async/Async.scala
@@ -78,12 +78,9 @@ abstract class AsyncBase {
     //  - no await calls in qualifiers or arguments,
     //  - if/match only used in statement position.
     val anfTree: Block = {
-      val transform = new AnfTransform[c.type](c)
-      val unique = transform.uniqueNames(body.tree)
-      val stats1 :+ expr1 = transform.anf.transformToList(unique)
-
+      val anf = AnfTranform(c)
+      val stats1 :+ expr1 = anf(body.tree)
       val block = Block(stats1, expr1)
-
       c.typeCheck(block).asInstanceOf[Block]
     }
 
diff --git a/src/test/scala/scala/async/TreeInterrogation.scala b/src/test/scala/scala/async/TreeInterrogation.scala
index 9e68005..16cbcf7 100644
--- a/src/test/scala/scala/async/TreeInterrogation.scala
+++ b/src/test/scala/scala/async/TreeInterrogation.scala
@@ -11,7 +11,7 @@ class TreeInterrogation {
   def `a minimal set of vals are lifted to vars`() {
     val cm = reflect.runtime.currentMirror
     val tb = mkToolbox("-cp target/scala-2.10/classes")
-    val tree = mkToolbox().parse(
+    val tree = tb.parse(
       """| import _root_.scala.async.AsyncId._
         | async {
         |   val x = await(1)
diff --git a/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala b/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
index 872e44d..8bdb80f 100644
--- a/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
+++ b/src/test/scala/scala/async/run/anf/AnfTransformSpec.scala
@@ -172,4 +172,37 @@ class AnfTransformSpec {
     }
     result mustBe (103)
   }
+
+  @Test
+  def nestedAwaitAsBareExpression() {
+    import ExecutionContext.Implicits.global
+    import _root_.scala.async.AsyncId.{async, await}
+    val result = async {
+      await(await("").isEmpty)
+    }
+    result mustBe (true)
+  }
+
+  @Test
+  def nestedAwaitInBlock() {
+    import ExecutionContext.Implicits.global
+    import _root_.scala.async.AsyncId.{async, await}
+    val result = async {
+      ()
+      await(await("").isEmpty)
+    }
+    result mustBe (true)
+  }
+
+  @Test
+  def nestedAwaitInIf() {
+    import ExecutionContext.Implicits.global
+    import _root_.scala.async.AsyncId.{async, await}
+    val result = async {
+      if ("".isEmpty)
+        await(await("").isEmpty)
+      else 0
+    }
+    result mustBe (true)
+  }
 }
-- 
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