1 files changed, 110 insertions, 0 deletions
diff --git a/src/main/scala/scala/async/AsyncAnalysis.scala b/src/main/scala/scala/async/AsyncAnalysis.scala
new file mode 100644
index 0000000..1b00620
--- /dev/null
+++ b/src/main/scala/scala/async/AsyncAnalysis.scala
@@ -0,0 +1,110 @@
+package scala.async
+
+import scala.reflect.macros.Context
+import collection.mutable
+
+private[async] final class AsyncAnalysis[C <: Context](override val c: C) extends TransformUtils(c) {
+  import c.universe._
+
+  /**
+   * Analyze the contents of an `async` block in order to:
+   * - Report unsupported `await` calls under nested templates, functions, by-name arguments.
+   *
+   * Must be called on the original tree, not on the ANF transformed tree.
+   */
+  def reportUnsupportedAwaits(tree: Tree) {
+    new UnsupportedAwaitAnalyzer().traverse(tree)
+  }
+
+  /**
+   * Analyze the contents of an `async` block in order to:
+   * - Find which local `ValDef`-s need to be lifted to fields of the state machine, based
+   * on whether or not they are accessed only from a single state.
+   *
+   * Must be called on the ANF transformed tree.
+   */
+  def valDefsUsedInSubsequentStates(tree: Tree): List[ValDef] = {
+    val analyzer = new AsyncDefinitionUseAnalyzer
+    analyzer.traverse(tree)
+    analyzer.valDefsToLift.toList
+  }
+
+  private class UnsupportedAwaitAnalyzer extends super.AsyncTraverser {
+    override def nestedClass(classDef: ClassDef) {
+      val kind = if (classDef.symbol.asClass.isTrait) "trait" else "class"
+      reportUnsupportedAwait(classDef, s"nested $kind")
+    }
+
+    override def nestedModule(module: ModuleDef) {
+      reportUnsupportedAwait(module, "nested object")
+    }
+
+    override def byNameArgument(arg: Tree) {
+      reportUnsupportedAwait(arg, "by-name argument")
+    }
+
+    override def function(function: Function) {
+      reportUnsupportedAwait(function, "nested function")
+    }
+
+    private def reportUnsupportedAwait(tree: Tree, whyUnsupported: String) {
+      val badAwaits = tree collect {
+        case rt: RefTree if isAwait(rt) => rt
+      }
+      badAwaits foreach {
+        tree =>
+          c.error(tree.pos, s"await must not be used under a $whyUnsupported.")
+      }
+   }
+  }
+
+  private class AsyncDefinitionUseAnalyzer extends super.AsyncTraverser {
+    private var chunkId = 0
+
+    private def nextChunk() = chunkId += 1
+
+    private var valDefChunkId = Map[Symbol, (ValDef, Int)]()
+
+    val valDefsToLift: mutable.Set[ValDef] = collection.mutable.Set[ValDef]()
+
+    override def traverse(tree: Tree) = {
+      tree match {
+        case If(cond, thenp, elsep) if tree exists isAwait =>
+          traverseChunks(List(cond, thenp, elsep))
+        case Match(selector, cases) if tree exists isAwait =>
+          traverseChunks(selector :: cases)
+        case Apply(fun, args) if isAwait(fun)              =>
+          super.traverse(tree)
+          nextChunk()
+        case vd: ValDef                                    =>
+          super.traverse(tree)
+          valDefChunkId += (vd.symbol ->(vd, chunkId))
+          if (isAwait(vd.rhs)) valDefsToLift += vd
+        case as: Assign                                    =>
+          if (isAwait(as.rhs)) {
+            // TODO test the orElse case, try to remove the restriction.
+            if (as.symbol != null) {
+              // synthetic added by the ANF transfor
+              val (vd, defBlockId) = valDefChunkId.getOrElse(as.symbol, c.abort(as.pos, "await may only be assigned to a var/val defined in the async block. " + as.symbol))
+              valDefsToLift += vd
+            }
+          }
+          super.traverse(tree)
+        case rt: RefTree                                   =>
+          valDefChunkId.get(rt.symbol) match {
+            case Some((vd, defChunkId)) if defChunkId != chunkId =>
+              valDefsToLift += vd
+            case _                                               =>
+          }
+          super.traverse(tree)
+        case _                                             => super.traverse(tree)
+      }
+    }
+
+    private def traverseChunks(trees: List[Tree]) {
+      trees.foreach {
+        t => traverse(t); nextChunk()
+      }
+    }
+  }
+}