From 08bd93c20bcdd1bddc172c1477e811e8fc7f8ebd Mon Sep 17 00:00:00 2001
From: Jason Zaugg <jzaugg@gmail.com>
Date: Fri, 23 Nov 2012 23:44:24 +0100
Subject: Prohibit return.

Closes #21
---
 src/main/scala/scala/async/AsyncAnalysis.scala  |  2 ++
 src/test/scala/scala/async/neg/NakedAwait.scala | 12 ++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/main/scala/scala/async/AsyncAnalysis.scala b/src/main/scala/scala/async/AsyncAnalysis.scala
index 38fd22f..e319fe8 100644
--- a/src/main/scala/scala/async/AsyncAnalysis.scala
+++ b/src/main/scala/scala/async/AsyncAnalysis.scala
@@ -62,6 +62,8 @@ private[async] final case class AsyncAnalysis[C <: Context](override val c: C) e
       tree match {
         case Try(_, _, _) if containsAwait =>
           reportUnsupportedAwait(tree, "try/catch")
+        case Return(_) =>
+          c.abort(tree.pos, "return is illegal within a async block")
         case _ =>
           super.traverse(tree)
       }
diff --git a/src/test/scala/scala/async/neg/NakedAwait.scala b/src/test/scala/scala/async/neg/NakedAwait.scala
index 61490e2..229feb6 100644
--- a/src/test/scala/scala/async/neg/NakedAwait.scala
+++ b/src/test/scala/scala/async/neg/NakedAwait.scala
@@ -127,4 +127,16 @@ class NakedAwait {
       """.stripMargin
     }
   }
+
+  @Test
+  def returnIllegal() {
+    expectError("return is illegal") {
+      """
+        | import _root_.scala.async.AsyncId._
+        | def foo(): Any = async { return false }
+        | ()
+        |
+        |""".stripMargin
+    }
+  }
 }
-- 
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