From 3abef46fdfa8a291d4efb0e6844e686742dc76f2 Mon Sep 17 00:00:00 2001
From: nomisRev <vergauwen.simon@gmail.com>
Date: Fri, 17 May 2019 17:11:06 +0200
Subject: [PATCH] Unkown IOs always need to be wrapped in Async

---
 .../main/scala/cats/effect/internals/IORunLoop.scala | 12 ++++++++----
 laws/shared/src/test/scala/cats/effect/IOTests.scala |  5 +++++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/core/shared/src/main/scala/cats/effect/internals/IORunLoop.scala b/core/shared/src/main/scala/cats/effect/internals/IORunLoop.scala
index 504c52aad8..a300cbcb84 100644
--- a/core/shared/src/main/scala/cats/effect/internals/IORunLoop.scala
+++ b/core/shared/src/main/scala/cats/effect/internals/IORunLoop.scala
@@ -210,10 +210,14 @@ private[effect] object IORunLoop {
           bFirst = bindNext.asInstanceOf[Bind]
           currentIO = fa
 
-        case _ =>
+        case Async(_, _) =>
           // Cannot inline the code of this method — as it would
           // box those vars in scala.runtime.ObjectRef!
-          return suspendInAsync(currentIO.asInstanceOf[IO[A]], bFirst, bRest)
+          return suspendAsync(currentIO.asInstanceOf[IO.Async[A]], bFirst, bRest)
+        case _ =>
+          return Async { (conn, cb) =>
+            loop(currentIO, conn, cb.asInstanceOf[Callback], null, bFirst, bRest)
+          }
       }
 
       if (hasUnboxed) {
@@ -234,8 +238,8 @@ private[effect] object IORunLoop {
     // $COVERAGE-ON$
   }
 
-  private def suspendInAsync[A](
-    currentIO: IO[A],
+  private def suspendAsync[A](
+    currentIO: IO.Async[A],
     bFirst: Bind,
     bRest: CallStack): IO[A] = {
 
diff --git a/laws/shared/src/test/scala/cats/effect/IOTests.scala b/laws/shared/src/test/scala/cats/effect/IOTests.scala
index 63520e3725..1365cbb356 100644
--- a/laws/shared/src/test/scala/cats/effect/IOTests.scala
+++ b/laws/shared/src/test/scala/cats/effect/IOTests.scala
@@ -495,6 +495,11 @@ class IOTests extends BaseTestsSuite {
     io.unsafeRunSync() shouldEqual 2
   }
 
+  test("uncancelable with unsafeRunSync") {
+    val io = IO.pure(1).uncancelable
+    io.unsafeRunSync() shouldBe 1
+  }
+
   test("map is stack-safe for unsafeRunSync") {
     import IOPlatform.{fusionMaxStackDepth => max}
     val f = (x: Int) => x + 1