1 files changed, 39 insertions, 0 deletions
diff --git a/tests/untried/pos/t4063.scala b/tests/untried/pos/t4063.scala
new file mode 100644
index 000000000..f7033f686
--- /dev/null
+++ b/tests/untried/pos/t4063.scala
@@ -0,0 +1,39 @@
+trait Parallel
+trait Parallelizable[+ParRepr <: Parallel]
+
+trait PIterableLike[+T, +Repr <: Parallel] extends Parallel with Parallelizable[PIterableLike[T, Repr]]
+
+trait PMap[K, V] extends PIterableLike[(K, V), PMap[K, V]]
+trait PSet[T] extends PIterableLike[T, PSet[T]]
+
+trait CIterableLike[+T, +Repr]
+
+trait CSet[T] extends CIterableLike[T, CSet[T]] with Parallelizable[PSet[T]]
+
+trait CMap[K, V] extends CIterableLike[(K, V), CMap[K, V]] with Parallelizable[PMap[K, V]]
+
+object Test {
+  var x = 0
+
+  def main(): Unit = {
+    val map: CMap[Int, CSet[Int]] = new CMap[Int, CSet[Int]] {}
+    val set: CSet[Int] = new CSet[Int] {}
+
+    // should infer type argument
+    //map.synchronized[CIterableLike[Any, Any] with Parallelizable[PIterableLike[Any, Parallel with Parallelizable[Parallel]]]] {
+    // or:
+    //map.synchronized[CIterableLike[Any, Any] with Parallelizable[PIterableLike[Any, Parallel]]] {
+    // or, maybe it could also infer existential types:
+    //map.synchronized[CIterableLike[Any, _] with Parallelizable[PIterableLike[Any, _]]] {
+
+    map.synchronized {
+      if (x == 0) {
+        map
+      } else {
+        set
+      }
+    }
+
+  }
+}
+