Test that #939 is fixed

Author: DarkDimius

tests/pos/i939.scala

@@ -0,0 +1,8 @@
+object IntMap {
+  private[immutable] case object Nil {
+    override def equals(that : Any) = that match {
+      case _: this.type => true
+      case _            => super.equals(that)
+    }
+  }
+}