Add test case

Author: biboudis

tests/pos/strawman-i79.scala

@@ -0,0 +1,22 @@
+object Empty
+  extends App {
+
+  trait Iterable[+A]
+      extends IterableOnce[A]
+
+  trait IterableOps[+A, +CC[X], +C] {
+    def ++[B >: A](xs: IterableOnce[B]): CC[B] = ???
+  }
+
+  trait IterableOnce[+A]
+
+  class LazyList[+A]()
+      extends IterableOps[A, LazyList, LazyList[A]]
+      with Iterable[A]
+
+  object LazyList {
+    def empty[A <: Any]: LazyList[A] = new LazyList[A]()
+  }
+
+  LazyList.empty ++ LazyList.empty
+}