fix #6643: add regression test

Author: bishabosha

compiler/test-resources/repl/i6643

@@ -0,0 +1,7 @@
+scala> import scala.collection._
+
+scala>:type 1
+Int
+
+scala> object IterableTest { def g[CC[_] <: Iterable[_] with IterableOps[_, _, _]](from: CC[Int]): IterableFactory[CC] = ??? }
+// defined object IterableTest