Fix #4167: Add regression test

Author: allanrenucci

tests/pos/i4167/Test_2.scala

@@ -0,0 +1,6 @@
+package collection
+
+object Test {
+  type AnyConstr[X] = Any
+  val test: SeqOps[Char, AnyConstr, _] = null.asInstanceOf[StringOps]
+}

tests/pos/i4167/collections_1.scala

@@ -0,0 +1,11 @@
+package collection
+
+trait Seq[+A] extends SeqOps[A, Seq, Seq[A]]
+trait SeqOps[+A, +CC[_], +C] extends Any
+
+package immutable {
+  trait Seq[+A] extends collection.Seq[A] with SeqOps[A, Seq, Seq[A]]
+  trait SeqOps[+A, +CC[_], +C] extends collection.SeqOps[A, CC, C]
+}
+
+class StringOps extends collection.SeqOps[Char, immutable.Seq, String]