add pdgadt-sub pos test

Author: Linyxus

tests/pos/pdgadt-sub.scala

@@ -0,0 +1,21 @@
+trait SubBase {
+  type A0
+  type B0
+  type C >: A0 <: B0
+}
+trait Tag { type A }
+
+type Sub[A, B] = SubBase { type A0 = A; type B0 = B }
+
+def foo(x: Tag, y: Tag, e: Sub[x.A, y.A]) = e.match {
+  case _: Object =>
+    val t1: y.A = ??? : x.A
+}
+
+def bar(x: Tag, e: Sub[Int, x.A]): x.A = e match {
+  case _: Object => 0
+}
+
+def baz(x: Tag, e: Sub[x.A, Int]): Int = e match {
+  case _: Object => ??? : x.A
+}