Fix #7068: Add regression test

Author: nicolasstucki

tests/pos/i7068-a.scala

@@ -0,0 +1,14 @@
+sealed trait Foo[T] {
+  def foo(s: Foo[T]): Nothing
+}
+
+inline def species[T](t: T) = {
+  case class FooT(x: T) extends Foo[T] {
+    def foo(s: Foo[T]) = s match {
+      case FooT(x) => ???
+    }
+  }
+  FooT(t)
+}
+
+val foo = species(0)

tests/pos/i7068-b.scala

@@ -0,0 +1,5 @@
+inline def species() = {
+  case class FooT()
+  FooT()
+}
+val foo = species()