Fix run test

Author: odersky

tests/run/enum-constrs.check

@@ -0,0 +1,3 @@
+Red
+S1
+Car

tests/run/enum-constrs.scala

@@ -10,4 +10,10 @@ enum E[+T] extends java.lang.Enum[E[_]] {
 enum Vehicle(wheels: Int) extends java.lang.Enum[Vehicle] {
   case Bike extends Vehicle(2)
   case Car extends Vehicle(4)
+}
+
+object Test extends App {
+  println(Color.Red)
+  println(E.S1)
+  println(Vehicle.Car)
 }