how to upcast an immutable list

Question

I have written a class ImmutableList<T> which is similar to ArrayList<T> except it does not have any add or remove operations.

Now let's say we have a class Animal and a subclass Cat.

I am aware that a cast from List<Cat> to List<Animal> is not safe, because it would allow one to insert a Dog object into a list of cats.

This problem does not exist with immutable lists, because one cannot insert anything into an immutable list anyway:

ImmutableList<Cat> cats = ImmutableList.of(berlioz, marie, toulouse);
ImmutableList<Animal> animals = cats;

is safe, but the compiler won't allow it.

Therefore I would like to add a method to ImmutableList that helps me to perform a safe cast, maybe like this

ImmutableList<Cat> cats = ImmutableList.of(berlioz, marie, toulouse);
ImmutableList<Animal> animals = cats.upcast();

or even

ImmutableList<Cat> cats = ImmutableList.of(berlioz, marie, toulouse);
ImmutableList<Animal> animals = cats.upcast(Animal.class);

I have tried

 public <S super T> ImmutableList<S> upcast() {
   return (ImmutableList) this;
 }

but that does not compile (you cannot say <S super T> here, only <S extends T>).

The desired method should satisfy some requirements

1. It must not allow unsafe casts, such as from ImmutableList<Animal> to ImmutableList<Cat>
2. It must be efficient, i.e. not copy the list
3. preferably not use reflection

Is it possible to write such a method? Failing that, how would you address the problem?