But in java generic collections are not covariant such as:
ArrayList<Animal> is not a supertype of ArrayList<Dog>

type Animal is tagged null record;
type Dog is new Animal with null record;

type Plain_Array is array (Positive range <>) of Animal;

type Class_Array is array (Positive range <>) of Animal'Class;

gnatmake -c -u -f covariant_arrays.ads
gcc -c covariant_arrays.ads
covariant_arrays.ads:8:59: unconstrained element type in array declaration
gnatmake: "covariant_arrays.ads" compilation error

type Access_Array is array (Positive range <>) of access Animal'Class;