Immutable lists are mutable

[mattulbrich]

Description

The immutable data structures are strictly immutable by design.

However currently, they allow indirect modification after initialisation.

Reproducible

always

Steps to reproduce

Add the following test cases to class ImmutableListArrayTest

    @Test
    void immutability1() {
        Integer[] array = { 0, 1, 4};
        ImmutableListArray<Integer> list = new ImmutableListArray<>(array);
        array[2] = 2;
        assertThat(list.get(2)).isEqualTo(4);
    }

    @Test
    void immutability2() {
        Integer[] array = { 0, 1, 4};
        ImmutableList<Integer> list = ImmutableList.fromArray(array);
        array[2] = 2;
        assertThat(list.get(2)).isEqualTo(4);
    }

They fail. In both cases the value list.get(2) is 2.

Additional information

---

• Commit: 555a763

[mattulbrich]

@wadoon: Since you have recently improved the data structures here, I assign you the issue. A simply clone in the constructor would do the trick but that might be unnecessarily inefficient in some cases. Perhaps another way of ensuring immutability is needed.

[wadoon]

1. Never use the classes directly. They are package-private.
2. The copy is documented but now missing on main:

   /// This method wraps the given array in an immutable wrapper. The input array is
   /// copied to ensure immutability guarantees are maintained.