box Node {
    public { weak parent, weak delegate }
    private { secret }
}

static box Main {
    main() {
        local n1 = new Node()
        local n2 = new Node()
        n1.parent = weak n2  // ✅ public weak field
        n1.delegate = weak n2  // ✅ public weak field
        print("OK: visibility block with weak")
        return 0
    }
}