Users are duplicated in a HashSet after this AI-generated class was added. Why?

public class UserKey {
    private String tenantId;
    private String email;

    @Override
    public boolean equals(Object o) {
        if (!(o instanceof UserKey other)) return false;
        return tenantId.equals(other.tenantId)
            && email.equalsIgnoreCase(other.email);
    }
    // no hashCode()
}