if ($this->get('security.context')->isGranted('IS_AUTHENTICATED_FULLY')) {
  ...

# app/config/security.yml
security:
    ...
    firewalls:
        secured_area:
            pattern: ^/
            security: true
            form_login:
                login_path:  /login
                check_path:  /login_check
            logout:
                path:   /logout
                target: /
            anonymous: ~

    access_control:
        - { path: ^/login, roles: IS_AUTHENTICATED_ANONYMOUSLY }
        - { path: ^/ , roles: IS_AUTHENTICATED_FULLY }