Symfony2:UsernamePasswordToken在方法getRoles处返回一个User对象

我在授权后经常收到这个错误：

RoleHierarchy.php第43行中的UndefinedMethodException：尝试在类"path''to''User"上调用方法"getRole"。你的意思是调用例如"getRoles"吗？

用户（无其他字段和方法）：

class User implements UserInterface {
    /**
     * @ORM'ManyToMany(targetEntity = "path'to'Role", inversedBy = "users")
     * @ORM'JoinTable(name = "user_roles", joinColumns = {@ORM'JoinColumn(name = "userid", referencedColumName = "id")}, inverseJoinColumns = {@ORM'JoinColumn(name = "roleid", referencedColumnName = "id")})
     */
    protected $roles;
    public function getRoles() { return $this->roles->toArray(); }
}

角色（无其他字段和方法）：

class Role implements RoleInterface {
    /**
     * @ORM'Column(name = "role", type = "string", unique = true)
     */
    protected $role;
    /**
     * @ORM'ManyToMany(targetEntity = "path'to'User", mappedBy = "roles")
     */
    protected $users;
    public function getRole() { return $this->role; }
}

security.yml:

security:
  encoders:
    path'to'User: bcrypt
  role_hierarchy:
    ROLE_ADMIN: ROLE_USER
    ROLE_SUPER_ADMIN: [ROLE_ADMIN]
  providers:
    main_provider:
      entity: { class: path'to'User, property: username }
  firewalls:
    dev:
      pattern: ^/(_(profiler|wdt)|css|images|js)/
      security: false
    main_signin:
      pattern: ^/signin$
      anonymous: ~
    main:
      pattern: ^/
      form_login:
        provider: main_provider
        login_path: security_signin
        check_path: security_signcheck
        username_parameter: signin[username]
        password_parameter: signin[password]
        target_path_parameter: signin[targetpath]
        default_target_path: main_index
        remember_me: true
      remember_me:
        key: "%secret%"
        lifetime: 86400
        path: /
        remember_me_parameter: signin[rememberme]
      logout:
        path: security_signout
        target: security_signin
  access_control:
    - { path: ^/signin$ roles: IS_AUTHENTICATED_ANONYMOUSLY }
    - { path: ^/, roles: ROLE_USER }

我试图向用户添加一个getRole方法，看看会发生什么，结果是：

RoleHierarchy.php第43行中的UndefinedMethodException：尝试在类"DateTime"上调用方法"getRole"。

由于某些原因，UsernamePasswordToken->getRoles（）不返回角色数组，而是返回另一个对象。我不知道我做错了什么。。。我试图清除一个开发缓存，但没有帮助。