how to properly compare enums and interface unions?

  public static async getLoggedInUser(): Promise<IxUser | IxApiException> {
    const res = await fetch(`${this.BASE_URL}/me`, {})

    if (res.ok) {
      return await res.json()
    } else {
      switch (res.status) {
        case 401: {
          return IxApiException.NOT_AUTHENTICATED;
        }
        default: {
          return IxApiException.UNKNOWN;
        }
      }
    }
  }

  const query = useQuery({
    queryKey: [],
    queryFn: IxApiClient.getLoggedInUser
  })

export interface IxUser {
  id: string,
  email: string,
  creation_timestamp: number,
  creation_source: UserCreationSource
}

export enum IxApiException {
  UNKNOWN = "Something went wrong, please try again later",
  NOT_AUTHENTICATED = "You are not logged in",

  REGISTER_INVALID_EMAIL_OR_PASSWORD = "The email or password are not valid",
  REGISTER_UNUSABLE_EMAIL = "This email cannot be used to register",

  LOGIN_INVALID_CREDENTIALS = "Email or password are incorrect",
  LOGIN_EMAIL_NOT_VERIFIED = "You must verify your email to login",

  EMAILS_RATE_LIMITED = "You requested too many emails, try again later",

  PASSWORD_RESET_USER_NOT_FOUND = "No user with the provided email has been found"
}