Scala 获取未使用的变量警告，即使我正在使用变量

在下面的代码中，我得到一个令牌，我正在查询返回Future的多个数据库。我想根据上一个查询的结果进行下一个查询

val result:Future[Result] = for{tokenOption:Option[UserToken] <- if(urlHost != "" && successUrlParameter != "" && failUrlParameter != "") {userTokenRepo.findOne(UserTokenKey(UUID.fromString(token)))} else {Future.successful(None)}  //generator 1 - get token from database
                                    userOption:Option[User] <- if (tokenOption.isDefined) {userRepo.findOne(tokenOption.get.userKeys)} else {Future.successful(None)} //generator2. found token, look for corresponding user to which the token belongs
                                    modifiedUser:Option[User] <- if (userOption.isDefined) {confirmSignupforUser(userOption.get)} else Future.successful(None) //generator 3. found user and token. Update profile
                                    deletedToken:Option[UserTokenKey] <- if(modifiedUser.isDefined) {userTokenRepo.delete(UserTokenKey(UUID.fromString(token)))} else Future.successful(None)
       }
         yield { //check if we have user and token and modified user here. If any is missing, return error else success
           if(urlHost == "" || successUrlParameter == "" || failUrlParameter == ""){//error in reading redirection url.
             InternalServerError(Json.toJson(JsonResultError("Internal Server Error. Redirection missing ")))
           } else { //read redirection url, so can redirect with success or failure parameter
             println("db query results tokenOption: " + tokenOption + ", userOption: " + userOption + " : modifiedUserOption: " + modifiedUser + ", deletedToken: " + deletedToken)
             //all db ops other than deletinng token should be successful. Error in deletinng token is not a critical error from user perspective and thus should not affect signup verification
             if (tokenOption.isDefined && userOption.isDefined && modifiedUser.isDefined /*&& deletedToken.isDefined*/) {
               Redirect(s"${urlHost};${successUrlParameter}") //TODOM - pick from config
             }
             else {
               /*TODOM - when redirecting with error, can provide additional info why sign up failed*/
               Redirect(s"${urlHost};${failUrlParameter}") //TODOM - pick from config
             }
           }
         }

---

这似乎是一个错误根据。下面的代码片段

object Hello {
  for {
    a <- Option(1)
    b <- Option(2) if a == 1
  } yield a + b
}

---

使用Scala 2.12.8和2.13在我的机器上重现此问题，但Scala 2.12.1似乎不会出现此问题，因此我建议尝试不同的版本，看看哪个版本适合您。

所有这些代码是否真的有必要显示此问题？请将其简化为@ManuChadha，您使用的是什么版本的scala？我想是2.12。我需要检查，但目前我使用的是2.12.2，我不在我的机器附近。如果我移动到2.12.1，那么-Ywarn unused:locals编译器选项将不被识别，我想这会违背我的目的。

object Hello {
  for {
    a <- Option(1)
    b <- Option(2) if a == 1
  } yield a + b
}