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scala - 为什么在代码中添加多行注释会使其无法编译

问题描述

在以下函数中，如果我添加多行注释，则代码不会编译。为什么？

def updateValues(tableName:String, model:User, id:UserKeys):Update.Where = {
    QueryBuilder.update(tableName).`with`/*WORKS*/(QueryBuilder.set("confirmed",model.profile.internalProfileDetails.get.confirmed))/*(QueryBuilder.set("authprovider",model.profile.internalProfileDetails.get.loginInfo.providerID)) //TODOM - remove hardcoding for bucket and also add bucket in User model*/
      .and(QueryBuilder.set("id",model.id))
      .and(QueryBuilder.set("password",model.profile.internalProfileDetails.get.passwordInfo.get.password))
      .and(QueryBuilder.set("hasher",model.profile.internalProfileDetails.get.passwordInfo.get.hasher))
      .and(QueryBuilder.set("salt",""/*model.profile.internalProfileDetails.get.passwordInfo.get.salt.get*/)) //salt is empty for BCryptSha256PasswordHasher. The 'hash' method of BCryptSha256PasswordHasher does not return the salt separately because it is embedded in the hashed password.
      .where(QueryBuilder.eq("bucket", id.bucket)) //TODOM - pick column names from config/env file
      .and(QueryBuilder.eq("email", id.email))
      .and(QueryBuilder.eq("authprovider", model.profile.internalProfileDetails.get.loginInfo.providerID))//TODOM - this should come from id
      .and(QueryBuilder.eq("firstname",model.profile.externalProfileDetails.firstName))
      .and(QueryBuilder.eq("lastname",model.profile.externalProfileDetails.lastName))

  }

但

    def updateValues(tableName:String, model:User, id:UserKeys):Update.Where = {
        QueryBuilder.update(tableName).`with`/*
DOESNT WORKS. I get error, cannot resolve and */(QueryBuilder.set("confirmed",model.profile.internalProfileDetails.get.confirmed))/*(QueryBuilder.set("authprovider",model.profile.internalProfileDetails.get.loginInfo.providerID)) //TODOM - remove hardcoding for bucket and also add bucket in User model*/
          .and(QueryBuilder.set("id",model.id))
          .and(QueryBuilder.set("password",model.profile.internalProfileDetails.get.passwordInfo.get.password))
          .and(QueryBuilder.set("hasher",model.profile.internalProfileDetails.get.passwordInfo.get.hasher))
          .and(QueryBuilder.set("salt",""/*model.profile.internalProfileDetails.get.passwordInfo.get.salt.get*/)) //salt is empty for BCryptSha256PasswordHasher. The 'hash' method of BCryptSha256PasswordHasher does not return the salt separately because it is embedded in the hashed password.
          .where(QueryBuilder.eq("bucket", id.bucket)) //TODOM - pick column names from config/env file
          .and(QueryBuilder.eq("email", id.email))
          .and(QueryBuilder.eq("authprovider", model.profile.internalProfileDetails.get.loginInfo.providerID))//TODOM - this should come from id
          .and(QueryBuilder.eq("firstname",model.profile.externalProfileDetails.firstName))
          .and(QueryBuilder.eq("lastname",model.profile.externalProfileDetails.lastName))

      }

标签： scala

解决方案

快速签入菊石：

val x = List/*
multi */(1, 2, 3) 
x: List.type = scala.collection.immutable.List$@3697a307

val x = List/* single */(1, 2, 3)
x: List[Int] = List(1, 2, 3)

表明解析器将它们解释为

val x = List
(1, 2, 3) 
x: List.type = scala.collection.immutable.List$@3697a307

val x = List(1, 2, 3)
x: List[Int] = List(1, 2, 3)

为什么？为什么不简单地删除评论并表现得好像它们不存在一样？

我的猜测是这是编译器中的一个错误，因为 Scala 的解析器试图跟踪创建 AST 的所有内容 - 包括空字符和注释 - 以及它何时分析它是否应该是：

method(arg1, arg2)

或者

value
(next expression in parenthesis)

它比较行号以区分它们。显然，当多行注释的这种处理会改变语义时，没有人考虑过极端情况。（请注意，与其他情况相比，这不会产生错误行为，这就是为什么可能没有人为解决此问题而烦恼）。

更新：您可以尝试通过强制编译器将其确认为一个表达式来解决此问题，例如通过在注释前移动左括号：

val x = List(/*
multi */1, 2, 3)
x: List[Int] = List(1, 2, 3)

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