为什么在代码中添加多行注释使其无法编译

Question

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))

      }

Answer 1

快速检查菊石：

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他们不在那里？

我的猜测是，它是编译器中的一个错误，来自Scala的解析器试图跟踪所有创建AST的事实 - 空字符和注释包括 - 当它分析它是否应该是：

method(arg1, arg2)

要么

value
(next expression in parenthesis)

它比较行号以区分它们。 显然，没有人会考虑角线情况，因为这种多行注释的处理会改变语义。 （注意，与其他情况相比，这不会产生错误的行为，这就是为什么可能没有人为解决这个问题而烦恼）。

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，例如通过在注释之前移动左括号：

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