为什么在代码中添加多行注释会使它无法编译

Question

在下面的函数中，如果我添加多行注释，则代码无法编译。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)

显示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？为什么它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，来自这样一个事实，即 Scala 的解析器试图跟踪创建 AST 的所有内容 - 空字符和注释，包括 - 以及何时分析它是否应该：

method(arg1, arg2)

或

value
(next expression in parenthesis)

它比较行号以区分它们。显然，当这种多行注释的处理会改变语义时，没有人考虑过极端情况。(请注意，在其他情况下，这不会产生错误的行为，这就是为什么可能没有人费心解决这个问题的原因(。

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)