为什么在运行时无法访问用Scala编写的注释? [英] Why annotations written in Scala are not accessible at runtime?

问题描述

我在scalatest文档中遇到了一条声明:

I have come across a statement in scalatest documentation:

It must be defined in Java instead of Scala so it will be accessible at runtime.

这很奇怪，因为我当时觉得Scala注释比Java注释更强大.为什么缺少此功能?有计划将其重新添加吗?

This is quite weird as I was under the impression that Scala annotation is stronger than its Java counterpart. Why this feature is missing? Is there a plan to add it back?

推荐答案

目前尚无计划在运行时保留Scala支持注释(这个问题已经有一段时间了，但名称为

There is no known plan to have Scala support annotations retained at runtime (the issue has been known for a while but as this page says, it won't be fixed).

Lukas Rytz ，Scala提交者，在

Lukas Rytz, a Scala committer, explained on a post on the scala-language mailing list:

这绝对是不平凡的. Java注释具有特定的 字节码表示形式[...]， 这将需要更改Scala的字节码生成器.

It's definitely non-trivial. Java annotations have specific representation in bytecode [...], which would require changes to Scala's bytecode generator.

Java注释的语言也很特殊，与 Java语言的其余部分，因此需要定义 如何在Scala类中表示这一点.

Also the language of java annotations is quite special, different from the rest of the Java language [...], so one would need to define how this can be represented in a Scala class.

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