How to create annotations and get them in scala

Question

I want to define some annotations and use them in Scala.

I looked into the source of Scala, found in scala.annotation package, there are some annotation

Answer 1

Could it have something to do with retention? I bet @tailrec is not included in the bytecode getting generated.

If I try to extend ClassfileAnnotation (in order to have runtime retention), Scala tells me that it can't be done, and it has to be done in Java:

./test.scala:1: warning: implementation restriction: subclassing Classfile does not
make your annotation visible at runtime.  If that is what
you want, you must write the annotation class in Java.
class A extends ClassfileAnnotation
      ^