How do you define an @interface in Scala?

Question

How does one create an @interface in Scala? I honestly feel stupid asking that question, but I can't find the syntax for this anywhere. I know that you can consume them, but how do you actually define new ones in Scala?

Java:

public @interface MyAnnotation { } 

Scala:

??? 

Answer 1

This answer is based on Scala 2.8.

// Will be visible to the Scala compiler, but not in the class file nor at runtime. // Like RetentionPolicy.SOURCE final class MyAnnotation extends StaticAnnotation  // Will be visible stored in the annotated class, but not retained at runtime. // This is an implementation restriction, the design is supposed to support // RetentionPolicy.RUNTIME final class MyAnnotation extends ClassfileAnnotation 

For the full details, see section 11 "User Defined Annotations" in the Scala Reference See, for example: @tailrec.

UPDATE The compiler warning says it best:

>cat test.scala final class MyAnnotation extends scala.ClassfileAnnotation  @MyAnnotation class Bar  >scalac test.scala 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. final class MyAnnotation extends scala.ClassfileAnnotation 

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