A base class for annotations.
Annotations extending this class directly are not preserved in the classfile. To enable storing annotations in the classfile's Scala signature and make it available to Scala reflection and other tools, the annotation needs to inherit from scala.annotation.StaticAnnotation.
Annotation classes defined in Scala are not stored in classfiles in a Java-compatible manner and therefore not visible in Java reflection. In order to achieve this, the annotation has to be written in Java.