Scala 3/scala.annotation/ConstantAnnotation

ConstantAnnotation

trait ConstantAnnotation extends StaticAnnotation

Annotation classes extending this trait only accept constant values as arguments.

Note that this trait extends StaticAnnotation, so constant annotations are persisted in the classfile.

The implementation requires arguments of constant annotations to be passed as named arguments, except if there is a single argument, which then defines the annotation's parameter named value.

Constant annotations may use default arguments. Note that the internal representation of an annotation usage (which is visible for compiler plugins, for example) only contains arguments that are explicitly provided.

Constant annotations are not allowed to define auxiliary constructors, and the primary constructor is required to have a single parameter list.

Example:

class Ann(value: Int, x: Int = 0) extends scala.annotation.ConstantAnnotation
class Test {
  def someInt = 0
  @Ann(value = 0, x = 1) def g = 0
  @Ann(0) def f = 0                 // Internal representation contains `@Ann(value = 0)`
  @Ann(someInt)                     // error: argument needs to be a compile-time constant
}

Source:: ConstantAnnotation.scala

trait StaticAnnotation

class Annotation

class Object

trait Matchable

class Any

class SerialVersionUID

class deprecated

class deprecatedInheritance

class deprecatedOverriding

trait ClassfileAnnotation

class elidable

class implicitAmbiguous

class implicitNotFound

class nowarn