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package scala
package reflect
package api
import scala.collection.immutable.ListMap
/**
* <span class="badge badge-red" style="float: right;">EXPERIMENTAL</span>
*
* This trait provides annotation support for the reflection API.
*
* The API distinguishes between two kinds of annotations:
*
* <ul>
* <li>''Java annotations'': annotations on definitions produced by the Java compiler, i.e., subtypes of [[java.lang.annotation.Annotation]]
* attached to program definitions. When read by Scala reflection, the [[scala.annotation.ClassfileAnnotation]] trait
* is automatically added as a subclass to every Java annotation.</li>
* <li>''Scala annotations'': annotations on definitions or types produced by the Scala compiler.</li>
* </ul>
*
* When a Scala annotation that inherits from [[scala.annotation.StaticAnnotation]] or [[scala.annotation.ClassfileAnnotation]] is compiled,
* it is stored as special attributes in the corresponding classfile, and not as a Java annotation. Note that subclassing
* just [[scala.annotation.Annotation]] is not enough to have the corresponding metadata persisted for runtime reflection.
*
* The distinction between Java and Scala annotations is manifested in the contract of [[scala.reflect.api.Annotations#Annotation]], which exposes
* both `scalaArgs` and `javaArgs`. For Scala or Java annotations extending [[scala.annotation.ClassfileAnnotation]] `scalaArgs` is empty
* and arguments are stored in `javaArgs`. For all other Scala annotations, arguments are stored in `scalaArgs` and `javaArgs` is empty.
*
* Arguments in `scalaArgs` are represented as typed trees. Note that these trees are not transformed by any phases
* following the type-checker. Arguments in `javaArgs` are repesented as a map from [[scala.reflect.api.Names#Name]] to
* [[scala.reflect.api.Annotations#JavaArgument]]. Instances of `JavaArgument` represent different kinds of Java annotation arguments:
* - literals (primitive and string constants),
* - arrays and
* - nested annotations.
*
* For more information about `Annotation`s, see the [[http://docs.scala-lang.org/overviews/reflection/annotations-names-scopes.html Reflection Guide: Annotations, Names, Scopes, and More]]
*
* @contentDiagram hideNodes "*Api"
* @group ReflectionAPI
*/
trait Annotations { self: Universe =>
/** Information about an annotation.
* @template
* @group Annotations
*/
type Annotation >: Null <: AnyRef with AnnotationApi
/** The constructor/extractor for `Annotation` instances.
* @group Extractors
*/
val Annotation: AnnotationExtractor
/** An extractor class to create and pattern match with syntax `Annotation(tpe, scalaArgs, javaArgs)`.
* Here, `tpe` is the annotation type, `scalaArgs` the payload of Scala annotations, and `javaArgs` the payload of Java annotations.
* @group Extractors
*/
abstract class AnnotationExtractor {
def apply(tpe: Type, scalaArgs: List[Tree], javaArgs: ListMap[Name, JavaArgument]): Annotation
def unapply(ann: Annotation): Option[(Type, List[Tree], ListMap[Name, JavaArgument])]
}
/** The API of `Annotation` instances.
* The main source of information about annotations is the [[scala.reflect.api.Annotations]] page.
* @group API
*/
trait AnnotationApi {
/** The type of the annotation. */
def tpe: Type
/** Payload of the Scala annotation: a list of abstract syntax trees that represent the argument.
* Empty for Java annotations.
*/
def scalaArgs: List[Tree]
/** Payload of the Java annotation: a list of name-value pairs.
* Empty for Scala annotations.
*/
def javaArgs: ListMap[Name, JavaArgument]
}
/** A Java annotation argument
* @template
* @group Annotations
*/
type JavaArgument >: Null <: AnyRef
/** A literal argument to a Java annotation as `"Use X instead"` in `@Deprecated("Use X instead")`
* @template
* @group Annotations
*/
type LiteralArgument >: Null <: AnyRef with JavaArgument with LiteralArgumentApi
/** The constructor/extractor for `LiteralArgument` instances.
* @group Extractors
*/
val LiteralArgument: LiteralArgumentExtractor
/** An extractor class to create and pattern match with syntax `LiteralArgument(value)`
* where `value` is the constant argument.
* @group Extractors
*/
abstract class LiteralArgumentExtractor {
def apply(value: Constant): LiteralArgument
def unapply(arg: LiteralArgument): Option[Constant]
}
/** The API of `LiteralArgument` instances.
* The main source of information about annotations is the [[scala.reflect.api.Annotations]] page.
* @group API
*/
trait LiteralArgumentApi {
/** The underlying compile-time constant value. */
def value: Constant
}
/** An array argument to a Java annotation as in `@Target(value={TYPE,FIELD,METHOD,PARAMETER})`
* @template
* @group Annotations
*/
type ArrayArgument >: Null <: AnyRef with JavaArgument with ArrayArgumentApi
/** The constructor/extractor for `ArrayArgument` instances.
* @group Extractors
*/
val ArrayArgument: ArrayArgumentExtractor
/** An extractor class to create and pattern match with syntax `ArrayArgument(args)`
* where `args` is the argument array.
* @group Extractors
*/
abstract class ArrayArgumentExtractor {
def apply(args: Array[JavaArgument]): ArrayArgument
def unapply(arg: ArrayArgument): Option[Array[JavaArgument]]
}
/** API of `ArrayArgument` instances.
* The main source of information about annotations is the [[scala.reflect.api.Annotations]] page.
* @group API
*/
trait ArrayArgumentApi {
/** The underlying array of Java annotation arguments. */
def args: Array[JavaArgument]
}
/** A nested annotation argument to a Java annotation as `@Nested` in `@Outer(@Nested)`.
* @template
* @group Annotations
*/
type NestedArgument >: Null <: AnyRef with JavaArgument with NestedArgumentApi
/** The constructor/extractor for `NestedArgument` instances.
* @group Extractors
*/
val NestedArgument: NestedArgumentExtractor
/** An extractor class to create and pattern match with syntax `NestedArgument(annotation)`
* where `annotation` is the nested annotation.
* @group Extractors
*/
abstract class NestedArgumentExtractor {
def apply(annotation: Annotation): NestedArgument
def unapply(arg: NestedArgument): Option[Annotation]
}
/** API of `NestedArgument` instances.
* The main source of information about annotations is the [[scala.reflect.api.Annotations]] page.
* @group API
*/
trait NestedArgumentApi {
/** The underlying nested annotation. */
def annotation: Annotation
}
}
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