scala.reflect.api

# Annotations

#### trait Annotations extends AnyRef

EXPERIMENTAL

This trait provides annotation support for the reflection API.

In Scala, annotations belong to one of the two categories:

- 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.
- Scala annotations: annotations on definitions or types produced by the Scala compiler.

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.

Both Java and Scala annotations are represented as typed trees carrying constructor invocations corresponding to the annotation. For instance, the annotation in `@ann(1, 2) class C` is represented as `q"@new ann(1, 2)"`.

Unlike Java reflection, Scala reflection does not support evaluation of constructor invocations stored in annotations into underlying objects. For instance it's impossible to go from `@ann(1, 2) class C` to `ann(1, 2)`, so one has to analyze trees representing annotation arguments to manually extract corresponding values. Towards that end, arguments of an annotation can be obtained via `annotation.tree.children.tail`.

For more information about `Annotation`s, see the Reflection Guide: Annotations, Names, Scopes, and More

Self Type
  Universe
Source
  Annotations.scala

Linear Supertypes
AnyRef, Any
Known Subclasses
JavaUniverse, Universe, Universe
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Inherited

1. Annotations
2. AnyRef
3. Any

Implicitly

1. by any2stringadd
2. by StringFormat
3. by Ensuring
4. by ArrowAssoc

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### Type Members

1. #### abstract type Annotation >: Null <: Universe.AnnotationApi

   Information about an annotation.

2. #### trait AnnotationApi extends AnyRef

   The API of `Annotation` instances.

   The API of `Annotation` instances. The main source of information about annotations is the scala.reflect.api.Annotations page.

3. #### abstract class AnnotationExtractor extends AnyRef

   An extractor class to create and pattern match with syntax `Annotation(tpe, scalaArgs, javaArgs)`.

   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.

4. #### abstract type ArrayArgument >: Null <: Universe.ArrayArgumentApi with Universe.JavaArgument

   An array argument to a Java annotation as in `@Target(value={TYPE,FIELD,METHOD,PARAMETER})`

   An array argument to a Java annotation as in `@Target(value={TYPE,FIELD,METHOD,PARAMETER})`

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

5. #### trait ArrayArgumentApi extends AnyRef

   API of `ArrayArgument` instances.

   API of `ArrayArgument` instances. The main source of information about annotations is the scala.reflect.api.Annotations page.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

6. #### abstract class ArrayArgumentExtractor extends AnyRef

   An extractor class to create and pattern match with syntax `ArrayArgument(args)` where `args` is the argument array.

   An extractor class to create and pattern match with syntax `ArrayArgument(args)` where `args` is the argument array.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

7. #### abstract type JavaArgument >: Null <: Universe.JavaArgumentApi

   A Java annotation argument

   A Java annotation argument

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

8. #### trait JavaArgumentApi extends AnyRef

   Has no special methods.

   Has no special methods. Is here to provides erased identity for `CompoundType`.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

9. #### abstract type LiteralArgument >: Null <: Universe.LiteralArgumentApi with Universe.JavaArgument

   A literal argument to a Java annotation as `"Use X instead"` in `@Deprecated("Use X instead")`

   A literal argument to a Java annotation as `"Use X instead"` in `@Deprecated("Use X instead")`

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

10. #### trait LiteralArgumentApi extends AnyRef

    The API of `LiteralArgument` instances.

    The API of `LiteralArgument` instances. The main source of information about annotations is the scala.reflect.api.Annotations page.

    Annotations
      @deprecated
    Deprecated

      (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

11. #### abstract class LiteralArgumentExtractor extends AnyRef

    An extractor class to create and pattern match with syntax `LiteralArgument(value)` where `value` is the constant argument.

    An extractor class to create and pattern match with syntax `LiteralArgument(value)` where `value` is the constant argument.

    Annotations
      @deprecated
    Deprecated

      (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

12. #### abstract type NestedArgument >: Null <: Universe.NestedArgumentApi with Universe.JavaArgument

    A nested annotation argument to a Java annotation as `@Nested` in `@Outer(@Nested)`.

    A nested annotation argument to a Java annotation as `@Nested` in `@Outer(@Nested)`.

    Annotations
      @deprecated
    Deprecated

      (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

13. #### trait NestedArgumentApi extends AnyRef

    API of `NestedArgument` instances.

    API of `NestedArgument` instances. The main source of information about annotations is the scala.reflect.api.Annotations page.

    Annotations
      @deprecated
    Deprecated

      (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

14. #### abstract class NestedArgumentExtractor extends AnyRef

    An extractor class to create and pattern match with syntax `NestedArgument(annotation)` where `annotation` is the nested annotation.

    An extractor class to create and pattern match with syntax `NestedArgument(annotation)` where `annotation` is the nested annotation.

    Annotations
      @deprecated
    Deprecated

      (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

### Abstract Value Members

1. #### abstract val Annotation: Universe.AnnotationExtractor

   The constructor/extractor for `Annotation` instances.

2. #### abstract def annotationToTree(ann: Universe.Annotation): Universe.Tree

   Attributes
     protected[scala]

3. #### abstract def treeToAnnotation(tree: Universe.Tree): Universe.Annotation

   Attributes
     protected[scala]

4. #### abstract val ArrayArgument: Universe.ArrayArgumentExtractor

   The constructor/extractor for `ArrayArgument` instances.

   The constructor/extractor for `ArrayArgument` instances.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

5. #### abstract val LiteralArgument: Universe.LiteralArgumentExtractor

   The constructor/extractor for `LiteralArgument` instances.

   The constructor/extractor for `LiteralArgument` instances.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

6. #### abstract val NestedArgument: Universe.NestedArgumentExtractor

   The constructor/extractor for `NestedArgument` instances.

   The constructor/extractor for `NestedArgument` instances.

   Annotations
     @deprecated
   Deprecated

     (Since version 2.11.0) Use `Annotation.tree` to inspect annotation arguments

### Concrete Value Members

1. #### final def !=(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

2. #### final def ##(): Int

   Definition Classes
     AnyRef → Any

3. #### def +(other: String): String

   Implicit information
     This member is added by an implicit conversion from Annotations to any2stringadd[Annotations] performed by method any2stringadd in scala.Predef.
   Definition Classes
     any2stringadd

4. #### def ->[B](y: B): (Annotations, B)

   Implicit information
     This member is added by an implicit conversion from Annotations to ArrowAssoc[Annotations] performed by method ArrowAssoc in scala.Predef.
   Definition Classes
     ArrowAssoc
   Annotations
     @inline()

5. #### final def ==(arg0: Any): Boolean

   Definition Classes
     AnyRef → Any

6. #### final def asInstanceOf[T0]: T0

   Definition Classes
     Any

7. #### def clone(): AnyRef

   Attributes
     protected[java.lang]
   Definition Classes
     AnyRef
   Annotations
     @throws( ... )

8. #### def ensuring(cond: (Annotations) ⇒ Boolean, msg: ⇒ Any): Annotations

   Implicit information
     This member is added by an implicit conversion from Annotations to Ensuring[Annotations] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

9. #### def ensuring(cond: (Annotations) ⇒ Boolean): Annotations

   Implicit information
     This member is added by an implicit conversion from Annotations to Ensuring[Annotations] performed by method Ensuring in scala.Predef.
   Definition Classes
     Ensuring

10. #### def ensuring(cond: Boolean, msg: ⇒ Any): Annotations

    Implicit information
      This member is added by an implicit conversion from Annotations to Ensuring[Annotations] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

11. #### def ensuring(cond: Boolean): Annotations

    Implicit information
      This member is added by an implicit conversion from Annotations to Ensuring[Annotations] performed by method Ensuring in scala.Predef.
    Definition Classes
      Ensuring

12. #### final def eq(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

13. #### def equals(arg0: Any): Boolean

    Definition Classes
      AnyRef → Any

14. #### def finalize(): Unit

    Attributes
      protected[java.lang]
    Definition Classes
      AnyRef
    Annotations
      @throws( classOf[java.lang.Throwable] )

15. #### def formatted(fmtstr: String): String

    Implicit information
      This member is added by an implicit conversion from Annotations to StringFormat[Annotations] performed by method StringFormat in scala.Predef.
    Definition Classes
      StringFormat
    Annotations
      @inline()

16. #### final def getClass(): Class[_]

    Definition Classes
      AnyRef → Any

17. #### def hashCode(): Int

    Definition Classes
      AnyRef → Any

18. #### final def isInstanceOf[T0]: Boolean

    Definition Classes
      Any

19. #### final def ne(arg0: AnyRef): Boolean

    Definition Classes
      AnyRef

20. #### final def notify(): Unit

    Definition Classes
      AnyRef

21. #### final def notifyAll(): Unit

    Definition Classes
      AnyRef

22. #### final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
      AnyRef

23. #### def toString(): String

    Definition Classes
      AnyRef → Any

24. #### final def wait(): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

25. #### final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

26. #### final def wait(arg0: Long): Unit

    Definition Classes
      AnyRef
    Annotations
      @throws( ... )

27. #### def →[B](y: B): (Annotations, B)

    Implicit information
      This member is added by an implicit conversion from Annotations to ArrowAssoc[Annotations] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
      ArrowAssoc

### Inherited from AnyRef

### Inherited from Any

### Inherited by implicit conversion any2stringadd from Annotations to any2stringadd[Annotations]

### Inherited by implicit conversion StringFormat from Annotations to StringFormat[Annotations]

### Inherited by implicit conversion Ensuring from Annotations to Ensuring[Annotations]

### Inherited by implicit conversion ArrowAssoc from Annotations to ArrowAssoc[Annotations]

### Annotations

### API

The methods available for each reflection entity, without the implementation. Since the reflection entities are later overridden by runtime reflection and macros, their API counterparts guarantee a minimum set of methods that are implemented.

### Extractors

Extractors provide the machinery necessary to allow pattern matching and construction of reflection entities that is similar to case classes, although the entities are only abstract types that are later overridden.

### Ungrouped