Class/Object

scala.annotation

elidable

Related Docs: object elidable | package annotation

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final class elidable extends Annotation with StaticAnnotation

An annotation for methods whose bodies may be excluded from compiler-generated bytecode.

Behavior is influenced by passing -Xelide-below <arg> to scalac. Calls to methods marked elidable (as well as the method body) will be omitted from generated code if the priority given the annotation is lower than that given on the command line.

@elidable(123)           // annotation priority
scalac -Xelide-below 456 // command line priority

The method call will be replaced with an expression which depends on the type of the elided expression. In decreasing order of precedence:

Unit            ()
Boolean         false
T <: AnyVal     0
T >: Null       null
T >: Nothing    Predef.???

Complete example:

import scala.annotation._, elidable._
object Test extends App {
  def expensiveComputation(): Int = { Thread.sleep(1000) ; 172 }

  @elidable(WARNING) def warning(msg: String) = println(msg)
  @elidable(FINE) def debug(msg: String)      = println(msg)
  @elidable(FINE) def computedValue           = expensiveComputation()

  warning("Warning! Danger! Warning!")
  debug("Debug! Danger! Debug!")
  println("I computed a value: " + computedValue)
}
% scalac example.scala && scala Test
Warning! Danger! Warning!
Debug! Danger! Debug!
I computed a value: 172

// INFO lies between WARNING and FINE
% scalac -Xelide-below INFO example.scala && scala Test
Warning! Danger! Warning!
I computed a value: 0
Since

2.8

Linear Supertypes
StaticAnnotation, Annotation, AnyRef, Any
Ordering
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Inherited
  1. elidable
  2. StaticAnnotation
  3. Annotation
  4. AnyRef
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Visibility
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Instance Constructors

  1. new elidable(level: Int)

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Value Members

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

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    Definition Classes
    AnyRef → Any

  2. final def ##(): Int

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    Definition Classes
    AnyRef → Any

  3. final def ==(arg0: Any): Boolean

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    AnyRef → Any

  4. final def asInstanceOf[T0]: T0

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    Any

  5. def clone(): AnyRef

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

  6. final def eq(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef

  7. def equals(arg0: Any): Boolean

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    Definition Classes
    AnyRef → Any

  8. def finalize(): Unit

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

  9. final def getClass(): Class[_]

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    AnyRef → Any

  10. def hashCode(): Int

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    AnyRef → Any

  11. final def isInstanceOf[T0]: Boolean

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    Definition Classes
    Any

  12. final val level: Int

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  13. final def ne(arg0: AnyRef): Boolean

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    Definition Classes
    AnyRef

  14. final def notify(): Unit

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    Definition Classes
    AnyRef

  15. final def notifyAll(): Unit

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    Definition Classes
    AnyRef

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

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    Definition Classes
    AnyRef

  17. def toString(): String

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    Definition Classes
    AnyRef → Any

  18. final def wait(): Unit

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    Definition Classes
    AnyRef
    Annotations
    @throws( ... )

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

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    AnyRef
    Annotations
    @throws( ... )

  20. final def wait(arg0: Long): Unit

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    Annotations
    @throws( ... )

Inherited from StaticAnnotation

Inherited from Annotation

Inherited from AnyRef

Inherited from Any

Ungrouped