Scala example source code file (Manifest.scala)

This example Scala source code file (Manifest.scala) is included in my "Source Code Warehouse" project. The intent of this project is to help you more easily find Scala source code examples by using tags.

All credit for the original source code belongs to scala-lang.org; I'm just trying to make examples easier to find. (For my Scala work, see my Scala examples and tutorials.)

Scala tags/keywords

any, anyref, anyvalmanifest, array, arraybuilder, boolean, classmanifest, collection, int, manifest, mutable, wrappedarray

The Manifest.scala Scala example source code

/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2007-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala
package reflect

import scala.collection.mutable.{ ArrayBuilder, WrappedArray }

/** A `Manifest[T]` is an opaque descriptor for type T.  Its supported use
 *  is to give access to the erasure of the type as a `Class` instance, as
 *  is necessary for the creation of native `Arrays` if the class is not
 *  known at compile time.
 *
 *  The type-relation operators `<:<` and `=:=` should be considered
 *  approximations only, as there are numerous aspects of type conformance
 *  which are not yet adequately represented in manifests.
 *
 *  Example usages:
{{{
  def arr[T] = new Array[T](0)                          // does not compile
  def arr[T](implicit m: Manifest[T]) = new Array[T](0) // compiles
  def arr[T: Manifest] = new Array[T](0)                // shorthand for the preceding

  // Methods manifest, classManifest, and optManifest are in [[scala.Predef]].
  def isApproxSubType[T: Manifest, U: Manifest] = manifest[T] <:< manifest[U]
  isApproxSubType[List[String], List[AnyRef]] // true
  isApproxSubType[List[String], List[Int]]    // false

  def methods[T: ClassManifest] = classManifest[T].erasure.getMethods
  def retType[T: ClassManifest](name: String) =
    methods[T] find (_.getName == name) map (_.getGenericReturnType)

  retType[Map[_, _]]("values")  // Some(scala.collection.Iterable<B>)
}}}
 *
 */
@scala.annotation.implicitNotFound(msg = "No Manifest available for ${T}.")
// TODO undeprecated until Scala reflection becomes non-experimental
// @deprecated("Use scala.reflect.ClassTag (to capture erasures) or scala.reflect.runtime.universe.TypeTag (to capture types) or both instead", "2.10.0")
trait Manifest[T] extends ClassManifest[T] with Equals {
  override def typeArguments: List[Manifest[_]] = Nil

  override def arrayManifest: Manifest[Array[T]] =
    Manifest.classType[Array[T]](arrayClass[T](runtimeClass), this)

  override def canEqual(that: Any): Boolean = that match {
    case _: Manifest[_]   => true
    case _                => false
  }
  /** Note: testing for erasure here is important, as it is many times
   *  faster than <:< and rules out most comparisons.
   */
  override def equals(that: Any): Boolean = that match {
    case m: Manifest[_] => (m canEqual this) && (this.runtimeClass == m.runtimeClass) && (this <:< m) && (m <:< this)
    case _              => false
  }
  override def hashCode = this.runtimeClass.##
}

// TODO undeprecated until Scala reflection becomes non-experimental
// @deprecated("Use type tags and manually check the corresponding class or type instead", "2.10.0")
@SerialVersionUID(1L)
abstract class AnyValManifest[T <: AnyVal](override val toString: String) extends Manifest[T] with Equals {
  override def <:<(that: ClassManifest[_]): Boolean =
    (that eq this) || (that eq Manifest.Any) || (that eq Manifest.AnyVal)
  override def canEqual(other: Any) = other match {
    case _: AnyValManifest[_] => true
    case _                    => false
  }
  override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
  @transient
  override val hashCode = System.identityHashCode(this)
}

/** `ManifestFactory` defines factory methods for manifests.
 *  It is intended for use by the compiler and should not be used in client code.
 *
 *  Unlike `Manifest`, this factory isn't annotated with a deprecation warning.
 *  This is done to prevent avalanches of deprecation warnings in the code that calls methods with manifests.
 *  Why so complicated? Read up the comments for `ClassManifestFactory`.
 */
object ManifestFactory {
  def valueManifests: List[AnyValManifest[_]] =
    List(Byte, Short, Char, Int, Long, Float, Double, Boolean, Unit)

  val Byte: AnyValManifest[Byte] = new AnyValManifest[scala.Byte]("Byte") {
    def runtimeClass = java.lang.Byte.TYPE
    override def newArray(len: Int): Array[Byte] = new Array[Byte](len)
    override def newWrappedArray(len: Int): WrappedArray[Byte] = new WrappedArray.ofByte(new Array[Byte](len))
    override def newArrayBuilder(): ArrayBuilder[Byte] = new ArrayBuilder.ofByte()
    private def readResolve(): Any = Manifest.Byte
  }

  val Short: AnyValManifest[Short] = new AnyValManifest[scala.Short]("Short") {
    def runtimeClass = java.lang.Short.TYPE
    override def newArray(len: Int): Array[Short] = new Array[Short](len)
    override def newWrappedArray(len: Int): WrappedArray[Short] = new WrappedArray.ofShort(new Array[Short](len))
    override def newArrayBuilder(): ArrayBuilder[Short] = new ArrayBuilder.ofShort()
    private def readResolve(): Any = Manifest.Short
  }

  val Char: AnyValManifest[Char] = new AnyValManifest[scala.Char]("Char") {
    def runtimeClass = java.lang.Character.TYPE
    override def newArray(len: Int): Array[Char] = new Array[Char](len)
    override def newWrappedArray(len: Int): WrappedArray[Char] = new WrappedArray.ofChar(new Array[Char](len))
    override def newArrayBuilder(): ArrayBuilder[Char] = new ArrayBuilder.ofChar()
    private def readResolve(): Any = Manifest.Char
  }

  val Int: AnyValManifest[Int] = new AnyValManifest[scala.Int]("Int") {
    def runtimeClass = java.lang.Integer.TYPE
    override def newArray(len: Int): Array[Int] = new Array[Int](len)
    override def newWrappedArray(len: Int): WrappedArray[Int] = new WrappedArray.ofInt(new Array[Int](len))
    override def newArrayBuilder(): ArrayBuilder[Int] = new ArrayBuilder.ofInt()
    private def readResolve(): Any = Manifest.Int
  }

  val Long: AnyValManifest[Long] = new AnyValManifest[scala.Long]("Long") {
    def runtimeClass = java.lang.Long.TYPE
    override def newArray(len: Int): Array[Long] = new Array[Long](len)
    override def newWrappedArray(len: Int): WrappedArray[Long] = new WrappedArray.ofLong(new Array[Long](len))
    override def newArrayBuilder(): ArrayBuilder[Long] = new ArrayBuilder.ofLong()
    private def readResolve(): Any = Manifest.Long
  }

  val Float: AnyValManifest[Float] = new AnyValManifest[scala.Float]("Float") {
    def runtimeClass = java.lang.Float.TYPE
    override def newArray(len: Int): Array[Float] = new Array[Float](len)
    override def newWrappedArray(len: Int): WrappedArray[Float] = new WrappedArray.ofFloat(new Array[Float](len))
    override def newArrayBuilder(): ArrayBuilder[Float] = new ArrayBuilder.ofFloat()
    private def readResolve(): Any = Manifest.Float
  }

  val Double: AnyValManifest[Double] = new AnyValManifest[scala.Double]("Double") {
    def runtimeClass = java.lang.Double.TYPE
    override def newArray(len: Int): Array[Double] = new Array[Double](len)
    override def newWrappedArray(len: Int): WrappedArray[Double] = new WrappedArray.ofDouble(new Array[Double](len))
    override def newArrayBuilder(): ArrayBuilder[Double] = new ArrayBuilder.ofDouble()
    private def readResolve(): Any = Manifest.Double
  }

  val Boolean: AnyValManifest[Boolean] = new AnyValManifest[scala.Boolean]("Boolean") {
    def runtimeClass = java.lang.Boolean.TYPE
    override def newArray(len: Int): Array[Boolean] = new Array[Boolean](len)
    override def newWrappedArray(len: Int): WrappedArray[Boolean] = new WrappedArray.ofBoolean(new Array[Boolean](len))
    override def newArrayBuilder(): ArrayBuilder[Boolean] = new ArrayBuilder.ofBoolean()
    private def readResolve(): Any = Manifest.Boolean
  }

  val Unit: AnyValManifest[Unit] = new AnyValManifest[scala.Unit]("Unit") {
    def runtimeClass = java.lang.Void.TYPE
    override def newArray(len: Int): Array[Unit] = new Array[Unit](len)
    override def newWrappedArray(len: Int): WrappedArray[Unit] = new WrappedArray.ofUnit(new Array[Unit](len))
    override def newArrayBuilder(): ArrayBuilder[Unit] = new ArrayBuilder.ofUnit()
    private def readResolve(): Any = Manifest.Unit
  }

  private val ObjectTYPE = classOf[java.lang.Object]
  private val NothingTYPE = classOf[scala.runtime.Nothing$]
  private val NullTYPE = classOf[scala.runtime.Null$]

  val Any: Manifest[scala.Any] = new PhantomManifest[scala.Any](ObjectTYPE, "Any") {
    override def newArray(len: Int) = new Array[scala.Any](len)
    override def <:<(that: ClassManifest[_]): Boolean = (that eq this)
    private def readResolve(): Any = Manifest.Any
  }

  val Object: Manifest[java.lang.Object] = new PhantomManifest[java.lang.Object](ObjectTYPE, "Object") {
    override def newArray(len: Int) = new Array[java.lang.Object](len)
    override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
    private def readResolve(): Any = Manifest.Object
  }

  val AnyRef: Manifest[scala.AnyRef] = Object.asInstanceOf[Manifest[scala.AnyRef]]

  val AnyVal: Manifest[scala.AnyVal] = new PhantomManifest[scala.AnyVal](ObjectTYPE, "AnyVal") {
    override def newArray(len: Int) = new Array[scala.AnyVal](len)
    override def <:<(that: ClassManifest[_]): Boolean = (that eq this) || (that eq Any)
    private def readResolve(): Any = Manifest.AnyVal
  }

  val Null: Manifest[scala.Null] = new PhantomManifest[scala.Null](NullTYPE, "Null") {
    override def newArray(len: Int) = new Array[scala.Null](len)
    override def <:<(that: ClassManifest[_]): Boolean =
      (that ne null) && (that ne Nothing) && !(that <:< AnyVal)
    private def readResolve(): Any = Manifest.Null
  }

  val Nothing: Manifest[scala.Nothing] = new PhantomManifest[scala.Nothing](NothingTYPE, "Nothing") {
    override def newArray(len: Int) = new Array[scala.Nothing](len)
    override def <:<(that: ClassManifest[_]): Boolean = (that ne null)
    private def readResolve(): Any = Manifest.Nothing
  }

  private class SingletonTypeManifest[T <: AnyRef](value: AnyRef) extends Manifest[T] {
    lazy val runtimeClass = value.getClass
    override lazy val toString = value.toString + ".type"
  }

  /** Manifest for the singleton type `value.type`. */
  def singleType[T <: AnyRef](value: AnyRef): Manifest[T] =
    new SingletonTypeManifest[T](value)

  /** Manifest for the class type `clazz[args]`, where `clazz` is
    * a top-level or static class.
    * @note This no-prefix, no-arguments case is separate because we
    *       it's called from ScalaRunTime.boxArray itself. If we
    *       pass varargs as arrays into this, we get an infinitely recursive call
    *       to boxArray. (Besides, having a separate case is more efficient)
    */
  def classType[T](clazz: Predef.Class[_]): Manifest[T] =
    new ClassTypeManifest[T](None, clazz, Nil)

  /** Manifest for the class type `clazz`, where `clazz` is
    * a top-level or static class and args are its type arguments. */
  def classType[T](clazz: Predef.Class[T], arg1: Manifest[_], args: Manifest[_]*): Manifest[T] =
    new ClassTypeManifest[T](None, clazz, arg1 :: args.toList)

  /** Manifest for the class type `clazz[args]`, where `clazz` is
    * a class with non-package prefix type `prefix` and type arguments `args`.
    */
  def classType[T](prefix: Manifest[_], clazz: Predef.Class[_], args: Manifest[_]*): Manifest[T] =
    new ClassTypeManifest[T](Some(prefix), clazz, args.toList)

  private abstract class PhantomManifest[T](_runtimeClass: Predef.Class[_],
                                            override val toString: String) extends ClassTypeManifest[T](None, _runtimeClass, Nil) {
    override def equals(that: Any): Boolean = this eq that.asInstanceOf[AnyRef]
    @transient
    override val hashCode = System.identityHashCode(this)
  }

  /** Manifest for the class type `clazz[args]`, where `clazz` is
    * a top-level or static class. */
  private class ClassTypeManifest[T](prefix: Option[Manifest[_]],
                                     val runtimeClass: Predef.Class[_],
                                     override val typeArguments: List[Manifest[_]]) extends Manifest[T] {
    override def toString =
      (if (prefix.isEmpty) "" else prefix.get.toString+"#") +
      (if (runtimeClass.isArray) "Array" else runtimeClass.getName) +
      argString
   }

  def arrayType[T](arg: Manifest[_]): Manifest[Array[T]] =
    arg.asInstanceOf[Manifest[T]].arrayManifest

  /** Manifest for the abstract type `prefix # name'. `upperBound` is not
    * strictly necessary as it could be obtained by reflection. It was
    * added so that erasure can be calculated without reflection. */
  def abstractType[T](prefix: Manifest[_], name: String, upperBound: Predef.Class[_], args: Manifest[_]*): Manifest[T] =
    new Manifest[T] {
      def runtimeClass = upperBound
      override val typeArguments = args.toList
      override def toString = prefix.toString+"#"+name+argString
    }

  /** Manifest for the unknown type `_ >: L <: U` in an existential.
    */
  def wildcardType[T](lowerBound: Manifest[_], upperBound: Manifest[_]): Manifest[T] =
    new Manifest[T] {
      def runtimeClass = upperBound.runtimeClass
      override def toString =
        "_" +
        (if (lowerBound eq Nothing) "" else " >: "+lowerBound) +
        (if (upperBound eq Nothing) "" else " <: "+upperBound)
    }

  /** Manifest for the intersection type `parents_0 with ... with parents_n'. */
  def intersectionType[T](parents: Manifest[_]*): Manifest[T] =
    new Manifest[T] {
      def runtimeClass = parents.head.runtimeClass
      override def toString = parents.mkString(" with ")
    }
}