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package scala
package reflect
import java.lang.{ Class => jClass }
import scala.runtime.ScalaRunTime.arrayElementClass
/**
*
* A `ClassTag[T]` stores the erased class of a given type `T`, accessible via the `runtimeClass`
* field. This is particularly useful for instantiating `Array`s whose element types are unknown
* at compile time.
*
* `ClassTag`s are a weaker special case of [[scala.reflect.api.TypeTags#TypeTag]]s, in that they
* wrap only the runtime class of a given type, whereas a `TypeTag` contains all static type
* information. That is, `ClassTag`s are constructed from knowing only the top-level class of a
* type, without necessarily knowing all of its argument types. This runtime information is enough
* for runtime `Array` creation.
*
* For example:
* {{{
* scala> def mkArray[T : ClassTag](elems: T*) = Array[T](elems: _*)
* mkArray: [T](elems: T*)(implicit evidence$1: scala.reflect.ClassTag[T])Array[T]
*
* scala> mkArray(42, 13)
* res0: Array[Int] = Array(42, 13)
*
* scala> mkArray("Japan","Brazil","Germany")
* res1: Array[String] = Array(Japan, Brazil, Germany)
* }}}
*
* See [[scala.reflect.api.TypeTags]] for more examples, or the
* [[http://docs.scala-lang.org/overviews/reflection/typetags-manifests.html Reflection Guide: TypeTags]]
* for more details.
*
*/
@scala.annotation.implicitNotFound(msg = "No ClassTag available for ${T}")
trait ClassTag[T] extends ClassManifestDeprecatedApis[T] with Equals with Serializable {
// please, don't add any APIs here, like it was with `newWrappedArray` and `newArrayBuilder`
// class tags, and all tags in general, should be as minimalistic as possible
/** A class representing the type `U` to which `T` would be erased.
* Note that there is no subtyping relationship between `T` and `U`.
*/
def runtimeClass: jClass[_]
/** Produces a `ClassTag` that knows how to instantiate an `Array[Array[T]]` */
def wrap: ClassTag[Array[T]] = ClassTag[Array[T]](arrayClass(runtimeClass))
/** Produces a new array with element type `T` and length `len` */
override def newArray(len: Int): Array[T] =
runtimeClass match {
case java.lang.Byte.TYPE => new Array[Byte](len).asInstanceOf[Array[T]]
case java.lang.Short.TYPE => new Array[Short](len).asInstanceOf[Array[T]]
case java.lang.Character.TYPE => new Array[Char](len).asInstanceOf[Array[T]]
case java.lang.Integer.TYPE => new Array[Int](len).asInstanceOf[Array[T]]
case java.lang.Long.TYPE => new Array[Long](len).asInstanceOf[Array[T]]
case java.lang.Float.TYPE => new Array[Float](len).asInstanceOf[Array[T]]
case java.lang.Double.TYPE => new Array[Double](len).asInstanceOf[Array[T]]
case java.lang.Boolean.TYPE => new Array[Boolean](len).asInstanceOf[Array[T]]
case java.lang.Void.TYPE => new Array[Unit](len).asInstanceOf[Array[T]]
case _ => java.lang.reflect.Array.newInstance(runtimeClass, len).asInstanceOf[Array[T]]
}
/** A ClassTag[T] can serve as an extractor that matches only objects of type T.
*
* The compiler tries to turn unchecked type tests in pattern matches into checked ones
* by wrapping a `(_: T)` type pattern as `ct(_: T)`, where `ct` is the `ClassTag[T]` instance.
* Type tests necessary before calling other extractors are treated similarly.
* `SomeExtractor(...)` is turned into `ct(SomeExtractor(...))` if `T` in `SomeExtractor.unapply(x: T)`
* is uncheckable, but we have an instance of `ClassTag[T]`.
*/
def unapply(x: Any): Option[T] =
if (null != x && (
(runtimeClass.isInstance(x))
|| (x.isInstanceOf[Byte] && runtimeClass.isAssignableFrom(classOf[Byte]))
|| (x.isInstanceOf[Short] && runtimeClass.isAssignableFrom(classOf[Short]))
|| (x.isInstanceOf[Char] && runtimeClass.isAssignableFrom(classOf[Char]))
|| (x.isInstanceOf[Int] && runtimeClass.isAssignableFrom(classOf[Int]))
|| (x.isInstanceOf[Long] && runtimeClass.isAssignableFrom(classOf[Long]))
|| (x.isInstanceOf[Float] && runtimeClass.isAssignableFrom(classOf[Float]))
|| (x.isInstanceOf[Double] && runtimeClass.isAssignableFrom(classOf[Double]))
|| (x.isInstanceOf[Boolean] && runtimeClass.isAssignableFrom(classOf[Boolean]))
|| (x.isInstanceOf[Unit] && runtimeClass.isAssignableFrom(classOf[Unit])))
) Some(x.asInstanceOf[T])
else None
// TODO: deprecate overloads in 2.12.0, remove in 2.13.0
def unapply(x: Byte) : Option[T] = unapplyImpl(x, classOf[Byte])
def unapply(x: Short) : Option[T] = unapplyImpl(x, classOf[Short])
def unapply(x: Char) : Option[T] = unapplyImpl(x, classOf[Char])
def unapply(x: Int) : Option[T] = unapplyImpl(x, classOf[Int])
def unapply(x: Long) : Option[T] = unapplyImpl(x, classOf[Long])
def unapply(x: Float) : Option[T] = unapplyImpl(x, classOf[Float])
def unapply(x: Double) : Option[T] = unapplyImpl(x, classOf[Double])
def unapply(x: Boolean) : Option[T] = unapplyImpl(x, classOf[Boolean])
def unapply(x: Unit) : Option[T] = unapplyImpl(x, classOf[Unit])
private[this] def unapplyImpl(x: Any, primitiveCls: java.lang.Class[_]): Option[T] =
if (runtimeClass.isInstance(x) || runtimeClass.isAssignableFrom(primitiveCls)) Some(x.asInstanceOf[T])
else None
// case class accessories
override def canEqual(x: Any) = x.isInstanceOf[ClassTag[_]]
override def equals(x: Any) = x.isInstanceOf[ClassTag[_]] && this.runtimeClass == x.asInstanceOf[ClassTag[_]].runtimeClass
override def hashCode = scala.runtime.ScalaRunTime.hash(runtimeClass)
override def toString = {
def prettyprint(clazz: jClass[_]): String =
if (clazz.isArray) s"Array[${prettyprint(arrayElementClass(clazz))}]" else
clazz.getName
prettyprint(runtimeClass)
}
}
/**
* Class tags corresponding to primitive types and constructor/extractor for ClassTags.
*/
object ClassTag {
private val ObjectTYPE = classOf[java.lang.Object]
private val NothingTYPE = classOf[scala.runtime.Nothing$]
private val NullTYPE = classOf[scala.runtime.Null$]
val Byte : ClassTag[scala.Byte] = Manifest.Byte
val Short : ClassTag[scala.Short] = Manifest.Short
val Char : ClassTag[scala.Char] = Manifest.Char
val Int : ClassTag[scala.Int] = Manifest.Int
val Long : ClassTag[scala.Long] = Manifest.Long
val Float : ClassTag[scala.Float] = Manifest.Float
val Double : ClassTag[scala.Double] = Manifest.Double
val Boolean : ClassTag[scala.Boolean] = Manifest.Boolean
val Unit : ClassTag[scala.Unit] = Manifest.Unit
val Any : ClassTag[scala.Any] = Manifest.Any
val Object : ClassTag[java.lang.Object] = Manifest.Object
val AnyVal : ClassTag[scala.AnyVal] = Manifest.AnyVal
val AnyRef : ClassTag[scala.AnyRef] = Manifest.AnyRef
val Nothing : ClassTag[scala.Nothing] = Manifest.Nothing
val Null : ClassTag[scala.Null] = Manifest.Null
def apply[T](runtimeClass1: jClass[_]): ClassTag[T] =
runtimeClass1 match {
case java.lang.Byte.TYPE => ClassTag.Byte.asInstanceOf[ClassTag[T]]
case java.lang.Short.TYPE => ClassTag.Short.asInstanceOf[ClassTag[T]]
case java.lang.Character.TYPE => ClassTag.Char.asInstanceOf[ClassTag[T]]
case java.lang.Integer.TYPE => ClassTag.Int.asInstanceOf[ClassTag[T]]
case java.lang.Long.TYPE => ClassTag.Long.asInstanceOf[ClassTag[T]]
case java.lang.Float.TYPE => ClassTag.Float.asInstanceOf[ClassTag[T]]
case java.lang.Double.TYPE => ClassTag.Double.asInstanceOf[ClassTag[T]]
case java.lang.Boolean.TYPE => ClassTag.Boolean.asInstanceOf[ClassTag[T]]
case java.lang.Void.TYPE => ClassTag.Unit.asInstanceOf[ClassTag[T]]
case ObjectTYPE => ClassTag.Object.asInstanceOf[ClassTag[T]]
case NothingTYPE => ClassTag.Nothing.asInstanceOf[ClassTag[T]]
case NullTYPE => ClassTag.Null.asInstanceOf[ClassTag[T]]
case _ => new ClassTag[T]{ def runtimeClass = runtimeClass1 }
}
def unapply[T](ctag: ClassTag[T]): Option[Class[_]] = Some(ctag.runtimeClass)
}
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