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package scala.reflect
package base
/** Attachments is a generalisation of Position.
* Typically it stores a Position of a tree, but this can be extended to encompass arbitrary payloads.
*
* Attachments have to carry positions, because we don't want to introduce even a single additional field in Tree
* imposing an unnecessary memory tax because of something that will not be used in most cases.
*/
abstract class Attachments { self =>
type Pos >: Null
/** Gets the underlying position */
def pos: Pos
/** Creates a copy of this attachment with its position updated */
def withPos(newPos: Pos): Attachments { type Pos = self.Pos }
/** Gets the underlying payload */
def all: Set[Any] = Set.empty
def get[T: ClassTag]: Option[T] =
(all find (_.getClass == classTag[T].runtimeClass)).asInstanceOf[Option[T]]
/** Creates a copy of this attachment with its payload updated */
def add(attachment: Any): Attachments { type Pos = self.Pos } =
new NonemptyAttachments(this.pos, all + attachment)
def remove[T: ClassTag]: Attachments { type Pos = self.Pos } = {
val newAll = all filterNot (_.getClass == classTag[T].runtimeClass)
if (newAll.isEmpty) pos.asInstanceOf[Attachments { type Pos = self.Pos }]
else new NonemptyAttachments(this.pos, newAll)
}
private class NonemptyAttachments(override val pos: Pos, override val all: Set[Any]) extends Attachments {
type Pos = self.Pos
def withPos(newPos: Pos) = new NonemptyAttachments(newPos, all)
}
}
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