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Scala example source code file (Attachments.scala)
The Attachments.scala Scala example source codepackage scala package reflect package macros /** * <span class="badge badge-red" style="float: right;">EXPERIMENTAL</span> * * Attachments provide a way to associate custom metadata with symbols and trees. * * Along with `symbol` and `tpe`, which represent core metadata of trees, each tree * carries the `attachments` field that can store other metadata: compiler-defined (e.g. positions) or user-defined. * Same story is true for symbols, which also have extensible metadata by the virtue * of the same `attachments` field. * * Typically attachments just store a [[scala.reflect.api.Position]], but they can be extended to * encompass arbitrary payloads. Payloads are stored in type-indexed slots, which can be read with `get[T]` and written * with `update[T]` and `remove[T]`. * * This API doesn't have much use in the runtime reflection API (the [[scala.reflect.api]] package), but it might be of help * for macro writers, providing a way to coordinate multiple macros operating on the same code. Therefore the `attachments` * field is only declared in trees and symbols belonging to [[scala.reflect.macros.Universe]]. */ abstract class Attachments { self => /** The position type of this attachment */ type Pos >: Null /** The underlying position */ def pos: Pos /** Creates a copy of this attachment with the position replaced by `newPos` */ def withPos(newPos: Pos): Attachments { type Pos = self.Pos } /** The underlying payload with the guarantee that no two elements have the same type. */ def all: Set[Any] = Set.empty private def matchesTag[T: ClassTag](datum: Any) = classTag[T].runtimeClass == datum.getClass /** An underlying payload of the given class type `T`. */ def get[T: ClassTag]: Option[T] = (all filter matchesTag[T]).headOption.asInstanceOf[Option[T]] /** Check underlying payload contains an instance of type `T`. */ def contains[T: ClassTag]: Boolean = !isEmpty && (all exists matchesTag[T]) /** Creates a copy of this attachment with the payload slot of T added/updated with the provided value. * Replaces an existing payload of the same type, if exists. */ def update[T: ClassTag](attachment: T): Attachments { type Pos = self.Pos } = new NonemptyAttachments[Pos](this.pos, remove[T].all + attachment) /** Creates a copy of this attachment with the payload of the given class type `T` removed. */ def remove[T: ClassTag]: Attachments { type Pos = self.Pos } = { val newAll = all filterNot matchesTag[T] if (newAll.isEmpty) pos.asInstanceOf[Attachments { type Pos = self.Pos }] else new NonemptyAttachments[Pos](this.pos, newAll) } def isEmpty: Boolean = true } // SI-7018: This used to be an inner class of `Attachments`, but that led to a memory leak in the // IDE via $outer pointers. private final class NonemptyAttachments[P >: Null](override val pos: P, override val all: Set[Any]) extends Attachments { type Pos = P def withPos(newPos: Pos) = new NonemptyAttachments(newPos, all) override def isEmpty: Boolean = false } Other Scala source code examplesHere is a short list of links related to this Scala Attachments.scala source code file: |
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