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package dotty.tools.dotc.util
/** A class inheriting from Attachment.Container supports
* adding, removing and lookup of attachments. Attachments are typed key/value pairs.
*/
object Attachment {
import Property.Key
/** An implementation trait for attachments.
* Clients should inherit from Container instead.
*/
trait LinkSource {
private[Attachment] var next: Link[_]
/** Optionally get attachment corresponding to `key` */
final def getAttachment[V](key: Key[V]): Option[V] = {
val nx = next
if (nx == null) None
else if (nx.key eq key) Some(nx.value.asInstanceOf[V])
else nx.getAttachment[V](key)
}
/** The attachment corresponding to `key`.
* @throws NoSuchElementException if no attachment with key exists
*/
final def attachment[V](key: Key[V]): V = {
val nx = next
if (nx == null) throw new NoSuchElementException
else if (nx.key eq key) nx.value.asInstanceOf[V]
else nx.attachment(key)
}
/** The attachment corresponding to `key`, or `default`
* if no attachment with `key` exists.
*/
final def attachmentOrElse[V](key: Key[V], default: V): V = {
val nx = next
if (nx == null) default
else if (nx.key eq key) nx.value.asInstanceOf[V]
else nx.attachmentOrElse(key, default)
}
/** Add attachment with given `key` and `value`.
* @return Optionally, the old attachment with given `key` if one existed before.
* The new attachment is added at the position of the old one, or at the end
* if no attachment with same `key` existed.
*/
final def putAttachment[V](key: Key[V], value: V): Option[V] = {
val nx = next
if (nx == null) {
next = new Link(key, value, null)
None
}
else if (nx.key eq key) {
next = new Link(key, value, nx.next)
Some(nx.value.asInstanceOf[V])
}
else nx.putAttachment(key, value)
}
/** Remove attachment with given `key`, if it exists.
* @return Optionally, the removed attachment with given `key` if one existed before.
*/
final def removeAttachment[V](key: Key[V]): Option[V] = {
val nx = next
if (nx == null)
None
else if (nx.key eq key) {
next = nx.next
Some(nx.value.asInstanceOf[V])
}
else nx.removeAttachment(key)
}
/** The list of all keys and values attached to this container. */
final def allAttachments: List[(Key[_], Any)] = {
val nx = next
if (nx == null) Nil else (nx.key, nx.value) :: nx.allAttachments
}
}
/** A private, concrete implementation class linking attachments.
*/
private[Attachment] class Link[+V](val key: Key[V], val value: V, var next: Link[_])
extends LinkSource
/** A trait for objects that can contain attachments */
trait Container extends LinkSource {
private[Attachment] var next: Link[_] = null
final def pushAttachment[V](key: Key[V], value: V): Unit = {
assert(!getAttachment(key).isDefined, s"duplicate attachment for key $key")
next = new Link(key, value, next)
}
}
}
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