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package scala
package reflect
package api
trait Liftables { self: Universe =>
/** A type class that defines a representation of `T` as a `Tree`.
*
* @see [[http://docs.scala-lang.org/overviews/quasiquotes/lifting.html]]
*/
trait Liftable[T] {
def apply(value: T): Tree
}
/** Companion to `Liftable` type class that contains standard instances
* and provides a helper `apply` method to simplify creation of new ones.
*/
object Liftable extends StandardLiftableInstances {
/** A helper method that simplifies creation of `Liftable` instances.
* Takes a type and a function that maps that type to a tree representation.
*
* For example to write Liftable for object one might use it like:
*
* {{{
* scala> object O
*
* scala> val Oref = symbolOf[O.type].asClass.module
*
* scala> implicit val liftO = Liftable[O.type] { _ => q"$Oref" }
*
* scala> val lifted = q"$O"
* lifted: universe.Tree = O
* }}}
*
* @see [[http://docs.scala-lang.org/overviews/quasiquotes/lifting.html]]
*/
def apply[T](f: T => Tree): Liftable[T] =
new Liftable[T] { def apply(value: T): Tree = f(value) }
}
/** A type class that defines a way to extract instance of `T` from a `Tree`.
*
* @see [[http://docs.scala-lang.org/overviews/quasiquotes/unlifting.html]]
*/
trait Unliftable[T] {
def unapply(tree: Tree): Option[T]
}
/** Companion to `Unliftable` type class that contains standard instances
* and provides a helper `apply` method to simplify creation of new ones.
*/
object Unliftable extends StandardUnliftableInstances {
/** A helper method that simplifies creation of `Unliftable` instances.
* Takes a partial function which is defined on correct representations of `T`
* and returns corresponding instances.
*
* For example to extract a reference to an object as object itself:
*
* {{{
* scala> object O
*
* scala> val Oref = symbolOf[O.type].asClass.module
*
* scala> implicit val unliftO = Unliftable[O.type] { case t if t.symbol == Oref => O }
*
* scala> val q"${_: O.type}" = q"$Oref"
* }}}
*
* @see [[http://docs.scala-lang.org/overviews/quasiquotes/unlifting.html]]
*/
def apply[T](pf: PartialFunction[Tree, T]): Unliftable[T] = new Unliftable[T] {
def unapply(value: Tree): Option[T] = pf.lift(value)
}
}
}
|
