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Move FunctionK macro into Scala 2-specific directory
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3 files changed

+101
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‎core/src/main/scala-2.x/src/main/scala/cats/arrow/FunctionKMacros.scala‎

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package cats
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package arrow
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import scala.reflect.macros.blackbox.Context
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private[arrow] class FunctionKMacroMethods {
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/**
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* Lifts function `f` of `F[A] => G[A]` into a `FunctionK[F, G]`.
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*
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* {{{
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* def headOption[A](list: List[A]): Option[A] = list.headOption
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* val lifted: FunctionK[List, Option] = FunctionK.lift(headOption)
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* }}}
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*
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* Note: This method has a macro implementation that returns a new
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* `FunctionK` instance as follows:
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*
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* {{{
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* new FunctionK[F, G] {
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* def apply[A](fa: F[A]): G[A] = f(fa)
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* }
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* }}}
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*
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* Additionally, the type parameters on `f` must not be specified.
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*/
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def lift[F[_], G[_]](f: (F[α] => G[α]) forSome { type α }): FunctionK[F, G] =
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macro FunctionKMacros.lift[F, G]
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}
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private[arrow] object FunctionKMacros {
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def lift[F[_], G[_]](c: Context)(
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f: c.Expr[(F[α] => G[α]) forSome { type α }]
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)(
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implicit evF: c.WeakTypeTag[F[_]],
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evG: c.WeakTypeTag[G[_]]
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): c.Expr[FunctionK[F, G]] =
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c.Expr[FunctionK[F, G]](new Lifter[c.type](c).lift[F, G](f.tree))
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// ^^note: extra space after c.type to appease scalastyle
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private[this] class Lifter[C <: Context](val c: C) {
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import c.universe._
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def lift[F[_], G[_]](tree: Tree)(
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implicit evF: c.WeakTypeTag[F[_]],
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evG: c.WeakTypeTag[G[_]]
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): Tree = unblock(tree) match {
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case q"($param) => $trans[..$typeArgs](${arg: Ident})" if param.name == arg.name =>
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typeArgs
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.collect { case tt: TypeTree => tt }
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.find(tt => Option(tt.original).isDefined)
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.foreach { param =>
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c.abort(param.pos, s"type parameter $param must not be supplied when lifting function $trans to FunctionK")
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}
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val F = punchHole(evF.tpe)
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val G = punchHole(evG.tpe)
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q"""
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new _root_.cats.arrow.FunctionK[$F, $G] {
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def apply[A](fa: $F[A]): $G[A] = $trans(fa)
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}
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"""
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case other =>
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c.abort(other.pos, s"Unexpected tree $other when lifting to FunctionK")
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}
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private[this] def unblock(tree: Tree): Tree = tree match {
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case Block(Nil, expr) => expr
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case _ => tree
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}
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private[this] def punchHole(tpe: Type): Tree = tpe match {
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case PolyType(undet :: Nil, underlying: TypeRef) =>
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val α = TypeName("α")
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def rebind(typeRef: TypeRef): Tree =
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if (typeRef.sym == undet) tq"$α"
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else {
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val args = typeRef.args.map {
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case ref: TypeRef => rebind(ref)
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case arg => tq"$arg"
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}
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tq"${typeRef.sym}[..$args]"
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}
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val rebound = rebind(underlying)
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tq"""({type λ[$α] = $rebound})#λ"""
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case TypeRef(pre, sym, Nil) =>
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tq"$sym"
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case _ =>
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c.abort(c.enclosingPosition, s"Unexpected type $tpe when lifting to FunctionK")
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}
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}
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}

‎core/src/main/scala-3.x/src/main/scala/cats/arrow/FunctionKMacros.scala‎

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package cats
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package arrow
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private[arrow] class FunctionKMacroMethods

‎core/src/main/scala/cats/arrow/FunctionK.scala‎

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Original file line numberDiff line numberDiff line change
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package cats
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package arrow
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import scala.reflect.macros.blackbox.Context
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import cats.data.{EitherK, Tuple2K}
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/**
@@ -63,100 +61,11 @@ trait FunctionK[F[_], G[_]] extends Serializable { self =>
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λ[FunctionK[F, Tuple2K[G, H, *]]](fa => Tuple2K(self(fa), h(fa)))
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}
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object FunctionK {
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object FunctionK extends FunctionKMacroMethods {
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/**
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* The identity transformation of `F` to `F`
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*/
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def id[F[_]]: FunctionK[F, F] = λ[FunctionK[F, F]](fa => fa)
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/**
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* Lifts function `f` of `F[A] => G[A]` into a `FunctionK[F, G]`.
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*
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* {{{
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* def headOption[A](list: List[A]): Option[A] = list.headOption
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* val lifted: FunctionK[List, Option] = FunctionK.lift(headOption)
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* }}}
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*
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* Note: This method has a macro implementation that returns a new
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* `FunctionK` instance as follows:
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*
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* {{{
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* new FunctionK[F, G] {
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* def apply[A](fa: F[A]): G[A] = f(fa)
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* }
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* }}}
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*
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* Additionally, the type parameters on `f` must not be specified.
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*/
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def lift[F[_], G[_]](f: (F[α] => G[α]) forSome { type α }): FunctionK[F, G] =
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macro FunctionKMacros.lift[F, G]
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}
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private[arrow] object FunctionKMacros {
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def lift[F[_], G[_]](c: Context)(
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f: c.Expr[(F[α] => G[α]) forSome { type α }]
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)(
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implicit evF: c.WeakTypeTag[F[_]],
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evG: c.WeakTypeTag[G[_]]
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): c.Expr[FunctionK[F, G]] =
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c.Expr[FunctionK[F, G]](new Lifter[c.type](c).lift[F, G](f.tree))
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// ^^note: extra space after c.type to appease scalastyle
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private[this] class Lifter[C <: Context](val c: C) {
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import c.universe._
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def lift[F[_], G[_]](tree: Tree)(
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implicit evF: c.WeakTypeTag[F[_]],
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evG: c.WeakTypeTag[G[_]]
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): Tree = unblock(tree) match {
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case q"($param) => $trans[..$typeArgs](${arg: Ident})" if param.name == arg.name =>
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typeArgs
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.collect { case tt: TypeTree => tt }
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.find(tt => Option(tt.original).isDefined)
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.foreach { param =>
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c.abort(param.pos, s"type parameter $param must not be supplied when lifting function $trans to FunctionK")
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}
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val F = punchHole(evF.tpe)
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val G = punchHole(evG.tpe)
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q"""
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new _root_.cats.arrow.FunctionK[$F, $G] {
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def apply[A](fa: $F[A]): $G[A] = $trans(fa)
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}
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"""
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case other =>
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c.abort(other.pos, s"Unexpected tree $other when lifting to FunctionK")
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}
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private[this] def unblock(tree: Tree): Tree = tree match {
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case Block(Nil, expr) => expr
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case _ => tree
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}
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private[this] def punchHole(tpe: Type): Tree = tpe match {
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case PolyType(undet :: Nil, underlying: TypeRef) =>
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val α = TypeName("α")
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def rebind(typeRef: TypeRef): Tree =
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if (typeRef.sym == undet) tq"$α"
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else {
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val args = typeRef.args.map {
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case ref: TypeRef => rebind(ref)
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case arg => tq"$arg"
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}
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tq"${typeRef.sym}[..$args]"
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}
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val rebound = rebind(underlying)
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tq"""({type λ[$α] = $rebound})#λ"""
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case TypeRef(pre, sym, Nil) =>
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tq"$sym"
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case _ =>
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c.abort(c.enclosingPosition, s"Unexpected type $tpe when lifting to FunctionK")
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}
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}
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}

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