scalaz.macros.DerivingMacros.scala Maven / Gradle / Ivy
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// Copyright: 2017 - 2018 Sam Halliday
// License: http://www.gnu.org/licenses/lgpl-3.0.en.html
package scalaz.macros
import scala.Predef.genericArrayOps
import scala.reflect.macros.blackbox
final class DerivingMacrosImpl(val c: blackbox.Context) {
import c.universe._
def deriving[F[_], A](
implicit
evF: c.WeakTypeTag[F[_]],
evA: c.WeakTypeTag[A]
): Tree = {
val F = evF.tpe
val A = evA.tpe
val fqn = F.dealias.typeSymbol.fullName
readConfig().targets.get(fqn) match {
case Some(target) => parseTerm(target)
case None => q"_root_.scalaz.Deriving.gen[$F, $A]"
}
}
def xderiving[F[_], A](
implicit
evF: c.WeakTypeTag[F[_]],
evA: c.WeakTypeTag[A]
): Tree = {
val F = evF.tpe
val A = evA.tpe
A.decls.collect {
case m: MethodSymbol if m.isParamAccessor => m.asMethod
}.toList match {
case value :: Nil =>
val access = value.name
val U = value.typeSignatureIn(A).resultType
q"""_root_.scala.Predef.implicitly[${F.typeSymbol}[$U]].xmap(
(u: $U) => new $A(u),
(a: $A) => a.$access)"""
case _ =>
c.abort(c.enclosingPosition, "only supports classes with one parameter")
}
}
private def readConfig(): DerivingConfig =
DerivingConfig.targets
.fold(
error => {
c.error(c.prefix.tree.pos, s"Failed to parse deriving config: $error")
throw new IllegalStateException
},
success => DerivingConfig(success)
)
private def parseTerm(s: String): Tree = {
def toSelect(parts: List[TermName]): Tree = parts match {
case Nil => Ident(termNames.ROOTPKG)
case head :: tail => Select(toSelect(tail), head)
}
toSelect(s.split("[.]").toList.map(TermName(_)).reverse)
}
}
object DerivingMacros {
def deriving[F[_], A]: F[A] = macro DerivingMacrosImpl.deriving[F, A]
def xderiving[F[_], A]: F[A] = macro DerivingMacrosImpl.xderiving[F, A]
}