CSV type class derivation using magnolia

CsvDerivationMagnolia.scala

import magnolia.{CaseClass, Magnolia, SealedTrait}
import scala.language.experimental.macros

trait Csv[A] { def apply(a: A): Seq[String] }

trait LPCsv {
  type Typeclass[A] = Csv[A]

  def combine[A](ctx: CaseClass[Csv, A]): Csv[A] =
    a => ctx.parameters.foldLeft(List[String]())((acc, p) => acc ++ p.typeclass(p.dereference(a)))

  def dispatch[A](ctx: SealedTrait[Csv, A]): Csv[A] =
    a => ctx.dispatch(a)(sub => sub.typeclass(sub.cast(a)))

  implicit def deriveCsv[A]: Csv[A] = macro Magnolia.gen[A]
}

object csv extends LPCsv {
  implicit val csvStr: Csv[String] = Seq(_)
  implicit def csvSeq[A](implicit ca: Csv[A]): Csv[Seq[A]] = _.flatMap(ca(_))
}

case class Foo(s: String)
case class TypeParam[A](a: A)
case class Wrapper(tp: TypeParam[Foo])

import csv._

implicitly[Csv[Seq[Wrapper]]]