wiring an "application" with generic components

GenericGrafter.scala

package grafterexample

import cats.data.Reader
import org.zalando.grafter.GenericReader.widenReader

case class Config()
object Application extends App {
  val x: Wants[Int] = Wants.reader[Config, Int].apply(Config())
  
  println(x.get)
}

trait Wants[T] { def get: T }
object Wants {
  implicit def reader[A, T](implicit implReader: Reader[A, WantsImpl[T]]): Reader[A, Wants[T]] =
    implReader
}

trait Provides[T] { def value: T }
object Provides {
  implicit def reader[A]: Reader[A, Provides[Int]] =
    ProvidesInt.reader[A]
}

// Generic; only uses the provider to do its thing.
case class WantsImpl[T](provider: Provides[T]) extends Wants[T] {
  def get: T = provider.value
}
object WantsImpl {
  implicit def reader[A, T](implicit providesReader: Reader[A, Provides[T]]): Reader[A, WantsImpl[T]] =
    providesReader.map(WantsImpl.apply)
}

// Non-generic; the provider needs to actually know the type of the thing it provides.
case class ProvidesInt(i: Int) extends Provides[Int] {
  def value: Int = i
}
object ProvidesInt {
  implicit def reader[A]: Reader[A, Provides[Int]] =
    Reader(_ => ProvidesInt(7))
}