build.sbt

scalaVersion := "2.13.17"

libraryDependencies += "com.chuusai" %% "shapeless" % "2.3.13"

Main.scala

package example

import shapeless.::
import shapeless.HList
import shapeless.HNil
import shapeless.Generic

class MyTypeClass[T](value: T) {
  def map[S](f: T => S): MyTypeClass[S] =
    new MyTypeClass[S](f(value))

  def flatMap[S](f: T => MyTypeClass[S]): MyTypeClass[S] =
    f(value)
}

object MyTypeClass {

  implicit def nil: MyTypeClass[HNil] =
    new MyTypeClass[HNil](HNil)

  implicit def cons[H, T <: HList](implicit H: => MyTypeClass[H], T: => MyTypeClass[T]): MyTypeClass[H :: T] =
    for {
      h <- H
      t <- T
    } yield h :: t

  implicit def gen[P, A <: HList](implicit
    m: Generic.Aux[P, A],
    w: MyTypeClass[A]
  ): MyTypeClass[P] =
    w.map(a => m.from(a))

  implicit def int: MyTypeClass[Int] = new MyTypeClass(3)
}

case class A(
  x: Int,
  y: C
)

sealed trait C
object C {
  case object C1 extends C
}

object Main {
  def main(args: Array[String]): Unit = {
    println(implicitly[MyTypeClass[A]])
  }
}