shapeless_and_applicative_functor6.scala

implicit def genericValidation[A, R](
  implicit gen: Generic.Aux[A, R], env: Validation[R]
): Validation[A] =
  new Validation[A] { 
    override def validate(b: A) = 
      env.validate(gen.to(b)).map(gen.from) 
  }

// Please note that Generic.Aux[A, R] === Generic[A] {type Repr = R} 
// as we cannot do env: Validation[gen.Repr]