ValidatorTag.scala

import jto.validation.{Rule, VA}
import shapeless.Witness
import shapeless.labelled.{FieldType, field}

trait Validator {
  this: String =>
  val rules: Rule[String, String]
  def validate: VA[String] = rules.validate(this)
}

object EmailValidator{
  this: String =>
  val rules: Rule[String, String] = Rules.email |+| Rules.notEmpty
}


type Email = FieldType[EmailValidator.type , String]
implicit def email(value: String): FieldType[EmailValidator.type , String] = field[EmailValidator.type ](value)

def getFieldName[K, V](value: FieldType[K, V])(implicit witness: Witness.Aux[K]): K = witness.value
def getFieldValue[K, V](value: FieldType[K, V]): V =  value


case class Row(email: Email) {

}

val invalidRow = Row("")
getFieldValue(invalidRow.email)

getFieldName(invalidRow.email) match {
  case EmailValidator => EmailValidator.rules.validate(invalidRow.email)
  case _ => EmailValidator.rules.validate("")
}