implicit_test.scala

trait Facade[A] {
  def decode(json: String): A
}

trait DecodeJson[A] {
  def apply(json: String): A
}

implicit def toDecode[A](implicit facade: Facade[A]): DecodeJson[A] = {
  new DecodeJson[A] {
    def apply(json: String): A = facade.decode(json)
  }
}

def parse[A](json: String)(implicit decode: DecodeJson[A]): A = decode(json)

implicit object LongDecoder extends Facade[Long] {
  def decode(json: String): Long = json.toLong
}

val x = parse[Long]("123")
//x: Long = 123

val x: Long = parse("123")
//x: Long = 123