Scala multiple generic parameter data structure typeclass instance

I'm using Scalaz as I'm loving a lot of aspects from Haskell's type class setup in the standard libraries. But exactly this is my current problem. I have a generic data structure with two generic parameters:

case class Parser[T,A](f: T => (T,A))

In Haskell I would implement the Alternative typeclass like this:

newtype Parser t a = Parser { runParser :: t -> (t,a) }

instance Alternative (Parser t) where
  ...

But how can I do something equivalent in Scala? As far as I know I can't do something like

object Parser {
  implicit def ins_Alternative[T] = new Alternative[Parser[T]] {
    // ...
  }
}

Has anybody an idea how to do this? Thx in advance!

Update:

I've found this:

implicit def eitherMonad[L]: Traverse[Either[L, ?]] with MonadError[Either[L, ?], L] with BindRec[Either[L, ?]] with Cozip[Either[L, ?]] = 
  new Traverse[Either[L, ?]] with MonadError[Either[L, ?], L] with BindRec[Either[L, ?]] with Cozip[Either[L, ?]] {
    def bind[A, B](fa: Either[L, A])(f: A => Either[L, B]) = fa match {
      case Left(a)  => Left(a)
      case Right(b) => f(b)
    }
  // ...
}

in the Scalaz sources (https://github.com/scalaz/scalaz/blob/series/7.3.x/core/src/main/scala/scalaz/std/Either.scala).

According to this I guess I have to write something like

object Parser {
  implicit def ins_Alternative[T] = new Alternative[Parser[T, ?]] {
    // ...
  }
}

which doesn't compile as the type ? is unknown.

I've found a solution.

implicit def ins_Alternative[T] = new Alternative[({type x[a] = Parser[T, a]})#x] {
  override def empty[A]: Parser[T, A] = ???

  override def plus[A](a: Parser[T, A], b: => Parser[T, A]): Parser[T, A] = ???

  override def point[A](a: => A): Parser[T, A] = ???

  override def ap[A, B](fa: => Parser[T, A])(f: => Parser[T, (A) => B]): Parser[T, B] = ???
}