Scalaz7 - Monoid instances for TupleX incorrect

[derekjw]

The current Monoid instances for Tuples cause stack overflow.

A working implementation for Tuple2:

implicit def Tuple2Monoid[A, B](implicit ma: Monoid[A], mb: Monoid[B]): Monoid[(A, B)] = {
  implicit val sa = ma.semigroup
  implicit val za = ma.zero
  implicit val sb = mb.semigroup
  implicit val zb = mb.zero
  monoid[(A, B)]
}

[nkpart]

Seems okay now:

scala> import scalaz.std.tuple._
scala> import scalaz.std.anyVal._
scala> import scalaz.syntax.monoid._

scala> mzero[Int]
res1: Int = 0

scala> mzero[(Int, Int)]
res2: (Int, Int) = (0,0)

scala>