Use Foldable foldRight for Traverse and TraverseFilter.

[takayahilton]

Now

scala> Chain(1, 2, 3, 4, 5, 6).traverse { x => println(x); if(x > 2) Left("err") else Right(x)  }
6
5
4
3
2
1
res: scala.util.Either[String,cats.data.Chain[Int]] = Left(err)

scala> List(1, 2, 3, 4, 5, 6).traverseFilter { x => println(x); if(x > 2) Left("err") else Right(Option(x))  }
6
5
4
3
2
1
res: scala.util.Either[String,List[Int]] = Left(err)

After

scala> Chain(1, 2, 3, 4, 5, 6).traverse { x => println(x); if(x > 2) Left("err") else Right(x)  }
1
2
3
res: scala.util.Either[String,cats.data.Chain[Int]] = Left(err)

scala> List(1, 2, 3, 4, 5, 6).traverseFilter { x => println(x); if(x > 2) Left("err") else Right(Option(x))  }
1
2
3
res: scala.util.Either[String,List[Int]] = Left(err)

[kailuowang]

Sorry Luka, I didn't mean to request your review, misclicked.

[travisbrown]

At a glance I was surprised this is stack-safe, but I checked and it seems to be. Looks reasonable to me.