How to sequence Either with Scala cats without a type alias (see Herding cats)

Question

I was reading Herding Cats

The final example on the Traverse page on sequencing List of Either failed for me.

in the example they do this:-

Answer 1

Your code lacks scalac option -Ypartial-unification.

In build.sbt you should add

scalaVersion := "2.12.6"

libraryDependencies += "org.typelevel" %% "cats-core" % "1.1.0"

scalacOptions += "-Ypartial-unification"

or start Scala console with command

scala -Ypartial-unification

http://eed3si9n.com/herding-cats/partial-unification.html