cats.data.ValidatedNel issue

Hi all,

I am trying to run docker:publishLocal where I am faced with this error:

[error] /path/to/ClassA.scala:60:8: Cannot prove that cats.data.ValidatedNel[String,path.to.classB] <:< G[A].
[error]       .sequence
[error]        ^

Class A resides in project A, and classB is in project B, and they have this kind of structure:

|--projectName
        |-----project A
        |-----project B
|--build.sbt

The build.sbt looks like this:

lazy val projectA =
  project
    .in(file("projectName/projectA"))
    .enablePlugins(JavaAppPackaging, DockerPlugin)
    .dependsOn(ProjectRef(file("."), "projectB"))
    .settings(
        libraryDependencies ++= Seq("org.typelevel" %% "cats-core" % 2.1.0),
        scalacOptions += "-Ypartial-unification"
        ...
    )

lazy val projectB =
  project
    .in(file("projectName/projectB"))
    .dependsOn(ProjectRef(file("."), "anotherProject"))
    ...

I have researched around and I have added stuff like the "-Ypartial-unification", but to no avail:

plugins.sbt has this:

addSbtPlugin("org.lyranthe.sbt" % "partial-unification" % "1.1.2")
The method that is throwing the error is:

def apply(v1: (crwm, icrwm)): Boolean = {
    val (_, cri) = v1

    validationCriteria
      .map(_.validate(cri))
      .sequence
      .map(_ => cri)
      .toEither
      .fold(validationErrors => {
        log.warn(s"""
             |CR didn't pass quality check(s):
             |${validationErrors.toList.mkString("\n")}
           """.stripMargin)
        false
      }, _ => true)
  }

Sorry I have to obfuscate the methods. If it is unclear, please let me know and I will provide any info that I could.

I'm running sbt version 1.2.7

Thank you so much.

Start with the build.sbt project definitions and plugins.sbt, then run docker:publishLocal to reproduce the compiler error in ClassA.scala:60. Inspect the apply method's validate and sequence calls along with the Scala, Cats, and partial-unification settings. Done means identifying a confirmed cause and documenting a reproducible resolution, but the obfuscated code limits how directly a newcomer can proceed.