Any wart triggers false positive for higher kinded typeclass

[stankoua]

I went through a warning with the following code snippet:

  trait One[F[_]] {}

  trait Two[F[_], A] {
    val arg: String
  }

  trait TypeClass1[F[_]] {
    def capability1: F[String]
  }

  object TypeClass1 {
    implicit val optionTC1: TypeClass1[Option] = new TypeClass1[Option] {
      def capability1: Option[String] = None
    }
  }

  def buildTwo[F[_]: TypeClass1](
      buildingArg: String
  ): Two[F, Two[F, One[F]]] =
    new Two[F, Two[F, One[F]]] {
      val arg: String = buildingArg
    }

  def myTwo: Two[Option, Two[Option, One[Option]]] =
    buildTwo("test")

During compilation, this warning is triggered:

[warn] Main.scala:35:5: [wartremover:Any] Inferred type containing Any: [+A]Option[A]
[warn]     buildTwo("test")
[warn]     ^
[warn] one warning found
[success] Total time: 1 s, completed 23 déc. 2019 23:01:31

I don't get this error when disabling the wartremoverWarnings ++= Warts.unsafe line in my build.sbt. I'm guessing I get this warning because the type parameter A of [+A]Option[A] is inferred to Any. Is there a way to avoid this warning without using suppressWarning annotation ?

[S11001001]

Almost certainly related to #455. @stankoua What scalac options are you using?

[stankoua]

@S11001001 I was using scala 2.13 with following compiler options:

val compilerOptions = Seq(
  // Common settings
  //
  "-deprecation", // Emit warning and location for usages of deprecated APIs.
  "-encoding",
  "utf-8", // Specify character encoding used by source files.
  "-explaintypes", // Explain type errors in more detail.
  "-feature", // Emit warning and location for usages of features that should be imported explicitly.
  "-unchecked", // Enable additional warnings where generated code depends on assumptions.
  "-Xcheckinit", // Wrap field accessors to throw an exception on uninitialized access.
  "-Werror", // Fail the compilation if there are any warnings.
  "-Ymacro-annotations",
  // Warning settings
  //
  // "-Wself-implicit",
  "-Wdead-code",
  "-Wextra-implicit",
  "-Wnumeric-widen",
  "-Wvalue-discard",
  "-Wunused:imports,patvars,privates,locals,explicits,implicits,params,linted",
  // Linting
  //
  "-Xlint:adapted-args",
  "-Xlint:inaccessible", // Warn about inaccessible types in method signatures.
  "-Xlint:infer-any", // Warn when a type argument is inferred to be `Any`.
  "-Xlint:missing-interpolator",
  "-Xlint:doc-detached",
  "-Xlint:private-shadow",
  "-Xlint:type-parameter-shadow",
  "-Xlint:poly-implicit-overload",
  "-Xlint:option-implicit",
  "-Xlint:package-object-classes",
  "-Xlint:stars-align",
  "-Xlint:constant",
  "-Xlint:nonlocal-return",
  "-Xlint:valpattern",
  "-Xlint:eta-zero,eta-sam",
  "-Xlint:deprecation",
  "-Xlint:nullary-override", // Warn when non-nullary `def f()' overrides nullary `def f'.
  "-Xlint:nullary-unit", // Warn when nullary methods return Unit.
  "-Ywarn-value-discard" // Warn when non-Unit expression results are unused.
)

Just in case I configured Wartremover like this: wartremoverErrors ++= Warts.unsafe

[stankoua]

Almost certainly related to #455. @stankoua What scalac options are you using?

Indeed I think the 2 issues are related. I have cats(+cats-effects) in my project and at first I got this error on a cats types (IO and Validated if I remember correctly). I tried to abstract it when creating the issue.

[Daenyth]

This triggers a lot on code invoking through on fs2.Stream

[solarmosaic-kflorence]

Same for Slick: Inferred type containing Any: [+A]Seq[A]