Merge pull request #206 from higherkindness/gb-scala3

.scalafmt.conf

@@ -1,3 +1,4 @@
+version = "2.7.5"
 style = defaultWithAlign
 maxColumn = 80
 

athema/src/main/scala/higherkindness/athema/expr.scala

@@ -55,15 +55,16 @@ object Div {
 private[athema] sealed trait ExprInstances {
   implicit def traverseExpr[V]: Traverse[Expr[V, *]] =
     new DefaultTraverse[Expr[V, *]] {
-      def traverse[G[_]: Applicative, A, B](fa: Expr[V, A])(
-          f: A => G[B]): G[Expr[V, B]] = fa match {
-        case v: Var[_, B @unchecked]   => (v: Expr[V, B]).pure[G]
-        case c: Const[_, B @unchecked] => (c: Expr[V, B]).pure[G]
-        case e: Neg[V, A]              => f(e.x) map (Neg(_))
-        case e: Add[V, A]              => (f(e.x), f(e.y)) mapN (Add(_, _))
-        case e: Sub[V, A]              => (f(e.x), f(e.y)) mapN (Sub(_, _))
-        case e: Prod[V, A]             => (f(e.x), f(e.y)) mapN (Prod(_, _))
-        case e: Div[V, A]              => (f(e.x), f(e.y)) mapN (Div(_, _))
+      def traverse[G[_]: Applicative, A, B](
+          fa: Expr[V, A]
+      )(f: A => G[B]): G[Expr[V, B]] = fa match {
+        case v: Var[V, A]   => (v.asInstanceOf[Expr[V, B]]).pure[G]
+        case c: Const[V, A] => (c.asInstanceOf[Expr[V, B]]).pure[G]
+        case e: Neg[V, A]   => f(e.x) map (Neg(_))
+        case e: Add[V, A]   => (f(e.x), f(e.y)) mapN (Add(_, _))
+        case e: Sub[V, A]   => (f(e.x), f(e.y)) mapN (Sub(_, _))
+        case e: Prod[V, A]  => (f(e.x), f(e.y)) mapN (Prod(_, _))
+        case e: Div[V, A]   => (f(e.x), f(e.y)) mapN (Div(_, _))
       }
     }
 }

athema/src/main/scala/higherkindness/athema/parser.scala

@@ -45,7 +45,7 @@ object ExprParser {
           case TSub      => shunt(op, 1).flatMap(_.traverse(enqueue))
           case TProd     => shunt(op, 2).flatMap(_.traverse(enqueue))
           case TDiv      => shunt(op, 2).flatMap(_.traverse(enqueue))
-        }).as(tail.asLeft)
+        }).map(_ => tail.asLeft)
       case Nil =>
         for {
           s0 <- StateT.get[FF, SS]
@@ -87,7 +87,8 @@ object ExprParser {
   private def binary(
       f: (
           Expr.Fixed[BigDecimal],
-          Expr.Fixed[BigDecimal]) => Expr.Fixed[BigDecimal]
+          Expr.Fixed[BigDecimal]
+      ) => Expr.Fixed[BigDecimal]
   ): StateT[FF, Output, Unit] =
     StateT.modifyF { output0 =>
       val y       = output0.head

build.sbt

@@ -1,3 +1,7 @@
+import ProjectPlugin.ScalaV
+import ProjectPlugin.on
+import ProjectPlugin.onVersion
+
 lazy val root = (project in file("."))
   .settings(noPublishSettings)
   .aggregate(coreJVM, coreJS)
@@ -9,7 +13,9 @@ lazy val root = (project in file("."))
   .aggregate(testsJVM, testsJS)
   .aggregate(athemaJVM, athemaJS)
   .aggregate(readme)
-  .settings(crossScalaVersions := List()) // work around https://github.com/sbt/sbt/issues/4181
+  .settings(
+    crossScalaVersions := List()
+  ) // work around https://github.com/sbt/sbt/issues/4181
 
 lazy val publish = (project in file(".publish"))
   .settings(noPublishSettings)
@@ -22,7 +28,11 @@ lazy val publish = (project in file(".publish"))
   .aggregate(testsJVM, testsJS)
 
 lazy val coverage = (project in file(".coverage"))
-  .settings(noPublishSettings)
+  .settings(
+    noPublishSettings,
+    crossScalaVersions := Seq(ScalaV.v212, ScalaV.v213),
+    scalaVersion := ScalaV.v213
+  )
   .settings(coverageEnabled := true)
   .aggregate(coreJVM)
   .aggregate(metaJVM)
@@ -44,10 +54,14 @@ lazy val V = new {
 lazy val meta = module("meta")
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value %%% moduleName.value % V.drostePrev),
-    libraryDependencies ++= Seq(
-      "org.scala-lang" % "scala-reflect"  % scalaVersion.value,
-      "org.scala-lang" % "scala-compiler" % scalaVersion.value % "provided")
+      organization.value %%% moduleName.value % V.drostePrev
+    ),
+    libraryDependencies ++= onVersion(2)(version =>
+      Seq(
+        "org.scala-lang" % "scala-reflect"  % version,
+        "org.scala-lang" % "scala-compiler" % version % "provided"
+      )
+    ).value.flatten
   )
 
 lazy val metaJVM = meta.jvm
@@ -57,31 +71,40 @@ lazy val core = module("core")
   .dependsOn(meta)
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value %%% moduleName.value % V.drostePrev),
+      organization.value %%% moduleName.value % V.drostePrev
+    ),
     mimaBinaryIssueFilters ++= {
       import com.typesafe.tools.mima.core.IncompatibleSignatureProblem
       import com.typesafe.tools.mima.core.ProblemFilters.exclude
       // See https://github.com/lightbend/mima/issues/423
       Seq(
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.Basis#Default.unapply"),
+          "higherkindness.droste.Basis#Default.unapply"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GAlgebra#Gathered.unapply"),
+          "higherkindness.droste.GAlgebra#Gathered.unapply"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GAlgebraArrow.algebra"),
+          "higherkindness.droste.GAlgebraArrow.algebra"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GAlgebraM#Gathered.unapply"),
+          "higherkindness.droste.GAlgebraM#Gathered.unapply"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GCoalgebra#Scattered.unapply"),
+          "higherkindness.droste.GCoalgebra#Scattered.unapply"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GCoalgebraArrow.algebra"),
+          "higherkindness.droste.GCoalgebraArrow.algebra"
+        ),
         exclude[IncompatibleSignatureProblem](
-          "higherkindness.droste.GCoalgebraM#Scattered.unapply")
+          "higherkindness.droste.GCoalgebraM#Scattered.unapply"
+        )
       )
     },
     libraryDependencies ++= Seq(
       "org.typelevel" %%% "cats-core" % V.cats,
-      "org.typelevel" %%% "cats-free" % V.cats)
+      "org.typelevel" %%% "cats-free" % V.cats
+    )
   )
 
 lazy val coreJVM = core.jvm
@@ -91,9 +114,21 @@ lazy val macros = module("macros")
   .dependsOn(core)
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value %%% moduleName.value % V.drostePrev),
-    libraryDependencies ++= on(2, 12)(compilerPlugin(
-      "org.scalamacros" %% "paradise" % "2.1.1" cross CrossVersion.patch)).value,
+      organization.value %%% moduleName.value % V.drostePrev
+    ),
+    libraryDependencies ++= on(2, 12)(
+      compilerPlugin(
+        "org.scalamacros" %% "paradise" % "2.1.1" cross CrossVersion.patch
+      )
+    ).value,
+    // For some reason dependencies using `%%%` don't work with our 'on' method.
+    // They give 'error: Illegal dynamic dependency'
+    libraryDependencies ++=
+      (CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((3, _)) =>
+          Seq("org.typelevel" %%% "shapeless3-deriving" % "3.0.1")
+        case _ => Nil
+      }),
     scalacOptions ++= on(2, 13)("-Ymacro-annotations").value
   )
 
@@ -102,20 +137,24 @@ lazy val macrosJS  = macros.js
 
 lazy val reftree = jvmModule("reftree")
   .dependsOn(coreJVM)
-  .settings(noScala213Settings)
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value                           %% moduleName.value % V.drostePrev),
-    libraryDependencies ++= Seq("io.github.stanch" %% "reftree"        % "1.4.0")
+      organization.value %% moduleName.value % V.drostePrev
+    ),
+    libraryDependencies ++= on(2, 12)(
+      "io.github.stanch" %% "reftree" % "1.4.0"
+    ).value
   )
 
 lazy val scalacheck = module("scalacheck")
   .dependsOn(core)
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value %%% moduleName.value % V.drostePrev),
+      organization.value %%% moduleName.value % V.drostePrev
+    ),
     libraryDependencies ++= Seq(
-      "org.scalacheck" %%% "scalacheck" % V.scalacheck)
+      "org.scalacheck" %%% "scalacheck" % V.scalacheck
+    )
   )
 
 lazy val scalacheckJVM = scalacheck.jvm
@@ -125,9 +164,11 @@ lazy val laws = module("laws")
   .dependsOn(core)
   .settings(
     mimaPreviousArtifacts := Set(
-      organization.value %%% moduleName.value % V.drostePrev),
+      organization.value %%% moduleName.value % V.drostePrev
+    ),
     libraryDependencies ++= Seq(
-      "org.scalacheck" %%% "scalacheck" % V.scalacheck)
+      "org.scalacheck" %%% "scalacheck" % V.scalacheck
+    )
   )
 
 lazy val lawsJVM = laws.jvm
@@ -145,9 +186,14 @@ lazy val tests = module("tests")
       "eu.timepit"             %%% "refined-scalacheck"      % V.refined,
       "org.scala-lang.modules" %%% "scala-collection-compat" % V.collectionCompat % Test
     ),
-    libraryDependencies ++= on(2, 12)(compilerPlugin(
-      "org.scalamacros" %% "paradise" % "2.1.1" cross CrossVersion.patch)).value,
-    scalacOptions ++= on(2, 13)("-Ymacro-annotations").value
+    libraryDependencies ++= on(2, 12)(
+      compilerPlugin(
+        "org.scalamacros" %% "paradise" % "2.1.1" cross CrossVersion.patch
+      )
+    ).value,
+    scalacOptions ++= on(2, 13)("-Ymacro-annotations").value,
+    // 'nowarn' doesn't work on scala3 yet, make warnings not fatal.
+    scalacOptions --= on(3)("-Xfatal-warnings").value
   )
 
 lazy val testsJVM = tests.jvm
@@ -165,7 +211,10 @@ lazy val athema = module("athema", prefix = "")
       ) ++
         Seq(
           "org.scalacheck" %%% "scalacheck" % V.scalacheck
-        ).map(_ % "test"))
+        ).map(_ % "test"),
+    // 'nowarn' doesn't work on scala3 yet, make warnings not fatal.
+    scalacOptions --= on(3)("-Xfatal-warnings").value
+  )
 
 lazy val athemaJVM = athema.jvm
 lazy val athemaJS  = athema.js
@@ -203,12 +252,4 @@ addCommandAlias(
 )
 addCommandAlias("ci-docs", ";github;mdoc")
 
-def on[A](major: Int, minor: Int)(a: A): Def.Initialize[Seq[A]] =
-  Def.setting {
-    CrossVersion.partialVersion(scalaVersion.value) match {
-      case Some(v) if v == (major, minor) => Seq(a)
-      case _                              => Nil
-    }
-  }
-
 ThisBuild / resolvers += Resolver.sonatypeRepo("public")

modules/core/src/main/scala/higherkindness/droste/data/AttrF.scala → modules/core/src/main/scala-2/higherkindness/droste/data/AttrF.scala

@@ -10,8 +10,8 @@ import cats.syntax.functor._
 import cats.syntax.traverse._
 
 import meta.Meta
-import data.prelude._
-import util.DefaultTraverse
+import higherkindness.droste.data.prelude._
+import higherkindness.droste.util.DefaultTraverse
 
 object AttrF {
   def apply[F[_], A, B](ask: A, lower: F[B]): AttrF[F, A, B] =

modules/core/src/main/scala/higherkindness/droste/data/CoattrF.scala → modules/core/src/main/scala-2/higherkindness/droste/data/CoattrF.scala

@@ -11,7 +11,7 @@ import cats.syntax.functor._
 import cats.syntax.traverse._
 
 import meta.Meta
-import util.DefaultTraverse
+import higherkindness.droste.util.DefaultTraverse
 
 object CoattrF {
   def apply[F[_], A, B](f: Either[A, F[B]]): CoattrF[F, A, B] =

modules/core/src/main/scala/higherkindness/droste/data/Fix.scala → modules/core/src/main/scala-2/higherkindness/droste/data/Fix.scala

@@ -11,4 +11,4 @@ object Fix {
 
   def algebra[F[_]]: Algebra[F, Fix[F]]     = Algebra(apply(_))
   def coalgebra[F[_]]: Coalgebra[F, Fix[F]] = Coalgebra(un(_))
-}
+}

modules/core/src/main/scala-3/higherkindness/droste/data/Attr.scala

@@ -0,0 +1,64 @@
+package higherkindness.droste
+package data
+
+import cats.Comonad
+import cats.Eval
+import cats.Functor
+
+import cats.syntax.functor._
+
+import prelude._
+
+object Attr {
+  def apply[F[_], A](head: A, tail: F[Attr[F, A]]): Attr[F, A] =
+    apply((head, tail))
+  def apply[F[_], A](f: (A, F[Attr[F, A]])): Attr[F, A]         = f.asInstanceOf
+  def un[F[_], A](f: Attr[F, A]): (A, F[Attr[F, A]])            = f.asInstanceOf
+  def unapply[F[_], A](f: Attr[F, A]): Some[(A, F[Attr[F, A]])] = Some(un(f))
+
+  def algebra[F[_], A]: Algebra[AttrF[F, A, *], Attr[F, A]] =
+    Algebra(fa => Attr(AttrF.un(fa)))
+
+  def coalgebra[F[_], A]: Coalgebra[AttrF[F, A, *], Attr[F, A]] =
+    Coalgebra(a => AttrF(Attr.un(a)))
+
+  def fromCats[F[_]: Functor, A](cofree: cats.free.Cofree[F, A]): Attr[F, A] =
+    ana(cofree)(_.tail.value, _.head)
+
+  def unfold[F[_]: Functor, A](a: A)(coalgebra: A => F[A]): Attr[F, A] =
+    ana(a)(coalgebra, identity)
+
+  /** An inlined anamorphism to `Attr` with a fused map */
+  def ana[F[_]: Functor, A, C](
+      a: A
+  )(coalgebra: A => F[A], f: A => C): Attr[F, C] =
+    Attr(f(a), coalgebra(a).map(ana(_)(coalgebra, f)))
+}
+
+private[data] trait AttrImplicits {
+  implicit final class AttrOps[F[_], A](attr: Attr[F, A]) {
+    def tuple: (A, F[Attr[F, A]]) = Attr.un(attr)
+    def head: A                   = tuple._1
+    def tail: F[Attr[F, A]]       = tuple._2
+
+    def toCats(implicit ev: Functor[F]): cats.free.Cofree[F, A] =
+      cats.free.Cofree(head, Eval.later(tail.map(_.toCats)))
+
+    def forget(implicit ev: Functor[F]): Fix[F] =
+      Fix(tail.map(_.forget))
+  }
+
+  implicit def drosteAttrComonad[F[_]: Functor]: Comonad[Attr[F, *]] =
+    new AttrComonad[F]
+}
+
+private[data] final class AttrComonad[F[_]: Functor]
+    extends Comonad[Attr[F, *]] {
+  def coflatMap[A, B](fa: Attr[F, A])(f: Attr[F, A] => B): Attr[F, B] =
+    Attr.ana(fa)(_.tail, f)
+
+  def extract[A](fa: Attr[F, A]): A = fa.head
+
+  def map[A, B](fa: Attr[F, A])(f: A => B): Attr[F, B] =
+    Attr(f(fa.head), fa.tail.map(_.map(f)))
+}