add Dotty cross-build

.travis.yml

@@ -6,6 +6,7 @@ language: scala
 
 scala:
   - 2.13.3
+  - 0.27.0-RC1
 
 env:
   - ADOPTOPENJDK=8

build.sbt

@@ -1,15 +1,26 @@
 Global / cancelable := true
 publish / skip := true // in root
 
+Global / scalacOptions ++= (
+  if (isDotty.value) Seq("-language:implicitConversions")  // TODO check again on 3.0.0-M1
+  else               Seq()
+)
+
 lazy val commonSettings: Seq[Setting[_]] =
   ScalaModulePlugin.scalaModuleSettings ++ Seq(
-    Compile / compile / scalacOptions += "-Werror"
+    Compile / compile / scalacOptions --= (if (isDotty.value) Seq("-Xlint")
+                                           else Seq()),
+    Compile / compile / scalacOptions ++= (if (isDotty.value) Seq()
+                                           else Seq("-Werror")),
   )
 
 lazy val core = project.in(file("core"))
   .settings(commonSettings)
   .settings(
-    name := "scala-parallel-collections"
+    name := "scala-parallel-collections",
+    // don't run Dottydoc, it errors and isn't needed anyway
+    Compile / doc / sources := (if (isDotty.value) Seq() else (Compile / doc/ sources).value),
+    Compile / packageDoc / publishArtifact := !isDotty.value,
   )
 
 lazy val junit = project.in(file("junit"))
@@ -20,13 +31,22 @@ lazy val junit = project.in(file("junit"))
     libraryDependencies += "javax.xml.bind" % "jaxb-api" % "2.3.1" % Test,
     testOptions += Tests.Argument(TestFrameworks.JUnit, "-a", "-v"),
     Test / fork := true,
-    publish / skip := true
+    publish / skip := true,
+    // https://github.com/sbt/sbt/pull/5919 adds this to sbt itself,
+    // so we should revisit once sbt 1.4.1 is available
+    Test / unmanagedSourceDirectories += {
+      val major = CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((0 | 3, _)) => "3"
+        case _ => "2"
+      }
+      baseDirectory.value / "src" / "test" / s"scala-$major"
+    },
   ).dependsOn(testmacros, core)
 
 lazy val scalacheck = project.in(file("scalacheck"))
   .settings(commonSettings)
   .settings(
-    libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.14.3",
+    libraryDependencies += "org.scalacheck" %% "scalacheck" % "1.15.0-M1" withDottyCompat(scalaVersion.value),
     Test / fork := true,
     Test / testOptions += Tests.Argument(TestFrameworks.ScalaCheck, "-workers", "1", "-minSize", "0", "-maxSize", "4000", "-minSuccessfulTests", "5"),
     publish / skip := true
@@ -36,5 +56,14 @@ lazy val testmacros = project.in(file("testmacros"))
   .settings(commonSettings)
   .settings(
     libraryDependencies += scalaOrganization.value % "scala-compiler" % scalaVersion.value,
-    publish / skip := true
+    publish / skip := true,
+    // https://github.com/sbt/sbt/pull/5919 adds this to sbt itself,
+    // so we should revisit once sbt 1.4.1 is available
+    Compile / unmanagedSourceDirectories += {
+      val major = CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((0 | 3, _)) => "3"
+        case _ => "2"
+      }
+      baseDirectory.value / "src" / "main" / s"scala-$major"
+    },
   )

core/src/main/scala/scala/collection/CustomParallelizable.scala

@@ -13,10 +13,8 @@
 package scala
 package collection
 
-import parallel.Combiner
-
 trait CustomParallelizable[+A, +ParRepr <: Parallel] extends Any with Parallelizable[A, ParRepr] {
   override def par: ParRepr
-  override protected[this] def parCombiner: Combiner[A, ParRepr] = throw new UnsupportedOperationException("")
+  override protected[this] def parCombiner = throw new UnsupportedOperationException("")
 }
 

core/src/main/scala/scala/collection/Parallelizable.scala

@@ -14,6 +14,7 @@ package scala
 package collection
 
 import parallel.Combiner
+import scala.annotation.unchecked.uncheckedVariance
 
 /** This trait describes collections which can be turned into parallel collections
  *  by invoking the method `par`. Parallelizable collections may be parameterized with
@@ -48,6 +49,6 @@ trait Parallelizable[+A, +ParRepr <: Parallel] extends Any {
    *
    *  @return  a combiner for the parallel collection of type `ParRepr`
    */
-  protected[this] def parCombiner: Combiner[A, ParRepr]
+  protected[this] def parCombiner: Combiner[A @uncheckedVariance, ParRepr]
 }
 

core/src/main/scala/scala/collection/generic/GenericParTemplate.scala

@@ -31,12 +31,9 @@ trait GenericParTemplate[+A, +CC[X] <: ParIterable[X]]
 {
   def companion: GenericParCompanion[CC]
 
-  protected[this] override def newBuilder: scala.collection.mutable.Builder[A, CC[A]] = newCombiner
+  protected[this] override def newBuilder = newCombiner
 
-  protected[this] override def newCombiner: Combiner[A, CC[A]] = {
-    val cb = companion.newCombiner[A]
-    cb
-  }
+  protected[this] override def newCombiner = companion.newCombiner[A]
 
   override def genericBuilder[B]: Combiner[B, CC[B]] = genericCombiner[B]
 
@@ -50,7 +47,7 @@ trait GenericParTemplate[+A, +CC[X] <: ParIterable[X]]
 
 trait GenericParMapTemplate[K, +V, +CC[X, Y] <: ParMap[X, Y]] extends GenericParTemplate[(K, V), ParIterable]
 {
-  protected[this] override def newCombiner: Combiner[(K, V), CC[K, V]] = {
+  protected[this] override def newCombiner: Combiner[(K, V @uncheckedVariance), CC[K, V @uncheckedVariance]] = {
     val cb = mapCompanion.newCombiner[K, V]
     cb
   }

core/src/main/scala/scala/collection/generic/GenericTraversableTemplate.scala

@@ -63,7 +63,7 @@ trait GenericTraversableTemplate[+A, +CC[X] <: ParIterable[X]] extends HasNewBui
 
   /** The builder that builds instances of type $Coll[A]
    */
-  protected[this] def newBuilder: Builder[A, CC[A]] = companion.newBuilder[A]
+  protected[this] def newBuilder: Builder[A @uncheckedVariance, CC[A @uncheckedVariance]] = companion.newBuilder[A]
 
   /** The generic builder that builds instances of $Coll
    *  at arbitrary element types.

core/src/main/scala/scala/collection/generic/HasNewBuilder.scala

@@ -15,8 +15,9 @@ package collection
 package generic
 
 import mutable.Builder
+import scala.annotation.unchecked.uncheckedVariance
 
 trait HasNewBuilder[+A, +Repr] extends Any {
   /** The builder that builds instances of Repr */
-  protected[this] def newBuilder: Builder[A, Repr]
+  protected[this] def newBuilder: Builder[A @uncheckedVariance, Repr]
 }

core/src/main/scala/scala/collection/generic/HasNewCombiner.scala

@@ -15,8 +15,9 @@ package collection
 package generic
 
 import scala.collection.parallel.Combiner
+import scala.annotation.unchecked.uncheckedVariance
 
 trait HasNewCombiner[+T, +Repr] {
-  protected[this] def newCombiner: Combiner[T, Repr]
+  protected[this] def newCombiner: Combiner[T @uncheckedVariance, Repr]
 }