Add support for Scala 2.13-M4

build.sbt

@@ -1,3 +1,5 @@
+import sbt.CrossVersion
+
 sourceDirectory := file("dummy source directory")
 
 scalaVersionSettings
@@ -11,7 +13,9 @@ lazy val travisCommit = Option(System.getenv().get("TRAVIS_COMMIT"))
 
 lazy val scalaVersionSettings = Seq(
   scalaVersion := "2.12.3",
-  crossScalaVersions := Seq("2.10.6", "2.11.11", "2.13.0-M3", scalaVersion.value)
+  // Temporary: we will eventually use 2.13.0-M4, which will be published to maven central
+  resolvers += "scala-pr" at "https://scala-ci.typesafe.com/artifactory/scala-integration/",
+  crossScalaVersions := Seq("2.10.6", "2.11.11", "2.13.0-pre-c577876", scalaVersion.value)
 )
 
 lazy val sharedSettings = MimaSettings.settings ++ scalaVersionSettings ++ Seq(
@@ -46,6 +50,17 @@ lazy val sharedSettings = MimaSettings.settings ++ scalaVersionSettings ++ Seq(
 
   unmanagedSourceDirectories in Test += (baseDirectory in LocalRootProject).value / "src" / "test" / "scala",
 
+  unmanagedSourceDirectories in Compile ++= {
+    (unmanagedSourceDirectories in Compile).value.map { dir =>
+      CrossVersion.partialVersion(scalaVersion.value) match {
+        case Some((2, 13)) => file(dir.getPath ++ "-2.13")
+        case _             => file(dir.getPath ++ "-2.10-2.12")
+      }
+    }
+  },
+
+  libraryDependencies += "org.scala-lang" %% "scala-collection-compat" % "0.1-SNAPSHOT",
+
   resolvers += "sonatype" at "https://oss.sonatype.org/content/repositories/releases",
 
   javacOptions += "-Xmx1024M",
@@ -55,7 +70,7 @@ lazy val sharedSettings = MimaSettings.settings ++ scalaVersionSettings ++ Seq(
     "-encoding", "UTF-8",
     "-feature",
     "-unchecked",
-    "-Xfatal-warnings",
+    //"-Xfatal-warnings", Disabled because “import scala.collection.compat._” causes “Unused import” warnings on 2.13.
     "-Xfuture",
     "-Yno-adapted-args",
     "-Ywarn-dead-code",

doc/UserGuide.md

@@ -873,15 +873,15 @@ object CounterSpecification extends Commands {
    *  (a singleton [[Sut]]), implement this method the following way:
    *
    *  {{{
-   *  def canCreateNewSut(newState: State, initSuts: Traversable[State]
-   *    runningSuts: Traversable[Sut]
+   *  def canCreateNewSut(newState: State, initSuts: Iterable[State]
+   *    runningSuts: Iterable[Sut]
    *  ) = {
    *    initSuts.isEmpty && runningSuts.isEmpty
    *  }
    *  }}}
    */
-  def canCreateNewSut(newState: State, initSuts: Traversable[State],
-    runningSuts: Traversable[Sut]): Boolean = true
+  def canCreateNewSut(newState: State, initSuts: Iterable[State],
+    runningSuts: Iterable[Sut]): Boolean = true
 
   /** The precondition for the initial state, when no commands yet have
    *  run. This is used by ScalaCheck when command sequences are shrinked

examples/commands-leveldb/src/test/scala/CommandsLevelDB.scala

@@ -30,8 +30,8 @@ object LevelDBSpec extends Commands {
     def path = s"db_$name"
   }
 
-  def canCreateNewSut(newState: State, initSuts: Traversable[State],
-    runningSuts: Traversable[Sut]
+  def canCreateNewSut(newState: State, initSuts: Iterable[State],
+    runningSuts: Iterable[Sut]
   ) = {
     !initSuts.exists(_.name == newState.name) &&
     !runningSuts.exists(_.name == newState.name)

examples/commands-nix/src/test/scala/CommandsNix.scala

@@ -100,8 +100,8 @@ object MachineSpec extends Commands {
   type Sut = Map[String, org.libvirt.Domain]
 
   // TODO we should check for example total amount of memory used here
-  def canCreateNewSut(newState: State, initSuts: Traversable[State],
-    runningSuts: Traversable[Sut]
+  def canCreateNewSut(newState: State, initSuts: Iterable[State],
+    runningSuts: Iterable[Sut]
   ): Boolean = true
 
   def newSut(state: State): Sut = {

examples/commands-redis/src/test/scala/CommandsRedis.scala

@@ -26,8 +26,8 @@ object RedisSpec extends Commands {
     connected: Boolean
   )
 
-  def canCreateNewSut(newState: State, initSuts: Traversable[State],
-    runningSuts: Traversable[Sut]
+  def canCreateNewSut(newState: State, initSuts: Iterable[State],
+    runningSuts: Iterable[Sut]
   ): Boolean = {
     initSuts.isEmpty && runningSuts.isEmpty
   }

jvm/src/test/scala/org/scalacheck/GenSpecification.scala

@@ -203,7 +203,7 @@ object GenSpecification extends Properties("Gen") {
   property("distributed pick") = {
     val lst = (0 to 7).toIterable
     val n = 2
-    forAll(pick(n, lst)) { xs: Seq[Int] =>
+    forAll(pick(n, lst)) { xs: collection.Seq[Int] =>
       xs.map { x: Int =>
         Prop.collect(x) {
           xs.size == n

jvm/src/test/scala/org/scalacheck/commands/CommandsSpecification.scala

@@ -30,8 +30,8 @@ object CommandsSpecification extends Properties("Commands") {
 
     override def shrinkState: Shrink[Int] = implicitly
 
-    def canCreateNewSut(newState: State, initSuts: Traversable[State],
-      runningSuts: Traversable[Sut]) = true
+    def canCreateNewSut(newState: State, initSuts: Iterable[State],
+      runningSuts: Iterable[Sut]) = true
 
     def newSut(state: State): Sut = Counter(state)
 

src/main/scala-2.10-2.12/org/scalacheck/util/ArrayListBuilder.scala

@@ -0,0 +1,17 @@
+package org.scalacheck.util
+
+import java.util
+import java.util.ArrayList
+
+import scala.collection.mutable
+
+private[scalacheck] class ArrayListBuilder[T]
+  extends mutable.Builder[T, util.ArrayList[T]] {
+  val al = new ArrayList[T]
+  def +=(x: T) = {
+    al.add(x)
+    this
+  }
+  def clear() = al.clear()
+  def result() = al
+}

src/main/scala-2.13/org/scalacheck/util/ArrayListBuilder.scala

@@ -0,0 +1,17 @@
+package org.scalacheck.util
+
+import java.util
+import java.util.ArrayList
+
+import scala.collection.mutable
+
+private[scalacheck] class ArrayListBuilder[T]
+  extends mutable.Builder[T, util.ArrayList[T]] {
+  val al = new ArrayList[T]
+  def addOne(x: T) = {
+    al.add(x)
+    this
+  }
+  def clear() = al.clear()
+  def result() = al
+}

src/main/scala/org/scalacheck/Arbitrary.scala

@@ -360,14 +360,14 @@ private[scalacheck] sealed trait ArbitraryLowPriority {
    *  (such as lists, arrays, streams, etc). The maximum size of the container
    *  depends on the size generation parameter. */
   implicit def arbContainer[C[_],T](implicit
-    a: Arbitrary[T], b: Buildable[T,C[T]], t: C[T] => Traversable[T]
+    a: Arbitrary[T], b: Buildable[T,C[T]], t: C[T] => Iterable[T]
   ): Arbitrary[C[T]] = Arbitrary(buildableOf[C[T],T](arbitrary[T]))
 
   /** Arbitrary instance of any [[org.scalacheck.util.Buildable]] container
    *  (such as maps). The maximum size of the container depends on the size
    *  generation parameter. */
   implicit def arbContainer2[C[_,_],T,U](implicit
-    a: Arbitrary[(T,U)], b: Buildable[(T,U),C[T,U]], t: C[T,U] => Traversable[(T,U)]
+    a: Arbitrary[(T,U)], b: Buildable[(T,U),C[T,U]], t: C[T,U] => Iterable[(T,U)]
   ): Arbitrary[C[T,U]] = Arbitrary(buildableOf[C[T,U],(T,U)](arbitrary[(T,U)]))
 
   implicit def arbEnum[A <: java.lang.Enum[A]](implicit A: reflect.ClassTag[A]): Arbitrary[A] = {

src/main/scala/org/scalacheck/Cogen.scala

@@ -17,6 +17,8 @@ import scala.concurrent.duration.{Duration, FiniteDuration}
 import java.math.BigInteger
 import rng.Seed
 
+import scala.collection.compat._
+
 sealed trait Cogen[T] extends Serializable {
 
   def perturb(seed: Seed, t: T): Seed
@@ -115,7 +117,7 @@ object Cogen extends CogenArities with CogenLowPriority {
     Cogen[String].contramap(_.name)
 
   implicit def cogenList[A: Cogen]: Cogen[List[A]] =
-    Cogen.it(_.iterator)
+    Cogen.it(_.iterator())
 
   implicit def cogenVector[A: Cogen]: Cogen[Vector[A]] =
     Cogen.it(_.iterator)

src/main/scala/org/scalacheck/Gen.scala

@@ -462,7 +462,7 @@ object Gen extends GenArities{
 
   /** Sequences generators. If any of the given generators fails, the
    *  resulting generator will also fail. */
-  def sequence[C,T](gs: Traversable[Gen[T]])(implicit b: Buildable[T,C]): Gen[C] = {
+  def sequence[C,T](gs: Iterable[Gen[T]])(implicit b: Buildable[T,C]): Gen[C] = {
     val g = gen { (p, seed) =>
       gs.foldLeft(r(Some(Vector.empty[T]), seed)) {
         case (rs,g) =>
@@ -595,55 +595,55 @@ object Gen extends GenArities{
 
   //// List Generators ////
 
-  /** Generates a container of any Traversable type for which there exists an
+  /** Generates a container of any Iterable type for which there exists an
    *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
    *  container will be generated by the given generator. The size of the
    *  generated container is limited by `n`. Depending on what kind of container
    *  that is generated, the resulting container may contain fewer elements than
    *  `n`, but not more. If the given generator fails generating a value, the
    *  complete container generator will also fail. */
   def buildableOfN[C,T](n: Int, g: Gen[T])(implicit
-    evb: Buildable[T,C], evt: C => Traversable[T]
+    evb: Buildable[T,C], evt: C => Iterable[T]
   ): Gen[C] =
-    sequence[C,T](Traversable.fill(n)(g)) suchThat { c =>
+    sequence[C,T](Iterable.fill(n)(g)) suchThat { c =>
       // TODO: Can we guarantee c.size == n (See issue #89)?
       c.forall(g.sieveCopy)
     }
 
-  /** Generates a container of any Traversable type for which there exists an
+  /** Generates a container of any Iterable type for which there exists an
    *  implicit [[org.scalacheck.util.Buildable]] instance. The elements in the
    *  container will be generated by the given generator. The size of the
    *  container is bounded by the size parameter used when generating values. */
   def buildableOf[C,T](g: Gen[T])(implicit
-    evb: Buildable[T,C], evt: C => Traversable[T]
+    evb: Buildable[T,C], evt: C => Iterable[T]
   ): Gen[C] =
     sized(s => choose(0, s max 0).flatMap(buildableOfN[C,T](_,g))) suchThat { c =>
       if (c == null) g.sieveCopy(null) else c.forall(g.sieveCopy)
     }
 
-  /** Generates a non-empty container of any Traversable type for which there
+  /** Generates a non-empty container of any Iterable type for which there
    *  exists an implicit [[org.scalacheck.util.Buildable]] instance. The
    *  elements in the container will be generated by the given generator. The
    *  size of the container is bounded by the size parameter used when
    *  generating values. */
   def nonEmptyBuildableOf[C,T](g: Gen[T])(implicit
-    evb: Buildable[T,C], evt: C => Traversable[T]
+    evb: Buildable[T,C], evt: C => Iterable[T]
   ): Gen[C] =
     sized(s => choose(1, s max 1).flatMap(buildableOfN[C,T](_,g))) suchThat(_.size > 0)
 
   /** A convenience method for calling `buildableOfN[C[T],T](n,g)`. */
   def containerOfN[C[_],T](n: Int, g: Gen[T])(implicit
-    evb: Buildable[T,C[T]], evt: C[T] => Traversable[T]
+    evb: Buildable[T,C[T]], evt: C[T] => Iterable[T]
   ): Gen[C[T]] = buildableOfN[C[T],T](n,g)
 
   /** A convenience method for calling `buildableOf[C[T],T](g)`. */
   def containerOf[C[_],T](g: Gen[T])(implicit
-    evb: Buildable[T,C[T]], evt: C[T] => Traversable[T]
+    evb: Buildable[T,C[T]], evt: C[T] => Iterable[T]
   ): Gen[C[T]] = buildableOf[C[T],T](g)
 
   /** A convenience method for calling `nonEmptyBuildableOf[C[T],T](g)`. */
   def nonEmptyContainerOf[C[_],T](g: Gen[T])(implicit
-    evb: Buildable[T,C[T]], evt: C[T] => Traversable[T]
+    evb: Buildable[T,C[T]], evt: C[T] => Iterable[T]
   ): Gen[C[T]] = nonEmptyBuildableOf[C[T],T](g)
 
   /** Generates a list of random length. The maximum length depends on the
@@ -706,7 +706,7 @@ object Gen extends GenArities{
     choose(1, gs.length+2).flatMap(pick(_, g1, g2, gs: _*))
 
   /** A generator that picks a given number of elements from a list, randomly */
-  def pick[T](n: Int, l: Iterable[T]): Gen[Seq[T]] = {
+  def pick[T](n: Int, l: Iterable[T]): Gen[collection.Seq[T]] = {
     if (n > l.size || n < 0) throw new IllegalArgumentException(s"invalid choice: $n")
     else if (n == 0) Gen.const(Nil)
     else gen { (p, seed0) =>

src/main/scala/org/scalacheck/Properties.scala

@@ -41,7 +41,7 @@ class Properties(val name: String) {
 
   /** Returns all properties of this collection in a list of name/property
    *  pairs.  */
-  def properties: Seq[(String,Prop)] = props
+  def properties: collection.Seq[(String,Prop)] = props
 
   /** Convenience method that checks the properties with the given parameters
    *  (or default parameters, if not specified)

src/main/scala/org/scalacheck/ScalaCheckFramework.scala

@@ -45,7 +45,7 @@ private abstract class ScalaCheckRunner extends Runner {
   abstract class BaseTask(override val taskDef: TaskDef) extends Task {
     val tags: Array[String] = Array()
 
-    val props: Seq[(String,Prop)] = {
+    val props: collection.Seq[(String,Prop)] = {
       val fp = taskDef.fingerprint.asInstanceOf[SubclassFingerprint]
       val obj = if (fp.isModule) Platform.loadModule(taskDef.fullyQualifiedName,loader)
                 else Platform.newInstance(taskDef.fullyQualifiedName, loader, Seq())(Seq())