Use immutable.Seq and Iterable

Preparation for the new collections library.

Cherry-picked from work on trying to:
Add support for Scala 2.13-M4

Author: julienrf

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

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

@@ -17,6 +17,7 @@ import Arbitrary._
 import Shrink._
 import java.util.Date
 import scala.util.{Try, Success, Failure}
+import scala.collection.immutable.Seq
 
 object GenSpecification extends Properties("Gen") {
 

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/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

@@ -114,7 +114,7 @@ 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

@@ -17,6 +17,7 @@ import util.Buildable
 import util.SerializableCanBuildFroms._
 
 import scala.annotation.tailrec
+import scala.collection.immutable.Seq
 import scala.collection.immutable.TreeMap
 import scala.collection.mutable.ArrayBuffer
 import scala.concurrent.duration.{Duration, FiniteDuration}
@@ -449,7 +450,7 @@ 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) =>
@@ -576,55 +577,55 @@ 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

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

@@ -51,7 +51,7 @@ 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())

src/main/scala/org/scalacheck/Shrink.scala

@@ -49,7 +49,7 @@ object Shrink extends ShrinkLowPriority {
     cons(x, s.shrink(x))
 
   /** Shrink instance of container */
-  implicit def shrinkContainer[C[_],T](implicit v: C[T] => Traversable[T], s: Shrink[T],
+  implicit def shrinkContainer[C[_],T](implicit v: C[T] => Iterable[T], s: Shrink[T],
     b: Buildable[T,C[T]]
   ): Shrink[C[T]] = Shrink { xs: C[T] =>
     val ys = v(xs)
@@ -58,7 +58,7 @@ object Shrink extends ShrinkLowPriority {
   }
 
   /** Shrink instance of container2 */
-  implicit def shrinkContainer2[C[_,_],T,U](implicit v: C[T,U] => Traversable[(T,U)], s: Shrink[(T,U)],
+  implicit def shrinkContainer2[C[_,_],T,U](implicit v: C[T,U] => Iterable[(T,U)], s: Shrink[(T,U)],
     b: Buildable[(T,U),C[T,U]]
   ): Shrink[C[T,U]] = Shrink { xs: C[T,U] =>
     val ys = v(xs)

src/main/scala/org/scalacheck/Test.scala

@@ -11,6 +11,8 @@ package org.scalacheck
 
 import Prop.Arg
 
+import scala.collection.immutable.Seq
+
 object Test {
 
   import util.{FreqMap, CmdLineParser, ConsoleReporter}