Move everything into the scala.collection.compat package

build.sbt

@@ -22,9 +22,6 @@ lazy val `scala-collection-compat` = crossProject(JSPlatform, JVMPlatform)
     }
   )
   .jvmSettings(
-    // NOTE: if this setting is not defined, the published jar doesn't contain any classfiles.
-    // Related to https://github.com/scala/scala-parser-combinators/issues/119.
-    // TODO: what should the setting be? This library also adds classes to other (existing) packages.
     OsgiKeys.exportPackage := Seq(s"scala.collection.compat.*;version=${version.value}"),
     libraryDependencies += "com.novocode" % "junit-interface" % "0.11" % "test"
   )

src/main/scala-2.11_2.12/scala/collection/BuildFrom.scala → src/main/scala-2.11_2.12/scala/collection/compat/BuildFrom.scala

@@ -1,6 +1,7 @@
-package scala.collection
+package scala.collection.compat
 
 import scala.collection.generic.CanBuildFrom
+import scala.collection.{Iterable, mutable}
 
 /** Builds a collection of type `C` from elements of type `A` when a source collection of type `From` is available.
   * Implicit instances of `BuildFrom` are available for all collection types.

src/main/scala-2.11_2.12/scala/collection/compat/CompatImpl.scala

@@ -2,14 +2,14 @@ package scala.collection.compat
 
 import scala.collection.generic.CanBuildFrom
 import scala.collection.mutable.Builder
-import scala.collection.{immutable, mutable}
+import scala.collection.{immutable => i, mutable => m}
 
 private[compat] object CompatImpl {
   def simpleCBF[A, C](f: => Builder[A, C]): CanBuildFrom[Any, A, C] = new CanBuildFrom[Any, A, C] {
     def apply(from: Any): Builder[A, C] = apply()
     def apply(): Builder[A, C] = f
   }
 
-  type ImmutableBitSetCC[X] = ({ type L[_] = immutable.BitSet })#L[X]
-  type MutableBitSetCC[X] = ({ type L[_] = mutable.BitSet })#L[X]
+  type ImmutableBitSetCC[X] = ({ type L[_] = i.BitSet })#L[X]
+  type MutableBitSetCC[X] = ({ type L[_] = m.BitSet })#L[X]
 }

src/main/scala-2.11_2.12/scala/collection/Factory.scala → src/main/scala-2.11_2.12/scala/collection/compat/Factory.scala

@@ -1,6 +1,7 @@
-package scala.collection
+package scala.collection.compat
 
 import scala.collection.generic.CanBuildFrom
+import scala.collection.{TraversableOnce, mutable}
 
 /**
   * A factory that builds a collection of type `C` with elements of type `A`.
@@ -33,4 +34,4 @@ object Factory {
   implicit def fromCanBuildFromConversion[X, A, C](x: X)(implicit toCanBuildFrom: X => CanBuildFrom[Nothing, A, C]): Factory[A, C] =
     fromCanBuildFrom(toCanBuildFrom(x))
 
-}
+}

src/main/scala-2.11_2.12/scala/collection/immutable/ArraySeq.scala → src/main/scala-2.11_2.12/scala/collection/compat/immutable/ArraySeq.scala

@@ -1,15 +1,14 @@
-package scala
-package collection
-package immutable
+package scala.collection.compat.immutable
 
-import scala.reflect.ClassTag
-import scala.runtime.BoxedUnit
+import java.util.Arrays
+
+import scala.annotation.unchecked.uncheckedVariance
+import scala.collection.AbstractSeq
 import scala.collection.generic._
-import scala.collection.mutable.{Builder, ArrayBuilder, ArrayBuffer, WrappedArrayBuilder}
+import scala.collection.immutable.IndexedSeq
+import scala.collection.mutable.{ArrayBuilder, Builder, WrappedArrayBuilder}
+import scala.reflect.ClassTag
 import scala.util.hashing.MurmurHash3
-import scala.annotation.unchecked.uncheckedVariance
-
-import java.util.Arrays
 
 /**
   * An immutable array.
@@ -42,9 +41,6 @@ abstract class ArraySeq[+T]
   /** The underlying array */
   def unsafeArray: Array[T @uncheckedVariance]
 
-  private def elementClass: Class[_] =
-    unsafeArray.getClass.getComponentType
-
   override def stringPrefix = "ArraySeq"
 
   /** Clones this object, including the underlying Array. */

src/main/scala-2.11_2.12/scala/collection/compat/package.scala

@@ -1,8 +1,8 @@
 package scala.collection
 
 import scala.collection.generic._
-import scala.collection.mutable.Builder
 import scala.reflect.ClassTag
+import scala.collection.{immutable => i, mutable => m}
 
 /** The collection compatibility API */
 package object compat {
@@ -26,10 +26,10 @@ package object compat {
   implicit def bitSetFactoryToCBF(fact: BitSetFactory[BitSet]): CanBuildFrom[Any, Int, BitSet] =
     simpleCBF(fact.newBuilder)
 
-  implicit def immutableBitSetFactoryToCBF(fact: BitSetFactory[immutable.BitSet]): CanBuildFrom[Any, Int, ImmutableBitSetCC[Int]] =
+  implicit def immutableBitSetFactoryToCBF(fact: BitSetFactory[i.BitSet]): CanBuildFrom[Any, Int, ImmutableBitSetCC[Int]] =
     simpleCBF(fact.newBuilder)
 
-  implicit def mutableBitSetFactoryToCBF(fact: BitSetFactory[mutable.BitSet]): CanBuildFrom[Any, Int, MutableBitSetCC[Int]] =
+  implicit def mutableBitSetFactoryToCBF(fact: BitSetFactory[m.BitSet]): CanBuildFrom[Any, Int, MutableBitSetCC[Int]] =
     simpleCBF(fact.newBuilder)
 
   implicit class IterableFactoryExtensionMethods[CC[X] <: GenTraversable[X]](private val fact: GenericCompanion[CC]) {
@@ -56,4 +56,5 @@ package object compat {
 
   // This really belongs into scala.collection but there's already a package object in scala-library so we can't add to it
   type IterableOnce[+X] = TraversableOnce[X]
+  val  IterableOnce     = TraversableOnce
 }

src/main/scala-2.13/scala/collection/compat/immutable/package.scala

@@ -0,0 +1,6 @@
+package scala.collection.compat
+
+package object immutable {
+  type ArraySeq[+T] = scala.collection.immutable.ArraySeq[T]
+  val ArraySeq      = scala.collection.immutable.ArraySeq
+}

src/main/scala-2.13/scala/collection/compat/package.scala

@@ -1,5 +1,12 @@
 package scala.collection
 
-// Empty dummy package to allow cross-building with Scala 2.12
 package object compat {
+  type Factory[-A, +C] = scala.collection.Factory[A, C]
+  val  Factory         = scala.collection.Factory
+
+  type BuildFrom[-From, -A, +C] = scala.collection.BuildFrom[From, A, C]
+  val  BuildFrom                = scala.collection.BuildFrom
+
+  type IterableOnce[+X] = scala.collection.IterableOnce[X]
+  val  IterableOnce     = scala.collection.IterableOnce
 }

src/test/scala/test/scala/collection/ArraySeqTest.scala

@@ -2,7 +2,7 @@ package test.scala.collection
 
 import org.junit.{Assert, Test}
 
-import scala.collection.immutable.ArraySeq
+import scala.collection.compat.immutable.ArraySeq
 
 // The unmodified ArraySeqTest from collection-strawman
 class ArraySeqTest {

src/test/scala/test/scala/collection/BuildFromTest.scala

@@ -5,7 +5,7 @@ import org.junit.Test
 import scala.collection.compat._
 import scala.collection.immutable.{HashMap, TreeMap, TreeSet}
 import scala.collection.mutable.{ArrayBuffer, Builder, ListBuffer}
-import scala.collection.{BitSet, BuildFrom, SortedMap, SortedSet, immutable, mutable}
+import scala.collection.{BitSet, SortedMap, SortedSet, immutable, mutable}
 
 // Tests copied from the 2.13 scala-library
 class BuildFromTest {

src/test/scala/test/scala/collection/FactoryTest.scala

@@ -3,7 +3,7 @@ package test.scala.collection
 import org.junit.{Assert, Test}
 
 import scala.collection.compat._
-import scala.collection.{BitSet, Factory, immutable, mutable}
+import scala.collection.{BitSet, immutable, mutable}
 
 class FactoryTest {