Dropped about 1.5 Mb off scala-library.jar.

This commit and the two subsequent commits were contributed by:

  Todd Vierling <tv@duh.org>.

I combined some commits and mangled his commit messages, but all the
credit is his. This pursues the same approach to classfile reduction
seen in r19989 when AbstractFunctionN was introduced, but applies it to
the collections. Thanks to -Xlint it's easy to verify that the private
types don't escape.

Design considerations as articulated by Todd:

* Don't necessarily create concrete types for _everything_. Where a
subtrait only provides a few additional methods, don't bother; instead,
use the supertrait's concrete class and retain the "with". For example,
"extends AbstractSeq[A] with LinearSeq[A]".

* Examine all classes with .class file size greater than 10k. Named
classes and class names ending in $$anon$<num> are candidates for
analysis.

* If a return type is currently inferred where an anon subclass would be
returned, make the return type explicit. Don't allow the library-private
abstract classes to leak into the public namespace [and scaladoc].

1 files changed, 5 insertions, 5 deletions

diff --git a/src/library/scala/collection/immutable/Set.scala b/src/library/scala/collection/immutable/Set.scala
index 89be64b1d2..fe3ce8fd0b 100644
--- a/src/library/scala/collection/immutable/Set.scala
+++ b/src/library/scala/collection/immutable/Set.scala
@@ -49,7 +49,7 @@ object Set extends ImmutableSetFactory[Set] {
   private val hashSeed = "Set".hashCode
 
   /** An optimized representation for immutable empty sets */
-  private object EmptySet extends Set[Any] with Serializable {
+  private object EmptySet extends AbstractSet[Any] with Set[Any] with Serializable {
     override def size: Int = 0
     def contains(elem: Any): Boolean = false
     def + (elem: Any): Set[Any] = new Set1(elem)
@@ -60,7 +60,7 @@ object Set extends ImmutableSetFactory[Set] {
 
   /** An optimized representation for immutable sets of size 1 */
   @SerialVersionUID(1233385750652442003L)
-  class Set1[A] private[collection] (elem1: A) extends Set[A] with Serializable {
+  class Set1[A] private[collection] (elem1: A) extends AbstractSet[A] with Set[A] with Serializable {
     override def size: Int = 1
     def contains(elem: A): Boolean =
       elem == elem1
@@ -79,7 +79,7 @@ object Set extends ImmutableSetFactory[Set] {
 
   /** An optimized representation for immutable sets of size 2 */
   @SerialVersionUID(-6443011234944830092L)
-  class Set2[A] private[collection] (elem1: A, elem2: A) extends Set[A] with Serializable {
+  class Set2[A] private[collection] (elem1: A, elem2: A) extends AbstractSet[A] with Set[A] with Serializable {
     override def size: Int = 2
     def contains(elem: A): Boolean =
       elem == elem1 || elem == elem2
@@ -99,7 +99,7 @@ object Set extends ImmutableSetFactory[Set] {
 
   /** An optimized representation for immutable sets of size 3 */
   @SerialVersionUID(-3590273538119220064L)
-  class Set3[A] private[collection] (elem1: A, elem2: A, elem3: A) extends Set[A] with Serializable {
+  class Set3[A] private[collection] (elem1: A, elem2: A, elem3: A) extends AbstractSet[A] with Set[A] with Serializable {
     override def size: Int = 3
     def contains(elem: A): Boolean =
       elem == elem1 || elem == elem2 || elem == elem3
@@ -120,7 +120,7 @@ object Set extends ImmutableSetFactory[Set] {
 
   /** An optimized representation for immutable sets of size 4 */
   @SerialVersionUID(-3622399588156184395L)
-  class Set4[A] private[collection] (elem1: A, elem2: A, elem3: A, elem4: A) extends Set[A] with Serializable {
+  class Set4[A] private[collection] (elem1: A, elem2: A, elem3: A, elem4: A) extends AbstractSet[A] with Set[A] with Serializable {
     override def size: Int = 4
     def contains(elem: A): Boolean =
       elem == elem1 || elem == elem2 || elem == elem3 || elem == elem4