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, 13 insertions, 10 deletions

diff --git a/src/library/scala/collection/IterableViewLike.scala b/src/library/scala/collection/IterableViewLike.scala
index df4710b1be..ce2daf08d4 100644
--- a/src/library/scala/collection/IterableViewLike.scala
+++ b/src/library/scala/collection/IterableViewLike.scala
@@ -42,6 +42,9 @@ trait IterableViewLike[+A,
     override def toString = viewToString
   }
 
+  /** Explicit instantiation of the `Transformed` trait to reduce class file size in subclasses. */
+  private[collection] abstract class AbstractTransformed[+B] extends super[TraversableViewLike].Transformed[B] with Transformed[B]
+
   trait EmptyView extends Transformed[Nothing] with super[TraversableViewLike].EmptyView with super[GenIterableViewLike].EmptyView
 
   trait Forced[B] extends super[TraversableViewLike].Forced[B] with super[GenIterableViewLike].Forced[B] with Transformed[B]
@@ -69,20 +72,20 @@ trait IterableViewLike[+A,
   /** Boilerplate method, to override in each subclass
    *  This method could be eliminated if Scala had virtual classes
    */
-  protected def newZipped[B](that: GenIterable[B]): Transformed[(A, B)] = new { val other = that } with Zipped[B]
+  protected def newZipped[B](that: GenIterable[B]): Transformed[(A, B)] = new { val other = that } with AbstractTransformed[(A, B)] with Zipped[B]
   protected def newZippedAll[A1 >: A, B](that: GenIterable[B], _thisElem: A1, _thatElem: B): Transformed[(A1, B)] = new {
     val other: GenIterable[B] = that
     val thisElem = _thisElem
     val thatElem = _thatElem
-  } with ZippedAll[A1, B]
-  protected override def newForced[B](xs: => GenSeq[B]): Transformed[B] = new { val forced = xs } with Forced[B]
-  protected override def newAppended[B >: A](that: GenTraversable[B]): Transformed[B] = new { val rest = that } with Appended[B]
-  protected override def newMapped[B](f: A => B): Transformed[B] = new { val mapping = f } with Mapped[B]
-  protected override def newFlatMapped[B](f: A => GenTraversableOnce[B]): Transformed[B] = new { val mapping = f } with FlatMapped[B]
-  protected override def newFiltered(p: A => Boolean): Transformed[A] = new { val pred = p } with Filtered
-  protected override def newSliced(_endpoints: SliceInterval): Transformed[A] = new { val endpoints = _endpoints } with Sliced
-  protected override def newDroppedWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with DroppedWhile
-  protected override def newTakenWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with TakenWhile
+  } with AbstractTransformed[(A1, B)] with ZippedAll[A1, B]
+  protected override def newForced[B](xs: => GenSeq[B]): Transformed[B] = new { val forced = xs } with AbstractTransformed[B] with Forced[B]
+  protected override def newAppended[B >: A](that: GenTraversable[B]): Transformed[B] = new { val rest = that } with AbstractTransformed[B] with Appended[B]
+  protected override def newMapped[B](f: A => B): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with Mapped[B]
+  protected override def newFlatMapped[B](f: A => GenTraversableOnce[B]): Transformed[B] = new { val mapping = f } with AbstractTransformed[B] with FlatMapped[B]
+  protected override def newFiltered(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with Filtered
+  protected override def newSliced(_endpoints: SliceInterval): Transformed[A] = new { val endpoints = _endpoints } with AbstractTransformed[A] with Sliced
+  protected override def newDroppedWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with DroppedWhile
+  protected override def newTakenWhile(p: A => Boolean): Transformed[A] = new { val pred = p } with AbstractTransformed[A] with TakenWhile
 
   // After adding take and drop overrides to IterableLike, these overrides (which do nothing
   // but duplicate the implementation in TraversableViewLike) had to be added to prevent the