AbstractPartialFunction.

Contributed by Todd Vierling with minor mods by extempore. This is an
obvious extension of AbstractFunctionN which I had some issue making
work at the time. Sounds kind of pitiful given that the compiler patch
is about two lines, but let's all agree to believe it was a different
world then.

This example program is impacted as follows:

    class A {
      def f: PartialFunction[Any, Int] = { case x: String => 1 }
      def g: PartialFunction[Any, Int] = f orElse { case x: List[_] => 2 }
      def h: PartialFunction[Any, Int] = g orElse { case x: Set[_] => 3 }
    }

Before: 34943 bytes of bytecode
 After:  4217 bytes of bytecode

A mere 88% reduction in size. "'Tis but a trifle!" Closes SI-5096,
SI-5097.

Author: paulp

src/actors/scala/actors/Actor.scala

@@ -246,7 +246,7 @@ object Actor extends Combinators {
     rawSelf.react(new RecursiveProxyHandler(rawSelf, f))
 
   private class RecursiveProxyHandler(a: ReplyReactor, f: PartialFunction[Any, Unit])
-          extends PartialFunction[Any, Unit] {
+          extends scala.runtime.AbstractPartialFunction[Any, Unit] {
     def isDefinedAt(m: Any): Boolean =
       true // events are immediately removed from the mailbox
     def apply(m: Any) {

src/actors/scala/actors/Future.scala

@@ -200,7 +200,7 @@ object Futures {
     Actor.timer.schedule(timerTask, timeout)
 
     def awaitWith(partFuns: Seq[PartialFunction[Any, Pair[Int, Any]]]) {
-      val reaction: PartialFunction[Any, Unit] = new PartialFunction[Any, Unit] {
+      val reaction: PartialFunction[Any, Unit] = new scala.runtime.AbstractPartialFunction[Any, Unit] {
         def isDefinedAt(msg: Any) = msg match {
           case TIMEOUT => true
           case _ => partFuns exists (_ isDefinedAt msg)

src/actors/scala/actors/Reactor.scala

@@ -38,11 +38,10 @@ private[actors] object Reactor {
     }
   }
 
-  val waitingForNone = new PartialFunction[Any, Unit] {
+  val waitingForNone: PartialFunction[Any, Unit] = new scala.runtime.AbstractPartialFunction[Any, Unit] {
     def isDefinedAt(x: Any) = false
     def apply(x: Any) {}
   }
-
 }
 
 /**

src/compiler/scala/reflect/internal/Definitions.scala

@@ -186,6 +186,7 @@ trait Definitions extends reflect.api.StandardDefinitions {
     // fundamental reference classes
     lazy val ScalaObjectClass           = getMember(ScalaPackageClass, tpnme.ScalaObject)
     lazy val PartialFunctionClass       = getClass("scala.PartialFunction")
+    lazy val AbstractPartialFunctionClass = getClass("scala.runtime.AbstractPartialFunction")
     lazy val SymbolClass                = getClass("scala.Symbol")
     lazy val StringClass                = getClass(sn.String)
     lazy val StringModule               = StringClass.linkedClassOfClass

src/compiler/scala/tools/cmd/FromString.scala

@@ -14,7 +14,7 @@ import scala.reflect.OptManifest
  *  example instances are in the companion object, but in general
  *  either IntFromString will suffice or you'll want custom transformers.
  */
-abstract class FromString[+T](implicit m: OptManifest[T]) extends PartialFunction[String, T] {
+abstract class FromString[+T](implicit m: OptManifest[T]) extends scala.runtime.AbstractPartialFunction[String, T] {
   def apply(s: String): T
   def isDefinedAt(s: String): Boolean = true
   def zero: T = apply("")

src/compiler/scala/tools/nsc/interpreter/AbstractOrMissingHandler.scala

@@ -6,7 +6,7 @@
 package scala.tools.nsc
 package interpreter
 
-class AbstractOrMissingHandler[T](onError: String => Unit, value: T) extends PartialFunction[Throwable, T] {
+class AbstractOrMissingHandler[T](onError: String => Unit, value: T) extends scala.runtime.AbstractPartialFunction[Throwable, T] {
   def isDefinedAt(t: Throwable) = t match {
     case _: AbstractMethodError     => true
     case _: NoSuchMethodError       => true

src/compiler/scala/tools/nsc/matching/ParallelMatching.scala

@@ -422,7 +422,7 @@ trait ParallelMatching extends ast.TreeDSL
       // Should the given pattern join the expanded pivot in the success matrix? If so,
       // this partial function will be defined for the pattern, and the result of the apply
       // is the expanded sequence of new patterns.
-      lazy val successMatrixFn = new PartialFunction[Pattern, List[Pattern]] {
+      lazy val successMatrixFn = new scala.runtime.AbstractPartialFunction[Pattern, List[Pattern]] {
         private def seqIsDefinedAt(x: SequenceLikePattern) = (hasStar, x.hasStar) match {
           case (true, true)   => true
           case (true, false)  => pivotLen <= x.nonStarLength

src/compiler/scala/tools/nsc/transform/UnCurry.scala

@@ -247,6 +247,7 @@ abstract class UnCurry extends InfoTransform
         val anonClass = owner newAnonymousFunctionClass fun.pos setFlag (FINAL | SYNTHETIC | inConstructorFlag)
         def parents =
           if (isFunctionType(fun.tpe)) List(abstractFunctionForFunctionType(fun.tpe), SerializableClass.tpe)
+          else if (isPartial) List(appliedType(AbstractPartialFunctionClass.typeConstructor, targs), SerializableClass.tpe)
           else List(ObjectClass.tpe, fun.tpe, SerializableClass.tpe)
 
         anonClass setInfo ClassInfoType(parents, new Scope, anonClass)

src/library/scala/Function.scala

@@ -39,7 +39,7 @@ object Function {
    *                f returns `Some(_)` and undefined where `f` returns `None`.
    *  @see [[scala.PartialFunction#lift]]
    */
-  def unlift[T, R](f: T => Option[R]): PartialFunction[T, R] = new PartialFunction[T, R] {
+  def unlift[T, R](f: T => Option[R]): PartialFunction[T, R] = new runtime.AbstractPartialFunction[T, R] {
     def apply(x: T): R = f(x).get
     def isDefinedAt(x: T): Boolean = f(x).isDefined
     override def lift: T => Option[R] = f

src/library/scala/PartialFunction.scala

@@ -36,7 +36,7 @@ trait PartialFunction[-A, +B] extends (A => B) {
    *           takes `x` to `this(x)` where `this` is defined, and to `that(x)` where it is not.
    */
   def orElse[A1 <: A, B1 >: B](that: PartialFunction[A1, B1]) : PartialFunction[A1, B1] =
-    new PartialFunction[A1, B1] {
+    new runtime.AbstractPartialFunction[A1, B1] {
     def isDefinedAt(x: A1): Boolean =
       PartialFunction.this.isDefinedAt(x) || that.isDefinedAt(x)
     def apply(x: A1): B1 =
@@ -51,7 +51,7 @@ trait PartialFunction[-A, +B] extends (A => B) {
    *   @return a partial function with the same domain as this partial function, which maps
    *           arguments `x` to `k(this(x))`.
    */
-  override def andThen[C](k: B => C) : PartialFunction[A, C] = new PartialFunction[A, C] {
+  override def andThen[C](k: B => C) : PartialFunction[A, C] = new runtime.AbstractPartialFunction[A, C] {
     def isDefinedAt(x: A): Boolean = PartialFunction.this.isDefinedAt(x)
     def apply(x: A): C = k(PartialFunction.this.apply(x))
   }
@@ -82,7 +82,7 @@ trait PartialFunction[-A, +B] extends (A => B) {
  *  @since   2.8
  */
 object PartialFunction {
-  private[this] final val empty_pf = new PartialFunction[Any, Nothing] {
+  private[this] final val empty_pf: PartialFunction[Any, Nothing] = new runtime.AbstractPartialFunction[Any, Nothing] {
     def isDefinedAt(x: Any) = false
     def apply(x: Any): Nothing = sys.error("undefined")
     override def orElse[A1, B1](that: PartialFunction[A1, B1]): PartialFunction[A1, B1] = that