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.

4 files changed, 17 insertions, 6 deletions

diff --git a/src/library/scala/Function.scala b/src/library/scala/Function.scala
index 23224b27e8..f1e93d6c76 100644
--- a/src/library/scala/Function.scala
+++ b/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
diff --git a/src/library/scala/PartialFunction.scala b/src/library/scala/PartialFunction.scala
index 51bb3dc93e..69e4dab675 100644
--- a/src/library/scala/PartialFunction.scala
+++ b/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
diff --git a/src/library/scala/runtime/AbstractPartialFunction.scala b/src/library/scala/runtime/AbstractPartialFunction.scala
new file mode 100644
index 0000000000..2f8b54356f
--- /dev/null
+++ b/src/library/scala/runtime/AbstractPartialFunction.scala
@@ -0,0 +1,11 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2011, LAMP/EPFL                  **
+**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+package scala.runtime
+
+abstract class AbstractPartialFunction[-T1, +R] extends AbstractFunction1[T1, R] with PartialFunction[T1, R]
diff --git a/src/library/scala/util/control/Exception.scala b/src/library/scala/util/control/Exception.scala
index c8470d2504..5fc938d18c 100644
--- a/src/library/scala/util/control/Exception.scala
+++ b/src/library/scala/util/control/Exception.scala
@@ -229,8 +229,8 @@ object Exception {
   private def wouldMatch(x: Throwable, classes: collection.Seq[Class[_]]): Boolean =
     classes exists (_ isAssignableFrom x.getClass)
 
-  private def pfFromExceptions(exceptions: Class[_]*) =
-    new PartialFunction[Throwable, Nothing] {
+  private def pfFromExceptions(exceptions: Class[_]*): PartialFunction[Throwable, Nothing] =
+    new scala.runtime.AbstractPartialFunction[Throwable, Nothing] {
       def apply(x: Throwable) = throw x
       def isDefinedAt(x: Throwable) = wouldMatch(x, exceptions)
     }