scala/scala — pull request #1530 by retronym (2012-10-28 22:25:26+00:00)
Title: SI-6575 Plug inference leak of AbstractPartialFunction

Usually this isn't needed, as partial functions can only be
defined with an expected type. But if that expected type is
and inherited method return type, the actual type of the partial
function literal is used, and the implementation detail of
`AbstractPartialFunction[A, B] with Serializable` leaks out.

After this change, the inferred types match those from
Scala 2.9.2.

```
ticket/6575 ~/code/scala scalac29 -Xprint:typer test/files/pos/t6575a.scala | grep def > 29.txt
ticket/6575 ~/code/scala squalac -Xprint:typer test/files/pos/t6575a.scala | grep def > 210.txt
ticket/6575 ~/code/scala diff -u 29.txt 210.txt
--- 29.txt	2012-10-28 13:51:07.000000000 +0100
+++ 210.txt	2012-10-28 13:51:20.000000000 +0100
@@ -1,7 +1,16 @@
def foo: PartialFunction[Int,Int]
def /*Y*/$init$(): Unit = {
- absoverride def foo: PartialFunction[Int,Int] = ((x0$1: Int) => x0$1 match {
+ absoverride def foo: PartialFunction[Int,Int] = {
+ def (): anonymous class $anonfun = {
+ final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+ final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
def /*Z*/$init$(): Unit = {
- absoverride def foo: PartialFunction[Int,Int] = ((x0$2: Int) => x0$2 match {
+ absoverride def foo: PartialFunction[Int,Int] = {
+ def (): anonymous class $anonfun = {
+ final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+ final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
def /*Comb*/$init$(): Unit = {
- absoverride def foo: PartialFunction[Int,Int] = ((x0$3: Int) => x0$3 match {
+ absoverride def foo: PartialFunction[Int,Int] = {
+ def (): anonymous class $anonfun = {
+ final override def applyOrElse[A1 >: Nothing <: Int, B1 >: Int <: Any](x$1: A1, default: A1 => B1): B1 = (x$1: A1 @unchecked) match {
+ final def isDefinedAt(x$1: Int): Boolean = (x$1: Int @unchecked) match {
```

review by @adriaanm
- submitting to 2.10.0-wip under the regression-discovered-in-RC1 banner.
- what's preferred, `tree.setType(tp)` or `Typed(tree, tp)`?