Generalizes catch blocks to include any Partial...

Generalizes catch blocks to include any PartialFunction[Throwable, T].
Existing catch blocks will compile exactly as before. Anything else
(which mean: the token after CATCH is not a left brace, or it is a left
brace not immediately followed by CASE) is desugared as follows:

  try body catch expr
  // becomes
  try body
  catch { case x =>
    val catchFn = expr
    if (catchFn isDefinedAt x) catchFn(x)
    else throw x
  }

Review by odersky.

1 files changed, 34 insertions, 0 deletions

diff --git a/test/files/run/pf-catch.scala b/test/files/run/pf-catch.scala
new file mode 100644
index 0000000000..f0b8baeeb3
--- /dev/null
+++ b/test/files/run/pf-catch.scala
@@ -0,0 +1,34 @@
+object Test {
+  def shortName(x: AnyRef) = x.getClass.getName split '.' last
+  type Handler[+T] = PartialFunction[Throwable, T]
+
+  val standardHandler: Handler[String] = {
+    case x: java.util.NoSuchElementException    => shortName(x)
+    case x: java.lang.IllegalArgumentException  => shortName(x)
+  }
+
+  def fn[T: Handler](body: => T): T = {
+    try body
+    catch implicitly[Handler[T]]
+  }
+
+  def f1 = {
+    implicit val myHandler = standardHandler
+    println(fn(Nil.head))
+    println(fn(null.toString))
+  }
+  def f2 = {
+    implicit val myHandler: Handler[String] = standardHandler orElse {
+      case x => "DEBUG: " + shortName(x)
+    }
+    println(fn(Nil.head))
+    println(fn(null.toString))
+  }
+
+  def main(args: Array[String]): Unit = {
+    try f1
+    catch { case x => println(shortName(x) + " slipped by.") }
+
+    f2
+  }
+}