something very odd going on with scalaz-stream

console.scala

Welcome to Scala version 2.10.3 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_37).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import scalaz._, Scalaz._, stream._
import scalaz._
import Scalaz._
import stream._

scala> val chan = io.fileChunkR("build.sbt").mapOut { s => new String(s) }
chan: scalaz.stream.Process.Channel[scalaz.concurrent.Task,Int,String] = Await(scalaz.concurrent.Task@8e8cc3b,<function1>,Halt(scalaz.stream.Process$End$),Halt(scalaz.stream.Process$End$))

scala> chan.runFoldMap { _(64).run }
res0: scalaz.concurrent.Task[String] = scalaz.concurrent.Task@37d46c68

scala> :type res0.run
String

scala> res0.run
scalaz.stream.Process$End$


scala> "wat?"
res2: String = wat?

scala> res1
<console>:17: error: not found: value res1
              res1
              ^

so, Process.End is a an object that extends Exception with no stack trace, calling run throws it.