I'm able to crash the compiler with the following code.

package foo

object Foo {
  final class Foo(val i: Int) extends AnyVal {
    def foo() = go(i)
    private[this] def go(i: Int) = i * 2
  }
}

Taking the [this] modifier off allows the code to fully compile.

[info] Compiling 1 Scala source to
/home/adam/src/default-project/target/scala-2.10/classes...
[error]
[error] while compiling:
/home/adam/src/default-project/src/main/scala/Code.scala
[error] during phase: extmethods
[error] library version: version 2.10.0
[error] compiler version: version 2.10.0
[error] reconstructed args: -classpath
/home/adam/src/default-project/target/scala-2.10/classes -d
/home/adam/src/default-project/target/scala-2.10/classes
-bootclasspath /usr/lib/jvm/java-6-openjdk-amd64/jre/lib/resources.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/rt.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/sunrsasign.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/jsse.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/jce.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/charsets.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/netx.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/plugin.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/rhino.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/lib/modules/jdk.boot.jar:/usr/lib/jvm/java-6-openjdk-amd64/jre/classes:/home/adam/.sbt/0.12.1/boot/scala-2.10.0/lib/scala-library.jar
[error]
[error] last tree to typer: Select(This(object Foo), Foo)
[error] symbol: object Foo in object Foo (flags:
)
[error] symbol definition: object Foo
[error] tpe: foo.Foo.Foo.type
[error] symbol owners: object Foo -> object Foo -> package foo
[error] context owners: method go -> class Foo -> object Foo ->
package foo
[error]
[error] == Enclosing template or block ==
[error]
[error] Apply( // val : in class , tree.tpe=
[error] Foo.this."Foo"."go$extension" // val : in
class , tree.tpe=
[error] This("Foo")final implicit class Foo extends AnyVal in object Foo
[error] )
[error]
[error] == Expanded type of tree ==
[error]
[error] TypeRef(
[error] pre = ThisType(object Foo)
[error] TypeSymbol(class Foo extends AnyRef)
[error] )
[error]
[error] uncaught exception during compilation:
scala.reflect.internal.Types$TypeError
[trace] Stack trace suppressed: run last compile:compile for the full output.
[error] (compile:compile) scala.reflect.internal.Types$TypeError:
method go$extension in object Foo cannot be accessed in object
foo.Foo.Foo
[error] Total time: 2 s, completed Jan 22, 2013 8:29:03 PM