Strange output from Camlp4

[Matt Gushee <matt@gushee.net>]

In the process of trying to learn the revised syntax for objects, I have
encountered a strange message from Camlp4.

I have a file, ox.ml, whose contents look like this:

  let conf = object
    val mutable data:(string * string) list = []

    method get k = List.assoc k data
  end

BTW, that is deliberately a let binding rather than a class definition.
Is that not supposed to work?

Anyway, as suggested by the Camlp4 manual, I run

  camlp4o pr_r.cmo ox.ml

With the result:

  value conf =<pr_r: not impl: expr; tag = 25>;

???

--
Matt Gushee
Englewood, CO, USA