[Caml-list] visitors.ppx and ppx_metaquot

[Caml-list] visitors.ppx and ppx_metaquot

[Christoph Höger]

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Dear OCaml users,

today I tried to recompile a project that uses both some janestreet
derivers and visitors.ppx. To my horror, it now fails to compile with an
error about the visitors argument:

utop # #require "visitors.ppx";;
utop # type foo = int list [@@deriving visitors {variety="reduce"}];;
Error: Reference to undefined global
`VisitorsRuntime'
utop # #require "ppx_sexp_conv";;
utop # type foo = int list [@@deriving visitors {variety="reduce"}];;
Error: non-optional labeled argument expected

There is another error that might be related when I try it combination with
ppx_metaquot:

utop # #require "visitors.ppx";;
utop # type foo = int list [@@deriving visitors {variety="reduce"}];;
Error: Reference to undefined global
`VisitorsRuntime'
utop # #require "ppx_metaquot";;
utop # type foo = int list [@@deriving visitors {variety="reduce"}];;
Error: Attribute `deriving' was not used


The first error looks like ppx_type_conv gets confused about what is a
janestreet deriver and what is something else. The second error, well I
have no idea...

Does anyone know a workaround?

thanks,

Christoph

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Re: [Caml-list] visitors.ppx and ppx_metaquot

[Emilio Jesús Gallego Arias]

Dear Christoph,

Christoph Höger <christoph.hoeger@celeraone.com> writes:

> Does anyone know a workaround?

I had a similar problem [but not with visitors] that I solved by pinning
ppx_deriving to the 4.1 version. I guess you lose little by not trying.

E.

Re: [Caml-list] visitors.ppx and ppx_metaquot

[Gabriel Scherer]

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I think that similar issues have been reported before, and seem to arise
out of a wrong interaction between ppx_deriving and ppx_type_conv:

  https://github.com/ocaml-ppx/ppx_deriving/issues/149
  https://github.com/janestreet/ppx_type_conv/issues/9

(Note: Jérémie Dimino, which has been handling most of the ppx_type_conv
maintenance, is currently in well-deserved holidays, so the safest bet for
the next couple months may indeed be to pin back to older versions that
work for you.)

On Fri, Oct 6, 2017 at 10:29 AM, Emilio Jesús Gallego Arias <e@x80.org>
wrote:

> Dear Christoph,
>
> Christoph Höger <christoph.hoeger@celeraone.com> writes:
>
> > Does anyone know a workaround?
>
> I had a similar problem [but not with visitors] that I solved by pinning
> ppx_deriving to the 4.1 version. I guess you lose little by not trying.
>
> E.
>
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