Support deriving from module type declarations.

[paurkedal]

I could use an extension of the deriving interface to allow deriving definitions from module types. The derived definitions would typically be a structure of the given signature or a functor producing or depending on it, though it could be regular functions involving first-class modules of the signature. My current use-case is to generate the RPC client and server parts for a Thrift service.

[paurkedal]

I noticed this breaks ppx_type_conv, since it registers Ppx_deriving with its own signature, see

• https://github.com/janestreet/ppx_type_conv/blob/master/ppx_deriving_exporter/ppx_type_conv_deriving.ml
• https://github.com/janestreet/ppx_type_conv/blob/master/src/type_conv.mli#L121-L135

It's documented as a private interface to be changed, so it may be a matter of synchronizing the releases.

[whitequark]

module_type_decl

[whitequark]

@diml How do we properly do releases in lockstep?

[ghost]

I suppose instead of passing (module Ppx_deriving) I could expand all the functions, that will make the glue code more robust to small changes in ppx_deriving. I'll add this change to the next minor release batch I'll do this week

[whitequark]

Thanks!

[paurkedal]

I pushed a version with modtype_* replaced by module_type_decl_*, I assume this is what you had in mind?

[whitequark]

Yep--thanks!

[ghost]

ppx_type_conv 113.33.03 has the change I described

[whitequark]

Ok--I will release a new ppx_deriving soon.

[paurkedal]

Thanks to both of you! (Not quite ready for a release myself.)