Fix compatibility with ppxlib 0.36.0

[andersfugmann]

No description provided.

[Copilot]

Pull Request Overview

This PR updates the library to work with ppxlib 0.36.0 by bumping dependencies, replacing function builders, and adding support for new AST shapes.

• Bump ppxlib dependency in the OPAM file
• Replace pexp_function with pexp_function_cases
• Handle the new Ptyp_open constructor and empty variant cases

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
ppx_protocol_conv.opam	Updated ppxlib version constraint to ≥ 0.36.0
ppx/ppx_protocol_conv.ml	Added empty-variant error branch, replaced builders, and included Ptyp_open in match clauses
Changelog	Added 5.2.3 entry noting compatibility with ppxlib 0.36.0

Comments suppressed due to low confidence (4)

ppx/ppx_protocol_conv.ml:282

• This new branch for empty variants should be covered by a unit test to ensure it raises the expected error at runtime.

  | Ptype_variant [] ->

ppx/ppx_protocol_conv.ml:356

• [nitpick] Consider adding a test case for Ptyp_open to verify that unsupported type descriptors raise the intended error.

  | Ptyp_open _

ppx/ppx_protocol_conv.ml:283

• Error messages should be consistent in punctuation; consider adding a period at the end to match other messages (e.g., "... not supported.").

    raise_errorf ~loc "ADTs with no constructors not supported"

ppx/ppx_protocol_conv.ml:723

• The comma after in introduces invalid OCaml syntax in a quoted expression; it should be removed and sequencing done with semicolons or line breaks.

             let f' = [%e e] in