ppx_gen_rec

A ppx rewriter that transforms a recursive module expression into a `struct`
README

A ppx rewriter that transforms a
recursive module
expression into a struct.

If you write a recursive module like this:

module rec Foo : sig
  type t = string
end = Foo

The compiler treats it like you wrote:

module rec Foo : sig
  type t = string
end = struct
  type t = string
end

If you try to use ppx_deriving, you get a Undefined_recursive_module exception, because ppx_deriving generates the signature but not the implementation:

module rec Foo : sig
  type t = string [@@deriving show]
end = Foo

(* is like writing *)
module rec Foo : sig
  type t = string
  val show: t -> string
end = struct
  type t = string
  let show _ = raise Undefined_recursive_module
end

Use ppx_gen_rec before ppx_deriving to generate an explicit struct, which will cause ppx_deriving to generate an implementation:

module%gen rec Foo : sig
  type t = string [@@deriving show]
end = Foo

(* becomes... *)
module rec Foo : sig
  type t = string [@@deriving show]
end = struct
  type t = string [@@deriving show]
end

(* which becomes... *)
module rec Foo : sig
  type t = string
  val show: t -> string
end = struct
  type t = string
  let show t = (* show stuff *)
end

Usage

Just use module%gen rec instead of module rec:

module%gen rec Foo : sig
  type t = string [@@deriving show]
end = Foo

License

ocaml-ppx_gen_rec is MIT licensed, as found in the LICENSE file.

Install
Published
09 Jul 2019
Sources
ppx_gen_rec-v1.1.0.tbz
sha256=7061496354023c182f189f02ee3dc5a8ae54dbb75b66a5effb09226ce722913b
sha512=37dded76035765673947d1d5d5e49ae7d36f80baaf7b5315d78e1392546c93d12ee164ce23baec6007879d3a8277c860c130d27b09be77b0caf736c7144881f0
Dependencies
Reverse Dependencies
flow_parser
>= "0.80.0"
flowtype
>= "0.78.0"