top: move compatibility functions to compat_top

This isolates `cppo` directives to a single file, as done in `mdx`
itself. In particular, the corresponding `.mli` does not have any
preprocessing directives.

lib/top/compat_top.ml

@@ -0,0 +1,285 @@
+open Mdx.Migrate_ast
+
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+let try_finally ~always f = Misc.try_finally f ~always
+#else
+let try_finally ~always f = Misc.try_finally f always
+#endif
+
+let map_error_loc ~f (error : Location.error) =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  let f_msg (msg : Location.msg) =
+    { msg with loc = f msg.loc}
+  in
+  { error with main = f_msg error.main;
+                sub = List.map f_msg error.sub; }
+#else
+  let rec aux (error : Location.error) =
+     {error with sub = List.map aux error.sub;
+                 loc = f error.loc}
+  in
+  aux error
+#endif
+
+let error_of_exn exn =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR > 5
+  match Location.error_of_exn exn with
+    | None -> None
+    | Some `Already_displayed -> None
+    | Some (`Ok error) -> Some error
+#else
+  Location.error_of_exn exn
+#endif
+
+let rec get_id_in_path = function
+  | Path.Pident id -> id
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  | Path.Pdot (p, _) -> get_id_in_path p
+#else
+  | Path.Pdot (p, _, _) -> get_id_in_path p
+#endif
+  | Path.Papply (_, p) -> get_id_in_path p
+
+let lookup_type typ env =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR < 4
+  Env.lookup_type typ env |> fst
+#else
+  Env.lookup_type typ env
+#endif
+
+let type_structure env str loc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  let tstr, _, _, env =
+#else
+  let tstr, _, env =
+#endif
+    Typemod.type_structure env str loc
+  in
+  tstr, env
+
+let sig_value id desc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_value (id, desc, Exported)
+#else
+  Types.Sig_value (id, desc)
+#endif
+
+let sig_type id desc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_type (id, desc, Trec_not, Exported)
+#else
+  Types.Sig_type (id, desc, Trec_not)
+#endif
+
+let sig_typext id ext =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_typext (id, ext, Text_exception, Exported)
+#else
+  Types.Sig_typext (id, ext, Text_exception)
+#endif
+
+let sig_module id md =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_module (id, Mp_present, md, Trec_not, Exported)
+#else
+  Types.Sig_module (id, md, Trec_not)
+#endif
+
+let mty_path =
+  let open Types in
+  function
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  | Mty_alias(path) -> Some path
+#elif OCAML_MAJOR >= 4 && OCAML_MINOR > 3
+  | Mty_alias(_, path) -> Some path
+#else
+  | Mty_alias path -> Some path
+#endif
+  | Mty_ident _
+  | Mty_signature _
+  | Mty_functor _ ->
+    None
+
+let sig_modtype id desc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_modtype (id, desc, Exported)
+#else
+  Types.Sig_modtype (id, desc)
+#endif
+
+let sig_class id desc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_class (id, desc, Trec_not, Exported)
+#else
+  Types.Sig_class (id, desc, Trec_not)
+#endif
+
+let sig_class_type id desc =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Types.Sig_class_type (id, desc, Trec_not, Exported)
+#else
+  Types.Sig_class_type (id, desc, Trec_not)
+#endif
+
+let add_directive ~name ~doc kind =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 3
+  let directive = match kind with
+    | `Bool f -> Toploop.Directive_bool f
+    | `Show_prim to_sig -> 
+        let show_prim to_sig lid =
+          let env = !Toploop.toplevel_env in
+          let loc = Location.none in
+          try
+            let s =
+              match lid with
+              | Longident.Lident s -> s
+              | Longident.Ldot (_,s) -> s
+              | Longident.Lapply _ ->
+                  Format.printf "Invalid path %a@." Printtyp.longident lid;
+                  raise Exit
+            in
+            let id = Ident.create_persistent s in
+            let sg = to_sig env loc id lid in
+            Printtyp.wrap_printing_env env (fun () ->
+                Format.printf "@[%a@]@." Printtyp.signature sg
+              )
+          with
+          | Not_found -> Format.printf "@[Unknown element.@]@."
+          | Exit -> ()
+        in
+    (Toploop.Directive_ident (show_prim to_sig))
+  in
+  Toploop.add_directive name
+    directive
+    { section = "Environment queries"; doc }
+#else
+  ignore (name, doc, kind)
+#endif
+
+let extension_constructor
+    ~ext_type_path
+    ~ext_type_params
+    ~ext_args
+    ~ext_ret_type
+    ~ext_private
+    ~ext_loc
+    ~ext_attributes
+  =
+  let open Types in
+  let ext_args =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR < 3
+    ext_args
+#else
+    Cstr_tuple ext_args
+#endif
+  in
+  { ext_type_path
+  ; ext_type_params
+  ; ext_args
+  ; ext_ret_type
+  ; ext_private
+  ; ext_loc
+  ; ext_attributes
+  }
+
+let is_predef_or_global id =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  Ident.is_predef id || Ident.global id
+#else
+  Ident.binding_time id < 1000
+#endif
+
+let map_sig_attributes ~f =
+  let open Types in
+  List.map (function
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+    | Sig_module (id, mp, md, rs, visibility) ->
+      Sig_module (
+        id,
+        mp,
+        {md with md_attributes = f md.md_attributes },
+        rs,
+        visibility
+      )
+#else
+    | Sig_module (id, md, rs) ->
+      Sig_module (
+        id,
+        {md with md_attributes = f md.md_attributes},
+        rs
+      )
+#endif
+    | item -> item
+)
+
+let attribute ~name ~payload =
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  { Parsetree_.attr_name = name
+  ; attr_payload = payload
+  ; attr_loc = Location.none
+  }
+#else
+  (name, payload)
+#endif
+
+module Linked = struct
+  include (Topdirs : sig end)
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 3
+  include (Ephemeron : sig end)
+#endif
+  include (Uchar : sig end)
+  include (Condition : sig end)
+end
+
+let match_env
+    ~value
+    ~empty
+    ~open_
+    ~functor_arg
+    ~constraints
+    ~copy_types
+    ~module_
+    ~persistent
+    ~type_
+    ~modtype
+    ~cltype
+    ~class_
+    ~extension
+    env =
+  ignore (constraints, persistent, copy_types);
+  match env with
+  | Env.Env_value (summary, id, _) ->
+    value summary id
+  | Env_empty -> empty ()
+#if OCAML_MAJOR = 4 && OCAML_MINOR = 7
+  | Env_open (summary, _, pid) ->
+#else
+  | Env_open (summary, pid) ->
+#endif
+    open_ summary pid
+  | Env_functor_arg (summary, id) -> functor_arg summary id
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  | Env_module (summary, id, presence, _) ->
+    let present = match presence with
+      | Mp_present -> true
+      | Mp_absent -> false
+    in
+    module_ summary id ~present
+#else
+  | Env_module (summary, id, _) ->
+    module_ summary id ~present:true
+#endif
+  | Env_type (summary, _, _) -> type_ summary
+  | Env_modtype (summary, _, _) -> modtype summary
+  | Env_cltype (summary, _, _) -> cltype summary
+  | Env_class (summary, id, _) -> class_ summary id
+  | Env_extension (summary, id, _) -> extension summary id
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 4
+  | Env_constraints (summary, _) -> constraints summary
+#endif
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 6
+  | Env_copy_types (summary, _) -> copy_types summary
+#endif
+#if OCAML_MAJOR >= 4 && OCAML_MINOR >= 8
+  | Env_persistent (summary, _) -> persistent summary
+#endif

lib/top/compat_top.mli

@@ -0,0 +1,73 @@
+open Mdx.Migrate_ast
+
+val try_finally : always:(unit -> unit) -> (unit -> 'a) -> 'a
+
+val map_error_loc : f:(Location.t -> Location.t)
+  -> Location.error -> Location.error
+
+val error_of_exn : exn -> Location.error option
+
+val get_id_in_path : Path.t -> Ident.t
+
+val lookup_type : Longident.t -> Env.t -> Path.t
+
+val type_structure : Env.t -> Parsetree.structure -> Location.t -> Typedtree.structure * Env.t
+
+val sig_value : Ident.t -> Types.value_description -> Types.signature_item
+
+val sig_type : Ident.t -> Types.type_declaration -> Types.signature_item
+
+val sig_typext : Ident.t -> Types.extension_constructor -> Types.signature_item
+
+val sig_module : Ident.t -> Types.module_declaration -> Types.signature_item
+
+val mty_path : Types.module_type -> Path.t option
+
+val sig_modtype : Ident.t -> Types.modtype_declaration -> Types.signature_item
+
+val sig_class : Ident.t -> Types.class_declaration -> Types.signature_item
+
+val sig_class_type : Ident.t -> Types.class_type_declaration -> Types.signature_item
+
+val add_directive : name:string -> doc:string ->
+  [ `Bool of bool -> unit
+  | `Show_prim of Env.t -> Location.t -> Ident.t -> Longident.t ->
+      Types.signature ] -> unit
+
+val extension_constructor :
+  ext_type_path:Path.t ->
+  ext_type_params:Types.type_expr list ->
+  ext_args:Types.type_expr list ->
+  ext_ret_type:Types.type_expr option ->
+  ext_private:Asttypes_.private_flag ->
+  ext_loc:Location.t ->
+  ext_attributes:Parsetree_.attributes ->
+  Types.extension_constructor
+
+val is_predef_or_global : Ident.t -> bool
+
+val map_sig_attributes :
+  f:(Parsetree_.attributes -> Parsetree_.attributes) ->
+  Types.signature -> Types.signature
+
+val attribute :
+  name:string Location.loc ->
+  payload:Parsetree_.payload ->
+  Parsetree_.attribute
+
+val match_env :
+  value:(Env.summary -> Ident.t -> 'a) ->
+  empty:(unit -> 'a) ->
+  open_:(Env.summary -> Path.t -> 'a) ->
+  functor_arg:(Env.summary -> Ident.t -> 'a) ->
+  constraints:(Env.summary -> 'a) ->
+  copy_types:(Env.summary -> 'a) ->
+  module_:(Env.summary -> Ident.t -> present:bool -> 'a) ->
+  persistent:(Env.summary -> 'a) ->
+  type_:(Env.summary -> 'a) ->
+  modtype:(Env.summary -> 'a) ->
+  cltype:(Env.summary -> 'a) ->
+  class_:(Env.summary -> Ident.t -> 'a) ->
+  extension:(Env.summary -> Ident.t -> 'a) ->
+  Env.summary ->
+  'a