Improve construction of unit_info

Author: liam923

src/kernel/mocaml.ml

@@ -35,12 +35,25 @@ let setup_reader_config config =
   let open Mconfig in
   let open Clflags in
   let ocaml = config.ocaml in
-  let to_unit_info name =
-    Some
-      (name |> Compilation_unit.of_string
-      |> Unit_info.make_dummy ~input_name:name)
+  let guessed_file_type : Unit_info.intf_or_impl =
+    (* We guess the file type based on the suffix of the file. This isn't very important
+       because we'll override the value that we use here later in Mpipeline, where we set
+       it based on the contents of the file.
+
+       At the moment, Merlin doesnt' actually use this value for anything, so it doesn't
+       matter what we set here. This is just a guard against future changes that might
+       start depending on this. *)
+    match String.split_on_char config.query.filename ~sep:'.' |> List.last with
+    | Some "ml" -> Impl
+    | Some "mli" -> Intf
+    | _ -> Impl
   in
-  Env.set_unit_name (Mconfig.unitname config |> to_unit_info);
+  let compilation_unit = Compilation_unit.of_string (Mconfig.unitname config) in
+  let unit_info =
+    Unit_info.make_with_known_compilation_unit
+      ~source_file:config.query.filename guessed_file_type "" compilation_unit
+  in
+  Env.set_unit_name (Some unit_info);
   Location.input_name := config.query.filename;
   fast := ocaml.unsafe;
   classic := ocaml.classic;

src/kernel/mpipeline.ml

@@ -270,6 +270,17 @@ let process ?state ?(pp_time = ref 0.0) ?(reader_time = ref 0.0)
          let cache_version =
            if Option.is_some cache_disabling then None else Some cache_version
          in
+         (* When we loaded the configuration in Mocaml, we guessed whether we're working
+            with an intf or impl file based on the suffix of the filename. But now we know
+            based on the contents of the file, so we update the value we wrote before. *)
+         Env.get_unit_name ()
+         |> Option.map
+              ~f:
+                (Unit_info.modify_kind ~f:(fun _ ->
+                     match result.parsetree with
+                     | `Interface _ -> Intf
+                     | `Implementation _ -> Impl))
+         |> Env.set_unit_name;
          { Reader.result; config; cache_version }))
   in
   let ppx =

src/ocaml/typing/unit_info.ml

@@ -152,3 +152,7 @@ let find_normalized_cmi f =
   let filename = (modname f |> Compilation_unit.name_as_string) ^ ".cmi" in
   let filename = Load_path.find_normalized filename in
   { Artifact.filename; modname = modname f; source_file = Some f.source_file  }
+
+(* Merlin-only *)
+
+let modify_kind t ~f = { t with kind = f t.kind }

src/ocaml/typing/unit_info.mli

@@ -187,3 +187,7 @@ val find_normalized_cmi: t -> Artifact.t
     [Unit_info.Artifact.t], using [dummy_source_file] as the filename if the
     artifact doesn't have one attached. *)
 val of_artifact : dummy_source_file:filename -> intf_or_impl -> Artifact.t -> t
+
+(* Merlin-only *)
+
+val modify_kind : t -> f:(intf_or_impl -> intf_or_impl) -> t