From 4f2bf79622ed8fb8601be0335ab034ad9e865138 Mon Sep 17 00:00:00 2001
From: Corentin De Souza <9597216+fantazio@users.noreply.github.com>
Date: Wed, 19 Aug 2026 11:28:52 +0200
Subject: [PATCH 1/5] [src][state][file_infos] unify `signature` and
 `cmt_struct`

They are now merged into the new `annots` fields, which expliclty states
whether the content of the compilation unit is a structure, a signature
or both. The initial case is Neither (no compilation unit), as is the
case when the content of a .cmt or .cmti file is not handled (e.g. a
Partial_implementation)
---
 src/deadCode.ml          | 31 +++++++++-------
 src/deadSign.ml          |  6 +--
 src/state/file_infos.ml  | 80 ++++++++++++++++++++++++++--------------
 src/state/file_infos.mli | 15 +++++---
 4 files changed, 82 insertions(+), 50 deletions(-)

diff --git a/src/deadCode.ml b/src/deadCode.ml
index c4a8dd4..71adeae 100644
--- a/src/deadCode.ml
+++ b/src/deadCode.ml
@@ -327,7 +327,8 @@ let regabs state =
     hashtbl_add_unique_to_list main_files (Utils.Filepath.unit fn) ()
 
 
-let read_interface fn (sign : State.File_infos.signature) state =
+(* annots must not be Neither *)
+let read_interface fn (annots : State.File_infos.annots) state =
   regabs state;
   if Config.must_report_main state.config then
     let comp_unit =
@@ -341,11 +342,14 @@ let read_interface fn (sign : State.File_infos.signature) state =
       |> Ident.create_persistent
     in
     let path = [module_id] in
-    begin match sign with
-    | Structure structure ->
-        DeadSign.collect_export_from_structure ~path ~comp_unit structure
-    | Signature signature ->
-        DeadSign.collect_export_from_signature ~path ~comp_unit signature
+    begin match annots with
+    | Structure strc ->
+        DeadSign.collect_export_from_structure ~path ~comp_unit strc
+    | Signature sign | Both {sign; _} ->
+        DeadSign.collect_export_from_signature ~path ~comp_unit sign
+    | Neither ->
+        (* TODO: better error handling *)
+        assert false
     end;
     last_loc := Lexing.dummy_pos
 
@@ -432,10 +436,9 @@ let load_file fn state =
       if state.State.config.verbose then
         Printf.eprintf "Scanning interface from %s\n%!" fn;
     init_and_continue state fn (fun state ->
-    match state.file_infos.signature with
-    | None -> report_error (fn ^ ": missing signature")
-    | Some sign ->
-        read_interface fn sign state
+    match state.file_infos.annots with
+    | Neither -> report_error (fn ^ ": missing signature")
+    | annots -> read_interface fn annots state
     )
   in
   let process_implementation fn =
@@ -443,16 +446,16 @@ let load_file fn state =
     if state.State.config.verbose then
       Printf.eprintf "Scanning implementation from %s\n%!" fn;
     init_and_continue state fn (fun state ->
-    match state.file_infos.cmt_struct with
-    | None -> report_error (fn ^ ": missing cmt_struct")
-    | Some structure ->
+    match state.file_infos.annots with
+    | Neither | Signature _ -> report_error (fn ^ ": missing structure")
+    | Structure strc | Both {strc; _} ->
         regabs state;
         let prepare (loc1, loc2) =
           DeadObj.add_equal loc1 loc2;
           VdNode.merge_locs ~force:true loc2 loc1
         in
         List.iter prepare state.file_infos.location_dependencies;
-        collect_references.Tast_mapper.structure collect_references structure
+        collect_references.Tast_mapper.structure collect_references strc
         |> ignore;
         let loc_dep =
           if Config.must_report_section state.config.sections.exported_values then
diff --git a/src/deadSign.ml b/src/deadSign.ml
index 36fa4ec..bb8157c 100644
--- a/src/deadSign.ml
+++ b/src/deadSign.ml
@@ -258,8 +258,8 @@ let rec collect_export_from_include ~path sig_item =
 
 let correct_export sig_item =
   let state = State.get_current () in
-  match state.file_infos.signature with
-  | Some (Signature _) ->
+  match state.file_infos.annots with
+  | Structure _ -> correct_export sig_item
+  | _ ->
       (* Typedtree signatures found in .cmti files do not need correction *)
       ()
-  | _ -> correct_export sig_item
diff --git a/src/state/file_infos.ml b/src/state/file_infos.ml
index 4ac88b6..f469fe6 100644
--- a/src/state/file_infos.ml
+++ b/src/state/file_infos.ml
@@ -1,12 +1,21 @@
-type signature =
+type annots =
   | Structure of Typedtree.structure
   | Signature of Typedtree.signature
+  | Both of { sign: Typedtree.signature; strc: Typedtree.structure }
+  | Neither
+
+let merge_annots sign strc =
+  match sign, strc with
+  | Structure _, _ -> Result.error "expected a signature first"
+  | _, Signature _ -> Result.error "expected a structure second"
+  | Neither, annots | annots, Neither -> Result.ok annots
+  | (Signature sign | Both {sign; _}), (Structure strc | Both {strc; _}) ->
+      Result.ok (Both {sign; strc})
 
 type t = {
   builddir : string;
   cm_file : string;
-  signature : signature option;
-  cmt_struct : Typedtree.structure option;
+  annots : annots;
   cmti_uid_to_decl : Location_dependencies.uid_to_decl option;
   location_dependencies : Location_dependencies.t;
   modname : string;
@@ -16,8 +25,7 @@ type t = {
 let empty = {
   builddir = "!!UNKNOWN_BUILDDIR!!";
   cm_file = "";
-  signature = None;
-  cmt_struct = None;
+  annots = Neither;
   cmti_uid_to_decl = None;
   location_dependencies = Location_dependencies.empty;
   modname = "!!UNKNOWN_MODNAME!!";
@@ -27,7 +35,7 @@ let empty = {
 (** [init_from_all_cm_infos ~cm_file cmt_infos] creates a [t] with:
     - information from [cmt_infos] : [builddir], [modname], [sourcepath];
     - [cm_file];
-    - [signature] is extracted from [cmt_infos.cmt_annots]
+    - [annots] is extracted from [cmt_infos.cmt_annots]
 *)
 let init_from_all_cm_infos ~cm_file cmt_infos =
   let builddir = cmt_infos.Cmt_format.cmt_builddir in
@@ -36,15 +44,15 @@ let init_from_all_cm_infos ~cm_file cmt_infos =
     |> Option.map (Filename.concat builddir)
   in
   let modname = cmt_infos.cmt_modname in
-  let signature =
+  let annots =
     match cmt_infos.cmt_annots with
-    | Interface sign -> Some (Signature sign)
-    | Implementation str -> Some (Structure str)
-    | _ -> None
+    | Interface sign -> Signature sign
+    | Implementation strc -> Structure strc
+    | _ -> Neither
   in
   {empty with builddir;
               cm_file;
-              signature;
+              annots;
               modname;
               sourcepath}
 
@@ -69,32 +77,43 @@ let ( let* ) x f = Result.bind x f
 let ( let+ ) x f = Result.map f x
 
 let init_from_cmti_file cmti_file =
-  let+ file_infos, cmt_infos = init_from_cm_file cmti_file in
+  let* file_infos, cmt_infos = init_from_cm_file cmti_file in
   let cmti_uid_to_decl = Some cmt_infos.cmt_uid_to_decl in
-  {file_infos with cmti_uid_to_decl}
+  match file_infos.annots with
+  | Signature _ | Both _ ->
+      let file_infos = {file_infos with cmti_uid_to_decl} in
+      Result.ok file_infos
+  | _ -> Result.error (cmti_file ^ ": does not contain an interface")
 
 let init_from_cmt_file ~comp_unit_to_path cmt_file =
   let* file_infos, cmt_infos = init_from_cm_file cmt_file in
-  let* cmt_struct =
-    match cmt_infos.cmt_annots with
-    | Implementation structure -> Result.ok structure
+  let* annots =
+    match file_infos.annots with
+    | Structure _ | Both _ -> Result.ok file_infos.annots
     | _ -> Result.error (cmt_file ^ ": does not contain an implementation")
   in
-  let cmt_struct = Some cmt_struct in
   (* Read the cmti if it exists. We always want to do it in case a user
      specified the cmt before the cmti to ensure the location_dependencies
      are idempotent. *)
-  let cmti_uid_to_decl =
+  let cmti_uid_to_decl, annots =
     let cmti_file = Filename.remove_extension cmt_file ^ ".cmti" in
     match init_from_cmti_file cmti_file with
-    | Error _ -> None
-    | Ok file_infos -> file_infos.cmti_uid_to_decl
+    | Error _ -> None, annots
+    | Ok file_infos ->
+        let annots =
+          match merge_annots file_infos.annots annots with
+          | Error _ ->
+              (* TODO: better error handling *)
+              assert false
+          | Ok annots -> annots
+        in
+        file_infos.cmti_uid_to_decl, annots
   in
   let+ location_dependencies =
     Location_dependencies.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
   in
   let file_infos =
-    {file_infos with cmt_struct; cmti_uid_to_decl; location_dependencies}
+    {file_infos with annots; cmti_uid_to_decl; location_dependencies}
   in
   file_infos, cmt_infos
 
@@ -115,9 +134,9 @@ let init ~comp_unit_to_path cm_file =
         {file_infos with location_dependencies}
       in
       match filled_with_cmt_infos with
-      | Ok {cmt_struct; cmti_uid_to_decl; location_dependencies; _} ->
+      | Ok {annots; cmti_uid_to_decl; location_dependencies; _} ->
           let+ res, _ = init_from_cm_file cm_file in
-          {res with cmt_struct; cmti_uid_to_decl; location_dependencies}
+          {res with annots; cmti_uid_to_decl; location_dependencies}
       | Error _ -> init_from_cmti_file cm_file
   )
   | _ -> Result.error (cm_file ^ ": not a .cmti or .cmt file")
@@ -126,7 +145,7 @@ let change_file ~comp_unit_to_path file_infos cm_file =
   let no_ext = Filename.remove_extension cm_file in
   assert(no_ext = Filename.remove_extension file_infos.cm_file);
   match Filename.extension cm_file, file_infos with
-  | ".cmt", {cmt_struct = (Some _ as cs); signature; cmti_uid_to_decl; _} ->
+  | ".cmt", {annots; cmti_uid_to_decl; _} ->
       let* res, cmt_infos = init_from_cm_file cm_file in
       let+ location_dependencies =
         match file_infos.location_dependencies with
@@ -134,10 +153,17 @@ let change_file ~comp_unit_to_path file_infos cm_file =
         | loc_dep -> (* They have already been computed *)
             Result.ok loc_dep
       in
-      {res with cmt_struct = cs; signature; cmti_uid_to_decl; location_dependencies}
-  | ".cmti", {cmti_uid_to_decl = (Some _ as cutd); cmt_struct; location_dependencies; _} ->
+      let annots =
+        match merge_annots annots res.annots with
+        | Error _ ->
+            (* TODO: better error handling *)
+            assert false
+        | Ok annots -> annots
+      in
+      {res with annots; cmti_uid_to_decl; location_dependencies}
+  | ".cmti", {cmti_uid_to_decl = (Some _ as cutd); annots; location_dependencies; _} ->
       let+ res, _ = init_from_cm_file cm_file in
-      {res with cmti_uid_to_decl = cutd; cmt_struct; location_dependencies}
+      {res with cmti_uid_to_decl = cutd; annots; location_dependencies}
   | _ ->
       (* invalid extension or the corresponding info is None *)
       init ~comp_unit_to_path cm_file
diff --git a/src/state/file_infos.mli b/src/state/file_infos.mli
index 8c50705..a946583 100644
--- a/src/state/file_infos.mli
+++ b/src/state/file_infos.mli
@@ -1,16 +1,19 @@
 (** Information about a analyzable file ([.cmti] or [.cmt] file) *)
 
-type signature =
+(** binary_annots of the compialtion unit *)
+type annots =
   | Structure of Typedtree.structure
-  | Signature of Typedtree.signature
+      (* only a .cmt was read (i.e. no .cmti available) *)
+  | Signature of Typedtree.signature (* only a .cmti was read *)
+  | Both of { sign: Typedtree.signature; strc: Typedtree.structure }
+      (* both the .cmti and .cmt were read *)
+  | Neither (* no file read or the content was discarded *)
 
 type t = {
   builddir : string; (** The [cmt_builddir] *)
   cm_file : string; (** The filepath currently analyzed *)
-  signature : signature option;
-    (** Extracted from [cmt_infos] in cmti files and [cmi_infos] in cmt files *)
-  cmt_struct : Typedtree.structure option;
-    (** Extracted from a cmt's [cmt_infos.cmt_annots] *)
+  annots : annots;
+    (** Extracted from [cmt_infos.cmt_annots] in .cmti and .cmt files. *)
   cmti_uid_to_decl : Location_dependencies.uid_to_decl option;
     (** Extracted from a cmti's [cmt_infos] *)
   location_dependencies : Location_dependencies.t;

From 71545d7d7bf9a83f5a3b1ffe24b611330b2c18c0 Mon Sep 17 00:00:00 2001
From: Corentin De Souza <9597216+fantazio@users.noreply.github.com>
Date: Wed, 19 Aug 2026 11:58:19 +0200
Subject: [PATCH 2/5] [src][state][file_infos] simplify code

Remove a lot of anticipated initialization (reading the .cmt for .cmti
and vice-versa). This results in simpler init functions.
Also errors when changing from .cmt to .cmti file of the same
compilation unit (the order must be .cmti then .cmt).
---
 src/state/file_infos.ml | 96 +++++++++++------------------------------
 1 file changed, 25 insertions(+), 71 deletions(-)

diff --git a/src/state/file_infos.ml b/src/state/file_infos.ml
index f469fe6..bfad1d7 100644
--- a/src/state/file_infos.ml
+++ b/src/state/file_infos.ml
@@ -1,3 +1,5 @@
+module Locdep = Location_dependencies
+
 type annots =
   | Structure of Typedtree.structure
   | Signature of Typedtree.signature
@@ -6,18 +8,19 @@ type annots =
 
 let merge_annots sign strc =
   match sign, strc with
-  | Structure _, _ -> Result.error "expected a signature first"
-  | _, Signature _ -> Result.error "expected a structure second"
-  | Neither, annots | annots, Neither -> Result.ok annots
+  | Structure _, _ | _, Signature _ ->
+      (* TODO: better error handling *)
+      assert false
+  | Neither, annots | annots, Neither -> annots
   | (Signature sign | Both {sign; _}), (Structure strc | Both {strc; _}) ->
-      Result.ok (Both {sign; strc})
+      Both {sign; strc}
 
 type t = {
   builddir : string;
   cm_file : string;
   annots : annots;
-  cmti_uid_to_decl : Location_dependencies.uid_to_decl option;
-  location_dependencies : Location_dependencies.t;
+  cmti_uid_to_decl : Locdep.uid_to_decl option;
+  location_dependencies : Locdep.t;
   modname : string;
   sourcepath : string option;
 }
@@ -27,7 +30,7 @@ let empty = {
   cm_file = "";
   annots = Neither;
   cmti_uid_to_decl = None;
-  location_dependencies = Location_dependencies.empty;
+  location_dependencies = Locdep.empty;
   modname = "!!UNKNOWN_MODNAME!!";
   sourcepath = None;
 }
@@ -80,65 +83,25 @@ let init_from_cmti_file cmti_file =
   let* file_infos, cmt_infos = init_from_cm_file cmti_file in
   let cmti_uid_to_decl = Some cmt_infos.cmt_uid_to_decl in
   match file_infos.annots with
-  | Signature _ | Both _ ->
+  | Signature _ ->
       let file_infos = {file_infos with cmti_uid_to_decl} in
       Result.ok file_infos
   | _ -> Result.error (cmti_file ^ ": does not contain an interface")
 
 let init_from_cmt_file ~comp_unit_to_path cmt_file =
   let* file_infos, cmt_infos = init_from_cm_file cmt_file in
-  let* annots =
-    match file_infos.annots with
-    | Structure _ | Both _ -> Result.ok file_infos.annots
-    | _ -> Result.error (cmt_file ^ ": does not contain an implementation")
-  in
-  (* Read the cmti if it exists. We always want to do it in case a user
-     specified the cmt before the cmti to ensure the location_dependencies
-     are idempotent. *)
-  let cmti_uid_to_decl, annots =
-    let cmti_file = Filename.remove_extension cmt_file ^ ".cmti" in
-    match init_from_cmti_file cmti_file with
-    | Error _ -> None, annots
-    | Ok file_infos ->
-        let annots =
-          match merge_annots file_infos.annots annots with
-          | Error _ ->
-              (* TODO: better error handling *)
-              assert false
-          | Ok annots -> annots
-        in
-        file_infos.cmti_uid_to_decl, annots
-  in
-  let+ location_dependencies =
-    Location_dependencies.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
-  in
-  let file_infos =
-    {file_infos with annots; cmti_uid_to_decl; location_dependencies}
-  in
-  file_infos, cmt_infos
+  match file_infos.annots with
+  | Structure _ ->
+      let+ location_dependencies =
+        Locdep.init ~comp_unit_to_path cmt_infos None
+      in
+      {file_infos with location_dependencies}
+  | _ -> Result.error (cmt_file ^ ": does not contain an implementation")
 
 let init ~comp_unit_to_path cm_file =
   match Filename.extension cm_file with
-  | ".cmt" ->
-      let+ file_infos, _ = init_from_cmt_file ~comp_unit_to_path cm_file in
-      file_infos
-  | ".cmti" -> (
-      (* Using cmt_infos is not critical. The intent is to mirror the behavior
-         on cmt files, where both cmt and cmti are read. *)
-      let filled_with_cmt_infos =
-        let cmt_file = Filename.remove_extension cm_file ^ ".cmt" in
-        let* file_infos, cmt_infos = init_from_cmt_file ~comp_unit_to_path cmt_file in
-        let+ location_dependencies =
-          Location_dependencies.init ~comp_unit_to_path cmt_infos file_infos.cmti_uid_to_decl
-        in
-        {file_infos with location_dependencies}
-      in
-      match filled_with_cmt_infos with
-      | Ok {annots; cmti_uid_to_decl; location_dependencies; _} ->
-          let+ res, _ = init_from_cm_file cm_file in
-          {res with annots; cmti_uid_to_decl; location_dependencies}
-      | Error _ -> init_from_cmti_file cm_file
-  )
+  | ".cmt" -> init_from_cmt_file ~comp_unit_to_path cm_file
+  | ".cmti" -> init_from_cmti_file cm_file
   | _ -> Result.error (cm_file ^ ": not a .cmti or .cmt file")
 
 let change_file ~comp_unit_to_path file_infos cm_file =
@@ -148,22 +111,13 @@ let change_file ~comp_unit_to_path file_infos cm_file =
   | ".cmt", {annots; cmti_uid_to_decl; _} ->
       let* res, cmt_infos = init_from_cm_file cm_file in
       let+ location_dependencies =
-        match file_infos.location_dependencies with
-        | [] -> Location_dependencies.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
-        | loc_dep -> (* They have already been computed *)
-            Result.ok loc_dep
-      in
-      let annots =
-        match merge_annots annots res.annots with
-        | Error _ ->
-            (* TODO: better error handling *)
-            assert false
-        | Ok annots -> annots
+        Locdep.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
       in
+      let annots = merge_annots annots res.annots in
       {res with annots; cmti_uid_to_decl; location_dependencies}
-  | ".cmti", {cmti_uid_to_decl = (Some _ as cutd); annots; location_dependencies; _} ->
-      let+ res, _ = init_from_cm_file cm_file in
-      {res with cmti_uid_to_decl = cutd; annots; location_dependencies}
+  | ".cmti", _ ->
+      (* .cmti files are alwasy read before the correpsonding.cmt *)
+      Result.error (cm_file ^ ": must be read before its correpsonding .cmt")
   | _ ->
       (* invalid extension or the corresponding info is None *)
       init ~comp_unit_to_path cm_file

From 76cc84880800362bbaf43cee287bf565afa1589c Mon Sep 17 00:00:00 2001
From: Corentin De Souza <9597216+fantazio@users.noreply.github.com>
Date: Wed, 19 Aug 2026 12:12:17 +0200
Subject: [PATCH 3/5] [src][state][cmt] only read cmt_infos

Both the cache and the `read` function used to store/return a tuple
containg the cmi_infos and the cmt_infos. Cmi_infos are not used anymore
anywhere, thus we can reduce this tuple to only the cmt_infos.
---
 src/state/cmt.ml                   | 25 ++++++++++++++-----------
 src/state/cmt.mli                  |  8 +++-----
 src/state/file_infos.ml            |  2 +-
 src/state/location_dependencies.ml |  3 +--
 4 files changed, 19 insertions(+), 19 deletions(-)

diff --git a/src/state/cmt.ml b/src/state/cmt.ml
index ce9c002..256f8ee 100644
--- a/src/state/cmt.ml
+++ b/src/state/cmt.ml
@@ -34,9 +34,8 @@ module Cache = struct
 
 end
 
-type cmi_cmt_infos = Cmi_format.cmi_infos option * Cmt_format.cmt_infos
-
-let cache_cmt : ((string * string), (string * cmi_cmt_infos)) Cache.t = Cache.create 64
+let cache_cmt : ((string * string), (string * Cmt_format.cmt_infos)) Cache.t =
+  Cache.create 64
 
 let set_cache_size capacity = Cache.update_capacity cache_cmt capacity
 
@@ -51,17 +50,21 @@ let read_no_cache filepath =
       Option.map (( ^ ) " Tip: ") tip
       |> Option.value ~default:""
     in
-    Printf.sprintf "%s: %s.%s" filepath msg tip
+    Printf.sprintf "%s: %s. %s" filepath msg tip
     |> Result.error
   in
-  match Cmt_format.read filepath with
+  match Cmt_format.read_cmt filepath with
   | exception Cmi_format.(Error (Not_an_interface _)) ->
       let tip =
-        "the file must be compiled with the same OCaml version as the dead_code_analyzer."
+        "The file must be compiled with the same OCaml version as the dead_code_analyzer."
       in
       error ~tip "invalid magic number"
-  | _, None -> error "missing cmt_infos"
-  | cmi_infos, Some cmt_infos -> Result.ok (cmi_infos, cmt_infos)
+  | exception Cmt_format.(Error (Not_a_typedtree _)) ->
+      let tip =
+        "The file must be a .cmt or .cmti file compiled with the same OCaml version as the dead_code_analyzer."
+      in
+      error ~tip "does not contain a typedtree"
+  | cmt_infos -> Result.ok cmt_infos
 
 let read filepath =
   let comp_unit = Utils.Filepath.unit filepath in
@@ -70,9 +73,9 @@ let read filepath =
   | Some (fp, res) when String.equal fp filepath -> Result.ok res
   | _ ->
       read_no_cache filepath
-      |> Result.map (fun cmi_cmt_infos ->
-        Cache.add cache_cmt (ext, comp_unit) (filepath, cmi_cmt_infos);
-        cmi_cmt_infos)
+      |> Result.map (fun cmt_infos ->
+        Cache.add cache_cmt (ext, comp_unit) (filepath, cmt_infos);
+        cmt_infos)
 
 let find_cached_from_comp_unit comp_unit ext =
   Cache.find_opt cache_cmt (ext, comp_unit)
diff --git a/src/state/cmt.mli b/src/state/cmt.mli
index 49432e9..dcc06ae 100644
--- a/src/state/cmt.mli
+++ b/src/state/cmt.mli
@@ -1,10 +1,8 @@
-type cmi_cmt_infos = Cmi_format.cmi_infos option * Cmt_format.cmt_infos
+val read : string -> (Cmt_format.cmt_infos, string) Result.t
 
-val read : string -> (cmi_cmt_infos, string) Result.t
+val cached_cmti : string -> Cmt_format.cmt_infos option
 
-val cached_cmti : string -> cmi_cmt_infos option
-
-val cached_cmt : string -> cmi_cmt_infos option
+val cached_cmt : string -> Cmt_format.cmt_infos option
 
 val set_cache_size : int -> unit
 
diff --git a/src/state/file_infos.ml b/src/state/file_infos.ml
index bfad1d7..d8267f2 100644
--- a/src/state/file_infos.ml
+++ b/src/state/file_infos.ml
@@ -70,7 +70,7 @@ let init_from_cm_file cm_file =
   else
     match Cmt.read cm_file with
     | Error _ as err -> err
-    | Ok (_, cmt_infos) ->
+    | Ok cmt_infos ->
         let file_infos =
           init_from_all_cm_infos ~cm_file cmt_infos
         in
diff --git a/src/state/location_dependencies.ml b/src/state/location_dependencies.ml
index e31078c..d951af2 100644
--- a/src/state/location_dependencies.ml
+++ b/src/state/location_dependencies.ml
@@ -42,12 +42,11 @@ let find_opt_external_uid_loc ~comp_unit_to_path = function
         in
         Cmt.read cm_path |> Result.to_option
       in
-      let* cmi_cmt_infos =
+      let* cmt_infos =
         match cached with
         | Some _ as some -> some
         | None  -> read_from_path ()
       in
-      let cmt_infos = snd cmi_cmt_infos in
       let cmt_uid_to_decl = cmt_infos.cmt_uid_to_decl in
       let* item_decl = UidTbl.find_opt cmt_uid_to_decl uid in
       loc_opt_of_item_decl item_decl

From cd3627926d61a235a734fa8658964a1c9cfaebae Mon Sep 17 00:00:00 2001
From: Corentin De Souza <9597216+fantazio@users.noreply.github.com>
Date: Wed, 19 Aug 2026 15:12:02 +0200
Subject: [PATCH 4/5] [src][state][file_infos] unify cmti_uid_to_decl and
 location_dependencies

The former is an intermediate result to produce the latter. They are now
represented via the same field `location_dependencies` of the new type
`loc_dep`.
---
 src/deadCode.ml          | 11 +++++++++--
 src/state/file_infos.ml  | 23 ++++++++++++++---------
 src/state/file_infos.mli | 16 +++++++++++++---
 3 files changed, 36 insertions(+), 14 deletions(-)

diff --git a/src/deadCode.ml b/src/deadCode.ml
index 71adeae..6e2c5ab 100644
--- a/src/deadCode.ml
+++ b/src/deadCode.ml
@@ -454,7 +454,14 @@ let load_file fn state =
           DeadObj.add_equal loc1 loc2;
           VdNode.merge_locs ~force:true loc2 loc1
         in
-        List.iter prepare state.file_infos.location_dependencies;
+        let location_dependencies =
+          match state.file_infos.location_dependencies with
+          | Set location_dependencies -> location_dependencies
+          | _ ->
+              (* TODO: better error handling *)
+              assert false
+        in
+        List.iter prepare location_dependencies;
         collect_references.Tast_mapper.structure collect_references strc
         |> ignore;
         let loc_dep =
@@ -471,7 +478,7 @@ let load_file fn state =
                    Some (loc1, loc2)
                  else None
               )
-              state.file_infos.location_dependencies
+              location_dependencies
           else []
         in
         eof loc_dep
diff --git a/src/state/file_infos.ml b/src/state/file_infos.ml
index d8267f2..43dbc49 100644
--- a/src/state/file_infos.ml
+++ b/src/state/file_infos.ml
@@ -15,12 +15,16 @@ let merge_annots sign strc =
   | (Signature sign | Both {sign; _}), (Structure strc | Both {strc; _}) ->
       Both {sign; strc}
 
+type loc_dep =
+  | In_progress of Location_dependencies.uid_to_decl
+  | Set of Location_dependencies.t
+  | Unset
+
 type t = {
   builddir : string;
   cm_file : string;
   annots : annots;
-  cmti_uid_to_decl : Locdep.uid_to_decl option;
-  location_dependencies : Locdep.t;
+  location_dependencies : loc_dep;
   modname : string;
   sourcepath : string option;
 }
@@ -29,8 +33,7 @@ let empty = {
   builddir = "!!UNKNOWN_BUILDDIR!!";
   cm_file = "";
   annots = Neither;
-  cmti_uid_to_decl = None;
-  location_dependencies = Locdep.empty;
+  location_dependencies = Unset;
   modname = "!!UNKNOWN_MODNAME!!";
   sourcepath = None;
 }
@@ -81,10 +84,10 @@ let ( let+ ) x f = Result.map f x
 
 let init_from_cmti_file cmti_file =
   let* file_infos, cmt_infos = init_from_cm_file cmti_file in
-  let cmti_uid_to_decl = Some cmt_infos.cmt_uid_to_decl in
+  let location_dependencies = In_progress cmt_infos.cmt_uid_to_decl in
   match file_infos.annots with
   | Signature _ ->
-      let file_infos = {file_infos with cmti_uid_to_decl} in
+      let file_infos = {file_infos with location_dependencies} in
       Result.ok file_infos
   | _ -> Result.error (cmti_file ^ ": does not contain an interface")
 
@@ -95,6 +98,7 @@ let init_from_cmt_file ~comp_unit_to_path cmt_file =
       let+ location_dependencies =
         Locdep.init ~comp_unit_to_path cmt_infos None
       in
+      let location_dependencies = Set location_dependencies in
       {file_infos with location_dependencies}
   | _ -> Result.error (cmt_file ^ ": does not contain an implementation")
 
@@ -108,13 +112,14 @@ let change_file ~comp_unit_to_path file_infos cm_file =
   let no_ext = Filename.remove_extension cm_file in
   assert(no_ext = Filename.remove_extension file_infos.cm_file);
   match Filename.extension cm_file, file_infos with
-  | ".cmt", {annots; cmti_uid_to_decl; _} ->
+  | ".cmt", {annots; location_dependencies = In_progress uid_to_decl; _} ->
       let* res, cmt_infos = init_from_cm_file cm_file in
       let+ location_dependencies =
-        Locdep.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
+        Locdep.init ~comp_unit_to_path cmt_infos (Some uid_to_decl)
       in
+      let location_dependencies = Set location_dependencies in
       let annots = merge_annots annots res.annots in
-      {res with annots; cmti_uid_to_decl; location_dependencies}
+      {res with annots; location_dependencies}
   | ".cmti", _ ->
       (* .cmti files are alwasy read before the correpsonding.cmt *)
       Result.error (cm_file ^ ": must be read before its correpsonding .cmt")
diff --git a/src/state/file_infos.mli b/src/state/file_infos.mli
index a946583..531a3f3 100644
--- a/src/state/file_infos.mli
+++ b/src/state/file_infos.mli
@@ -9,14 +9,24 @@ type annots =
       (* both the .cmti and .cmt were read *)
   | Neither (* no file read or the content was discarded *)
 
+(** Dependencies similar to [cmt_infos.cmt_value_dependencies] in OCaml 5.2.
+    Because the .cmti file is processed before its correpsonding .cmt file,
+    they are In_progress when processing the .cmti, and Set when processing
+    the .cmt.
+*)
+type loc_dep =
+  | In_progress of Location_dependencies.uid_to_decl
+      (** Extracted from a .cmti's [cmt_infos.cmt_uid_to_decl].
+          Temporary storage before processing the corresponding .cmt file.*)
+  | Set of Location_dependencies.t
+  | Unset (* no file read *)
+
 type t = {
   builddir : string; (** The [cmt_builddir] *)
   cm_file : string; (** The filepath currently analyzed *)
   annots : annots;
     (** Extracted from [cmt_infos.cmt_annots] in .cmti and .cmt files. *)
-  cmti_uid_to_decl : Location_dependencies.uid_to_decl option;
-    (** Extracted from a cmti's [cmt_infos] *)
-  location_dependencies : Location_dependencies.t;
+  location_dependencies : loc_dep;
     (** Dependencies similar to [cmt_infos.cmt_value_dependencies] in OCaml 5.2 *)
   modname : string; (** Either [cmti_name] or [cmt_modname] *)
   sourcepath : string option; (** The path to the associated source file *)

From 8268157256dcce5c1da5b0f9c960d7fd65bca84f Mon Sep 17 00:00:00 2001
From: Corentin De Souza <9597216+fantazio@users.noreply.github.com>
Date: Wed, 19 Aug 2026 16:02:25 +0200
Subject: [PATCH 5/5] [src][state][file_infos] group annots and
 location_dependencies

The shape of location_dependenices depends on the file being processed,
as does annots. Therefore, they are now grouped under the new field and
type `cm_infos` which binds them to their reprensentation depending on
the file type (.cmt or .cmti).

This helps simplifying the code a little. This includes a small refactor
of the interface processing in SeadCode.
---
 src/deadCode.ml          |  39 ++++++---------
 src/deadSign.ml          |   4 +-
 src/state/file_infos.ml  | 101 ++++++++++++++++++---------------------
 src/state/file_infos.mli |  44 ++++++++---------
 4 files changed, 81 insertions(+), 107 deletions(-)

diff --git a/src/deadCode.ml b/src/deadCode.ml
index 6e2c5ab..6181baf 100644
--- a/src/deadCode.ml
+++ b/src/deadCode.ml
@@ -327,8 +327,7 @@ let regabs state =
     hashtbl_add_unique_to_list main_files (Utils.Filepath.unit fn) ()
 
 
-(* annots must not be Neither *)
-let read_interface fn (annots : State.File_infos.annots) state =
+let read_interface fn export_collector state =
   regabs state;
   if Config.must_report_main state.config then
     let comp_unit =
@@ -342,15 +341,7 @@ let read_interface fn (annots : State.File_infos.annots) state =
       |> Ident.create_persistent
     in
     let path = [module_id] in
-    begin match annots with
-    | Structure strc ->
-        DeadSign.collect_export_from_structure ~path ~comp_unit strc
-    | Signature sign | Both {sign; _} ->
-        DeadSign.collect_export_from_signature ~path ~comp_unit sign
-    | Neither ->
-        (* TODO: better error handling *)
-        assert false
-    end;
+    export_collector ~path ~comp_unit;
     last_loc := Lexing.dummy_pos
 
 
@@ -433,12 +424,17 @@ let load_file fn state =
   in
   let process_interface fn =
     last_loc := Lexing.dummy_pos;
-      if state.State.config.verbose then
-        Printf.eprintf "Scanning interface from %s\n%!" fn;
+    if state.State.config.verbose then
+      Printf.eprintf "Scanning interface from %s\n%!" fn;
     init_and_continue state fn (fun state ->
-    match state.file_infos.annots with
+    match state.file_infos.cm_infos with
     | Neither -> report_error (fn ^ ": missing signature")
-    | annots -> read_interface fn annots state
+    | Cmti {sign; _} | Cmt {sign = Some sign; _} ->
+        let export_collector = DeadSign.collect_export_from_signature sign in
+        read_interface fn export_collector state
+    | Cmt {strc; _} ->
+        let export_collector = DeadSign.collect_export_from_structure strc in
+        read_interface fn export_collector state
     )
   in
   let process_implementation fn =
@@ -446,21 +442,14 @@ let load_file fn state =
     if state.State.config.verbose then
       Printf.eprintf "Scanning implementation from %s\n%!" fn;
     init_and_continue state fn (fun state ->
-    match state.file_infos.annots with
-    | Neither | Signature _ -> report_error (fn ^ ": missing structure")
-    | Structure strc | Both {strc; _} ->
+    match state.file_infos.cm_infos with
+    | Neither | Cmti _ -> report_error (fn ^ ": missing structure")
+    | Cmt {strc; location_dependencies; _} ->
         regabs state;
         let prepare (loc1, loc2) =
           DeadObj.add_equal loc1 loc2;
           VdNode.merge_locs ~force:true loc2 loc1
         in
-        let location_dependencies =
-          match state.file_infos.location_dependencies with
-          | Set location_dependencies -> location_dependencies
-          | _ ->
-              (* TODO: better error handling *)
-              assert false
-        in
         List.iter prepare location_dependencies;
         collect_references.Tast_mapper.structure collect_references strc
         |> ignore;
diff --git a/src/deadSign.ml b/src/deadSign.ml
index bb8157c..0f5a5d4 100644
--- a/src/deadSign.ml
+++ b/src/deadSign.ml
@@ -258,8 +258,8 @@ let rec collect_export_from_include ~path sig_item =
 
 let correct_export sig_item =
   let state = State.get_current () in
-  match state.file_infos.annots with
-  | Structure _ -> correct_export sig_item
+  match state.file_infos.cm_infos with
+  | Cmt {sign = None; _} -> correct_export sig_item
   | _ ->
       (* Typedtree signatures found in .cmti files do not need correction *)
       ()
diff --git a/src/state/file_infos.ml b/src/state/file_infos.ml
index 43dbc49..76e0386 100644
--- a/src/state/file_infos.ml
+++ b/src/state/file_infos.ml
@@ -1,30 +1,21 @@
 module Locdep = Location_dependencies
 
-type annots =
-  | Structure of Typedtree.structure
-  | Signature of Typedtree.signature
-  | Both of { sign: Typedtree.signature; strc: Typedtree.structure }
+type cm_infos =
+  | Cmti of {
+        sign : Typedtree.signature;
+        cmti_uid_to_decl : Location_dependencies.uid_to_decl;
+      }
+  | Cmt of {
+        strc : Typedtree.structure;
+        sign : Typedtree.signature option;
+        location_dependencies : Location_dependencies.t;
+      }
   | Neither
 
-let merge_annots sign strc =
-  match sign, strc with
-  | Structure _, _ | _, Signature _ ->
-      (* TODO: better error handling *)
-      assert false
-  | Neither, annots | annots, Neither -> annots
-  | (Signature sign | Both {sign; _}), (Structure strc | Both {strc; _}) ->
-      Both {sign; strc}
-
-type loc_dep =
-  | In_progress of Location_dependencies.uid_to_decl
-  | Set of Location_dependencies.t
-  | Unset
-
 type t = {
   builddir : string;
   cm_file : string;
-  annots : annots;
-  location_dependencies : loc_dep;
+  cm_infos : cm_infos;
   modname : string;
   sourcepath : string option;
 }
@@ -32,8 +23,7 @@ type t = {
 let empty = {
   builddir = "!!UNKNOWN_BUILDDIR!!";
   cm_file = "";
-  annots = Neither;
-  location_dependencies = Unset;
+  cm_infos = Neither;
   modname = "!!UNKNOWN_MODNAME!!";
   sourcepath = None;
 }
@@ -41,7 +31,8 @@ let empty = {
 (** [init_from_all_cm_infos ~cm_file cmt_infos] creates a [t] with:
     - information from [cmt_infos] : [builddir], [modname], [sourcepath];
     - [cm_file];
-    - [annots] is extracted from [cmt_infos.cmt_annots]
+    - [cm_infos] is built with [cmt_infos.cmt_annots] and
+      [cmt_infos.cmt_uid_to_decl]
 *)
 let init_from_all_cm_infos ~cm_file cmt_infos =
   let builddir = cmt_infos.Cmt_format.cmt_builddir in
@@ -50,17 +41,17 @@ let init_from_all_cm_infos ~cm_file cmt_infos =
     |> Option.map (Filename.concat builddir)
   in
   let modname = cmt_infos.cmt_modname in
-  let annots =
+  let cm_infos =
     match cmt_infos.cmt_annots with
-    | Interface sign -> Signature sign
-    | Implementation strc -> Structure strc
+    | Interface sign ->
+        let cmti_uid_to_decl = cmt_infos.cmt_uid_to_decl in
+        Cmti {sign; cmti_uid_to_decl}
+    | Implementation strc ->
+        let location_dependencies = Location_dependencies.empty in
+        Cmt {strc; sign = None; location_dependencies}
     | _ -> Neither
   in
-  {empty with builddir;
-              cm_file;
-              annots;
-              modname;
-              sourcepath}
+  {builddir; cm_file; cm_infos; modname; sourcepath}
 
 (** [init_from_cm_file cm_file] returns an [Ok t] with [t] filled with general
     info expected for both cmt and cmti files, using the [cm_file] (see
@@ -83,23 +74,25 @@ let ( let* ) x f = Result.bind x f
 let ( let+ ) x f = Result.map f x
 
 let init_from_cmti_file cmti_file =
-  let* file_infos, cmt_infos = init_from_cm_file cmti_file in
-  let location_dependencies = In_progress cmt_infos.cmt_uid_to_decl in
-  match file_infos.annots with
-  | Signature _ ->
-      let file_infos = {file_infos with location_dependencies} in
-      Result.ok file_infos
+  let* file_infos, _ = init_from_cm_file cmti_file in
+  match file_infos.cm_infos with
+  | Cmti _ -> Result.ok file_infos
   | _ -> Result.error (cmti_file ^ ": does not contain an interface")
 
-let init_from_cmt_file ~comp_unit_to_path cmt_file =
+let init_from_cmt_file ~comp_unit_to_path ?(cmi_infos = Neither) cmt_file =
   let* file_infos, cmt_infos = init_from_cm_file cmt_file in
-  match file_infos.annots with
-  | Structure _ ->
+  match file_infos.cm_infos with
+  | Cmt cmt ->
+      let sign, cmti_uid_to_decl =
+        match cmi_infos with
+        | Cmti {sign; cmti_uid_to_decl} -> Some sign, Some cmti_uid_to_decl
+        | _ -> None, None
+      in
       let+ location_dependencies =
-        Locdep.init ~comp_unit_to_path cmt_infos None
+        Locdep.init ~comp_unit_to_path cmt_infos cmti_uid_to_decl
       in
-      let location_dependencies = Set location_dependencies in
-      {file_infos with location_dependencies}
+      let cm_infos = Cmt {cmt with sign; location_dependencies} in
+      {file_infos with cm_infos}
   | _ -> Result.error (cmt_file ^ ": does not contain an implementation")
 
 let init ~comp_unit_to_path cm_file =
@@ -112,20 +105,18 @@ let change_file ~comp_unit_to_path file_infos cm_file =
   let no_ext = Filename.remove_extension cm_file in
   assert(no_ext = Filename.remove_extension file_infos.cm_file);
   match Filename.extension cm_file, file_infos with
-  | ".cmt", {annots; location_dependencies = In_progress uid_to_decl; _} ->
-      let* res, cmt_infos = init_from_cm_file cm_file in
-      let+ location_dependencies =
-        Locdep.init ~comp_unit_to_path cmt_infos (Some uid_to_decl)
-      in
-      let location_dependencies = Set location_dependencies in
-      let annots = merge_annots annots res.annots in
-      {res with annots; location_dependencies}
+  | ".cmt", {cm_infos = Cmti _ as cmi_infos; _} ->
+        init_from_cmt_file ~comp_unit_to_path ~cmi_infos cm_file
+  | ".cmt",  _ ->
+      (* The only other possible file read before a .cmt is the
+         corresponding .cmti *)
+      Result.error (cm_file ^ ": must be read after its corresponding .cmti")
   | ".cmti", _ ->
-      (* .cmti files are alwasy read before the correpsonding.cmt *)
-      Result.error (cm_file ^ ": must be read before its correpsonding .cmt")
+      (* .cmti files are always read before the corresponding .cmt *)
+      Result.error (cm_file ^ ": must be read before its corresponding .cmt")
   | _ ->
-      (* invalid extension or the corresponding info is None *)
-      init ~comp_unit_to_path cm_file
+      (* invalid extension *)
+      Result.error (cm_file ^ ": not a .cmti or .cmt file")
 
 let has_sourcepath file_infos = Option.is_some file_infos.sourcepath
 
diff --git a/src/state/file_infos.mli b/src/state/file_infos.mli
index 531a3f3..8b17458 100644
--- a/src/state/file_infos.mli
+++ b/src/state/file_infos.mli
@@ -1,33 +1,27 @@
-(** Information about a analyzable file ([.cmti] or [.cmt] file) *)
-
-(** binary_annots of the compialtion unit *)
-type annots =
-  | Structure of Typedtree.structure
-      (* only a .cmt was read (i.e. no .cmti available) *)
-  | Signature of Typedtree.signature (* only a .cmti was read *)
-  | Both of { sign: Typedtree.signature; strc: Typedtree.structure }
-      (* both the .cmti and .cmt were read *)
+(** Information about an analyzable file ([.cmti] or [.cmt] file) *)
+
+(** Data specific to the file type (.cmt or .cmti) *)
+type cm_infos =
+  | Cmti of {
+        sign : Typedtree.signature;
+        cmti_uid_to_decl : Location_dependencies.uid_to_decl;
+          (** Extracted from [cmt_infos.cmt_uid_to_decl] *)
+      } (* only a .cmti was read *)
+  | Cmt of {
+        strc : Typedtree.structure;
+        sign : Typedtree.signature option;
+          (** signature read in the corresponding .cmti (if available) *)
+        location_dependencies : Location_dependencies.t;
+          (** Dependencies similar to [cmt_infos.cmt_value_dependencies]
+              in OCaml 5.2. *)
+      } (* infos coming from a .cmt *)
   | Neither (* no file read or the content was discarded *)
 
-(** Dependencies similar to [cmt_infos.cmt_value_dependencies] in OCaml 5.2.
-    Because the .cmti file is processed before its correpsonding .cmt file,
-    they are In_progress when processing the .cmti, and Set when processing
-    the .cmt.
-*)
-type loc_dep =
-  | In_progress of Location_dependencies.uid_to_decl
-      (** Extracted from a .cmti's [cmt_infos.cmt_uid_to_decl].
-          Temporary storage before processing the corresponding .cmt file.*)
-  | Set of Location_dependencies.t
-  | Unset (* no file read *)
-
 type t = {
   builddir : string; (** The [cmt_builddir] *)
   cm_file : string; (** The filepath currently analyzed *)
-  annots : annots;
-    (** Extracted from [cmt_infos.cmt_annots] in .cmti and .cmt files. *)
-  location_dependencies : loc_dep;
-    (** Dependencies similar to [cmt_infos.cmt_value_dependencies] in OCaml 5.2 *)
+  cm_infos : cm_infos;
+    (** Data specific to the file type (.cmt or .cmti) *)
   modname : string; (** Either [cmti_name] or [cmt_modname] *)
   sourcepath : string option; (** The path to the associated source file *)
 }