diff --git a/.depend b/.depend
index 8a2dd0deff0..2d8fb662dc2 100644
--- a/.depend
+++ b/.depend
@@ -744,6 +744,7 @@ typing/datarepr.cmx : \
     parsing/asttypes.cmi \
     typing/datarepr.cmi
 typing/datarepr.cmi : \
+    parsing/unit_info.cmi \
     typing/types.cmi \
     typing/path.cmi \
     typing/ident.cmi \
@@ -1449,6 +1450,7 @@ typing/printtyped.cmx : \
 typing/printtyped.cmi : \
     typing/typedtree.cmi
 typing/shape.cmo : \
+    parsing/unit_info.cmi \
     typing/path.cmi \
     utils/misc.cmi \
     utils/identifiable.cmi \
@@ -1456,6 +1458,7 @@ typing/shape.cmo : \
     utils/compilation_unit.cmi \
     typing/shape.cmi
 typing/shape.cmx : \
+    parsing/unit_info.cmx \
     typing/path.cmx \
     utils/misc.cmx \
     utils/identifiable.cmx \
@@ -1463,6 +1466,7 @@ typing/shape.cmx : \
     utils/compilation_unit.cmx \
     typing/shape.cmi
 typing/shape.cmi : \
+    parsing/unit_info.cmi \
     typing/path.cmi \
     utils/identifiable.cmi \
     typing/ident.cmi \
diff --git a/Changes b/Changes
index 7e0c9c2fbfd..a9352fea1c3 100644
--- a/Changes
+++ b/Changes
@@ -661,6 +661,15 @@ OCaml 5.2.0
   usages index
   (Ulysse Gérard, review by Gabriel Scherer and Nathanaëlle Courant)
 
+- #13286: Distinguish unique identifiers `Shape.Uid.t` according to their
+  provenance: either an implementation or an interface.
+  (Ulysse Gérard, review by Florian Angeletti and Leo White)
+
+- #13308: keep track of relations between declaration in the cmt files. This is
+  useful information for external tools for navigation and analysis purposis.
+  (Ulysse Gérard, Florian Angeletti, review by Florian Angeletti and Gabriel
+  Scherer)
+
 ### Build system:
 
 - #12198, #12321, #12586, #12616, #12706, #13048: continue the merge of the
diff --git a/boot/ocamlc b/boot/ocamlc
new file mode 100755
index 00000000000..3fb10ea2e00
Binary files /dev/null and b/boot/ocamlc differ
diff --git a/bytecomp/bytepackager.ml b/bytecomp/bytepackager.ml
index 398242755ac..d1c803d1e9e 100644
--- a/bytecomp/bytepackager.ml
+++ b/bytecomp/bytepackager.ml
@@ -355,7 +355,7 @@ let package_files ~ppf_dump initial_env files targetfile =
     CU.create (CU.Prefix.from_clflags ())
       (Unit_info.Artifact.modname target |> CU.Name.of_string)
   in
-  CU.set_current (Some comp_unit);
+  CU.set_current (Some (comp_unit, Impl));
   Misc.try_finally (fun () ->
       let coercion =
         Typemod.package_units initial_env files (Unit_info.companion_cmi target)
diff --git a/driver/compile.ml b/driver/compile.ml
index 8aabea0df7a..3ceb0781326 100644
--- a/driver/compile.ml
+++ b/driver/compile.ml
@@ -22,7 +22,7 @@ let with_info =
   Compile_common.with_info ~native:false ~tool_name
 
 let interface ~source_file ~output_prefix =
-  with_info ~source_file ~output_prefix ~dump_ext:"cmi"
+  with_info ~source_file ~kind:Intf ~output_prefix ~dump_ext:"cmi"
     ~compilation_unit:Inferred_from_output_prefix
   @@ fun info ->
   Compile_common.interface
@@ -101,7 +101,8 @@ let starting_point_of_compiler_pass start_from =
 let implementation_aux ~start_from ~source_file ~output_prefix
     ~keep_symbol_tables:_
     ~(compilation_unit : Compile_common.compilation_unit_or_inferred) =
-  with_info ~source_file ~output_prefix ~dump_ext:"cmo" ~compilation_unit
+  with_info ~source_file ~kind:Impl ~output_prefix
+    ~dump_ext:"cmo" ~compilation_unit
   @@ fun info ->
   match start_from with
   | Parsing ->
diff --git a/driver/compile_common.ml b/driver/compile_common.ml
index ed200f90e85..6543e039976 100644
--- a/driver/compile_common.ml
+++ b/driver/compile_common.ml
@@ -28,11 +28,11 @@ type compilation_unit_or_inferred =
   | Exactly of Compilation_unit.t
   | Inferred_from_output_prefix
 
-let with_info ~native ~tool_name ~source_file ~output_prefix
+let with_info ~native ~tool_name ~source_file ~kind ~output_prefix
       ~compilation_unit ~dump_ext k =
   Compmisc.init_path ();
   Compmisc.init_parameters ();
-  let target = Unit_info.make ~source_file output_prefix in
+  let target = Unit_info.make ~source_file output_prefix  in
   let compilation_unit =
     match compilation_unit with
     | Exactly compilation_unit -> compilation_unit
@@ -42,8 +42,8 @@ let with_info ~native ~tool_name ~source_file ~output_prefix
         Compilation_unit.create for_pack_prefix
           (module_name |> Compilation_unit.Name.of_string)
   in
-  Compilation_unit.set_current (Some compilation_unit);
-  Env.set_unit_name (Some compilation_unit);
+  Compilation_unit.set_current (Some (compilation_unit, kind));
+  Env.set_unit_name (Some (compilation_unit, kind));
   let env = Compmisc.initial_env() in
   let dump_file = String.concat "." [output_prefix; dump_ext] in
   Compmisc.with_ppf_dump ~file_prefix:dump_file (fun ppf_dump ->
@@ -85,7 +85,7 @@ let typecheck_intf info ast =
         Format.(fprintf std_formatter) "%a@."
           (Printtyp.printed_signature (Unit_info.source_file info.target))
           sg);
-  ignore (Includemod.signatures info.env ~mark:Mark_both
+  ignore (Includemod.signatures info.env ~mark:true
     ~modes:(Legacy None) sg sg);
   Typecore.force_delayed_checks ();
   Builtin_attributes.warn_unused ();
diff --git a/driver/compile_common.mli b/driver/compile_common.mli
index 3a3f756f8f8..b4cdb4ff984 100644
--- a/driver/compile_common.mli
+++ b/driver/compile_common.mli
@@ -34,6 +34,7 @@ val with_info :
   native:bool ->
   tool_name:string ->
   source_file:string ->
+  kind:Compilation_unit.intf_or_impl ->
   output_prefix:string ->
   compilation_unit:compilation_unit_or_inferred ->
   dump_ext:string ->
diff --git a/driver/optcompile.ml b/driver/optcompile.ml
index 569a53ff941..7901373339b 100644
--- a/driver/optcompile.ml
+++ b/driver/optcompile.ml
@@ -23,7 +23,7 @@ let tool_name = "ocamlopt"
 let with_info = Compile_common.with_info ~native:true ~tool_name
 
 let interface ~source_file ~output_prefix =
-  with_info ~source_file ~output_prefix ~dump_ext:"cmi"
+  with_info ~source_file ~kind:Intf ~output_prefix ~dump_ext:"cmi"
     ~compilation_unit:Inferred_from_output_prefix
   @@ fun info ->
   Compile_common.interface
@@ -115,7 +115,8 @@ let implementation_aux unix ~(flambda2 : flambda2) ~start_from
   let pipeline : Asmgen.pipeline =
     Direct_to_cmm (flambda2 ~keep_symbol_tables)
   in
-  with_info ~source_file ~output_prefix ~dump_ext:"cmx" ~compilation_unit
+  with_info ~source_file ~kind:Impl ~output_prefix
+    ~dump_ext:"cmx" ~compilation_unit
   @@ fun info ->
   if !Flambda_backend_flags.internal_assembler then
       Emitaux.binary_backend_available := true;
diff --git a/file_formats/cms_format.ml b/file_formats/cms_format.ml
index 6b75dc4f401..82b33ccfcf3 100644
--- a/file_formats/cms_format.ml
+++ b/file_formats/cms_format.ml
@@ -17,6 +17,8 @@
 
 (** cms and cmsi files format. *)
 
+module Uid = Shape.Uid
+
 let read_magic_number ic =
   let len_magic_number = String.length Config.cms_magic_number in
   really_input_string ic len_magic_number
@@ -32,7 +34,9 @@ type cms_infos = {
   cms_uid_to_attributes : Parsetree.attributes Shape.Uid.Tbl.t;
   cms_impl_shape : Shape.t option; (* None for mli *)
   cms_ident_occurrences :
-    (Longident.t Location.loc * Shape_reduce.result) array
+    (Longident.t Location.loc * Shape_reduce.result) array;
+  cms_declaration_dependencies :
+    (Cmt_format.dependency_kind * Uid.t * Uid.t) list;
 }
 
 type error =
@@ -114,6 +118,9 @@ let save_cms target modname binary_annots initial_env shape =
         let cms_uid_to_loc, cms_uid_to_attributes =
           uid_tables_of_binary_annots binary_annots
         in
+        let cms_declaration_dependencies =
+          Cmt_format.get_declaration_dependencies ()
+        in
         let cms =
           {
             cms_modname = modname;
@@ -125,7 +132,8 @@ let save_cms target modname binary_annots initial_env shape =
             cms_uid_to_loc;
             cms_uid_to_attributes;
             cms_impl_shape = shape;
-            cms_ident_occurrences
+            cms_ident_occurrences;
+            cms_declaration_dependencies;
           }
         in
         output_cms oc cms)
diff --git a/file_formats/cms_format.mli b/file_formats/cms_format.mli
index af1dcba9884..4c172ddee5f 100644
--- a/file_formats/cms_format.mli
+++ b/file_formats/cms_format.mli
@@ -17,6 +17,8 @@
 
 (** cms and cmsi files format. *)
 
+module Uid = Shape.Uid
+
 type cms_infos = {
   cms_modname : Compilation_unit.t;
   cms_comments : (string * Location.t) list;
@@ -28,7 +30,9 @@ type cms_infos = {
   cms_uid_to_attributes : Parsetree.attributes Shape.Uid.Tbl.t;
   cms_impl_shape : Shape.t option; (* None for mli *)
   cms_ident_occurrences :
-    (Longident.t Location.loc * Shape_reduce.result) array
+    (Longident.t Location.loc * Shape_reduce.result) array;
+  cms_declaration_dependencies :
+    (Cmt_format.dependency_kind * Uid.t * Uid.t) list;
 }
 
 type error =
diff --git a/file_formats/cmt_format.ml b/file_formats/cmt_format.ml
index 89b7638721e..9d8c5f3a9ca 100644
--- a/file_formats/cmt_format.ml
+++ b/file_formats/cmt_format.ml
@@ -45,11 +45,11 @@ and binary_part =
   | Partial_signature_item of signature_item
   | Partial_module_type of module_type
 
+type dependency_kind =  Definition_to_declaration | Declaration_to_declaration
 type cmt_infos = {
   cmt_modname : Compilation_unit.t;
   cmt_annots : binary_annots;
-  cmt_value_dependencies :
-    (Types.value_description * Types.value_description) list;
+  cmt_declaration_dependencies : (dependency_kind * Uid.t * Uid.t) list;
   cmt_comments : (string * Location.t) list;
   cmt_args : string array;
   cmt_sourcefile : string option;
@@ -452,19 +452,19 @@ let read_cmi filename =
     | Some cmi, _ -> cmi
 
 let saved_types = ref []
-let value_deps = ref []
+let uids_deps : (dependency_kind * Uid.t * Uid.t) list ref = ref []
 
 let clear () =
   saved_types := [];
-  value_deps := []
+  uids_deps := []
 
 let add_saved_type b = saved_types := b :: !saved_types
 let get_saved_types () = !saved_types
 let set_saved_types l = saved_types := l
 
-let record_value_dependency vd1 vd2 =
-  if vd1.Types.val_loc <> vd2.Types.val_loc then
-    value_deps := (vd1, vd2) :: !value_deps
+let record_declaration_dependency (rk, uid1, uid2) =
+  if not (Uid.equal uid1 uid2) then
+    uids_deps := (rk, uid1, uid2) :: !uids_deps
 
 let save_cmt target cu binary_annots initial_env cmi shape =
   if !Clflags.binary_annotations && not !Clflags.print_types then begin
@@ -499,7 +499,7 @@ let save_cmt target cu binary_annots initial_env cmi shape =
          let cmt = {
            cmt_modname = cu;
            cmt_annots;
-           cmt_value_dependencies = !value_deps;
+           cmt_declaration_dependencies = !uids_deps;
            cmt_comments = Lexer.comments ();
            cmt_args = Sys.argv;
            cmt_sourcefile = sourcefile;
@@ -518,3 +518,5 @@ let save_cmt target cu binary_annots initial_env cmi shape =
          output_cmt oc cmt)
   end;
   clear ()
+
+let get_declaration_dependencies () = !uids_deps
diff --git a/file_formats/cmt_format.mli b/file_formats/cmt_format.mli
index a58d24c6ef2..06e4fbde1fe 100644
--- a/file_formats/cmt_format.mli
+++ b/file_formats/cmt_format.mli
@@ -48,11 +48,11 @@ and binary_part =
   | Partial_signature_item of signature_item
   | Partial_module_type of module_type
 
+type dependency_kind = Definition_to_declaration | Declaration_to_declaration
 type cmt_infos = {
   cmt_modname : Compilation_unit.t;
   cmt_annots : binary_annots;
-  cmt_value_dependencies :
-    (Types.value_description * Types.value_description) list;
+  cmt_declaration_dependencies : (dependency_kind * Uid.t * Uid.t) list;
   cmt_comments : (string * Location.t) list;
   cmt_args : string array;
   cmt_sourcefile : string option;
@@ -108,8 +108,7 @@ val add_saved_type : binary_part -> unit
 val get_saved_types : unit -> binary_part list
 val set_saved_types : binary_part list -> unit
 
-val record_value_dependency:
-  Types.value_description -> Types.value_description -> unit
+val record_declaration_dependency: dependency_kind * Uid.t * Uid.t -> unit
 
 val index_occurrences :
   binary_annots -> (Longident.t Location.loc * Shape_reduce.result) array
@@ -134,3 +133,6 @@ val need_to_clear_env : bool
   val read_signature : 'a -> string -> Types.signature * 'b list * 'c list
 
 *)
+
+val get_declaration_dependencies :
+  unit -> (dependency_kind * Uid.t * Uid.t) list
diff --git a/lambda/translprim.ml b/lambda/translprim.ml
index 158e2ac4a74..a61b51c8434 100644
--- a/lambda/translprim.ml
+++ b/lambda/translprim.ml
@@ -1610,7 +1610,7 @@ let lambda_of_loc kind sloc =
     let module_name =
       match name with
       | None -> "//"^filename^"//"
-      | Some comp_unit ->
+      | Some (comp_unit, _) ->
         Compilation_unit.name_as_string comp_unit
     in
     Lconst (Const_immstring module_name)
diff --git a/middle_end/compilenv.ml b/middle_end/compilenv.ml
index 6200880d2c1..986a7a51d39 100644
--- a/middle_end/compilenv.ml
+++ b/middle_end/compilenv.ml
@@ -68,7 +68,7 @@ let current_unit =
 let reset compilation_unit =
   Infos_table.clear global_infos_table;
   Zero_alloc_info.reset cached_zero_alloc_info;
-  CU.set_current (Some compilation_unit);
+  CU.set_current (Some (compilation_unit, Impl));
   current_unit.ui_unit <- compilation_unit;
   current_unit.ui_defines <- [compilation_unit];
   current_unit.ui_arg_descr <- None;
diff --git a/middle_end/flambda2/cmx/flambda_cmx.ml b/middle_end/flambda2/cmx/flambda_cmx.ml
index 43ec1943e59..2292fb72863 100644
--- a/middle_end/flambda2/cmx/flambda_cmx.ml
+++ b/middle_end/flambda2/cmx/flambda_cmx.ml
@@ -83,7 +83,7 @@ let all_predefined_exception_symbols () =
 
 let predefined_exception_typing_env () =
   let comp_unit = Compilation_unit.get_current () in
-  Compilation_unit.set_current (Some Compilation_unit.predef_exn);
+  Compilation_unit.set_current (Some (Compilation_unit.predef_exn, Impl));
   let typing_env =
     TE.Serializable.predefined_exceptions (all_predefined_exception_symbols ())
   in
diff --git a/middle_end/flambda2/cmx/flambda_cmx_format.ml b/middle_end/flambda2/cmx/flambda_cmx_format.ml
index ac28a8d62b3..4069379fef9 100644
--- a/middle_end/flambda2/cmx/flambda_cmx_format.ml
+++ b/middle_end/flambda2/cmx/flambda_cmx_format.ml
@@ -213,7 +213,7 @@ let merge t1_opt t2_opt =
 let print0 ~sections ~print_typing_env ~print_code ~print_offsets ppf t =
   Format.fprintf ppf "@[<hov>Original unit:@ %a@]@;" Compilation_unit.print
     t.original_compilation_unit;
-  Compilation_unit.set_current (Some t.original_compilation_unit);
+  Compilation_unit.set_current (Some (t.original_compilation_unit, Impl));
   let typing_env, code = import_typing_env_and_code0 ~sections t in
   if print_typing_env
   then
diff --git a/middle_end/flambda2/parser/parse_flambda.ml b/middle_end/flambda2/parser/parse_flambda.ml
index 6fdd0ddbc02..1cff65e6415 100644
--- a/middle_end/flambda2/parser/parse_flambda.ml
+++ b/middle_end/flambda2/parser/parse_flambda.ml
@@ -154,7 +154,7 @@ let parse filename =
   |> Result.map (fun fexpr ->
          let comp_unit = make_compilation_unit ~extension:".fl" ~filename () in
          let old_comp_unit = Compilation_unit.get_current () in
-         Compilation_unit.set_current (Some comp_unit);
+         Compilation_unit.set_current (Some (comp_unit, Impl));
          let flambda = Fexpr_to_flambda.conv comp_unit fexpr in
          Compilation_unit.set_current old_comp_unit;
          flambda)
diff --git a/middle_end/flambda2/tests/api_tests/extension_meet.ml b/middle_end/flambda2/tests/api_tests/extension_meet.ml
index c2d3d1b07a3..5eab05c3c7a 100644
--- a/middle_end/flambda2/tests/api_tests/extension_meet.ml
+++ b/middle_end/flambda2/tests/api_tests/extension_meet.ml
@@ -188,5 +188,5 @@ let _ =
     let linkage_name = Compilation_unit.Name.of_string "camlTest" in
     Compilation_unit.create Compilation_unit.Prefix.empty linkage_name
   in
-  Compilation_unit.set_current (Some comp_unit);
+  Compilation_unit.set_current (Some (comp_unit, Impl));
   test_double_recursion ()
diff --git a/middle_end/flambda2/tests/meet_test.ml b/middle_end/flambda2/tests/meet_test.ml
index 0af29852d5a..bf0f831ee4e 100644
--- a/middle_end/flambda2/tests/meet_test.ml
+++ b/middle_end/flambda2/tests/meet_test.ml
@@ -260,7 +260,7 @@ let test_meet_bottom_after_alias () =
 
 let () =
   let comp_unit = "Meet_test" |> Compilation_unit.of_string in
-  Compilation_unit.set_current (Some comp_unit);
+  Compilation_unit.set_current (Some (comp_unit, Impl));
   Format.eprintf "MEET CHAINS WITH TWO VARS@\n@.";
   test_meet_chains_two_vars ();
   Format.eprintf "@.MEET CHAINS WITH THREE VARS@\n@.";
diff --git a/middle_end/flambda2/tests/tools/fldiff.ml b/middle_end/flambda2/tests/tools/fldiff.ml
index 9dca939ef92..7e2d886a0be 100644
--- a/middle_end/flambda2/tests/tools/fldiff.ml
+++ b/middle_end/flambda2/tests/tools/fldiff.ml
@@ -9,7 +9,7 @@ let _ =
     let modname1 =
       Parse_flambda.make_compilation_unit ~filename:file1 ~extension:".fl" ()
     in
-    Compilation_unit.set_current (Some modname1);
+    Compilation_unit.set_current (Some (modname1, Impl));
     Format.printf "%a@."
       (Compare.Comparison.print Flambda_unit.print)
       (Compare.flambda_units unit1 unit2)
diff --git a/middle_end/flambda2/tests/tools/flexpect.ml b/middle_end/flambda2/tests/tools/flexpect.ml
index 63cfc7f4cbc..6791c74a209 100644
--- a/middle_end/flambda2/tests/tools/flexpect.ml
+++ b/middle_end/flambda2/tests/tools/flexpect.ml
@@ -35,7 +35,7 @@ end
 let run_expect_test ~get_module_info ~extension ~filename
     ({ before; after = expected } : Fexpr.expect_test_spec) : Test_outcome.t =
   let comp_unit = Parse_flambda.make_compilation_unit ~extension ~filename () in
-  Compilation_unit.set_current (Some comp_unit);
+  Compilation_unit.set_current (Some (comp_unit, Impl));
   let before_fl = Fexpr_to_flambda.conv comp_unit before in
   check_invariants before_fl;
   let cmx_loader = Flambda_cmx.create_loader ~get_module_info in
diff --git a/middle_end/flambda2/tests/tools/parseflambda.ml b/middle_end/flambda2/tests/tools/parseflambda.ml
index 5223e016c70..e6d777c134f 100644
--- a/middle_end/flambda2/tests/tools/parseflambda.ml
+++ b/middle_end/flambda2/tests/tools/parseflambda.ml
@@ -15,7 +15,7 @@ let parse_flambda filename =
     let comp_unit =
       Parse_flambda.make_compilation_unit ~extension:".fl" ~filename ()
     in
-    Compilation_unit.set_current comp_unit;
+    Compilation_unit.set_current (Some (comp_unit, Impl));
     Format.printf "%a@.@." Print_fexpr.flambda_unit unit;
     let fl2 = Fexpr_to_flambda.conv comp_unit unit in
     Format.printf "flambda:@.%a@.@." Flambda_unit.print fl2;
diff --git a/middle_end/flambda2/tests/tools/roundtrip.ml b/middle_end/flambda2/tests/tools/roundtrip.ml
index 8774d6fa813..f53048561fe 100644
--- a/middle_end/flambda2/tests/tools/roundtrip.ml
+++ b/middle_end/flambda2/tests/tools/roundtrip.ml
@@ -30,7 +30,7 @@ let () =
     in
     (* Need to get this right or the conversion will complain about binding
        non-local symbols *)
-    Compilation_unit.set_current (Some modname);
+    Compilation_unit.set_current (Some (modname, Impl));
     let unit =
       match Parse_flambda.parse file with
       | Ok unit -> unit
diff --git a/ocamldoc/odoc_analyse.ml b/ocamldoc/odoc_analyse.ml
index f79d78ddffc..0f9cbf47def 100644
--- a/ocamldoc/odoc_analyse.ml
+++ b/ocamldoc/odoc_analyse.ml
@@ -30,7 +30,7 @@ let init_path () = Compmisc.init_path ()
 let initial_env () =
   let current =
     match Env.get_unit_name () with
-    | Some cu -> cu |> Compilation_unit.full_path_as_string
+    | Some (cu, _) -> cu |> Compilation_unit.full_path_as_string
     | None -> ""
   in
   let initial = !Odoc_global.initially_opened_module in
@@ -81,7 +81,7 @@ let process_implementation_file sourcefile =
     Compilation_unit.create (Compilation_unit.Prefix.from_clflags ())
       (Unit_info.modname source |> Compilation_unit.Name.of_string)
   in
-  Env.set_unit_name (Some compilation_unit);
+  Env.set_unit_name (Some (compilation_unit, Impl));
   let inputfile = preprocess sourcefile in
   let env = initial_env () in
   try
@@ -119,7 +119,7 @@ let process_interface_file sourcefile =
     Compilation_unit.create (Compilation_unit.Prefix.from_clflags ())
       (modulename |> Compilation_unit.Name.of_string)
   in
-  Env.set_unit_name (Some compilation_unit);
+  Env.set_unit_name (Some (compilation_unit, Intf));
   let inputfile = preprocess sourcefile in
   let ast =
     Pparse.file ~tool_name inputfile
diff --git a/testsuite/tests/shape-index/index.reference b/testsuite/tests/shape-index/index.reference
index ab08854ebe2..e62b460632b 100644
--- a/testsuite/tests/shape-index/index.reference
+++ b/testsuite/tests/shape-index/index.reference
@@ -34,30 +34,30 @@ Resolved: Index.3 : t (File "index.ml", line 25, characters 11-12)
 Resolved: Index.0 : t (File "index.ml", line 20, characters 10-11)
 
 Uid of decls:
-Index.10: y (File "index.ml", line 40, characters 4-5)
-Index.21: MS (File "index.ml", line 51, characters 12-14)
-Index.5: A (File "index.ml", line 23, characters 7-8)
-Index.15: G (File "index.ml", line 48, characters 7-8)
 Index.0: t (File "index.ml", line 19, characters 7-8)
-Index.28: MSB (File "index.ml", line 65, characters 12-15)
-Index.3: t (File "index.ml", line 24, characters 7-8)
-Index.17: MT (File "index.ml", line 52, characters 14-16)
-Index.11: a (File "index.ml", line 44, characters 4-5)
-Index.25: u (File "index.ml", line 66, characters 7-8)
-Index.24: MSA (File "index.ml", line 57, characters 12-15)
 Index.1: x (File "index.ml", line 20, characters 6-7)
-Index.16: u (File "index.ml", line 49, characters 5-6)
+Index.2: AS (File "index.ml", line 18, characters 12-14)
+Index.3: t (File "index.ml", line 24, characters 7-8)
+Index.4: x (File "index.ml", line 25, characters 7-8)
+Index.5: A (File "index.ml", line 23, characters 7-8)
+Index.6: B (File "index.ml", line 28, characters 7-8)
+Index.7: c (File "index.ml", line 35, characters 6-7)
 Index.8: c (File "index.ml", line 32, characters 6-7)
 Index.9: C (File "index.ml", line 30, characters 7-8)
-Index.23: u (File "index.ml", line 60, characters 11-12)
-Index.14: F (File "index.ml", line 47, characters 7-8)
+Index.10: y (File "index.ml", line 40, characters 4-5)
+Index.11: a (File "index.ml", line 44, characters 4-5)
 Index.12: _ (File "index.ml", line 45, characters 7-8)
-Index.27: G (File "index.ml", line 68, characters 9-10)
+Index.14: F (File "index.ml", line 47, characters 7-8)
+Index.15: G (File "index.ml", line 48, characters 7-8)
+Index.16: u (File "index.ml", line 49, characters 5-6)
+Index.17: MT (File "index.ml", line 52, characters 14-16)
+Index.18: M (File "index.ml", line 53, characters 9-10)
+Index.19: X (File "index.ml", line 54, characters 9-10)
 Index.20: u (File "index.ml", line 55, characters 7-8)
+Index.21: MS (File "index.ml", line 51, characters 12-14)
+Index.23: u (File "index.ml", line 60, characters 11-12)
+Index.24: MSA (File "index.ml", line 57, characters 12-15)
+Index.25: u (File "index.ml", line 66, characters 7-8)
 Index.26: t (File "index.ml", line 67, characters 23-24)
-Index.19: X (File "index.ml", line 54, characters 9-10)
-Index.6: B (File "index.ml", line 28, characters 7-8)
-Index.4: x (File "index.ml", line 25, characters 7-8)
-Index.18: M (File "index.ml", line 53, characters 9-10)
-Index.7: c (File "index.ml", line 35, characters 6-7)
-Index.2: AS (File "index.ml", line 18, characters 12-14)
+Index.27: G (File "index.ml", line 68, characters 9-10)
+Index.28: MSB (File "index.ml", line 65, characters 12-15)
diff --git a/testsuite/tests/shape-index/index_aliases.reference b/testsuite/tests/shape-index/index_aliases.reference
index e433d55b2a8..ca456ec6fb1 100644
--- a/testsuite/tests/shape-index/index_aliases.reference
+++ b/testsuite/tests/shape-index/index_aliases.reference
@@ -38,29 +38,29 @@ Resolved: Index_aliases.1 :
   A (File "index_aliases.ml", line 19, characters 11-12)
 
 Uid of decls:
-Index_aliases.12: M (File "index_aliases.ml", line 32, characters 9-10)
+Index_aliases.0: t (File "index_aliases.ml", line 18, characters 23-24)
 Index_aliases.1: A (File "index_aliases.ml", line 18, characters 7-8)
 Index_aliases.2: B (File "index_aliases.ml", line 19, characters 7-8)
-Index_aliases.18: s (File "index_aliases.ml", line 36, characters 26-27)
-Index_aliases.17: x (File "index_aliases.ml", line 35, characters 4-5)
+Index_aliases.3: t (File "index_aliases.ml", line 21, characters 23-24)
 Index_aliases.5: F (File "index_aliases.ml", line 21, characters 7-8)
-Index_aliases.26: FArg (File "index_aliases.ml", line 48, characters 7-11)
+Index_aliases.6: F' (File "index_aliases.ml", line 22, characters 7-9)
 Index_aliases.7: C (File "index_aliases.ml", line 23, characters 7-8)
-Index_aliases.24: Z (File "index_aliases.ml", line 42, characters 7-8)
-Index_aliases.20: t (File "index_aliases.ml", line 37, characters 41-42)
+Index_aliases.8: C' (File "index_aliases.ml", line 25, characters 7-9)
 Index_aliases.9: D (File "index_aliases.ml", line 26, characters 7-8)
+Index_aliases.10: G (File "index_aliases.ml", line 28, characters 7-8)
+Index_aliases.11: s (File "index_aliases.ml", line 32, characters 21-22)
+Index_aliases.12: M (File "index_aliases.ml", line 32, characters 9-10)
+Index_aliases.14: t (File "index_aliases.ml", line 33, characters 48-49)
 Index_aliases.15: F (File "index_aliases.ml", line 33, characters 9-10)
+Index_aliases.16: S (File "index_aliases.ml", line 31, characters 12-13)
+Index_aliases.17: x (File "index_aliases.ml", line 35, characters 4-5)
+Index_aliases.18: s (File "index_aliases.ml", line 36, characters 26-27)
 Index_aliases.19: M (File "index_aliases.ml", line 36, characters 11-12)
-Index_aliases.8: C' (File "index_aliases.ml", line 25, characters 7-9)
-Index_aliases.23: Y (File "index_aliases.ml", line 41, characters 7-8)
-Index_aliases.14: t (File "index_aliases.ml", line 33, characters 48-49)
-Index_aliases.10: G (File "index_aliases.ml", line 28, characters 7-8)
-Index_aliases.27: u (File "index_aliases.ml", line 52, characters 5-6)
+Index_aliases.20: t (File "index_aliases.ml", line 37, characters 41-42)
+Index_aliases.21: F (File "index_aliases.ml", line 37, characters 11-12)
 Index_aliases.22: X (File "index_aliases.ml", line 40, characters 7-8)
-Index_aliases.16: S (File "index_aliases.ml", line 31, characters 12-13)
+Index_aliases.23: Y (File "index_aliases.ml", line 41, characters 7-8)
+Index_aliases.24: Z (File "index_aliases.ml", line 42, characters 7-8)
 Index_aliases.25: Arg (File "index_aliases.ml", line 47, characters 7-10)
-Index_aliases.21: F (File "index_aliases.ml", line 37, characters 11-12)
-Index_aliases.6: F' (File "index_aliases.ml", line 22, characters 7-9)
-Index_aliases.3: t (File "index_aliases.ml", line 21, characters 23-24)
-Index_aliases.11: s (File "index_aliases.ml", line 32, characters 21-22)
-Index_aliases.0: t (File "index_aliases.ml", line 18, characters 23-24)
+Index_aliases.26: FArg (File "index_aliases.ml", line 48, characters 7-11)
+Index_aliases.27: u (File "index_aliases.ml", line 52, characters 5-6)
diff --git a/testsuite/tests/shape-index/index_bindingops.reference b/testsuite/tests/shape-index/index_bindingops.reference
index 38c4f70b4d1..8892fd4ecf8 100644
--- a/testsuite/tests/shape-index/index_bindingops.reference
+++ b/testsuite/tests/shape-index/index_bindingops.reference
@@ -39,9 +39,9 @@ Unresolved: CU Stdlib . "Option"[module] . "map"[value]  :
   Option.map (File "index_bindingops.ml", line 17, characters 17-27)
 
 Uid of decls:
-Index_bindingops.8:
-  minus_three (File "index_bindingops.ml", line 23, characters 4-15)
 Index_bindingops.0:
   let+ (File "index_bindingops.ml", line 17, characters 4-10)
 Index_bindingops.3:
   and+ (File "index_bindingops.ml", line 19, characters 4-10)
+Index_bindingops.8:
+  minus_three (File "index_bindingops.ml", line 23, characters 4-15)
diff --git a/testsuite/tests/shape-index/index_constrs.reference b/testsuite/tests/shape-index/index_constrs.reference
index 3fe533e8b6b..c8cec480385 100644
--- a/testsuite/tests/shape-index/index_constrs.reference
+++ b/testsuite/tests/shape-index/index_constrs.reference
@@ -17,10 +17,10 @@ Resolved: Index_constrs.0 :
   E (File "index_constrs.ml", line 20, characters 16-17)
 
 Uid of decls:
-Index_constrs.6: f (File "index_constrs.ml", line 27, characters 4-5)
-Index_constrs.5: x_ (File "index_constrs.ml", line 25, characters 4-6)
 Index_constrs.0: E (File "index_constrs.ml", line 18, characters 10-11)
-Index_constrs.2: M (File "index_constrs.ml", line 19, characters 7-8)
 Index_constrs.1: F (File "index_constrs.ml", line 20, characters 12-13)
+Index_constrs.2: M (File "index_constrs.ml", line 19, characters 7-8)
 Index_constrs.3: t (File "index_constrs.ml", line 23, characters 5-6)
 Index_constrs.4: E (File "index_constrs.ml", line 23, characters 9-10)
+Index_constrs.5: x_ (File "index_constrs.ml", line 25, characters 4-6)
+Index_constrs.6: f (File "index_constrs.ml", line 27, characters 4-5)
diff --git a/testsuite/tests/shape-index/index_constrs_records.reference b/testsuite/tests/shape-index/index_constrs_records.reference
index e876416599e..e4a6f808fb4 100644
--- a/testsuite/tests/shape-index/index_constrs_records.reference
+++ b/testsuite/tests/shape-index/index_constrs_records.reference
@@ -57,37 +57,37 @@ Resolved: Index_constrs_records.4 :
   A (File "index_constrs_records.ml", line 22, characters 10-11)
 
 Uid of decls:
-Index_constrs_records.4:
-  A (File "index_constrs_records.ml", line 21, characters 11-12)
-Index_constrs_records.12:
-  l_c (File "index_constrs_records.ml", line 19, characters 18-21)
+Index_constrs_records.0:
+  l (File "index_constrs_records.ml", line 17, characters 5-6)
+Index_constrs_records.1:
+  lbl (File "index_constrs_records.ml", line 17, characters 11-14)
 Index_constrs_records.2:
   t (File "index_constrs_records.ml", line 21, characters 7-8)
-Index_constrs_records.34:
-  l_exn (File "index_constrs_records.ml", line 39, characters 18-23)
-Index_constrs_records.29:
-  Ext (File "index_constrs_records.ml", line 33, characters 10-13)
 Index_constrs_records.3:
   l_c (File "index_constrs_records.ml", line 21, characters 18-21)
-Index_constrs_records.21:
-  M (File "index_constrs_records.ml", line 18, characters 7-8)
-Index_constrs_records.35:
-  Exn (File "index_constrs_records.ml", line 39, characters 10-13)
-Index_constrs_records.13:
-  A (File "index_constrs_records.ml", line 19, characters 11-12)
-Index_constrs_records.37:
-  e (File "index_constrs_records.ml", line 41, characters 4-5)
-Index_constrs_records.31:
-  f (File "index_constrs_records.ml", line 35, characters 4-5)
+Index_constrs_records.4:
+  A (File "index_constrs_records.ml", line 21, characters 11-12)
 Index_constrs_records.11:
   t (File "index_constrs_records.ml", line 19, characters 7-8)
+Index_constrs_records.12:
+  l_c (File "index_constrs_records.ml", line 19, characters 18-21)
+Index_constrs_records.13:
+  A (File "index_constrs_records.ml", line 19, characters 11-12)
+Index_constrs_records.21:
+  M (File "index_constrs_records.ml", line 18, characters 7-8)
+Index_constrs_records.23:
+  f (File "index_constrs_records.ml", line 30, characters 4-5)
 Index_constrs_records.27:
   u (File "index_constrs_records.ml", line 32, characters 5-6)
 Index_constrs_records.28:
   l_ext (File "index_constrs_records.ml", line 33, characters 19-24)
-Index_constrs_records.0:
-  l (File "index_constrs_records.ml", line 17, characters 5-6)
-Index_constrs_records.23:
-  f (File "index_constrs_records.ml", line 30, characters 4-5)
-Index_constrs_records.1:
-  lbl (File "index_constrs_records.ml", line 17, characters 11-14)
+Index_constrs_records.29:
+  Ext (File "index_constrs_records.ml", line 33, characters 10-13)
+Index_constrs_records.31:
+  f (File "index_constrs_records.ml", line 35, characters 4-5)
+Index_constrs_records.34:
+  l_exn (File "index_constrs_records.ml", line 39, characters 18-23)
+Index_constrs_records.35:
+  Exn (File "index_constrs_records.ml", line 39, characters 10-13)
+Index_constrs_records.37:
+  e (File "index_constrs_records.ml", line 41, characters 4-5)
diff --git a/testsuite/tests/shape-index/index_functor.reference b/testsuite/tests/shape-index/index_functor.reference
index 89867f0bafe..04746c8d555 100644
--- a/testsuite/tests/shape-index/index_functor.reference
+++ b/testsuite/tests/shape-index/index_functor.reference
@@ -11,7 +11,7 @@ Resolved: Index_functor.0 :
   X (File "index_functor.ml", line 18, characters 43-44)
 
 Uid of decls:
+Index_functor.1: M (File "index_functor.ml", line 18, characters 39-40)
+Index_functor.2: F (File "index_functor.ml", line 18, characters 7-8)
 Index_functor.3: N (File "index_functor.ml", line 19, characters 7-8)
 Index_functor.4: O (File "index_functor.ml", line 20, characters 7-8)
-Index_functor.2: F (File "index_functor.ml", line 18, characters 7-8)
-Index_functor.1: M (File "index_functor.ml", line 18, characters 39-40)
diff --git a/testsuite/tests/shape-index/index_labels.reference b/testsuite/tests/shape-index/index_labels.reference
index 797744dfe31..ae84539a8ef 100644
--- a/testsuite/tests/shape-index/index_labels.reference
+++ b/testsuite/tests/shape-index/index_labels.reference
@@ -17,9 +17,9 @@ Resolved: Index_labels.1 :
   a (File "index_labels.ml", line 20, characters 10-11)
 
 Uid of decls:
-Index_labels.5: f (File "index_labels.ml", line 25, characters 4-5)
+Index_labels.0: t (File "index_labels.ml", line 18, characters 5-6)
+Index_labels.1: a (File "index_labels.ml", line 18, characters 19-20)
 Index_labels.2: b (File "index_labels.ml", line 18, characters 27-28)
 Index_labels.3: x (File "index_labels.ml", line 20, characters 4-5)
-Index_labels.1: a (File "index_labels.ml", line 18, characters 19-20)
 Index_labels.4: _y (File "index_labels.ml", line 21, characters 4-6)
-Index_labels.0: t (File "index_labels.ml", line 18, characters 5-6)
+Index_labels.5: f (File "index_labels.ml", line 25, characters 4-5)
diff --git a/testsuite/tests/shape-index/index_objects.reference b/testsuite/tests/shape-index/index_objects.reference
index 1a0b3a3ab25..4d44a656558 100644
--- a/testsuite/tests/shape-index/index_objects.reference
+++ b/testsuite/tests/shape-index/index_objects.reference
@@ -23,10 +23,10 @@ Resolved: Index_objects.0 :
   o (File "index_objects.ml", line 23, characters 9-10)
 
 Uid of decls:
+Index_objects.0: o (File "index_objects.ml", line 18, characters 4-5)
+Index_objects.5: c (File "index_objects.ml", line 25, characters 6-7)
 Index_objects.10: d (File "index_objects.ml", line 31, characters 6-7)
-Index_objects.15: M (File "index_objects.ml", line 35, characters 12-13)
+Index_objects.13: ct (File "index_objects.ml", line 36, characters 8-10)
 Index_objects.14: dt (File "index_objects.ml", line 40, characters 8-10)
-Index_objects.5: c (File "index_objects.ml", line 25, characters 6-7)
-Index_objects.0: o (File "index_objects.ml", line 18, characters 4-5)
+Index_objects.15: M (File "index_objects.ml", line 35, characters 12-13)
 Index_objects.16: ins_var (File "index_objects.ml", line 43, characters 6-13)
-Index_objects.13: ct (File "index_objects.ml", line 36, characters 8-10)
diff --git a/testsuite/tests/shape-index/index_types.reference b/testsuite/tests/shape-index/index_types.reference
index 330c8e29244..b7887fa3be3 100644
--- a/testsuite/tests/shape-index/index_types.reference
+++ b/testsuite/tests/shape-index/index_types.reference
@@ -12,15 +12,15 @@ Resolved: Index_types.0 : t (File "index_types.ml", line 20, characters 8-9)
 Resolved: Index_types.0 : t (File "index_types.ml", line 20, characters 8-9)
 
 Uid of decls:
-Index_types.11: u (File "index_types.ml", line 41, characters 5-6)
-Index_types.3: poly (File "index_types.ml", line 27, characters 5-9)
+Index_types.0: t (File "index_types.ml", line 18, characters 5-6)
+Index_types.1: x (File "index_types.ml", line 20, characters 4-5)
 Index_types.2: M (File "index_types.ml", line 22, characters 7-8)
-Index_types.6: S (File "index_types.ml", line 31, characters 12-13)
-Index_types.10: N (File "index_types.ml", line 40, characters 7-8)
-Index_types.5: B (File "index_types.ml", line 33, characters 13-14)
-Index_types.9: t (File "index_types.ml", line 40, characters 23-24)
+Index_types.3: poly (File "index_types.ml", line 27, characters 5-9)
 Index_types.4: t2 (File "index_types.ml", line 32, characters 7-9)
-Index_types.1: x (File "index_types.ml", line 20, characters 4-5)
-Index_types.8: B (File "index_types.ml", line 37, characters 11-12)
-Index_types.0: t (File "index_types.ml", line 18, characters 5-6)
+Index_types.5: B (File "index_types.ml", line 33, characters 13-14)
+Index_types.6: S (File "index_types.ml", line 31, characters 12-13)
 Index_types.7: t1 (File "index_types.ml", line 36, characters 5-7)
+Index_types.8: B (File "index_types.ml", line 37, characters 11-12)
+Index_types.9: t (File "index_types.ml", line 40, characters 23-24)
+Index_types.10: N (File "index_types.ml", line 40, characters 7-8)
+Index_types.11: u (File "index_types.ml", line 41, characters 5-6)
diff --git a/testsuite/tests/shape-index/index_unboxed_labels.reference b/testsuite/tests/shape-index/index_unboxed_labels.reference
index ad75879c736..701e06820b1 100644
--- a/testsuite/tests/shape-index/index_unboxed_labels.reference
+++ b/testsuite/tests/shape-index/index_unboxed_labels.reference
@@ -29,35 +29,35 @@ Resolved: Index_unboxed_labels.1 :
   a (File "index_unboxed_labels.ml", line 21, characters 10-11)
 
 Uid of decls:
-Index_unboxed_labels.2:
-  b (File "index_unboxed_labels.ml", line 18, characters 19-20)
-Index_unboxed_labels.16:
-  f (File "index_unboxed_labels.ml", line 40, characters 4-5)
-Index_unboxed_labels.7:
-  f (File "index_unboxed_labels.ml", line 24, characters 4-5)
+Index_unboxed_labels.0:
+  t (File "index_unboxed_labels.ml", line 18, characters 5-6)
 Index_unboxed_labels.1:
   a (File "index_unboxed_labels.ml", line 18, characters 11-12)
-Index_unboxed_labels.13:
-  b (File "index_unboxed_labels.ml", line 35, characters 12-13)
-Index_unboxed_labels.6:
-  _y (File "index_unboxed_labels.ml", line 22, characters 4-6)
-Index_unboxed_labels.4:
-  a (File "index_unboxed_labels.ml", line 19, characters 13-14)
+Index_unboxed_labels.2:
+  b (File "index_unboxed_labels.ml", line 18, characters 19-20)
 Index_unboxed_labels.3:
   tu (File "index_unboxed_labels.ml", line 19, characters 5-7)
-Index_unboxed_labels.11:
-  f (File "index_unboxed_labels.ml", line 31, characters 4-5)
+Index_unboxed_labels.4:
+  a (File "index_unboxed_labels.ml", line 19, characters 13-14)
 Index_unboxed_labels.5:
   x (File "index_unboxed_labels.ml", line 21, characters 4-5)
+Index_unboxed_labels.6:
+  _y (File "index_unboxed_labels.ml", line 22, characters 4-6)
+Index_unboxed_labels.7:
+  f (File "index_unboxed_labels.ml", line 24, characters 4-5)
+Index_unboxed_labels.9:
+  x (File "index_unboxed_labels.ml", line 28, characters 4-5)
+Index_unboxed_labels.10:
+  _y (File "index_unboxed_labels.ml", line 29, characters 4-6)
+Index_unboxed_labels.11:
+  f (File "index_unboxed_labels.ml", line 31, characters 4-5)
+Index_unboxed_labels.12:
+  tb (File "index_unboxed_labels.ml", line 35, characters 5-7)
+Index_unboxed_labels.13:
+  b (File "index_unboxed_labels.ml", line 35, characters 12-13)
 Index_unboxed_labels.14:
   x (File "index_unboxed_labels.ml", line 37, characters 4-5)
 Index_unboxed_labels.15:
   _y (File "index_unboxed_labels.ml", line 38, characters 4-6)
-Index_unboxed_labels.12:
-  tb (File "index_unboxed_labels.ml", line 35, characters 5-7)
-Index_unboxed_labels.0:
-  t (File "index_unboxed_labels.ml", line 18, characters 5-6)
-Index_unboxed_labels.10:
-  _y (File "index_unboxed_labels.ml", line 29, characters 4-6)
-Index_unboxed_labels.9:
-  x (File "index_unboxed_labels.ml", line 28, characters 4-5)
+Index_unboxed_labels.16:
+  f (File "index_unboxed_labels.ml", line 40, characters 4-5)
diff --git a/testsuite/tests/shape-index/index_vb.reference b/testsuite/tests/shape-index/index_vb.reference
index a48f72fff64..cb96c56c3d4 100644
--- a/testsuite/tests/shape-index/index_vb.reference
+++ b/testsuite/tests/shape-index/index_vb.reference
@@ -16,9 +16,9 @@ Resolved: Index_vb.2 : b (File "index_vb.ml", line 20, characters 9-10)
 Resolved: Index_vb.1 : a (File "index_vb.ml", line 20, characters 6-7)
 
 Uid of decls:
-Index_vb.3: a (File "index_vb.ml", line 20, characters 6-7)
-Index_vb.1: a (File "index_vb.ml", line 18, characters 11-12)
 Index_vb.0: t (File "index_vb.ml", line 18, characters 5-6)
+Index_vb.1: a (File "index_vb.ml", line 18, characters 11-12)
 Index_vb.2: b (File "index_vb.ml", line 18, characters 20-21)
-Index_vb.5: a (File "index_vb.ml", line 20, characters 6-7)
+Index_vb.3: a (File "index_vb.ml", line 20, characters 6-7)
 Index_vb.4: a (File "index_vb.ml", line 20, characters 6-7)
+Index_vb.5: a (File "index_vb.ml", line 20, characters 6-7)
diff --git a/testsuite/tests/uid-deps/link_intf_impl.ml b/testsuite/tests/uid-deps/link_intf_impl.ml
new file mode 100644
index 00000000000..6d2090a1313
--- /dev/null
+++ b/testsuite/tests/uid-deps/link_intf_impl.ml
@@ -0,0 +1,59 @@
+(* TEST
+
+flags = "-bin-annot -bin-annot-occurrences";
+compile_only = "true";
+setup-ocamlc.byte-build-env;
+all_modules = "link_intf_impl.mli link_intf_impl.ml";
+ocamlc.byte;
+check-ocamlc.byte-output;
+
+program = "-quiet -uid-deps link_intf_impl.cmt";
+output = "out_objinfo";
+ocamlobjinfo;
+
+check-program-output;
+*)
+
+let x (* 0 *) = 42
+
+type t (* 1 *) = int
+
+module type S (* 3 *) = sig
+  val y (* 2 *) : t
+end
+
+module M (* 5 *) : S = struct
+  let y (* 4 *) = 36
+end
+
+module N (* 8 *) : sig
+  val y (* 7 *) : int
+end = struct
+  let y (* 6 *) = 2
+end
+
+let _ = (module N : S)
+
+module P (* 10 *)= struct
+  let y (* 9 *) = 12
+end
+
+module F (* 12 *) (X (* 11 *) : S) = X
+
+module G (* 13 *) = F(P)
+
+module type Initial (* 16 *) = sig
+  module type Nested (* 15 *) = sig
+    type t (* 14 *)
+  end
+end
+
+module MF (* 23 *) : sig
+   module F (* 22 *) (X (* 21 *) : sig val x (* 20 *) : int end) : sig end
+end = struct
+  module F (* 19 *) (X (* 18 *) : sig val x (* 17 *) : int end) = struct end
+end
+
+module FMT (* 27 *) (X (* 26 *) : sig
+  module type MT (* 25 *) = sig val x (* 24 *) : int end
+end) : sig end = struct end
diff --git a/testsuite/tests/uid-deps/link_intf_impl.mli b/testsuite/tests/uid-deps/link_intf_impl.mli
new file mode 100644
index 00000000000..fa4403c9c10
--- /dev/null
+++ b/testsuite/tests/uid-deps/link_intf_impl.mli
@@ -0,0 +1,19 @@
+type t (* 0 *)
+
+val x (* 1 *) : t
+
+module type S (* 3 *) = sig
+  val y (* 2 *) : t
+end
+
+module M (* 4 *) : S
+
+module type Initial (* 7 *) = sig
+  module type Nested (* 6 *) = sig
+    type t (* 5 *)
+  end
+end
+
+module FMT (* 11 *) (X (* 10 *) : sig
+  module type MT (* 9 *) = sig val x (* 8 *) : int end
+end) : sig end
diff --git a/testsuite/tests/uid-deps/link_intf_impl.reference b/testsuite/tests/uid-deps/link_intf_impl.reference
new file mode 100644
index 00000000000..3e6ffa226ad
--- /dev/null
+++ b/testsuite/tests/uid-deps/link_intf_impl.reference
@@ -0,0 +1,19 @@
+
+Uid dependencies:
+Link_intf_impl.0 <- [intf]Link_intf_impl.1
+Link_intf_impl.1 <- [intf]Link_intf_impl.0
+Link_intf_impl.2 <-> [intf]Link_intf_impl.2
+Link_intf_impl.3 <- [intf]Link_intf_impl.3
+Link_intf_impl.4 <- Link_intf_impl.2
+Link_intf_impl.5 <- [intf]Link_intf_impl.4
+Link_intf_impl.6 <- Link_intf_impl.7
+Link_intf_impl.7 <-> Link_intf_impl.2
+Link_intf_impl.9 <-> Link_intf_impl.2
+Link_intf_impl.14 <-> [intf]Link_intf_impl.5
+Link_intf_impl.15 <-> [intf]Link_intf_impl.6
+Link_intf_impl.16 <- [intf]Link_intf_impl.7
+Link_intf_impl.17 <-> Link_intf_impl.20
+Link_intf_impl.19 <- Link_intf_impl.22
+Link_intf_impl.24 <-> [intf]Link_intf_impl.8
+Link_intf_impl.25 <-> [intf]Link_intf_impl.9
+Link_intf_impl.27 <- [intf]Link_intf_impl.11
diff --git a/testsuite/tests/uids/intf_uids.ml b/testsuite/tests/uids/intf_uids.ml
new file mode 100644
index 00000000000..af315bf6033
--- /dev/null
+++ b/testsuite/tests/uids/intf_uids.ml
@@ -0,0 +1,3 @@
+type u (* has uid Intf_uids.0 *)
+
+type t (* has uid Intf_uids.1 *)
diff --git a/testsuite/tests/uids/intf_uids.mli b/testsuite/tests/uids/intf_uids.mli
new file mode 100644
index 00000000000..21cfde35a94
--- /dev/null
+++ b/testsuite/tests/uids/intf_uids.mli
@@ -0,0 +1,3 @@
+type t (* has uid [intf]Intf_uids.0 *)
+
+type u (* has uid [intf]Intf_uids.1 *)
diff --git a/testsuite/tests/uids/intf_uids_test.ml b/testsuite/tests/uids/intf_uids_test.ml
new file mode 100644
index 00000000000..a5faf8e2c99
--- /dev/null
+++ b/testsuite/tests/uids/intf_uids_test.ml
@@ -0,0 +1,22 @@
+(* TEST
+
+flags = "-bin-annot";
+compile_only = "true";
+modules = "intf_uids.ml";
+
+setup-ocamlc.byte-build-env;
+all_modules = "intf_uids.mli intf_uids.ml";
+ocamlc.byte;
+check-ocamlc.byte-output;
+
+program = "-quiet -decls intf_uids.cmti intf_uids.cmt";
+output = "out_objinfo";
+ocamlobjinfo;
+
+check-program-output;
+*)
+
+(* This test illustrates the fact that uids are tagged to indicate if they
+  originate from an interface of an implementation: it prints the delcarations
+  written in the cmt file for the interface and then for the implementation.
+  These should not overlap.  *)
diff --git a/testsuite/tests/uids/intf_uids_test.reference b/testsuite/tests/uids/intf_uids_test.reference
new file mode 100644
index 00000000000..a1963210cec
--- /dev/null
+++ b/testsuite/tests/uids/intf_uids_test.reference
@@ -0,0 +1,8 @@
+
+Uid of decls:
+[intf]Intf_uids.0: t (File "intf_uids.mli", line 1, characters 5-6)
+[intf]Intf_uids.1: u (File "intf_uids.mli", line 3, characters 5-6)
+
+Uid of decls:
+Intf_uids.0: u (File "intf_uids.ml", line 1, characters 5-6)
+Intf_uids.1: t (File "intf_uids.ml", line 3, characters 5-6)
diff --git a/tools/objinfo.ml b/tools/objinfo.ml
index 49cbc43f607..61b76418af2 100644
--- a/tools/objinfo.ml
+++ b/tools/objinfo.ml
@@ -39,6 +39,7 @@ let no_crc = ref false
 let shape = ref false
 let index = ref false
 let decls = ref false
+let uid_deps = ref false
 
 module Magic_number = Misc.Magic_number
 module String = Misc.Stdlib.String
@@ -213,9 +214,32 @@ let print_cmt_infos cmt =
       cmt.cmt_ident_occurrences;
     Format.print_flush ()
   end;
+  if !uid_deps then begin
+    printf "\nUid dependencies:\n";
+    let arr = Array.of_list cmt.cmt_declaration_dependencies in
+    let () =
+      Array.sort (fun (_tr, u1, u2) (_tr', u1', u2') ->
+                    match Shape.Uid.compare u1 u1' with
+                    | 0 -> Shape.Uid.compare u2 u2'
+                    | n -> n) arr
+    in
+    Format.printf "@[<v>";
+    Array.iter (fun (rk, u1, u2) ->
+      let rk = match rk with
+        | Definition_to_declaration -> "<-"
+        | Declaration_to_declaration -> "<->"
+      in
+      Format.printf "@[<h>%a %s %a@]@;"
+        Shape.Uid.print u1
+        rk
+        Shape.Uid.print u2) arr;
+    Format.printf "@]";
+  end;
   if !decls then begin
     printf "\nUid of decls:\n";
-    Shape.Uid.Tbl.iter (fun uid item ->
+    let decls = Array.of_list (Shape.Uid.Tbl.to_list cmt.cmt_uid_to_decl) in
+    Array.sort (fun (uid, _) (uid', _) -> Shape.Uid.compare uid uid') decls;
+    Array.iter (fun (uid, item) ->
       let loc = match (item : Typedtree.item_declaration) with
         | Value vd -> vd.val_name
         | Value_binding vb ->
@@ -245,8 +269,8 @@ let print_cmt_infos cmt =
       Format.printf "@[<hov 2>%a:@ %a@]@;"
         Shape.Uid.print uid
         pp_loc loc)
-      cmt.cmt_uid_to_decl;
-      Format.print_flush ()
+      decls;
+    Format.print_flush ()
   end
 
 let print_cms_infos cms =
@@ -569,6 +593,8 @@ let arg_list = [
     " Print a list of all usages of values, types, etc. in the module";
   "-decls", Arg.Set decls,
     " Print a list of all declarations in the module";
+  "-uid-deps", Arg.Set uid_deps,
+    " Print the declarations' uids dependencies of the module";
   "-null-crc", Arg.Set no_crc, " Print a null CRC for imported interfaces";
   "-args", Arg.Expand Arg.read_arg,
      "<file> Read additional newline separated command line arguments \n\
diff --git a/toplevel/byte/topeval.ml b/toplevel/byte/topeval.ml
index 6c4d051e12a..1922fa12238 100644
--- a/toplevel/byte/topeval.ml
+++ b/toplevel/byte/topeval.ml
@@ -125,8 +125,7 @@ let execute_phrase print_outcome ppf phr =
       in
       if !Clflags.dump_typedtree then Printtyped.implementation ppf str;
       let sg' = Typemod.Signature_names.simplify newenv sn sg in
-      ignore (Includemod.signatures ~mark:Mark_positive oldenv
-        ~modes:(Legacy None) sg sg');
+      Includemod.check_implementation oldenv ~modes:(Legacy None) sg sg';
       Typecore.force_delayed_checks ();
       let shape = Shape_reduce.local_reduce Env.empty shape in
       if !Clflags.dump_shape then Shape.print ppf shape;
diff --git a/toplevel/native/opttoploop.ml b/toplevel/native/opttoploop.ml
index 0316c3b85e7..5082c51f0af 100644
--- a/toplevel/native/opttoploop.ml
+++ b/toplevel/native/opttoploop.ml
@@ -401,7 +401,7 @@ let execute_phrase print_outcome ppf phr =
       if !Clflags.dump_typedtree then Printtyped.implementation ppf str;
       let sg' = Typemod.Signature_names.simplify newenv names sg in
       let coercion =
-        Includemod.signatures oldenv ~mark:Mark_positive
+        Includemod.signatures oldenv ~mark:true
           ~modes:(Legacy None) sg sg'
       in
       Typecore.force_delayed_checks ();
diff --git a/toplevel/native/topeval.ml b/toplevel/native/topeval.ml
index 22b6a9c2475..fdfb4a1cc1e 100644
--- a/toplevel/native/topeval.ml
+++ b/toplevel/native/topeval.ml
@@ -185,7 +185,7 @@ let execute_phrase print_outcome ppf phr =
       in
       if !Clflags.dump_typedtree then Printtyped.implementation ppf str;
       let sg' = Typemod.Signature_names.simplify newenv names sg in
-      ignore (Includemod.signatures oldenv ~mark:Mark_positive sg sg');
+      Includemod.check_implementation oldenv ~modes:(Legacy None) sg sg';
       Typecore.force_delayed_checks ();
       let shape = Shape_reduce.local_reduce Env.empty shape in
       if !Clflags.dump_shape then Shape.print ppf shape;
diff --git a/typing/datarepr.mli b/typing/datarepr.mli
index 606fa6eab1b..0a1d507174f 100644
--- a/typing/datarepr.mli
+++ b/typing/datarepr.mli
@@ -19,8 +19,8 @@
 open Types
 
 val extension_descr:
-  current_unit:Compilation_unit.t option -> Path.t -> extension_constructor ->
-  constructor_description
+  current_unit:Compilation_unit.with_kind option ->
+  Path.t -> extension_constructor -> constructor_description
 
 val labels_of_type:
   Path.t -> type_declaration ->
@@ -29,8 +29,8 @@ val unboxed_labels_of_type:
   Path.t -> type_declaration ->
   (Ident.t * unboxed_label_description) list
 val constructors_of_type:
-  current_unit:Compilation_unit.t option -> Path.t -> type_declaration ->
-  (Ident.t * constructor_description) list
+  current_unit:Compilation_unit.with_kind option -> Path.t ->
+  type_declaration -> (Ident.t * constructor_description) list
 
 
 exception Constr_not_found
diff --git a/typing/env.ml b/typing/env.ml
index 9222de63292..0f550efaec8 100644
--- a/typing/env.ml
+++ b/typing/env.ml
@@ -1007,8 +1007,8 @@ let rec address_head = function
 
 (* The name of the compilation unit currently compiled. *)
 module Current_unit_name : sig
-  val get : unit -> Compilation_unit.t option
-  val set : Compilation_unit.t option -> unit
+  val get : unit -> (Compilation_unit.with_kind) option
+  val set : (Compilation_unit.with_kind) option -> unit
   val is : string -> bool
   val is_ident : Ident.t -> bool
   val is_path : Path.t -> bool
@@ -1018,7 +1018,7 @@ end = struct
   let set comp_unit =
     Compilation_unit.set_current comp_unit
   let get_name () =
-    Option.map Compilation_unit.name (get ())
+    Option.map (fun (cu, _) -> Compilation_unit.name cu) (get ())
   let is name =
     let current_name_string =
       Option.map Compilation_unit.Name.to_string (get_name ())
diff --git a/typing/env.mli b/typing/env.mli
index 507ce49d348..36d2d092d6e 100644
--- a/typing/env.mli
+++ b/typing/env.mli
@@ -518,8 +518,8 @@ val reset_cache: preserve_persistent_env:bool -> unit
 val reset_cache_toplevel: unit -> unit
 
 (* Remember the name of the current compilation unit. *)
-val set_unit_name: Compilation_unit.t option -> unit
-val get_unit_name: unit -> Compilation_unit.t option
+val set_unit_name: (Compilation_unit.with_kind) option -> unit
+val get_unit_name: unit -> (Compilation_unit.with_kind) option
 
 (* Read, save a signature to/from a file. *)
 val read_signature:
diff --git a/typing/includemod.ml b/typing/includemod.ml
index e097fbc8245..bb8717aad81 100644
--- a/typing/includemod.ml
+++ b/typing/includemod.ml
@@ -120,21 +120,88 @@ module Error = struct
 
 end
 
-type mark =
+module Directionality = struct
+
+
+  type mark =
   | Mark_both
   | Mark_positive
-  | Mark_negative
   | Mark_neither
 
-let negate_mark = function
-  | Mark_both -> Mark_both
-  | Mark_positive -> Mark_negative
-  | Mark_negative -> Mark_positive
-  | Mark_neither -> Mark_neither
+  type pos =
+    | Strictly_positive
+      (** Strictly positive positions are notable for tools since they are the
+          the case where we match a implementation definition with an interface
+          declaration. Oherwise in the positive case we are matching
+          declatations inside functor arguments at even level of nesting.*)
+    | Positive
+    | Negative
+
+
+(**
+   When checking inclusion, the [Directionality.t] type tracks the
+   subtyping direction at the syntactic level.
+
+   The [posivity] field is used in the [cmt_declaration_dependencies] to
+   distinguish between directed and undirected edges, and to avoid recording
+   matched declarations twice.
+
+   The [mark_as_used] field describes if we should record only positive use,
+   any use (because there is no clear implementation side), or none (because we
+   are inside an auxiliary check function.)
+
+   The [in_eq] field is [true] when we are checking both directions inside of
+   module types which allows optimizing module type equality checks. The module
+   subtyping relation [A <: B] checks that [A.T = B.T] when [A] and [B] define a
+   module type [T]. The relation [A.T = B.T] is equivalent to [(A.T <: B.T) and
+   (B.T <: A.T)], but checking both recursively would lead to an exponential
+   slowdown (see #10598 and #10616). To avoid this issue, when [in_eq] is
+   [true], we compute a coarser relation [A << B] which is the same as [A <: B]
+   except that module types [T] are checked only for [A.T << B.T] and not the
+   reverse. Thus, we can implement a cheap module type equality check [A.T =
+   B.T] by computing [(A.T << B.T) and (B.T << A.T)], avoiding the exponential
+   slowdown described above.
+*)
+  type t = {
+      in_eq:bool;
+      mark_as_used:mark;
+      pos:pos;
+    }
+
+  let strictly_positive ~mark =
+    let mark_as_used = if mark then Mark_positive else Mark_neither in
+    { in_eq=false; pos=Strictly_positive; mark_as_used }
+
+  let unknown ~mark =
+    let mark_as_used = if mark then Mark_both else Mark_neither in
+    { in_eq=false; pos=Positive; mark_as_used }
 
-let mark_positive = function
-  | Mark_both | Mark_positive -> true
-  | Mark_negative | Mark_neither -> false
+  let negate_pos = function
+    | Positive | Strictly_positive -> Negative
+    | Negative -> Positive
+
+  let negate d = { d with pos = negate_pos d.pos }
+
+  let at_most_positive = function
+    | Strictly_positive -> Positive
+    | Positive | Negative as non_strict -> non_strict
+
+  let enter_eq d =
+    {
+      in_eq = true;
+      pos = at_most_positive d.pos;
+      mark_as_used = d.mark_as_used
+    }
+
+  let mark_as_used d = match d.mark_as_used with
+    | Mark_neither -> false
+    | Mark_both -> true
+    | Mark_positive ->
+       match d.pos with
+       | Positive | Strictly_positive -> true
+       | Negative -> false
+
+end
 
 (* All functions "blah env x1 x2" check that x1 is included in x2,
    i.e. that x1 is the type of an implementation that fulfills the
@@ -153,9 +220,8 @@ let append_ldot s = function
 
 (* Inclusion between value descriptions *)
 
-let value_descriptions ~loc env ~mark subst id ~mmodes vd1 vd2 =
-  Cmt_format.record_value_dependency vd1 vd2;
-  if mark_positive mark then
+let value_descriptions ~loc env ~direction subst id ~mmodes vd1 vd2 =
+  if Directionality.mark_as_used direction then
     Env.mark_value_used vd1.val_uid;
   let vd2 = Subst.value_description subst vd2 in
   try
@@ -165,8 +231,8 @@ let value_descriptions ~loc env ~mark subst id ~mmodes vd1 vd2 =
 
 (* Inclusion between type declarations *)
 
-let type_declarations ~loc env ~mark subst id decl1 decl2 =
-  let mark = mark_positive mark in
+let type_declarations ~loc env ~direction subst id decl1 decl2 =
+  let mark = Directionality.mark_as_used direction in
   if mark then
     Env.mark_type_used decl1.type_uid;
   let decl2 = Subst.type_declaration subst decl2 in
@@ -180,8 +246,8 @@ let type_declarations ~loc env ~mark subst id decl1 decl2 =
 
 (* Inclusion between extension constructors *)
 
-let extension_constructors ~loc env ~mark  subst id ext1 ext2 =
-  let mark = mark_positive mark in
+let extension_constructors ~loc env ~direction subst id ext1 ext2 =
+  let mark = Directionality.mark_as_used direction in
   let ext2 = Subst.extension_constructor subst ext2 in
   match Includecore.extension_constructors ~loc env ~mark id ext1 ext2 with
   | None -> Ok Tcoerce_none
@@ -505,24 +571,8 @@ and shallow_module_paths env subst p1 mty2 p2 =
     | Mty_alias _ | Mty_ident _ | Mty_signature _ | Mty_functor _
     | exception Not_found -> false
 
-(**
-   In the group of mutual functions below, the [~in_eq] argument is [true] when
-   we are in fact checking equality of module types.
-
-   The module subtyping relation [A <: B] checks that [A.T = B.T] when [A]
-   and [B] define a module type [T]. The relation [A.T = B.T] is equivalent
-   to [(A.T <: B.T) and (B.T <: A.T)], but checking both recursively would lead
-   to an exponential slowdown (see #10598 and #10616).
-   To avoid this issue, when [~in_eq] is [true], we compute a coarser relation
-   [A << B] which is the same as [A <: B] except that module types [T] are
-   checked only for [A.T << B.T] and not the reverse.
-   Thus, we can implement a cheap module type equality check [A.T = B.T] by
-   computing [(A.T << B.T) and (B.T << A.T)], avoiding the exponential slowdown
-   described above.
-*)
-
-let rec modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape =
-  match try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape with
+let rec modtypes ~direction ~loc env subst ~modes mty1 mty2 shape =
+  match try_modtypes ~direction ~loc env subst ~modes mty1 mty2 shape with
   | Ok _ as ok -> ok
   | Error reason ->
     let mty1 = Subst.Lazy.force_modtype mty1 in
@@ -531,7 +581,7 @@ let rec modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape =
     in
     Error Error.(diff mty1 mty2 reason)
 
-and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
+and try_modtypes ~direction ~loc env subst ~modes mty1 mty2 orig_shape =
   let open Subst.Lazy in
   (* Do a quick nominal comparison for simple types and if that fails, try to
       unfold one of them. For structured types, do a deep comparison. *)
@@ -553,7 +603,7 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
     | p1 ->
         begin match Env.find_module_lazy p1 env with
         | md -> begin
-            match strengthened_modtypes ~in_eq ~loc ~aliasable:true env ~mark
+            match strengthened_modtypes ~direction ~loc ~aliasable:true env
                     subst ~modes md.md_type p1 mty2 orig_shape
             with
             | Ok _ as x -> x
@@ -565,7 +615,7 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
     end
   | (Mty_signature sig1, Mty_signature sig2) ->
       begin match
-        signatures ~in_eq ~loc env ~mark subst ~modes sig1 sig2 orig_shape
+        signatures ~direction ~loc env subst ~modes sig1 sig2 orig_shape
       with
       | Ok _ as ok -> ok
       | Error e -> Error (Error.Signature e)
@@ -574,7 +624,8 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
   | Mty_functor (param1, res1), Mty_functor (param2, res2) ->
       walk_locks ~env ~item:Module modes;
       let cc_arg, env, subst =
-        functor_param ~in_eq ~loc env ~mark:(negate_mark mark)
+        let direction = Directionality.negate direction in
+        functor_param ~direction ~loc env
           subst param1 param2
       in
       let var, res_shape =
@@ -592,7 +643,7 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
             var, Shape.app orig_shape ~arg:shape_var
       in
       let cc_res =
-        modtypes ~in_eq ~loc env ~mark subst res1 res2 res_shape
+        modtypes ~direction ~loc env subst res1 res2 res_shape
           ~modes:(Legacy None)
       in
       begin match cc_arg, cc_res with
@@ -650,7 +701,7 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
     in
     match red with
     | Some (mty1,mty2) ->
-        try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape
+        try_modtypes ~direction ~loc env subst ~modes mty1 mty2 orig_shape
     | None ->
         (* Report error *)
         match mty1, mty2 with
@@ -682,7 +733,7 @@ and try_modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 orig_shape =
 
 (* Functor parameters *)
 
-and functor_param ~in_eq ~loc env ~mark subst param1 param2 =
+and functor_param ~direction ~loc env subst param1 param2 =
   let open Subst.Lazy in
   match param1, param2 with
   | Unit, Unit ->
@@ -691,7 +742,7 @@ and functor_param ~in_eq ~loc env ~mark subst param1 param2 =
       let arg2' = Subst.Lazy.modtype Keep subst arg2 in
       let cc_arg =
         match
-          modtypes ~in_eq ~loc env ~mark Subst.identity arg2' arg1
+          modtypes ~direction ~loc env Subst.identity arg2' arg1
                 Shape.dummy_mod ~modes:(Legacy None)
         with
         | Ok (cc, _) -> Ok cc
@@ -721,22 +772,22 @@ and equate_one_functor_param subst env arg2' name1 name2  =
   | None, None ->
       env, subst
 
-and strengthened_modtypes ~in_eq ~loc ~aliasable env ~mark
+and strengthened_modtypes ~direction ~loc ~aliasable env
     subst ~modes mty1 path1 mty2 shape =
   let mty1 = Mtype.strengthen_lazy ~aliasable mty1 path1 in
-  modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape
+  modtypes ~direction ~loc env subst ~modes mty1 mty2 shape
 
-and strengthened_module_decl ~loc ~aliasable env ~mark
+and strengthened_module_decl ~loc ~aliasable ~direction env
     subst ~mmodes  md1 path1 md2 shape =
   let md1 = Subst.Lazy.of_module_decl md1 in
   let md1 = Mtype.strengthen_lazy_decl ~aliasable md1 path1 in
   let mty2 = Subst.Lazy.of_modtype md2.md_type in
   let modes = mmodes in
-  modtypes ~in_eq:false ~loc env ~mark subst ~modes md1.md_type mty2 shape
+  modtypes ~direction ~loc env subst ~modes md1.md_type mty2 shape
 
 (* Inclusion between signatures *)
 
-and signatures ~in_eq ~loc env ~mark subst ~modes sig1 sig2 mod_shape =
+and signatures ~direction ~loc env subst ~modes sig1 sig2 mod_shape =
   let open Subst.Lazy in
   (* Environment used to check inclusion of components *)
   let sig1 = force_signature_once sig1 in
@@ -764,7 +815,7 @@ and signatures ~in_eq ~loc env ~mark subst ~modes sig1 sig2 mod_shape =
   (* Do the pairing and checking, and return the final coercion *)
   let paired, unpaired, subst = pair_components subst comps1 sig2 in
   let d =
-    signature_components ~in_eq ~loc ~mark new_env subst mod_shape
+    signature_components ~direction ~loc new_env subst mod_shape
       Shape.Map.empty ~mmodes:modes
       (List.rev paired)
   in
@@ -789,19 +840,19 @@ and signatures ~in_eq ~loc env ~mark subst ~modes sig1 sig2 mod_shape =
 
 (* Inclusion between signature components *)
 and signature_components :
-  'a. in_eq:_ -> loc:_ -> mark:_ -> _ -> _ -> _ -> _ -> mmodes:_ -> (_ * _ * 'a) list -> 'a Sign_diff.t =
-  fun ~in_eq ~loc ~mark env subst orig_shape shape_map ~mmodes paired ->
+  'a. direction:_ -> loc:_ -> _ -> _ -> _ -> _ -> mmodes:_ -> (_ * _ * 'a) list -> 'a Sign_diff.t =
+  fun ~direction ~loc env subst orig_shape shape_map ~mmodes paired ->
   let open Subst.Lazy in
   match paired with
   | [] -> Sign_diff.{ empty with shape_map }
   | (sigi1, sigi2, pos) :: rem ->
       let shape_modified = ref false in
-      let id, item, shape_map, present_at_runtime =
+      let id, item, paired_uids, shape_map, present_at_runtime =
         match sigi1, sigi2 with
         | Sig_value(id1, valdecl1, _) ,Sig_value(_id2, valdecl2, _) ->
             let mmodes = append_ldot (Ident.name id1) mmodes in
             let item =
-              value_descriptions ~loc env ~mark subst id1 ~mmodes
+              value_descriptions ~loc ~direction env subst id1 ~mmodes
                 (Subst.Lazy.force_value_description valdecl1)
                 (Subst.Lazy.force_value_description valdecl2)
             in
@@ -811,25 +862,26 @@ and signature_components :
               | _ -> true
             in
             let shape_map = Shape.Map.add_value_proj shape_map id1 orig_shape in
-            id1, item, shape_map, present_at_runtime
+            let paired_uids = (valdecl1.val_uid, valdecl2.val_uid) in
+            id1, item, paired_uids, shape_map, present_at_runtime
         | Sig_type(id1, tydec1, _, _), Sig_type(_id2, tydec2, _, _) ->
             let item =
-              type_declarations ~loc env ~mark subst id1 tydec1 tydec2
+              type_declarations ~loc ~direction env subst id1 tydec1 tydec2
             in
             let item = mark_error_as_unrecoverable item in
             (* Right now we don't filter hidden constructors / labels from the
             shape. *)
             let shape_map = Shape.Map.add_type_proj shape_map id1 orig_shape in
-            id1, item, shape_map, false
+            id1, item, (tydec1.type_uid, tydec2.type_uid), shape_map, false
         | Sig_typext(id1, ext1, _, _), Sig_typext(_id2, ext2, _, _) ->
             let item =
-              extension_constructors ~loc env ~mark  subst id1 ext1 ext2
+              extension_constructors ~loc ~direction env subst id1 ext1 ext2
             in
             let item = mark_error_as_unrecoverable item in
             let shape_map =
               Shape.Map.add_extcons_proj shape_map id1 orig_shape
             in
-            id1, item, shape_map, true
+            id1, item, (ext1.ext_uid, ext2.ext_uid), shape_map, true
         | Sig_module(id1, pres1, mty1, _, _), Sig_module(_, pres2, mty2, _, _)
           -> begin
               let mmodes = append_ldot (Ident.name id1) mmodes in
@@ -837,7 +889,7 @@ and signature_components :
                 Shape.(proj orig_shape (Item.module_ id1))
               in
               let item =
-                module_declarations ~in_eq ~loc env ~mark subst id1 mty1 mty2
+                module_declarations ~direction ~loc env subst id1 mty1 mty2
                   ~mmodes orig_shape
               in
               let item, shape_map =
@@ -862,17 +914,18 @@ and signature_components :
                 | Mp_absent, Mp_present, _ -> assert false
               in
               let item = mark_error_as_unrecoverable item in
-              id1, item, shape_map, present_at_runtime
+              let paired_uids = (mty1.md_uid, mty2.md_uid) in
+              id1, item, paired_uids, shape_map, present_at_runtime
             end
         | Sig_modtype(id1, info1, _), Sig_modtype(_id2, info2, _) ->
             let item =
-              modtype_infos ~in_eq ~loc env ~mark  subst id1 info1 info2
+              modtype_infos ~direction ~loc env  subst id1 info1 info2
             in
             let shape_map =
               Shape.Map.add_module_type_proj shape_map id1 orig_shape
             in
             let item = mark_error_as_unrecoverable item in
-            id1, item, shape_map, false
+            id1, item, (info1.mtd_uid, info2.mtd_uid), shape_map, false
         | Sig_class(id1, decl1, _, _), Sig_class(_id2, decl2, _, _) ->
             walk_locks ~env ~item:Class (append_ldot (Ident.name id1) mmodes);
             let item =
@@ -882,7 +935,7 @@ and signature_components :
               Shape.Map.add_class_proj shape_map id1 orig_shape
             in
             let item = mark_error_as_unrecoverable item in
-            id1, item, shape_map, true
+            id1, item, (decl1.cty_uid, decl2.cty_uid), shape_map, true
         | Sig_class_type(id1, info1, _, _), Sig_class_type(_id2, info2, _, _) ->
             let item =
               class_type_declarations ~loc env subst info1 info2
@@ -891,7 +944,7 @@ and signature_components :
             let shape_map =
               Shape.Map.add_class_type_proj shape_map id1 orig_shape
             in
-            id1, item, shape_map, false
+            id1, item, (info1.clty_uid, info2.clty_uid), shape_map, false
         | _ ->
             assert false
       in
@@ -899,6 +952,25 @@ and signature_components :
       let first =
         match item with
         | Ok x ->
+            begin match direction with
+            | { Directionality.in_eq = true; pos = Negative }
+            | { Directionality.mark_as_used = Mark_neither; _ } ->
+              (* We do not store paired uids when checking for reverse
+                module-type inclusion as it would introduce duplicates. *)
+                ()
+            | { Directionality.pos; _} ->
+              let paired_uids =
+                let elt1, elt2 = paired_uids in
+                match pos with
+                | Negative ->
+                    (Cmt_format.Declaration_to_declaration, elt2, elt1)
+                | Positive ->
+                    (Cmt_format.Declaration_to_declaration, elt1, elt2)
+                | Strictly_positive ->
+                    (Cmt_format. Definition_to_declaration, elt1, elt2)
+              in
+              Cmt_format.record_declaration_dependency paired_uids
+            end;
             let runtime_coercions =
               if present_at_runtime then [pos,x] else []
             in
@@ -912,7 +984,7 @@ and signature_components :
       in
       let rest =
         if continue then
-          signature_components ~in_eq ~loc ~mark env subst
+          signature_components ~direction ~loc env subst
             orig_shape shape_map ~mmodes rem
         else
           let rem = List.map
@@ -926,7 +998,7 @@ and signature_components :
        in
        Sign_diff.merge first rest
 
-and module_declarations  ~in_eq ~loc env ~mark  subst id1 ~mmodes md1 md2 orig_shape =
+and module_declarations ~direction ~loc env subst id1 ~mmodes md1 md2 orig_shape =
   let open Subst.Lazy in
   Builtin_attributes.check_alerts_inclusion
     ~def:md1.md_loc
@@ -935,15 +1007,15 @@ and module_declarations  ~in_eq ~loc env ~mark  subst id1 ~mmodes md1 md2 orig_s
     md1.md_attributes md2.md_attributes
     (Ident.name id1);
   let p1 = Path.Pident id1 in
-  if mark_positive mark then
+  if Directionality.mark_as_used direction then
     Env.mark_module_used md1.md_uid;
   let modes = mmodes in
-  strengthened_modtypes  ~in_eq ~loc ~aliasable:true env ~mark subst ~modes
+  strengthened_modtypes ~direction ~loc ~aliasable:true env subst ~modes
     md1.md_type p1 md2.md_type orig_shape
 
 (* Inclusion between module type specifications *)
 
-and modtype_infos ~in_eq ~loc env ~mark subst id info1 info2 =
+and modtype_infos ~direction ~loc env subst id info1 info2 =
   let open Subst.Lazy in
   Builtin_attributes.check_alerts_inclusion
     ~def:info1.mtd_loc
@@ -957,10 +1029,10 @@ and modtype_infos ~in_eq ~loc env ~mark subst id info1 info2 =
       (None, None) -> Ok Tcoerce_none
     | (Some _, None) -> Ok Tcoerce_none
     | (Some mty1, Some mty2) ->
-        check_modtype_equiv ~in_eq ~loc env ~mark mty1 mty2
+        check_modtype_equiv ~direction ~loc env mty1 mty2
     | (None, Some mty2) ->
         let mty1 = Mty_ident(Path.Pident id) in
-        check_modtype_equiv ~in_eq ~loc env ~mark mty1 mty2 in
+        check_modtype_equiv ~direction ~loc env mty1 mty2 in
   match r with
   | Ok _ as ok -> ok
   | Error e ->
@@ -968,9 +1040,11 @@ and modtype_infos ~in_eq ~loc env ~mark subst id info1 info2 =
       let info2 = Subst.Lazy.force_modtype_decl info2 in
       Error Error.(Module_type_declaration (diff info1 info2 e))
 
-and check_modtype_equiv ~in_eq ~loc env ~mark mty1 mty2 =
+and check_modtype_equiv ~direction ~loc env mty1 mty2 =
+  let nested_eq = direction.Directionality.in_eq in
+  let direction = Directionality.enter_eq direction in
   let c1 =
-    modtypes ~in_eq:true ~loc env ~mark Subst.identity mty1 mty2 Shape.dummy_mod
+    modtypes ~direction ~loc env Subst.identity mty1 mty2 Shape.dummy_mod
       ~modes:All
   in
   let c2 =
@@ -978,11 +1052,11 @@ and check_modtype_equiv ~in_eq ~loc env ~mark mty1 mty2 =
        the outer module type is the one responsible for checking the other side
        of the equivalence.
      *)
-    if in_eq then None
+    if nested_eq then None
     else
-      let mark = negate_mark mark in
+      let direction = Directionality.negate direction in
       Some (
-        modtypes ~in_eq:true ~loc env ~mark Subst.identity ~modes:All
+        modtypes ~direction ~loc env Subst.identity ~modes:All
           mty2 mty1 Shape.dummy_mod
       )
   in
@@ -997,10 +1071,10 @@ and check_modtype_equiv ~in_eq ~loc env ~mark mty1 mty2 =
   | Error less_than, Some Error greater_than ->
       Error Error.(Incomparable {less_than; greater_than})
 
-let include_functor_signatures ~loc env ~mark subst sig1 sig2 mod_shape =
+let include_functor_signatures ~direction ~loc env subst sig1 sig2 mod_shape =
   let _, _, comps1 = build_component_table (fun _pos name -> name) sig1 in
   let paired, unpaired, subst = pair_components subst comps1 sig2 in
-  let d = signature_components ~in_eq:false ~loc ~mark env subst mod_shape
+  let d = signature_components ~direction ~loc env subst mod_shape
             Shape.Map.empty ~mmodes:(Legacy None)
             (List.rev paired)
   in
@@ -1021,21 +1095,21 @@ let can_alias env path =
   no_apply path && not (Env.is_functor_arg path env)
 
 
-let signatures ~in_eq ~loc env ~mark subst sig1 sig2 mod_shape =
+let signatures ~direction ~loc env subst sig1 sig2 mod_shape =
   let sig1 = Subst.Lazy.of_signature sig1 in
   let sig2 = Subst.Lazy.of_signature sig2 in
-  signatures ~in_eq ~loc env ~mark subst sig1 sig2 mod_shape
+  signatures ~direction ~loc env subst sig1 sig2 mod_shape
 
-let modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape =
+let modtypes ~direction ~loc env subst ~modes mty1 mty2 shape =
   let mty1 = Subst.Lazy.of_modtype mty1 in
   let mty2 = Subst.Lazy.of_modtype mty2 in
-  modtypes ~in_eq ~loc env ~mark subst ~modes mty1 mty2 shape
+  modtypes ~direction ~loc env subst ~modes mty1 mty2 shape
 
-let strengthened_modtypes ~in_eq ~loc ~aliasable env ~mark
+let strengthened_modtypes ~direction ~loc ~aliasable env
   subst mty1 path1 mty2 shape =
   let mty1 = Subst.Lazy.of_modtype mty1 in
   let mty2 = Subst.Lazy.of_modtype mty2 in
-  strengthened_modtypes ~in_eq ~loc ~aliasable env ~mark subst mty1
+  strengthened_modtypes ~direction ~loc ~aliasable env subst mty1
     path1 mty2 shape
 
 type explanation = Env.t * Error.all
@@ -1055,7 +1129,8 @@ exception Apply_error of {
 
 let check_modtype_inclusion_raw ~loc env mty1 path1 mty2 =
   let aliasable = can_alias env path1 in
-  strengthened_modtypes ~in_eq:false ~loc ~aliasable env ~mark:Mark_both
+  let direction = Directionality.unknown ~mark:true in
+  strengthened_modtypes ~direction ~loc ~aliasable env
     Subst.identity ~modes:(Legacy None) mty1 path1 mty2 Shape.dummy_mod
   |> Result.map fst
 
@@ -1092,8 +1167,9 @@ let () =
 
 let compunit0
     ~comparison env ~mark impl_name impl_sig intf_name intf_sig unit_shape =
+  let direction = Directionality.strictly_positive ~mark in
   match
-    signatures ~in_eq:false ~loc:(Location.in_file impl_name) env ~mark
+    signatures ~direction ~loc:(Location.in_file impl_name) env
       Subst.identity ~modes:(Legacy None) impl_sig intf_sig unit_shape
   with Result.Error reasons ->
     let diff = Error.diff impl_name intf_name reasons in
@@ -1110,7 +1186,7 @@ let compunit = compunit0 ~comparison:Implementation_vs_interface
 let compunit_as_argument env arg_name arg_sig param_name param_sig =
   let cc, _shape =
     compunit0 env arg_name arg_sig param_name param_sig Shape.dummy_mod
-      ~comparison:Argument_vs_parameter ~mark:Mark_positive
+      ~comparison:Argument_vs_parameter ~mark:true
   in
   cc
 
@@ -1214,7 +1290,8 @@ module Functor_inclusion_diff = struct
           let res, _, _ =
             let mty1 = Subst.Lazy.of_functor_parameter mty1 in
             let mty2 = Subst.Lazy.of_functor_parameter mty2 in
-            functor_param ~in_eq:false ~loc st.env ~mark:Mark_neither
+            let direction = Directionality.unknown ~mark:false in
+            functor_param ~direction ~loc st.env
               st.subst mty1 mty2
           in
           res
@@ -1308,8 +1385,9 @@ module Functor_app_diff = struct
             | Unit, Named _ | (Anonymous | Named _), Unit ->
                 Result.Error (Error.Incompatible_params(arg,param))
             | ( Anonymous | Named _ | Empty_struct ), Named (_, param) ->
+               let direction = Directionality.unknown ~mark:false in
                 match
-                  modtypes ~in_eq:false ~loc state.env ~mark:Mark_neither
+                  modtypes ~direction ~loc state.env
                     state.subst ~modes:(Legacy None) arg_mty param
                     Shape.dummy_mod
                 with
@@ -1332,44 +1410,58 @@ end
 (* Hide the context and substitution parameters to the outside world *)
 
 let modtypes_with_shape ~shape ~loc env ~mark ~modes mty1 mty2 =
-  match modtypes ~in_eq:false ~loc env ~mark
+  (* modtypes with shape is used when typing module expressions in [Typemod] *)
+  let direction = Directionality.strictly_positive ~mark in
+  match modtypes ~direction ~loc env
           Subst.identity ~modes mty1 mty2 shape
   with
   | Ok (cc, shape) -> cc, shape
   | Error reason -> raise (Error (env, Error.(In_Module_type reason)))
 
 let modtypes ~loc env ~mark ~modes mty1 mty2 =
-  match modtypes ~in_eq:false ~loc env ~mark
+  let direction = Directionality.unknown ~mark in
+  match modtypes ~direction ~loc env
           Subst.identity ~modes mty1 mty2 Shape.dummy_mod
   with
   | Ok (cc, _) -> cc
   | Error reason -> raise (Error (env, Error.(In_Module_type reason)))
 
-let signatures env ~mark ~modes  sig1 sig2 =
-  match signatures ~in_eq:false ~loc:Location.none env ~mark
+let gen_signatures env ~direction ~modes sig1 sig2 =
+  match signatures ~direction ~loc:Location.none env
           Subst.identity ~modes sig1 sig2 Shape.dummy_mod
   with
   | Ok (cc, _) -> cc
   | Error reason -> raise (Error(env,Error.(In_Signature reason)))
 
+let signatures env ~mark ~modes sig1 sig2 =
+  let direction = Directionality.unknown ~mark in
+  gen_signatures env ~direction ~modes sig1 sig2
+
+let check_implementation env ~modes impl intf =
+  let direction = Directionality.strictly_positive ~mark:true in
+  ignore (gen_signatures env ~direction ~modes impl intf)
+
 let include_functor_signatures env ~mark sig1 sig2 =
   let sig1 = List.map Subst.Lazy.of_signature_item sig1 in
   let sig2 = List.map Subst.Lazy.of_signature_item sig2 in
-  match include_functor_signatures ~loc:Location.none env ~mark
+  let direction = Directionality.unknown ~mark in
+  match include_functor_signatures ~direction ~loc:Location.none env
           Subst.identity sig1 sig2 Shape.dummy_mod
   with
   | Ok cc -> cc
   | Error reason -> raise (Error(env,Error.(In_Include_functor_signature reason)))
 
 let type_declarations ~loc env ~mark id decl1 decl2 =
-  match type_declarations ~loc env ~mark Subst.identity id decl1 decl2 with
+  let direction = Directionality.unknown ~mark in
+  match type_declarations ~loc env ~direction Subst.identity id decl1 decl2 with
   | Ok _ -> ()
   | Error (Error.Core reason) ->
       raise (Error(env,Error.(In_Type_declaration(id,reason))))
   | Error _ -> assert false
 
 let strengthened_module_decl ~loc ~aliasable env ~mark ~mmodes md1 path1 md2 =
-  match strengthened_module_decl ~loc ~aliasable env ~mark Subst.identity
+  let direction = Directionality.unknown ~mark in
+  match strengthened_module_decl ~loc ~aliasable ~direction env Subst.identity
     ~mmodes md1 path1 md2 Shape.dummy_mod with
   | Ok (x, _shape) -> x
   | Error mdiff ->
@@ -1384,7 +1476,8 @@ let expand_module_alias ~strengthen env path =
 let check_modtype_equiv ~loc env id mty1 mty2 =
   let mty1' = Subst.Lazy.of_modtype mty1 in
   let mty2' = Subst.Lazy.of_modtype mty2 in
-  match check_modtype_equiv ~in_eq:false ~loc env ~mark:Mark_both mty1' mty2' with
+  let direction = Directionality.unknown ~mark:true in
+  match check_modtype_equiv ~direction ~loc env mty1' mty2' with
   | Ok _ -> ()
   | Error e ->
       raise (Error(env,
diff --git a/typing/includemod.mli b/typing/includemod.mli
index 4100f806d98..7f476404851 100644
--- a/typing/includemod.mli
+++ b/typing/includemod.mli
@@ -18,18 +18,6 @@
 open Typedtree
 open Types
 
-(** Type describing which arguments of an inclusion to consider as used
-    for the usage warnings. [Mark_both] is the default. *)
-type mark =
-  | Mark_both
-      (** Mark definitions used from both arguments *)
-  | Mark_positive
-      (** Mark definitions used from the positive (first) argument *)
-  | Mark_negative
-      (** Mark definitions used from the negative (second) argument *)
-  | Mark_neither
-      (** Do not mark definitions used from either argument *)
-
 module Error: sig
 
   type ('elt,'explanation) diff = {
@@ -155,15 +143,15 @@ type modes = Includecore.mmodes
 (* Typechecking *)
 
 val modtypes:
-  loc:Location.t -> Env.t -> mark:mark -> modes:modes ->
+  loc:Location.t -> Env.t -> mark:bool -> modes:modes ->
   module_type -> module_type -> module_coercion
 
 val modtypes_with_shape:
-  shape:Shape.t -> loc:Location.t -> Env.t -> mark:mark -> modes:modes ->
+  shape:Shape.t -> loc:Location.t -> Env.t -> mark:bool -> modes:modes ->
   module_type -> module_type -> module_coercion * Shape.t
 
 val strengthened_module_decl:
-  loc:Location.t -> aliasable:bool -> Env.t -> mark:mark -> mmodes:modes ->
+  loc:Location.t -> aliasable:bool -> Env.t -> mark:bool -> mmodes:modes ->
   module_declaration -> Path.t -> module_declaration -> module_coercion
 
 val check_modtype_inclusion :
@@ -176,21 +164,24 @@ val check_modtype_inclusion :
 val check_modtype_equiv:
   loc:Location.t -> Env.t -> Ident.t -> module_type -> module_type -> unit
 
-val signatures: Env.t -> mark:mark -> modes:modes ->
+val signatures: Env.t -> mark:bool -> modes:modes ->
   signature -> signature -> module_coercion
 
-val include_functor_signatures : Env.t -> mark:mark ->
+val include_functor_signatures : Env.t -> mark:bool ->
   signature -> signature -> (Ident.t * module_coercion) list
 
+val check_implementation: Env.t -> modes:modes -> signature -> signature -> unit
+(** Check an implementation against an interface *)
+
 val compunit:
-      Env.t -> mark:mark -> string -> signature ->
+      Env.t -> mark:bool -> string -> signature ->
       string -> signature -> Shape.t -> module_coercion * Shape.t
 
 val compunit_as_argument:
       Env.t -> string -> signature -> string -> signature -> module_coercion
 
 val type_declarations:
-  loc:Location.t -> Env.t -> mark:mark ->
+  loc:Location.t -> Env.t -> mark:bool ->
   Ident.t -> type_declaration -> type_declaration -> unit
 
 val print_coercion: Format.formatter -> module_coercion -> unit
diff --git a/typing/persistent_env.ml b/typing/persistent_env.ml
index 5b21ff835a2..e0e1eb50426 100644
--- a/typing/persistent_env.ml
+++ b/typing/persistent_env.ml
@@ -349,7 +349,7 @@ let acknowledge_import penv ~check modname pers_sig =
         | Opaque -> register_import_as_opaque penv modname)
     flags;
   begin match kind, CU.get_current () with
-  | Normal { cmi_impl = imported_unit }, Some current_unit ->
+  | Normal { cmi_impl = imported_unit }, Some (current_unit, _) ->
       let access_allowed =
         CU.can_access_by_name imported_unit ~accessed_by:current_unit
       in
@@ -500,7 +500,7 @@ let rec approximate_global_by_name penv global_name =
 let current_unit_is_aux name ~allow_args =
   match CU.get_current () with
   | None -> false
-  | Some current ->
+  | Some (current, _) ->
       match CU.to_global_name current with
       | Some { head; args } ->
           (args = [] || allow_args)
diff --git a/typing/shape.ml b/typing/shape.ml
index af15989695d..26dc7a1e5ce 100644
--- a/typing/shape.ml
+++ b/typing/shape.ml
@@ -16,7 +16,10 @@
 module Uid = struct
   type t =
     | Compilation_unit of string
-    | Item of { comp_unit: string; id: int }
+    | Item of {
+        comp_unit: string;
+        id: int;
+        from: Compilation_unit.intf_or_impl }
     | Internal
     | Predef of string
     | Unboxed_version of t
@@ -29,7 +32,10 @@ module Uid = struct
       | Compilation_unit s1, Compilation_unit s2 -> String.compare s1 s2
       | Item c1, Item c2 ->
         let c = Int.compare c1.id c2.id in
-        if c <> 0 then c else String.compare c1.comp_unit c2.comp_unit
+        let c =
+          if c <> 0 then c else String.compare c1.comp_unit c2.comp_unit
+        in
+        if c <> 0 then c else Stdlib.compare c1.from c2.from
       | Internal, Internal -> 0
       | Predef s1, Predef s2 -> String.compare s1 s2
       | Unboxed_version t1, Unboxed_version t2 -> compare t1 t2
@@ -50,11 +56,16 @@ module Uid = struct
 
     let hash (x : t) = Hashtbl.hash x
 
+    let pp_intf_or_impl fmt = function
+      | Compilation_unit.Intf -> Format.pp_print_string fmt "[intf]"
+      | Compilation_unit.Impl -> ()
+
     let rec print fmt = function
       | Internal -> Format.pp_print_string fmt "<internal>"
       | Predef name -> Format.fprintf fmt "<predef:%s>" name
       | Compilation_unit s -> Format.pp_print_string fmt s
-      | Item { comp_unit; id } -> Format.fprintf fmt "%s.%d" comp_unit id
+      | Item { comp_unit; id; from } ->
+          Format.fprintf fmt "%a%s.%d" pp_intf_or_impl from comp_unit id
       | Unboxed_version t -> Format.fprintf fmt "%a#" print t
 
     let output oc t =
@@ -67,13 +78,13 @@ module Uid = struct
   let reinit () = id := (-1)
 
   let mk  ~current_unit =
-      incr id;
-      let comp_unit =
+      let comp_unit, from =
         match current_unit with
-        | Some cu -> cu |> Compilation_unit.full_path_as_string
-        | None -> ""
+        | None -> "", Compilation_unit.Impl
+        | Some (cu, kind) -> Compilation_unit.full_path_as_string cu, kind
       in
-      Item { comp_unit; id = !id }
+      incr id;
+      Item { comp_unit; id = !id; from }
 
   let of_compilation_unit_id id =
     Compilation_unit (id |> Compilation_unit.full_path_as_string)
diff --git a/typing/shape.mli b/typing/shape.mli
index 53f0d818d47..37aec51de96 100644
--- a/typing/shape.mli
+++ b/typing/shape.mli
@@ -43,9 +43,9 @@
       [cmt_format.cmt_uid_to_decl] table of the corresponding compilation unit.
 
   See:
-  - {{: https://icfp22.sigplan.org/details/mlfamilyworkshop-2022-papers/10/Module-Shapes-for-Modern-Tooling }
+  - {{:https://icfp22.sigplan.org/details/mlfamilyworkshop-2022-papers/10/Module-Shapes-for-Modern-Tooling}
     the design document}
-  - {{: https://www.lix.polytechnique.fr/Labo/Gabriel.Scherer/research/shapes/2022-ml-workshop-shapes-talk.pdf }
+  - {{:https://www.lix.polytechnique.fr/Labo/Gabriel.Scherer/research/shapes/2022-ml-workshop-shapes-talk.pdf}
     a talk about the reduction strategy
 *)
 
@@ -57,14 +57,18 @@
 module Uid : sig
   type t = private
     | Compilation_unit of string
-    | Item of { comp_unit: string; id: int }
+    | Item of {
+        comp_unit: string;
+        id: int;
+        from: Compilation_unit.intf_or_impl }
     | Internal
     | Predef of string
     | Unboxed_version of t
 
   val reinit : unit -> unit
 
-  val mk : current_unit:Compilation_unit.t option -> t
+  val mk :
+    current_unit:(Compilation_unit.with_kind) option -> t
   val of_compilation_unit_id : Compilation_unit.t -> t
   val of_compilation_unit_name : Compilation_unit.Name.t -> t
   val of_predef_id : Ident.t -> t
diff --git a/typing/typemod.ml b/typing/typemod.ml
index 741d198ca98..77c4360bad4 100644
--- a/typing/typemod.ml
+++ b/typing/typemod.ml
@@ -147,7 +147,7 @@ let extract_sig_functor_open funct_body env loc mty sig_acc =
       in
       let coercion =
         try
-          Includemod.include_functor_signatures ~mark:Mark_both env
+          Includemod.include_functor_signatures ~mark:true env
             sig_acc sg_param
         with Includemod.Error msg ->
           raise (Error(loc, env, Not_included_functor msg))
@@ -316,7 +316,7 @@ let check_type_decl env sg loc id row_id newdecl decl =
     | Some fresh_row_id -> Env.add_type ~check:false fresh_row_id newdecl env
   in
   let env = Env.add_signature sg env in
-  Includemod.type_declarations ~mark:Mark_both ~loc env fresh_id newdecl decl;
+  Includemod.type_declarations ~mark:true ~loc env fresh_id newdecl decl;
   ignore (Typedecl.check_coherence env loc path newdecl)
 
 let make_variance p n i =
@@ -833,7 +833,7 @@ let merge_constraint initial_env loc sg lid constr =
         in
         let md'' = { md' with md_type = mty } in
         let newmd = Mtype.strengthen_decl ~aliasable:false md'' path in
-        ignore(Includemod.modtypes  ~mark:Mark_both ~loc sig_env
+        ignore(Includemod.modtypes  ~mark:true ~loc sig_env
           ~modes:(Legacy None) newmd.md_type md.md_type);
         return
           ~replace_by:(Some(Sig_module(id, pres, newmd, rs, priv)))
@@ -843,7 +843,7 @@ let merge_constraint initial_env loc sg lid constr =
         let sig_env = Env.add_signature sg_for_env outer_sig_env in
         let aliasable = not (Env.is_functor_arg path sig_env) in
         ignore
-          (Includemod.strengthened_module_decl ~loc ~mark:Mark_both
+          (Includemod.strengthened_module_decl ~loc ~mark:true
              ~aliasable sig_env ~mmodes:(Legacy None) md' path md);
         real_ids := [Pident id];
         return ~replace_by:None
@@ -1732,7 +1732,7 @@ and transl_modtype_aux env smty =
       try
         ignore
           (Includemod.modtypes ~loc env ~modes:(Legacy None)
-            ~mark:Includemod.Mark_both md.md_type tmty.mty_type);
+            ~mark:true md.md_type tmty.mty_type);
         mkmty
           (Tmty_strengthen (tmty, path, mod_id))
           (Mty_strengthen
@@ -2426,7 +2426,7 @@ let check_recmodule_inclusion env bindings =
         let coercion, shape =
           try
             Includemod.modtypes_with_shape ~shape
-              ~loc:modl.mod_loc ~mark:Mark_both
+              ~loc:modl.mod_loc ~mark:true
               env ~modes:(Legacy None) mty_actual' mty_decl'
           with Includemod.Error msg ->
             raise(Error(modl.mod_loc, env, Not_included msg)) in
@@ -2517,14 +2517,13 @@ let package_subtype env p1 fl1 p2 fl2 =
   | exception Error(_, _, Cannot_scrape_package_type _) -> false
   | mty1, mty2 ->
     let loc = Location.none in
-    match Includemod.modtypes ~loc ~mark:Mark_both env ~modes:All mty1 mty2 with
+    match Includemod.modtypes ~loc ~mark:true env ~modes:All mty1 mty2 with
     | Tcoerce_none -> true
     | _ | exception Includemod.Error _ -> false
 
 let () = Ctype.package_subtype := package_subtype
 
 let wrap_constraint_package env mark arg held_locks mty explicit =
-  let mark = if mark then Includemod.Mark_both else Includemod.Mark_neither in
   let mty1 = Subst.modtype Keep Subst.identity arg.mod_type in
   let mty2 = Subst.modtype Keep Subst.identity mty in
   let coercion =
@@ -2540,7 +2539,6 @@ let wrap_constraint_package env mark arg held_locks mty explicit =
 
 let wrap_constraint_with_shape env mark arg held_locks mty
   shape explicit =
-  let mark = if mark then Includemod.Mark_both else Includemod.Mark_neither in
   let coercion, shape =
     try
       Includemod.modtypes_with_shape ~shape ~loc:arg.mod_loc env ~mark
@@ -2896,7 +2894,7 @@ and type_one_application ~ctx:(apply_loc,sfunct,md_f,args)
           arg = Some { shape = arg_shape; path = arg_path; arg; held_locks } } ->
       let coercion =
         try Includemod.modtypes
-              ~loc:arg.mod_loc ~mark:Mark_both env arg.mod_type mty_param
+              ~loc:arg.mod_loc ~mark:true env arg.mod_type mty_param
               ~modes:(Legacy held_locks)
         with Includemod.Error _ -> apply_error ()
       in
@@ -2928,7 +2926,7 @@ and type_one_application ~ctx:(apply_loc,sfunct,md_f,args)
             in
             begin match
               Includemod.modtypes
-                ~loc:app_loc ~mark:Mark_neither env mty_res nondep_mty
+                ~loc:app_loc ~mark:false env mty_res nondep_mty
                 ~modes:(Legacy None)
             with
             | Tcoerce_none -> ()
@@ -3860,7 +3858,7 @@ let type_implementation target modulename initial_env ast =
                        old_arg_type = arg_type_from_cmi });
           let coercion, shape =
             Profile.record_call "check_sig" (fun () ->
-              Includemod.compunit initial_env ~mark:Mark_positive
+              Includemod.compunit initial_env ~mark:true
                 sourcefile sg compiled_intf_file_name dclsig shape)
           in
           (* Check the _mli_ against the argument type, since the mli determines
@@ -3896,7 +3894,7 @@ let type_implementation target modulename initial_env ast =
             Warnings.Missing_mli;
           let coercion, shape =
             Profile.record_call "check_sig" (fun () ->
-              Includemod.compunit initial_env ~mark:Mark_positive
+              Includemod.compunit initial_env ~mark:true
                 sourcefile sg "(inferred signature)" simple_sg shape)
           in
           check_nongen_signature finalenv simple_sg;
@@ -4067,7 +4065,7 @@ let package_units initial_env objfiles target_cmi modulename =
     let name = Compilation_unit.to_global_name_without_prefix modulename in
     let dclsig = Env.read_signature name target_cmi in
     let cc, _shape =
-      Includemod.compunit initial_env ~mark:Mark_both
+      Includemod.compunit initial_env ~mark:true
         "(obtained by packing)" sg mli dclsig shape
     in
     Cmt_format.save_cmt  (Unit_info.companion_cmt target_cmi) modulename
diff --git a/utils/compilation_unit.ml b/utils/compilation_unit.ml
index a172da7ab71..93ad77d762a 100644
--- a/utils/compilation_unit.ml
+++ b/utils/compilation_unit.ml
@@ -637,17 +637,25 @@ let print_debug ppf t =
       "@[<hov 1>(@[<hov 1>(for_pack_prefix@ %a)@]@;@[<hov 1>(name@ %a)@]"
       Prefix.print for_pack_prefix Name.print name
 
+type intf_or_impl =
+  | Intf
+  | Impl
+
+type with_kind = t * intf_or_impl
+
 let current = ref None
 
 let set_current t_opt = current := t_opt
 
 let get_current () = !current
 
-let get_current_or_dummy () = Option.value !current ~default:dummy
+let get_current_or_dummy () =
+  Option.value !current ~default:(dummy, Impl) |> fst
 
 let get_current_exn () =
   match !current with
-  | Some t -> t
+  | Some (t, _) -> t
   | None -> Misc.fatal_error "No compilation unit set"
 
-let is_current t = match !current with None -> false | Some t' -> equal t t'
+let is_current t =
+  match !current with None -> false | Some (t', _) -> equal t t'
diff --git a/utils/compilation_unit.mli b/utils/compilation_unit.mli
index 5e42151075a..d09aa94b511 100644
--- a/utils/compilation_unit.mli
+++ b/utils/compilation_unit.mli
@@ -297,9 +297,21 @@ type error = private
 (** The exception raised by conversion functions in this module. *)
 exception Error of error
 
-val set_current : t option -> unit
+(* CR ugerard: there might be a cleaner way to do that. Upstream this info is
+   part of a `Unit_info.t` record that is stored as the "current unit" in the
+   environement. But here in flambda-backend `Compilation_unit.t` instead. This
+   looks like conflicting refactorings that it would be useful to reconcile.
 
-val get_current : unit -> t option
+   Here, for the prototype, we use a tuple to add that information. *)
+type intf_or_impl =
+  | Intf
+  | Impl
+
+type with_kind = t * intf_or_impl
+
+val set_current : with_kind option -> unit
+
+val get_current : unit -> with_kind option
 
 val get_current_or_dummy : unit -> t