Better names, and a comment

ocaml/typing/typedtree.ml

@@ -1036,17 +1036,18 @@ let rev_let_bound_idents_full bindings =
   !idents_full
 
 let let_bound_idents_with_modes_sorts_and_checks bindings =
-  let modes_and_sorts = Ident.Tbl.create 3 in
+  let modes_sorts_and_checks = Ident.Tbl.create 3 in
   let f id sloc _ _uid mode sort =
-    Ident.Tbl.add modes_and_sorts id
+    Ident.Tbl.add modes_sorts_and_checks id
       (sloc.loc, mode, sort, Builtin_attributes.Default_check)
   in
   List.iter (fun vb ->
     iter_pattern_full ~both_sides_of_or:true f vb.vb_sort vb.vb_pat;
      match vb.vb_pat.pat_desc, vb.vb_expr.exp_desc with
      | Tpat_var (id, _, _, _), Texp_function fn ->
-       let (loc, mode, sort, _) = Ident.Tbl.find modes_and_sorts id in
-       Ident.Tbl.replace modes_and_sorts id (loc, mode, sort, fn.zero_alloc)
+       let (loc, mode, sort, _) = Ident.Tbl.find modes_sorts_and_checks id in
+       Ident.Tbl.replace modes_sorts_and_checks id
+         (loc, mode, sort, fn.zero_alloc)
      | _ -> ()
   )
     bindings;

ocaml/typing/typedtree.mli

@@ -1102,6 +1102,18 @@ val exists_pattern: (pattern -> bool) -> pattern -> bool
 val let_bound_idents: value_binding list -> Ident.t list
 val let_bound_idents_full:
     value_binding list -> (Ident.t * string loc * Types.type_expr * Uid.t) list
+
+(* [let_bound_idents_with_modes_sorts_and_checks] finds all the idents in the
+   let bindings and computes their modes, sorts, and whether they have any check
+   attributes (zero_alloc).
+
+   Note that:
+   * The list associated with each ident can only have more than one element in
+     the case of or pattern, where the ident is bound on both sides.
+   * Check attributes are only supported in the case of a simple variable
+     pattern bound to a function ([Default_check] will be returned in all other
+     cases).
+*)
 val let_bound_idents_with_modes_sorts_and_checks:
   value_binding list
   -> (Ident.t * (Location.t * Mode.Value.l * Jkind.sort

ocaml/typing/typemod.ml

@@ -2795,7 +2795,7 @@ and type_structure ?(toplevel = None) funct_body anchor env sstr =
            will be marked as being used during the signature inclusion test. *)
         let items, shape_map =
           List.fold_left
-            (fun (acc, shape_map) (id, modes) ->
+            (fun (acc, shape_map) (id, id_info) ->
               List.iter
                 (fun (loc, mode, sort, _) ->
                    Typecore.escape ~loc ~env:newenv ~reason:Other mode;
@@ -2806,13 +2806,13 @@ and type_structure ?(toplevel = None) funct_body anchor env sstr =
                    then raise (Error (loc, env,
                                    Toplevel_nonvalue (Ident.name id,sort)))
                 )
-                modes;
+                id_info;
               let zero_alloc =
                 (* We only allow "Check" attributes in signatures.  Here we
                    convert "Assume"s in structures to the equivalent "Check" for
                    the signature. *)
                 let open Builtin_attributes in
-                match[@warning "+9"] modes with
+                match[@warning "+9"] id_info with
                 | [(_, _, _, (Default_check | Ignore_assert_all _))] ->
                   Default_check
                 | [(_, _, _, (Check _ as zero_alloc))] -> zero_alloc
@@ -2821,7 +2821,7 @@ and type_structure ?(toplevel = None) funct_body anchor env sstr =
                   Check { strict; property; arity; loc; opt = false }
                 | _ -> Default_check
               in
-              let (first_loc, _, _, _) = List.hd modes in
+              let (first_loc, _, _, _) = List.hd id_info in
               Signature_names.check_value names first_loc id;
               let vd =  Env.find_value (Pident id) newenv in
               let vd = Subst.Lazy.force_value_description vd in