refactor: introduces a struct for mixin data

Author: christoph-dfinity

src/mo_frontend/scope.ml

@@ -14,9 +14,14 @@ type lib_env = T.typ T.Env.t
 type typ_env = T.con T.Env.t
 type con_env = T.ConSet.t
 type fld_src_env = Field_sources.srcs_map
-
-type mixin_env = (S.import list * S.pat * S.dec_field list * T.typ) T.Env.t
-and obj_env = scope T.Env.t  (* internal object scopes *)
+type mixin_env = mixin_data T.Env.t
+and mixin_data =  {
+  imports : S.import list;
+  arg : S.pat;
+  decs : S.dec_field list;
+  typ : T.typ;
+}
+type obj_env = scope T.Env.t  (* internal object scopes *)
 and scope =
   { val_env : val_env;
     lib_env : lib_env;

src/mo_frontend/scope.mli

@@ -6,10 +6,14 @@ type lib_env = Mo_types.Type.typ Env.t
 type typ_env = con Env.t
 type con_env = ConSet.t
 type fld_src_env = Mo_types.Field_sources.srcs_map
-
-(* TODO: make this a record *)
-type mixin_env = (Mo_def.Syntax.import list * Mo_def.Syntax.pat * Mo_def.Syntax.dec_field list * typ) Env.t
-and obj_env = scope Env.t  (* internal object scopes *)
+type mixin_env = mixin_data Env.t
+and mixin_data =  {
+  imports : Mo_def.Syntax.import list;
+  arg : Mo_def.Syntax.pat;
+  decs : Mo_def.Syntax.dec_field list;
+  typ : typ;
+}
+type obj_env = scope Env.t  (* internal object scopes *)
 and scope =
   { val_env : val_env;
     lib_env : lib_env;
@@ -26,4 +30,4 @@ val adjoin : scope -> scope -> scope
 
 val adjoin_val_env : scope -> val_env -> scope
 val lib : string -> typ -> scope
-val mixin : string -> Mo_def.Syntax.import list * Mo_def.Syntax.pat * Mo_def.Syntax.dec_field list * typ -> scope
+val mixin : string -> mixin_data -> scope

src/mo_frontend/typing.ml

@@ -4070,7 +4070,7 @@ and infer_dec env dec : T.typ =
         error env dec.at "M0227" "mixins can only be included in an actor context";
       match T.Env.find_opt i.it env.mixins with
       | None -> error env i.at "M0226" "unknown mixin %s" i.it
-      | Some (_, pat, _, _) -> check_exp env pat.note arg
+      | Some mix -> check_exp env mix.Scope.arg.note arg
     end;
     T.unit
   | ExpD exp -> infer_exp env exp
@@ -4263,9 +4263,9 @@ and gather_dec env scope dec : Scope.t =
     }
   | LetD (pat, exp, _) -> (match is_mixin_import env exp.it with
     | None -> gather_pat env scope pat
-    | Some (imports, args, t, decs) ->
+    | Some mix ->
       match pat.it with
-      | VarP id -> Scope.adjoin scope (Scope.mixin id.it (imports, args, t, decs))
+      | VarP id -> Scope.adjoin scope (Scope.mixin id.it mix)
       | _ -> error env pat.at "M0229" "mixins may only be imported by binding to a name"
   )
   | VarD (id, _) -> Scope.adjoin_val_env scope (gather_id env scope.Scope.val_env id Scope.Declaration)
@@ -4307,9 +4307,9 @@ and gather_dec env scope dec : Scope.t =
   | IncludeD(i, _, _) -> begin
     match T.Env.find_opt i.it env.mixins with
     | None -> error env i.at "M0226" "unknown mixin %s" i.it
-    | Some(imports, pat, decs, t) ->
+    | Some mix ->
       let open Scope in
-      let (_, fields) = T.as_obj t in
+      let (_, fields) = T.as_obj mix.typ in
       let add_field acc = function
         | T.{ lab; typ = T.Typ t; _ } ->
           if T.Env.mem lab acc.typ_env then error_duplicate env "type " { it = lab; at = i.at; note = () };
@@ -4373,12 +4373,13 @@ and infer_dec_typdecs env dec : Scope.t =
   | IncludeD (i, _, n) -> begin
     match T.Env.find_opt i.it env.mixins with
     | None -> error env i.at "M0226" "unknown mixin %s" i.it
-    | Some(imports, pat, decs, t) ->
-      n := Some({ imports; pat; decs });
-      let (_, fields) = T.as_obj t in
+    | Some mix ->
+      let open Scope in
+      n := Some({ imports = mix.imports; pat = mix.arg; decs = mix.decs });
+      let (_, fields) = T.as_obj mix.typ in
       let scope = scope_of_object env fields in
       (* Mark all included idents as used to avoid spurious warnings *)
-      T.Env.iter (fun i _ -> use_identifier env i) scope.Scope.val_env;
+      T.Env.iter (fun i _ -> use_identifier env i) scope.val_env;
       scope
     end
   (* TODO: generalize beyond let <id> = <obje> *)
@@ -4401,9 +4402,9 @@ and infer_dec_typdecs env dec : Scope.t =
   (* TODO: generalize beyond let <id> = <valpath> *)
   | LetD ({it = VarP id; _}, exp, _) ->
      begin match is_mixin_import env exp.it with
-     | Some (imports, args, t, decs) ->
+     | Some mix ->
         (* Format.printf "Adding mixin %s at %a\n" id.it display_typ t; *)
-        Scope.mixin id.it (imports, args, t, decs)
+        Scope.mixin id.it mix
      | None ->
     (match infer_val_path env exp with
      | None -> Scope.empty
@@ -4648,8 +4649,8 @@ let check_lib scope pkg_opt lib : Scope.t Diag.result =
                 ("system", obj Module [id.it, install_typ (List.map (close cs) ts1) class_typ])
               ]) in
               Scope.lib lib.note.filename typ
-            | MixinU (pat, decs) ->
-              Scope.mixin lib.note.filename (imports, pat, decs, typ)
+            | MixinU (arg, decs) ->
+              Scope.mixin lib.note.filename Scope.{ imports; arg; decs; typ }
             | ActorU _ ->
               error env cub.at "M0144" "bad import: expected a module or actor class but found an actor"
             | ProgU _ ->