Support for structure updates

Closes #592

A new node is added in `desugared`, and translated into an exploded structure
literal during translation to `scopelang`. The main reason to put it there is
that it needs to be after disambiguation, since that is used to discover the
type of the structure that is being updated.

compiler/desugared/from_surface.ml

@@ -559,6 +559,18 @@ let rec translate_expr
       Expr.make_abs (Array.of_list vs) (rec_helper ~local_vars e2) taus pos
     in
     Expr.eapp ~f ~args:[rec_helper e1] ~tys:[] emark
+  | StructReplace (e, fields) ->
+    let fields =
+      List.fold_left
+        (fun acc (field_id, field_expr) ->
+          if Ident.Map.mem (Mark.remove field_id) acc then
+            Message.error ~pos:(Mark.get field_expr)
+              "Duplicate redefinition of field@ %a" Ident.format
+              (Mark.remove field_id);
+          Ident.Map.add (Mark.remove field_id) (rec_helper field_expr) acc)
+        Ident.Map.empty fields
+    in
+    Expr.edstructamend ~fields ~e:(rec_helper e) ~name_opt:None emark
   | StructLit (((path, s_name), _), fields) ->
     let ctxt = Name_resolution.module_ctx ctxt path in
     let s_uid =

compiler/scopelang/from_desugared.ml

@@ -83,7 +83,50 @@ let rec translate_expr (ctx : ctx) (e : D.expr) : untyped Ast.expr boxed =
          })
       m
   | ELocation (ToplevelVar v) -> Expr.elocation (ToplevelVar v) m
-  | EDStructAccess _ ->
+  | EDStructAmend { name_opt = Some name; e; fields } ->
+    let str_fields = StructName.Map.find name ctx.decl_ctx.ctx_structs in
+    let fields =
+      Ident.Map.fold
+        (fun id e ->
+          match
+            StructName.Map.find name
+              (Ident.Map.find id ctx.decl_ctx.ctx_struct_fields)
+          with
+          | field -> StructField.Map.add field (translate_expr ctx e)
+          | exception (Ident.Map.Not_found _ | StructName.Map.Not_found _) ->
+            Message.error ~pos:(Expr.pos e)
+              ~fmt_pos:
+                [
+                  ( (fun ppf ->
+                      Format.fprintf ppf "Declaration of structure %a"
+                        StructName.format name),
+                    Mark.get (StructName.get_info name) );
+                ]
+              "Field %a@ does@ not@ belong@ to@ structure@ %a" Ident.format id
+              StructName.format name)
+        fields StructField.Map.empty
+    in
+    if StructField.Map.cardinal fields = StructField.Map.cardinal str_fields
+    then
+      Message.warning ~pos:(Expr.mark_pos m)
+        "All fields of@ %a@ are@ rewritten@ in@ this@ replacement."
+        StructName.format name;
+    let orig_var = Var.make "orig" in
+    let orig_e = Expr.evar orig_var (Mark.get e) in
+    let fields =
+      StructField.Map.mapi
+        (fun field _ty ->
+          match StructField.Map.find_opt field fields with
+          | Some e -> e
+          | None -> Expr.estructaccess ~name ~field ~e:orig_e m)
+        str_fields
+    in
+    Expr.make_let_in orig_var
+      (TStruct name, Expr.pos e)
+      (translate_expr ctx e)
+      (Expr.estruct ~name ~fields m)
+      (Expr.mark_pos m)
+  | EDStructAmend { name_opt = None; _ } | EDStructAccess _ ->
     assert false (* This shouldn't appear in desugared after disambiguation *)
   | EScopeCall { scope; args } ->
     Expr.escopecall ~scope

compiler/shared_ast/definitions.ml

@@ -527,6 +527,12 @@ and ('a, 'b, 'm) base_gexpr =
       args : ('a, 'm) gexpr ScopeVar.Map.t;
     }
       -> ('a, < explicitScopes : yes ; .. >, 'm) base_gexpr
+  | EDStructAmend : {
+      name_opt : StructName.t option;
+      e : ('a, 'm) gexpr;
+      fields : ('a, 'm) gexpr Ident.Map.t;
+    }
+      -> ('a, < syntacticNames : yes ; .. >, 'm) base_gexpr
   | EDStructAccess : {
       name_opt : StructName.t option;
       e : ('a, 'm) gexpr;

compiler/shared_ast/expr.ml

@@ -56,6 +56,10 @@ module Box = struct
   let lift : ('a, 't) boxed_gexpr -> ('a, 't) gexpr B.box =
    fun em -> B.box_apply (fun e -> Mark.add (Mark.get em) e) (Mark.remove em)
 
+  module LiftIdentMap = Bindlib.Lift (Ident.Map)
+
+  let lift_identmap = LiftIdentMap.lift_box
+
   module LiftStruct = Bindlib.Lift (StructField.Map)
 
   let lift_struct = LiftStruct.lift_box
@@ -156,6 +160,14 @@ let estruct ~name ~(fields : ('a, 't) boxed_gexpr StructField.Map.t) mark =
        (fun fields -> EStruct { name; fields })
        (Box.lift_struct (StructField.Map.map Box.lift fields))
 
+let edstructamend ~name_opt ~e ~(fields : ('a, 't) boxed_gexpr Ident.Map.t) mark
+    =
+  Mark.add mark
+  @@ Bindlib.box_apply2
+       (fun e fields -> EDStructAmend { name_opt; e; fields })
+       (Box.lift e)
+       (Box.lift_identmap (Ident.Map.map Box.lift fields))
+
 let edstructaccess ~name_opt ~field ~e =
   Box.app1 e @@ fun e -> EDStructAccess { name_opt; field; e }
 
@@ -305,6 +317,9 @@ let map
   | EStruct { name; fields } ->
     let fields = StructField.Map.map f fields in
     estruct ~name ~fields m
+  | EDStructAmend { name_opt; e; fields } ->
+    let fields = Ident.Map.map f fields in
+    edstructamend ~name_opt ~e:(f e) ~fields m
   | EDStructAccess { name_opt; field; e } ->
     edstructaccess ~name_opt ~field ~e:(f e) m
   | EStructAccess { name; field; e } -> estructaccess ~name ~field ~e:(f e) m
@@ -345,6 +360,8 @@ let shallow_fold
   | EErrorOnEmpty e -> acc |> f e
   | ECatch { body; handler; _ } -> acc |> f body |> f handler
   | EStruct { fields; _ } -> acc |> StructField.Map.fold (fun _ -> f) fields
+  | EDStructAmend { e; fields; _ } ->
+    acc |> f e |> Ident.Map.fold (fun _ -> f) fields
   | EDStructAccess { e; _ } -> acc |> f e
   | EStructAccess { e; _ } -> acc |> f e
   | EMatch { e; cases; _ } ->
@@ -434,6 +451,16 @@ let map_gather
         (acc, StructField.Map.empty)
     in
     acc, estruct ~name ~fields m
+  | EDStructAmend { name_opt; e; fields } ->
+    let acc, e = f e in
+    let acc, fields =
+      Ident.Map.fold
+        (fun cons e (acc, fields) ->
+          let acc1, e = f e in
+          join acc acc1, Ident.Map.add cons e fields)
+        fields (acc, Ident.Map.empty)
+    in
+    acc, edstructamend ~name_opt ~e ~fields m
   | EDStructAccess { name_opt; field; e } ->
     let acc, e = f e in
     acc, edstructaccess ~name_opt ~field ~e m
@@ -618,6 +645,11 @@ and equal : type a. (a, 't) gexpr -> (a, 't) gexpr -> bool =
   | ( EStruct { name = s1; fields = fields1 },
       EStruct { name = s2; fields = fields2 } ) ->
     StructName.equal s1 s2 && StructField.Map.equal equal fields1 fields2
+  | ( EDStructAmend { name_opt = s1; e = e1; fields = fields1 },
+      EDStructAmend { name_opt = s2; e = e2; fields = fields2 } ) ->
+    Option.equal StructName.equal s1 s2
+    && equal e1 e2
+    && Ident.Map.equal equal fields1 fields2
   | ( EDStructAccess { e = e1; field = f1; name_opt = s1 },
       EDStructAccess { e = e2; field = f2; name_opt = s2 } ) ->
     Option.equal StructName.equal s1 s2 && Ident.equal f1 f2 && equal e1 e2
@@ -641,8 +673,8 @@ and equal : type a. (a, 't) gexpr -> (a, 't) gexpr -> bool =
   | ( ( EVar _ | EExternal _ | ETuple _ | ETupleAccess _ | EArray _ | ELit _
       | EAbs _ | EApp _ | EAppOp _ | EAssert _ | EDefault _ | EPureDefault _
       | EIfThenElse _ | EEmptyError | EErrorOnEmpty _ | ERaise _ | ECatch _
-      | ELocation _ | EStruct _ | EDStructAccess _ | EStructAccess _ | EInj _
-      | EMatch _ | EScopeCall _ | ECustom _ ),
+      | ELocation _ | EStruct _ | EDStructAmend _ | EDStructAccess _
+      | EStructAccess _ | EInj _ | EMatch _ | EScopeCall _ | ECustom _ ),
       _ ) ->
     false
 
@@ -685,6 +717,11 @@ let rec compare : type a. (a, _) gexpr -> (a, _) gexpr -> int =
     EStruct {name=name2; fields=field_map2 } ->
     StructName.compare name1 name2 @@< fun () ->
     StructField.Map.compare compare field_map1 field_map2
+  | EDStructAmend {name_opt=n1; e=e1; fields=field_map1},
+    EDStructAmend {name_opt=n2; e=e2; fields=field_map2} ->
+    compare e1 e2 @@< fun () ->
+    Ident.Map.compare compare field_map1 field_map2 @@< fun () ->
+    Option.compare StructName.compare n1 n2
   | EDStructAccess {e=e1; field=field_name1; name_opt=struct_name1},
     EDStructAccess {e=e2; field=field_name2; name_opt=struct_name2} ->
     compare e1 e2 @@< fun () ->
@@ -748,6 +785,7 @@ let rec compare : type a. (a, _) gexpr -> (a, _) gexpr -> int =
   | EIfThenElse _, _ -> -1 | _, EIfThenElse _ -> 1
   | ELocation _, _ -> -1 | _, ELocation _ -> 1
   | EStruct _, _ -> -1 | _, EStruct _ -> 1
+  | EDStructAmend _, _ -> -1 | _, EDStructAmend _ -> 1
   | EDStructAccess _, _ -> -1 | _, EDStructAccess _ -> 1
   | EStructAccess _, _ -> -1 | _, EStructAccess _ -> 1
   | EMatch _, _ -> -1 | _, EMatch _ -> 1
@@ -895,6 +933,8 @@ let rec size : type a. (a, 't) gexpr -> int =
   | ELocation _ -> 1
   | EStruct { fields; _ } ->
     StructField.Map.fold (fun _ e acc -> acc + 1 + size e) fields 0
+  | EDStructAmend { e; fields; _ } ->
+    1 + size e + Ident.Map.fold (fun _ e acc -> acc + 1 + size e) fields 0
   | EDStructAccess { e; _ } -> 1 + size e
   | EStructAccess { e; _ } -> 1 + size e
   | EMatch { e; cases; _ } ->

compiler/shared_ast/expr.mli

@@ -132,6 +132,13 @@ val estruct :
   'm mark ->
   ('a any, 'm) boxed_gexpr
 
+val edstructamend :
+  name_opt:StructName.t option ->
+  e:('a, 'm) boxed_gexpr ->
+  fields:('a, 'm) boxed_gexpr Ident.Map.t ->
+  'm mark ->
+  ((< syntacticNames : yes ; .. > as 'a), 'm) boxed_gexpr
+
 val edstructaccess :
   name_opt:StructName.t option ->
   field:Ident.t ->

compiler/shared_ast/print.ml

@@ -423,6 +423,7 @@ module Precedence = struct
     | ETupleAccess _ -> Dot
     | ELocation _ -> Contained
     | EScopeCall _ -> App
+    | EDStructAmend _ -> App
     | EDStructAccess _ | EStructAccess _ -> Dot
     | EAssert _ -> App
     | EDefault _ -> Contained
@@ -681,6 +682,14 @@ module ExprGen (C : EXPR_PARAM) = struct
       | EDStructAccess { e; field; _ } ->
         Format.fprintf fmt "@[<hv 2>%a%a@,%a%a%a@]" (lhs exprc) e punctuation
           "." punctuation "\"" Ident.format field punctuation "\""
+      | EDStructAmend { e; fields; _ } ->
+        Format.fprintf fmt "@[<hv 2>@[<hov>%a %a@ with@]@ %a@;<1 -2>%a@]"
+          punctuation "{" (lhs exprc) e
+          (Ident.Map.format_bindings ~pp_sep:Format.pp_print_space
+             (fun fmt pp_field_name field_expr ->
+               Format.fprintf fmt "@[<hv 2>%t %a@ %a%a@]" pp_field_name
+                 punctuation "=" (lhs exprc) field_expr punctuation ";"))
+          fields punctuation "}"
       | EStruct { name; fields } ->
         if StructField.Map.is_empty fields then (
           punctuation fmt "{";
@@ -1127,7 +1136,7 @@ module UserFacing = struct
     | EApp _ | EAppOp _ | EVar _ | EIfThenElse _ | EMatch _ | ETupleAccess _
     | EStructAccess _ | EAssert _ | EDefault _ | EPureDefault _
     | EErrorOnEmpty _ | ERaise _ | ECatch _ | ELocation _ | EScopeCall _
-    | EDStructAccess _ | ECustom _ ->
+    | EDStructAmend _ | EDStructAccess _ | ECustom _ ->
       fallback ppf e
 
   let expr :

compiler/shared_ast/typing.ml

@@ -548,6 +548,25 @@ and typecheck_expr_top_down :
         fields
     in
     Expr.estruct ~name ~fields mark
+  | A.EDStructAmend { name_opt = _; e; fields } ->
+    let e = typecheck_expr_top_down ctx env tau e in
+    let name =
+      match UnionFind.get (ty e) with
+      | TStruct name, _ -> name
+      | TAny _, _ -> failwith "Disambiguation failure"
+      | _ ->
+        Message.error ~pos:(Expr.pos e)
+          "This expression has type %a, where a structure was expected"
+          (format_typ ctx) (ty e)
+    in
+    let fields = A.Ident.Map.map (typecheck_expr_bottom_up ctx env) fields in
+    (* Note: here we identify the structure name, and type the fields
+       individually, but without enforcing any consistency constraint between
+       the two. This is fine because this construction only appears in
+       Desugared, where it is used for disambiguation. In later passes this is
+       rewritten into a struct literal, so no need to anticipate name resolution
+       and duplicate the checks here. *)
+    Expr.edstructamend ~name_opt:(Some name) ~e ~fields context_mark
   | A.EDStructAccess { e = e_struct; name_opt; field } ->
     let t_struct =
       match name_opt with

compiler/surface/ast.ml

@@ -187,6 +187,7 @@ and naked_expression =
   | EnumInject of (path * uident Mark.pos) Mark.pos * expression option
   | StructLit of
       (path * uident Mark.pos) Mark.pos * (lident Mark.pos * expression) list
+  | StructReplace of expression * (lident Mark.pos * expression) list
   | ArrayLit of expression list
   | Tuple of expression list
   | Ident of path * lident Mark.pos * lident Mark.pos option

compiler/surface/lexer.cppo.ml

@@ -206,6 +206,9 @@ module R = Re.Pcre
 #ifndef MR_LIST_EMPTY
   #define MR_LIST_EMPTY MS_LIST_EMPTY
 #endif
+#ifndef MR_BUT_REPLACE
+  #define MR_BUT_REPLACE MS_BUT_REPLACE
+#endif
 #ifndef MR_CARDINAL
   #define MR_CARDINAL MS_CARDINAL
 #endif
@@ -316,6 +319,7 @@ let token_list : (string * token) list =
     (MS_MINIMUM, MINIMUM);
     (MS_IS, IS);
     (MS_LIST_EMPTY, LIST_EMPTY);
+    (MS_BUT_REPLACE, BUT_REPLACE);
     (MS_CARDINAL, CARDINAL);
     (MS_YEAR, YEAR);
     (MS_MONTH, MONTH);
@@ -570,6 +574,9 @@ let rec lex_code (lexbuf : lexbuf) : token =
   | MR_LIST_EMPTY ->
       L.update_acc lexbuf;
       LIST_EMPTY
+  | MR_BUT_REPLACE ->
+      L.update_acc lexbuf;
+      BUT_REPLACE
   | MR_CARDINAL ->
       L.update_acc lexbuf;
       CARDINAL

compiler/surface/lexer_en.cppo.ml

@@ -83,6 +83,8 @@
 #define MS_IS "is"
 #define MS_LIST_EMPTY "list empty"
 #define MR_LIST_EMPTY "list", space_plus, "empty"
+#define MS_BUT_REPLACE "but replace"
+#define MR_BUT_REPLACE "but", space_plus, "replace"
 #define MS_CARDINAL "number"
 #define MS_YEAR "year"
 #define MS_MONTH "month"

compiler/surface/lexer_fr.cppo.ml

@@ -103,6 +103,8 @@
 #define MS_IS "est"
 #define MS_LIST_EMPTY "liste vide"
 #define MR_LIST_EMPTY "liste", space_plus, "vide"
+#define MS_BUT_REPLACE "mais en rempla\195\167ant"
+#define MR_BUT_REPLACE "mais", space_plus, "en", space_plus, "rempla", 0xE7, "ant"
 #define MS_CARDINAL "nombre"
 #define MS_YEAR "an"
 #define MS_MONTH "mois"

compiler/surface/lexer_pl.cppo.ml

@@ -95,6 +95,8 @@
 #define MS_IS "jest"
 #define MS_LIST_EMPTY "lista pusta"
 #define MR_LIST_EMPTY "lista", space_plus, "pusta"
+#define MS_BUT_REPLACE "ale zastąpić"
+#define MR_BUT_REPLACE "ale", space_plus, "zast", 0x0105, "pi", 0x0107
 #define MS_CARDINAL "liczba"
 #define MS_YEAR "rok"
 #define MS_MONTH "miesiąc"