Switch to use Python enums as a tag for tagged unions

compiler/scalc/to_python.ml

@@ -204,8 +204,8 @@ let rec format_expression (ctx : Dcalc.Ast.decl_ctx) (fmt : Format.formatter) (e
   | EStructFieldAccess (e1, field, _) ->
       Format.fprintf fmt "%a.%a" (format_expression ctx) e1 format_struct_field_name field
   | EInj (e, cons, enum_name) ->
-      Format.fprintf fmt "%a_%a(%a)" format_enum_name enum_name format_enum_cons_name cons
-        (format_expression ctx) e
+      Format.fprintf fmt "%a(%a_Code.%a,@ %a)" format_enum_name enum_name format_enum_name enum_name
+        format_enum_cons_name cons (format_expression ctx) e
   | EArray es ->
       Format.fprintf fmt "[%a]"
         (Format.pp_print_list
@@ -217,7 +217,7 @@ let rec format_expression (ctx : Dcalc.Ast.decl_ctx) (fmt : Format.formatter) (e
       Format.fprintf fmt "%a(%a,@ %a)" format_binop (op, Pos.no_pos) (format_expression ctx) arg1
         (format_expression ctx) arg2
   | EApp ((EOp (Binop op), _), [ arg1; arg2 ]) ->
-      Format.fprintf fmt "(%a %a %a)" (format_expression ctx) arg1 format_binop (op, Pos.no_pos)
+      Format.fprintf fmt "(%a %a@ %a)" (format_expression ctx) arg1 format_binop (op, Pos.no_pos)
         (format_expression ctx) arg2
   | EApp ((EApp ((EOp (Unop (D.Log (D.BeginCall, info))), _), [ f ]), _), [ arg ])
     when !Cli.trace_flag ->
@@ -281,7 +281,7 @@ let rec format_statement (ctx : Dcalc.Ast.decl_ctx) (fmt : Format.formatter) (s
         (Format.pp_print_list
            ~pp_sep:(fun fmt () -> Format.fprintf fmt "@]@\n@[<hov 4>elif ")
            (fun fmt (case_block, payload_var, cons_name) ->
-             Format.fprintf fmt "%a is %a_%a:@\n%a = %a.value@\n%a" format_var tmp_var
+             Format.fprintf fmt "%a.code == %a_Code.%a:@\n%a = %a.value@\n%a" format_var tmp_var
                format_enum_name e_name format_enum_cons_name cons_name format_var payload_var
                format_var tmp_var (format_block ctx) case_block))
         cases
@@ -318,21 +318,24 @@ let format_ctx (type_ordering : Scopelang.Dependency.TVertex.t list) (fmt : Form
         struct_fields
   in
   let format_enum_decl fmt (enum_name, enum_cons) =
-    if List.length enum_cons = 0 then
-      Format.fprintf fmt
-        "class %a(Unit):@\n\tdef __init__(self, value: Any) -> None:@\n\t\tself.value = value@\n@\n"
-        format_enum_name enum_name
+    if List.length enum_cons = 0 then failwith "no constructors in the enum"
     else
       Format.fprintf fmt
-        "class %a:@\n\tdef __init__(self, value: Any) -> None:@\n\t\tself.value = value@\n@\n%a"
-        format_enum_name enum_name
+        "@[<hov 4>class %a_Code(Enum):@\n\
+         %a@]@\n\
+         @\n\
+         class %a:@\n\
+         \tdef __init__(self, code: %a_Code, value: Any) -> None:@\n\
+         \t\tself.code = code@\n\
+         \t\tself.value = value" format_enum_name enum_name
         (Format.pp_print_list
-           ~pp_sep:(fun fmt () -> Format.fprintf fmt "@\n@\n")
-           (fun _fmt (enum_cons, enum_cons_type) ->
-             Format.fprintf fmt "class %a_%a(%a):@\n\tpass" format_enum_name enum_name
-               format_enum_cons_name enum_cons format_enum_name enum_name))
-        enum_cons
+           ~pp_sep:(fun fmt () -> Format.fprintf fmt "@\n")
+           (fun _fmt (i, enum_cons, enum_cons_type) ->
+             Format.fprintf fmt "%a = %d" format_enum_cons_name enum_cons i))
+        (List.mapi (fun i (x, y) -> (i, x, y)) enum_cons)
+        format_enum_name enum_name format_enum_name enum_name
   in
+
   let is_in_type_ordering s =
     List.exists
       (fun struct_or_enum ->
@@ -366,6 +369,7 @@ let format_program (fmt : Format.formatter) (p : Ast.program)
      @\n\
      from .catala_runtime import *@\n\
      from typing import Any, List, Callable, Tuple\n\
+     from enum import Enum\n\
      @\n\
      %a@\n\
      @\n\