diff --git a/src/passes/7-self_ast_core/helpers.ml b/src/passes/7-self_ast_core/helpers.ml
new file mode 100644
index 000000000..8d669ddb6
--- /dev/null
+++ b/src/passes/7-self_ast_core/helpers.ml
@@ -0,0 +1,296 @@
+open Ast_core
+open Trace
+open Stage_common.Helpers
+
+type 'a folder = 'a -> expression -> 'a result
+let rec fold_expression : 'a folder -> 'a -> expression -> 'a result = fun f init e ->
+  let self = fold_expression f in 
+  let%bind init' = f init e in
+  match e.expression_content with
+  | E_literal _ | E_variable _ -> ok init'
+  | E_constant {arguments=lst} -> (
+    let%bind res = bind_fold_list self init' lst in
+    ok res
+  )
+  | E_application {lamb;args} -> (
+      let ab = (lamb,args) in
+      let%bind res = bind_fold_pair self init' ab in
+      ok res
+    )
+  | E_lambda { binder = _ ; input_type = _ ; output_type = _ ; result = e }
+  | E_ascription {anno_expr=e; _} | E_constructor {element=e} -> (
+      let%bind res = self init' e in
+      ok res
+    )
+  | E_matching {matchee=e; cases} -> (
+      let%bind res = self init' e in
+      let%bind res = fold_cases f res cases in
+      ok res
+    )
+  | E_record m -> (
+    let aux init'' _ expr =
+      let%bind res = fold_expression self init'' expr in
+      ok res
+    in
+    let%bind res = bind_fold_lmap aux (ok init') m in
+    ok res
+  )
+  | E_record_update {record;update} -> (
+    let%bind res = self init' record in
+    let%bind res = fold_expression self res update in
+    ok res 
+  )
+  | E_record_accessor {record} -> (
+     let%bind res = self init' record in
+     ok res
+    )
+  | E_let_in { let_binder = _ ; rhs ; let_result } -> (
+      let%bind res = self init' rhs in
+      let%bind res = self res let_result in
+      ok res
+    )
+  | E_recursive { lambda={result=e;_}; _} ->
+      let%bind res = self init' e in
+      ok res
+
+and fold_cases : 'a folder -> 'a -> matching_expr -> 'a result = fun f init m ->
+  match m with
+  | Match_bool { match_true ; match_false } -> (
+      let%bind res = fold_expression f init match_true in
+      let%bind res = fold_expression f res match_false in
+      ok res
+    )
+  | Match_list { match_nil ; match_cons = (_ , _ , cons, _) } -> (
+      let%bind res = fold_expression f init match_nil in
+      let%bind res = fold_expression f res cons in
+      ok res
+    )
+  | Match_option { match_none ; match_some = (_ , some, _) } -> (
+      let%bind res = fold_expression f init match_none in
+      let%bind res = fold_expression f res some in
+      ok res
+    )
+  | Match_tuple ((_ , e), _) -> (
+      let%bind res = fold_expression f init e in
+      ok res
+    )
+  | Match_variant (lst, _) -> (
+      let aux init' ((_ , _) , e) =
+        let%bind res' = fold_expression f init' e in
+        ok res' in
+      let%bind res = bind_fold_list aux init lst in
+      ok res
+    )
+
+type exp_mapper = expression -> expression result
+type ty_exp_mapper = type_expression -> type_expression result
+type abs_mapper =
+  | Expression of exp_mapper
+  | Type_expression of ty_exp_mapper 
+let rec map_expression : exp_mapper -> expression -> expression result = fun f e ->
+  let self = map_expression f in
+  let%bind e' = f e in
+  let return expression_content = ok { e' with expression_content } in
+  match e'.expression_content with
+  | E_ascription ascr -> (
+      let%bind e' = self ascr.anno_expr in
+      return @@ E_ascription {ascr with anno_expr=e'}
+    )
+  | E_matching {matchee=e;cases} -> (
+      let%bind e' = self e in
+      let%bind cases' = map_cases f cases in
+      return @@ E_matching {matchee=e';cases=cases'}
+    )
+  | E_record_accessor acc -> (
+      let%bind e' = self acc.record in
+      return @@ E_record_accessor {acc with record = e'}
+    )
+  | E_record m -> (
+    let%bind m' = bind_map_lmap self m in
+    return @@ E_record m'
+  )
+  | E_record_update {record; path; update} -> (
+    let%bind record = self record in
+    let%bind update = self update in
+    return @@ E_record_update {record;path;update}
+  )
+  | E_constructor c -> (
+      let%bind e' = self c.element in
+      return @@ E_constructor {c with element = e'}
+  )
+  | E_application {lamb;args} -> (
+      let ab = (lamb,args) in
+      let%bind (lamb,args) = bind_map_pair self ab in
+      return @@ E_application {lamb;args}
+    )
+  | E_let_in { let_binder ; rhs ; let_result; inline } -> (
+      let%bind rhs = self rhs in
+      let%bind let_result = self let_result in
+      return @@ E_let_in { let_binder ; rhs ; let_result; inline }
+    )
+  | E_lambda { binder ; input_type ; output_type ; result } -> (
+      let%bind result = self result in
+      return @@ E_lambda { binder ; input_type ; output_type ; result }
+    )
+  | E_recursive { fun_name; fun_type; lambda} ->
+      let%bind result = self lambda.result in
+      let lambda = {lambda with result} in
+      return @@ E_recursive { fun_name; fun_type; lambda}
+  | E_constant c -> (
+      let%bind args = bind_map_list self c.arguments in
+      return @@ E_constant {c with arguments=args}
+    )
+  | E_literal _ | E_variable _ as e' -> return e'
+
+and map_type_expression : ty_exp_mapper -> type_expression -> type_expression result = fun f ({type_content ; location ; type_meta} as te) ->
+  let self = map_type_expression f in
+  let%bind te' = f te in
+  let return type_content = ok { type_content; location ; type_meta } in
+  match type_content with
+  | T_sum temap ->
+    let%bind temap' = bind_map_cmap self temap in
+    return @@ (T_sum temap')
+  | T_record temap ->
+    let%bind temap' = bind_map_lmap self temap in
+    return @@ (T_record temap')
+  | T_arrow {type1 ; type2} ->
+    let%bind type1' = self type1 in
+    let%bind type2' = self type2 in
+    return @@ (T_arrow {type1=type1' ; type2=type2'})
+  | T_operator _
+  | T_variable _ | T_constant _ -> ok te'
+
+and map_cases : exp_mapper -> matching_expr -> matching_expr result = fun f m ->
+  match m with
+  | Match_bool { match_true ; match_false } -> (
+      let%bind match_true = map_expression f match_true in
+      let%bind match_false = map_expression f match_false in
+      ok @@ Match_bool { match_true ; match_false }
+    )
+  | Match_list { match_nil ; match_cons = (hd , tl , cons, _) } -> (
+      let%bind match_nil = map_expression f match_nil in
+      let%bind cons = map_expression f cons in
+      ok @@ Match_list { match_nil ; match_cons = (hd , tl , cons, ()) }
+    )
+  | Match_option { match_none ; match_some = (name , some, _) } -> (
+      let%bind match_none = map_expression f match_none in
+      let%bind some = map_expression f some in
+      ok @@ Match_option { match_none ; match_some = (name , some, ()) }
+    )
+  | Match_tuple ((names , e), _) -> (
+      let%bind e' = map_expression f e in
+      ok @@ Match_tuple ((names , e'), [])
+    )
+  | Match_variant (lst, _) -> (
+      let aux ((a , b) , e) =
+        let%bind e' = map_expression f e in
+        ok ((a , b) , e')
+      in
+      let%bind lst' = bind_map_list aux lst in
+      ok @@ Match_variant (lst', ())
+    )
+
+and map_program : abs_mapper -> program -> program result = fun m p ->
+  let aux = fun (x : declaration) ->
+    match x,m with
+    | (Declaration_constant (t , o , i, e), Expression m') -> (
+        let%bind e' = map_expression m' e in
+        ok (Declaration_constant (t , o , i, e'))
+      )
+    | (Declaration_type (tv,te), Type_expression m') -> (
+        let%bind te' = map_type_expression m' te in
+        ok (Declaration_type (tv, te'))
+      )
+    | decl,_ -> ok decl
+  (* | Declaration_type of (type_variable * type_expression) *)
+  in
+  bind_map_list (bind_map_location aux) p
+
+type 'a fold_mapper = 'a -> expression -> (bool * 'a * expression) result
+let rec fold_map_expression : 'a fold_mapper -> 'a -> expression -> ('a * expression) result = fun f a e ->
+  let self = fold_map_expression f in
+  let%bind (continue, init',e') = f a e in
+  if (not continue) then ok(init',e')
+  else
+  let return expression_content = { e' with expression_content } in
+  match e'.expression_content with
+  | E_ascription ascr -> (
+      let%bind (res,e') = self init' ascr.anno_expr in
+      ok (res, return @@ E_ascription {ascr with anno_expr=e'})
+    )
+  | E_matching {matchee=e;cases} -> (
+      let%bind (res, e') = self init' e in
+      let%bind (res,cases') = fold_map_cases f res cases in
+      ok (res, return @@ E_matching {matchee=e';cases=cases'})
+    )
+  | E_record_accessor acc -> (
+      let%bind (res, e') = self init' acc.record in
+      ok (res, return @@ E_record_accessor {acc with record = e'})
+    )
+  | E_record m -> (
+    let%bind (res, lst') = bind_fold_map_list (fun res (k,e) -> let%bind (res,e) = self res e in ok (res,(k,e))) init' (LMap.to_kv_list m) in
+    let m' = LMap.of_list lst' in
+    ok (res, return @@ E_record m')
+  )
+  | E_record_update {record; path; update} -> (
+    let%bind (res, record) = self init' record in
+    let%bind (res, update) = self res update in
+    ok (res, return @@ E_record_update {record;path;update})
+  )
+  | E_constructor c -> (
+      let%bind (res,e') = self init' c.element in
+      ok (res, return @@ E_constructor {c with element = e'})
+  )
+  | E_application {lamb;args} -> (
+      let ab = (lamb,args) in
+      let%bind (res,(a,b)) = bind_fold_map_pair self init' ab in
+      ok (res, return @@ E_application {lamb=a;args=b})
+    )
+  | E_let_in { let_binder ; rhs ; let_result; inline } -> (
+      let%bind (res,rhs) = self init' rhs in
+      let%bind (res,let_result) = self res let_result in
+      ok (res, return @@ E_let_in { let_binder ; rhs ; let_result ; inline })
+    )
+  | E_lambda { binder ; input_type ; output_type ; result } -> (
+      let%bind (res,result) = self init' result in
+      ok ( res, return @@ E_lambda { binder ; input_type ; output_type ; result })
+    )
+  | E_recursive { fun_name; fun_type; lambda} ->
+      let%bind (res, result) = self init' lambda.result in
+      let lambda = {lambda with result} in
+      ok ( res, return @@ E_recursive { fun_name; fun_type; lambda})
+  | E_constant c -> (
+      let%bind (res,args) = bind_fold_map_list self init' c.arguments in
+      ok (res, return @@ E_constant {c with arguments=args})
+    )
+  | E_literal _ | E_variable _ as e' -> ok (init', return e')
+
+and fold_map_cases : 'a fold_mapper -> 'a -> matching_expr -> ('a * matching_expr) result = fun f init m ->
+  match m with
+  | Match_bool { match_true ; match_false } -> (
+      let%bind (init, match_true) = fold_map_expression f init match_true in
+      let%bind (init, match_false) = fold_map_expression f init match_false in
+      ok @@ (init, Match_bool { match_true ; match_false })
+    )
+  | Match_list { match_nil ; match_cons = (hd , tl , cons, _) } -> (
+      let%bind (init, match_nil) = fold_map_expression f init match_nil in
+      let%bind (init, cons) = fold_map_expression f init cons in
+      ok @@ (init, Match_list { match_nil ; match_cons = (hd , tl , cons, ()) })
+    )
+  | Match_option { match_none ; match_some = (name , some, _) } -> (
+      let%bind (init, match_none) = fold_map_expression f init match_none in
+      let%bind (init, some) = fold_map_expression f init some in
+      ok @@ (init, Match_option { match_none ; match_some = (name , some, ()) })
+    )
+  | Match_tuple ((names , e), _) -> (
+      let%bind (init, e') = fold_map_expression f init e in
+      ok @@ (init, Match_tuple ((names , e'), []))
+    )
+  | Match_variant (lst, _) -> (
+      let aux init ((a , b) , e) =
+        let%bind (init,e') = fold_map_expression f init e in
+        ok (init, ((a , b) , e'))
+      in
+      let%bind (init,lst') = bind_fold_map_list aux init lst in
+      ok @@ (init, Match_variant (lst', ()))
+    )