diff --git a/src/ast_simplified/PP.ml b/src/ast_simplified/PP.ml
index 22a16b58f..5cd46827c 100644
--- a/src/ast_simplified/PP.ml
+++ b/src/ast_simplified/PP.ml
@@ -30,7 +30,7 @@ let literal ppf (l:literal) = match l with
   | Literal_address s -> fprintf ppf "@%S" s
   | Literal_operation _ -> fprintf ppf "Operation(...bytes)"
 
-let rec expression ppf (e:expression) = match e with
+let rec expression ppf (e:expression) = match Location.unwrap e with
   | E_literal l -> literal ppf l
   | E_variable name -> fprintf ppf "%s" name
   | E_application (f, arg) -> fprintf ppf "(%a)@(%a)" expression f expression arg
diff --git a/src/ast_simplified/combinators.ml b/src/ast_simplified/combinators.ml
index 7fd963b0f..654d55024 100644
--- a/src/ast_simplified/combinators.ml
+++ b/src/ast_simplified/combinators.ml
@@ -35,76 +35,79 @@ let t_map key value = (T_constant ("map", [key ; value]))
 
 let make_name (s : string) : name = s
 
-let e_var (s : string) : expression = E_variable s
+let e_var ?loc (s : string) : expression = Location.wrap ?loc @@ E_variable s
+let e_literal ?loc l : expression = Location.wrap ?loc @@ E_literal l
+let e_unit ?loc () : expression = Location.wrap ?loc @@ E_literal (Literal_unit)
+let e_int ?loc n : expression = Location.wrap ?loc @@ E_literal (Literal_int n)
+let e_nat ?loc n : expression = Location.wrap ?loc @@ E_literal (Literal_nat n)
+let e_bool ?loc   b : expression = Location.wrap ?loc @@ E_literal (Literal_bool b)
+let e_string ?loc s : expression = Location.wrap ?loc @@ E_literal (Literal_string s)
+let e_address ?loc s : expression = Location.wrap ?loc @@ E_literal (Literal_address s)
+let e_tez ?loc s : expression = Location.wrap ?loc @@ E_literal (Literal_tez s)
+let e_bytes ?loc  b : expression = Location.wrap ?loc @@ E_literal (Literal_bytes (Bytes.of_string b))
+let e_record ?loc map : expression = Location.wrap ?loc @@ E_record map
+let e_tuple ?loc lst : expression = Location.wrap ?loc @@ E_tuple lst
+let e_some ?loc s : expression = Location.wrap ?loc @@ E_constant ("SOME", [s])
+let e_none ?loc () : expression = Location.wrap ?loc @@ E_constant ("NONE", [])
+let e_map_update ?loc k v old : expression = Location.wrap ?loc @@ E_constant ("MAP_UPDATE" , [k ; v ; old])
+let e_map ?loc lst : expression = Location.wrap ?loc @@ E_map lst
+let e_list ?loc lst : expression = Location.wrap ?loc @@ E_list lst
+let e_pair ?loc a b : expression = Location.wrap ?loc @@ E_tuple [a; b]
+let e_constructor ?loc s a : expression = Location.wrap ?loc @@ E_constructor (s , a)
+let e_matching ?loc a b : expression = Location.wrap ?loc @@ E_matching (a , b)
+let e_matching_bool ?loc a b c : expression = e_matching ?loc a (Match_bool {match_true = b ; match_false = c})
+let e_accessor ?loc a b = Location.wrap ?loc @@ E_accessor (a , b)
+let e_accessor_props ?loc a b = e_accessor ?loc a (List.map (fun x -> Access_record x) b)
+let e_variable ?loc v = Location.wrap ?loc @@ E_variable v
+let e_failwith ?loc v = Location.wrap ?loc @@ E_failwith v
+let e_skip ?loc () = Location.wrap ?loc @@ E_skip
+let e_loop ?loc cond body = Location.wrap ?loc @@ E_loop (cond , body)
+let e_sequence ?loc a b = Location.wrap ?loc @@ E_sequence (a , b)
+let e_let_in ?loc binder rhs result = Location.wrap ?loc @@ E_let_in { binder ; rhs ; result }
+let e_annotation ?loc expr ty = Location.wrap ?loc @@ E_annotation (expr , ty)
+let e_application ?loc a b = Location.wrap ?loc @@ E_application (a , b)
+let e_binop ?loc name a b = Location.wrap ?loc @@ E_constant (name , [a ; b])
+let e_constant ?loc name lst = Location.wrap ?loc @@ E_constant (name , lst)
+let e_look_up ?loc x y = Location.wrap ?loc @@ E_look_up (x , y)
+let e_assign ?loc a b c = Location.wrap ?loc @@ E_assign (a , b , c)
 
-let e_unit () : expression = E_literal (Literal_unit)
-let e_int n : expression = E_literal (Literal_int n)
-let e_nat n : expression = E_literal (Literal_nat n)
-let e_bool   b : expression = E_literal (Literal_bool b)
-let e_string s : expression = E_literal (Literal_string s)
-let e_address s : expression = E_literal (Literal_address s)
-let e_tez s : expression = E_literal (Literal_tez s)
-let e_bytes  b : expression = E_literal (Literal_bytes (Bytes.of_string b))
-let e_record map : expression = E_record map
-let e_tuple lst : expression = E_tuple lst
-let e_some s : expression = E_constant ("SOME", [s])
-let e_none : expression = E_constant ("NONE", [])
-let e_map_update k v old : expression = E_constant ("MAP_UPDATE" , [k ; v ; old])
-let e_map lst : expression = E_map lst
-let e_list lst : expression = E_list lst
-let e_pair a b : expression = E_tuple [a; b]
-let e_constructor s a : expression = E_constructor (s , a)
-let e_match a b : expression = E_matching (a , b)
-let e_match_bool a b c : expression = e_match a (Match_bool {match_true = b ; match_false = c})
-let e_accessor a b = E_accessor (a , b)
-let e_accessor_props a b = e_accessor a (List.map (fun x -> Access_record x) b)
-let e_variable v = E_variable v
-let e_failwith v = E_failwith v
-let e_skip = E_skip
-let e_loop cond body = E_loop (cond , body)
-let e_sequence a b = E_sequence (a , b)
-let e_let_in binder rhs result = E_let_in { binder ; rhs ; result }
-let e_annotation expr ty = E_annotation (expr , ty)
-let e_application a b = E_application (a , b)
-
-let e_binop name a b = E_constant (name , [a ; b])
-
-let make_option_typed e t_opt =
+let make_option_typed ?loc e t_opt =
   match t_opt with
   | None -> e
-  | Some t -> e_annotation e t
+  | Some t -> e_annotation ?loc e t
 
 
-let ez_e_record lst =
+let ez_e_record ?loc lst =
   let aux prev (k, v) = SMap.add k v prev in
   let map = List.fold_left aux SMap.empty lst in
-  e_record map
+  e_record ?loc map
 
-let e_typed_none t_opt =
+let e_typed_none ?loc t_opt =
   let type_annotation = t_option t_opt in
-  e_annotation e_none type_annotation
+  e_annotation ?loc (e_none ?loc ()) type_annotation
 
-let e_typed_list lst t =
-  e_annotation (e_list lst) (t_list t)
+let e_typed_list ?loc lst t =
+  e_annotation ?loc (e_list lst) (t_list t)
 
-let e_map lst k v = e_annotation (e_map lst) (t_map k v)
+let e_typed_map ?loc lst k v = e_annotation ?loc (e_map lst) (t_map k v)
 
-let e_lambda (binder : string)
+let e_lambda ?loc (binder : string)
     (input_type : type_expression option)
     (output_type : type_expression option)
     (result : expression)
   : expression =
-  E_lambda {
+  Location.wrap ?loc @@ E_lambda {
     binder = (make_name binder , input_type) ;
     input_type = input_type ;
     output_type = output_type ;
     result ;
   }
 
-let e_record (lst : (string * expr) list) : expression =
-  let aux prev (k, v) = SMap.add k v prev in
-  let map = List.fold_left aux SMap.empty lst in
-  E_record map
+let e_record ?loc map = Location.wrap ?loc @@ E_record map
+
+let e_ez_record ?loc (lst : (string * expr) list) : expression =
+  let map = SMap.of_list lst in
+  e_record ?loc map
 
 let get_e_accessor = fun t ->
   match t with
@@ -130,3 +133,10 @@ let get_e_list = fun t ->
   match t with
   | E_list lst -> ok lst
   | _ -> simple_fail "not a pair"
+
+let get_e_failwith = fun e ->
+  match Location.unwrap e with
+  | E_failwith fw -> ok fw
+  | _ -> simple_fail "not a failwith"
+
+let is_e_failwith e = to_bool @@ get_e_failwith e
diff --git a/src/ast_simplified/misc.ml b/src/ast_simplified/misc.ml
index 168a3f672..05b8e2601 100644
--- a/src/ast_simplified/misc.ml
+++ b/src/ast_simplified/misc.ml
@@ -35,7 +35,7 @@ let rec assert_value_eq (a, b: (expression * expression )) : unit result =
     Format.asprintf "\n@[<v>- %a@;- %a]" PP.expression a PP.expression b
   in
   trace (fun () -> error (thunk "not equal") error_content ()) @@
-  match (a , b) with
+  match (Location.unwrap a , Location.unwrap b) with
   | E_literal a , E_literal b ->
       assert_literal_eq (a, b)
   | E_literal _ , _ ->
@@ -113,8 +113,8 @@ let rec assert_value_eq (a, b: (expression * expression )) : unit result =
     )
   | E_list _, _ ->
       simple_fail "comparing list with other stuff"
-  | (E_annotation (a , _) ,  b) -> assert_value_eq (a , b)
-  | (a , E_annotation (b , _)) -> assert_value_eq (a , b)
+  | (E_annotation (a , _) ,  _b') -> assert_value_eq (a , b)
+  | (_a' , E_annotation (b , _)) -> assert_value_eq (a , b)
   | (E_variable _, _) | (E_lambda _, _)
   | (E_application _, _) | (E_let_in _, _)
   | (E_accessor _, _)
diff --git a/src/ast_simplified/types.ml b/src/ast_simplified/types.ml
index 6e47aa936..4693546b8 100644
--- a/src/ast_simplified/types.ml
+++ b/src/ast_simplified/types.ml
@@ -42,7 +42,7 @@ and let_in = {
   result : expr ;
 }
 
-and expression =
+and expression' =
   (* Base *)
   | E_literal of literal
   | E_constant of (name * expr list) (* For language constants, like (Cons hd tl) or (plus i j) *)
@@ -72,6 +72,8 @@ and expression =
   (* Annotate *)
   | E_annotation of expr * type_expression
 
+and expression = expression' Location.wrap
+
 and access =
   | Access_tuple of int
   | Access_record of string
diff --git a/src/ast_typed/combinators.ml b/src/ast_typed/combinators.ml
index ce3c6902c..f5859806e 100644
--- a/src/ast_typed/combinators.ml
+++ b/src/ast_typed/combinators.ml
@@ -2,7 +2,13 @@ open Trace
 open Types
 
 let make_t type_value' simplified = { type_value' ; simplified }
-let make_a_e expression type_annotation environment = { expression ; type_annotation ; dummy_field = () ; environment }
+let make_a_e ?(location = Location.generated) expression type_annotation environment = {
+  expression ;
+  type_annotation ;
+  dummy_field = () ;
+  environment ;
+  location ;
+}
 let make_n_e name a_e = { name ; annotated_expression = a_e }
 let make_n_t type_name type_value = { type_name ; type_value }
 
diff --git a/src/ast_typed/types.ml b/src/ast_typed/types.ml
index 9dbd2fc64..a1bfd46d3 100644
--- a/src/ast_typed/types.ml
+++ b/src/ast_typed/types.ml
@@ -34,10 +34,11 @@ and small_environment = (environment * type_environment)
 and full_environment = small_environment List.Ne.t
 
 and annotated_expression = {
-  expression: expression ;
-  type_annotation: tv ;
-  environment: full_environment ;
-  dummy_field: unit ;
+  expression : expression ;
+  type_annotation : tv ;
+  environment : full_environment ;
+  location : Location.t ;
+  dummy_field : unit ;
 }
 
 and named_expression = {
@@ -162,6 +163,6 @@ let get_entry (p:program) (entry : string) : annotated_expression result =
 let get_functional_entry (p:program) (entry : string) : (lambda * type_value) result =
   let%bind entry = get_entry p entry in
   match entry.expression with
-  | E_lambda l -> ok (l, entry.type_annotation)
+  | E_lambda l -> ok (l , entry.type_annotation)
   | _ -> simple_fail "given entry point is not functional"
 
diff --git a/src/contracts/counter.mligo b/src/contracts/counter.mligo
index b15f67905..466a68ed7 100644
--- a/src/contracts/counter.mligo
+++ b/src/contracts/counter.mligo
@@ -1,4 +1,4 @@
 type storage = int
 
 let%entry main (p:int) storage =
-  ((list [] : operation list) , p + storage)
+  (([] : operation list) , p + storage)
diff --git a/src/parser/ligodity/AST.ml b/src/parser/ligodity/AST.ml
index 7da14760e..9d3be1095 100644
--- a/src/parser/ligodity/AST.ml
+++ b/src/parser/ligodity/AST.ml
@@ -327,7 +327,7 @@ and let_in = {
 
 and fun_expr = {
   kwd_fun : kwd_fun;
-  param   : variable;
+  params  : pattern list;
   p_annot : (colon * type_expr) option;
   arrow   : arrow;
   body    : expr
@@ -737,10 +737,10 @@ and print_let_in (bind: let_in) =
   print_expr body
 
 and print_fun_expr {value; _} =
-  let {kwd_fun; param; p_annot; arrow; body} = value in
+  let {kwd_fun; params; p_annot; arrow; body} = value in
   print_token kwd_fun "fun";
   (match p_annot with
-     None -> print_var param
+     None -> List.iter print_pattern params
    | Some (colon, type_expr) ->
       print_token colon ":";
       print_type_expr type_expr);
diff --git a/src/parser/ligodity/AST.mli b/src/parser/ligodity/AST.mli
index ea400b6d5..fbad9289e 100644
--- a/src/parser/ligodity/AST.mli
+++ b/src/parser/ligodity/AST.mli
@@ -336,7 +336,7 @@ and let_in = {
 
 and fun_expr = {
   kwd_fun : kwd_fun;
-  param   : variable;
+  params  : pattern list;
   p_annot : (colon * type_expr) option;
   arrow   : arrow;
   body    : expr
diff --git a/src/parser/ligodity/Parser.mly b/src/parser/ligodity/Parser.mly
index a492f2624..7221f6fd8 100644
--- a/src/parser/ligodity/Parser.mly
+++ b/src/parser/ligodity/Parser.mly
@@ -7,10 +7,10 @@ open AST
 
 module VMap = Utils.String.Map
 
-let ghost_of value = Region.{region=ghost; value}
+(*let ghost_of value = Region.{region=ghost; value}*)
 let ghost = Region.ghost
 
-let fail_syn_unif type1 type2 : 'a =
+(* let fail_syn_unif type1 type2 : 'a =
   let reg = AST.region_of_type_expr type1 in
   let reg = reg#compact ~file:false `Byte in
   let value =
@@ -25,22 +25,18 @@ let mk_component rank =
   let par = {lpar=ghost; inside = ghost_of num; rpar=ghost}
   in Component (ghost_of par)
 
+
 let rec mk_field_path (rank, tail) =
   let head = mk_component rank in
   match tail with
         [] -> head, []
   | hd::tl -> mk_field_path (hd,tl) |> Utils.nsepseq_cons head ghost
 
-let mk_projection fresh (path : int Utils.nseq) = {
+ let mk_projection fresh (path : int Utils.nseq) = {
   struct_name = fresh;
   selector    = ghost;
   field_path  = Utils.nsepseq_rev (mk_field_path path)
-}
-
-let rec sub_rec fresh path (map, rank) pattern =
-  let path' = Utils.nseq_cons rank path in
-  let map'  = split fresh map path' pattern
-  in map', rank+1
+} *)
 
 
 (* We rewrite "fun p -> e" into "fun x -> match x with p -> e" *)
@@ -198,7 +194,7 @@ declarations:
 declaration:
   reg(kwd(LetEntry) entry_binding {$1,$2})          { LetEntry $1, [] }
 | reg(type_decl)                                    { TypeDecl $1, [] }
-| let_declaration                                   {              $1 }
+| let_declaration                                   {          $1, [] }
 
 (* Type declarations *)
 
@@ -284,36 +280,32 @@ field_decl:
 entry_binding:
   ident nseq(sub_irrefutable) type_annotation? eq expr {
     let let_rhs = $5 in
-    {bindings = ($1 , $2); lhs_type=$3; eq=$4; let_rhs}
+    let pattern = PVar $1 in
+    let (hd , tl) = $2 in
+    {bindings = pattern :: hd :: tl; lhs_type=$3; eq=$4; let_rhs}
   }
-| ident type_annotation? eq fun_expr(expr) {
-    {bindings = ($1 , []); lhs_type=$2; eq=$3; let_rhs=$4} }
+  | ident type_annotation? eq fun_expr(expr) {
+    let pattern = PVar $1 in	    
+    {bindings = [pattern]; lhs_type=$2; eq=$3; let_rhs=$4} }
 
 (* Top-level non-recursive definitions *)
 
 let_declaration:
   reg(kwd(Let) let_binding {$1,$2}) {
-    let kwd_let, (binding, map) = $1.value in
-    let let0 = Let {$1 with value = kwd_let, binding}
-    in
-    mk_let_bindings map (let0,[])
+    let kwd_let, binding = $1.value in
+    Let {$1 with value = kwd_let, binding}
   }
 
 let_binding:
   ident nseq(sub_irrefutable) type_annotation? eq expr {
     let let_rhs = $5 in
-    let map = VMap.empty in
-    {bindings= ($1 , $2); lhs_type=$3; eq=$4; let_rhs}, map
+    let ident_pattern = PVar $1 in
+    let (hd , tl) = $2 in
+    {bindings= (ident_pattern :: hd :: tl); lhs_type=$3; eq=$4; let_rhs}
   }
 | irrefutable type_annotation? eq expr {
-    let variable, type_opt, map = split_pattern $1 in
-    match type_opt, $2 with
-      Some type1, Some (_,type2) when type1 <> type2 ->
-        fail_syn_unif type1 type2
-    | Some type1, None ->
-         let lhs_type = Some (ghost, type1) in
-         {variable; lhs_type; eq=$3; let_rhs=$4}, map
-    | _ -> {variable; lhs_type=$2; eq=$3; let_rhs=$4}, map
+    let pattern = $1 in
+    {bindings = [pattern]; lhs_type=$2; eq=$3; let_rhs=$4}
   }
 
 type_annotation:
@@ -459,14 +451,24 @@ case_clause(right_expr):
 
 let_expr(right_expr):
   reg(kwd(Let) let_binding kwd(In) right_expr {$1,$2,$3,$4}) {
-    let kwd_let, (binding, map), kwd_in, body = $1.value in
-    let body = mk_let_in_bindings map body in
+    let kwd_let, binding , kwd_in, body = $1.value in
     let let_in = {kwd_let; binding; kwd_in; body}
     in ELetIn {region=$1.region; value=let_in} }
 
 fun_expr(right_expr):
-  kwd(Fun) nseq(irrefutable) arrow right_expr   { norm_fun_expr $2 $4 }
-
+  reg(kwd(Fun) nseq(irrefutable) arrow right_expr {$1,$2,$3,$4}) {
+    let kwd_fun, bindings, arrow, body = $1.value in
+    let (hd , tl) = bindings in
+    let f = {
+      kwd_fun ;
+      params = hd :: tl ;
+      p_annot = None ;
+      arrow ;
+      body ;
+    } in
+    EFun { region=$1.region; value=f }
+  }
+	 
 disj_expr_level:
   reg(disj_expr)                          { ELogic (BoolExpr (Or $1)) }
 | conj_expr_level                                                { $1 }
diff --git a/src/simplify/camligo.ml b/src/simplify/camligo.ml
index 151116253..f32ffb86e 100644
--- a/src/simplify/camligo.ml
+++ b/src/simplify/camligo.ml
@@ -206,7 +206,7 @@ and ifthenelse
   let%bind cond' = bind_map_location expression cond in
   let%bind branch_true' = bind_map_location expression branch_true in
   let%bind branch_false' = bind_map_location expression branch_false in
-  ok @@ O.(e_match_bool (unwrap cond') (unwrap branch_true') (unwrap branch_false'))
+  ok @@ O.(e_matching_bool (unwrap cond') (unwrap branch_true') (unwrap branch_false'))
 
 and ifthen
   : (I.expression Location.wrap * I.expression Location.wrap) -> O.expression result
@@ -214,7 +214,7 @@ and ifthen
   let (cond , branch_true) = it in
   let%bind cond' = bind_map_location expression cond in
   let%bind branch_true' = bind_map_location expression branch_true in
-  ok @@ O.(e_match_bool (unwrap cond') (unwrap branch_true') (e_unit ()))
+  ok @@ O.(e_matching_bool (unwrap cond') (unwrap branch_true') (e_unit ()))
 
 and match_
   : I.expression Location.wrap * I.e_match_clause Location.wrap list -> O.expression result
@@ -231,7 +231,7 @@ and match_
         ok (x' , y') in
       bind_map_list aux clauses in
     let%bind matching = match_clauses clauses' in
-    ok O.(e_match expr' matching)
+    ok O.(e_matching expr' matching)
 
 and record
   = fun r ->
@@ -244,7 +244,7 @@ and record
   in
   let%bind r' = bind_map_list (bind_map_location aux) r in
   let lst = List.map ((fun (x, y) -> unwrap x, unwrap y) >| unwrap) r' in
-  ok @@ O.(e_record lst)
+  ok @@ O.(e_ez_record lst)
 
 and expression_main : I.expression_main Location.wrap -> O.expression result = fun em ->
   let return x = ok @@ x in
@@ -334,13 +334,13 @@ and expression_main : I.expression_main Location.wrap -> O.expression result = f
 and identifier_application : (string Location.wrap) list * string Location.wrap -> O.expression option -> _ result = fun (lst , v) param_opt ->
   let constant_name = String.concat "." ((List.map unwrap lst) @ [unwrap v]) in
   match List.assoc_opt constant_name constants , param_opt with
-  | Some s , None -> ok O.(E_constant (s , []))
+  | Some s , None -> ok O.(e_constant s [])
   | Some s , Some param -> (
       let params =
-        match param with
+        match Location.unwrap param with
         | E_tuple lst -> lst
         | _ -> [ param ] in
-      ok O.(E_constant (s , params))
+      ok O.(e_constant s params)
     )
   | None , param_opt -> (
       let%bind () =
diff --git a/src/simplify/ligodity.ml b/src/simplify/ligodity.ml
index 9381fb251..77c2954c8 100644
--- a/src/simplify/ligodity.ml
+++ b/src/simplify/ligodity.ml
@@ -19,6 +19,35 @@ let get_value : 'a Raw.reg -> 'a = fun x -> x.value
 
 open Operators.Simplify.Ligodity
 
+let r_split = Location.r_split
+
+let rec pattern_to_var : Raw.pattern -> _ = fun p ->
+  match p with
+  | Raw.PPar p -> pattern_to_var p.value.inside
+  | Raw.PVar v -> ok v
+  | _ -> simple_fail "not a var"
+
+let rec pattern_to_typed_var : Raw.pattern -> _ = fun p ->
+  match p with
+  | Raw.PPar p -> pattern_to_typed_var p.value.inside
+  | Raw.PTyped tp -> (
+      let tp = tp.value in
+      let%bind v = pattern_to_var tp.pattern in
+      ok (v , Some tp.type_expr)
+    )
+  | Raw.PVar v -> ok (v , None)
+  | _ -> simple_fail "not a var"
+
+let rec expr_to_typed_expr : Raw.expr -> _ = fun e ->
+  match e with
+  | EPar e -> expr_to_typed_expr e.value.inside
+  | EAnnot a -> ok (fst a.value , Some (snd a.value))
+  | _ -> ok (e , None)
+
+let patterns_to_var : Raw.pattern list -> _ = fun ps ->
+  let%bind () = Assert.assert_list_size ps 1 in
+  pattern_to_var @@ List.hd ps
+
 let rec simpl_type_expression : Raw.type_expr -> type_expression result =
   function
   | TPar x -> simpl_type_expression x.value.inside
@@ -79,9 +108,10 @@ and simpl_list_type_expression (lst:Raw.type_expr list) : type_expression result
       ok @@ T_tuple lst
 
 let rec simpl_expression :
-  ?te_annot:type_expression -> Raw.expr -> expr result = fun ?te_annot t ->
-  let return x = ok @@ make_option_typed x te_annot in
-  let simpl_projection = fun (p:Raw.projection) ->
+  Raw.expr -> expr result = fun t ->
+  let return x = ok x in
+  let simpl_projection = fun (p:Raw.projection Region.reg) ->
+    let (p , loc) = r_split p in
     let var =
       let name = p.struct_name.value in
       e_variable name in
@@ -95,10 +125,8 @@ let rec simpl_expression :
             Access_tuple (Z.to_int (snd index.value))
       in
       List.map aux @@ npseq_to_list path in
-    return @@ E_accessor (var, path')
+    return @@ e_accessor ~loc var path'
   in
-  let mk_let_in binder rhs result =
-    E_let_in {binder; rhs; result} in
 
   trace (
     let title () = "simplifying expression" in
@@ -110,100 +138,123 @@ let rec simpl_expression :
   ) @@
   match t with
   | Raw.ELetIn e -> (
-      let Raw.{binding; body; _} = e.value in
-      let Raw.{variable; lhs_type; let_rhs; _} = binding in
-      let%bind type_annotation = bind_map_option
-          (fun (_,type_expr) -> simpl_type_expression type_expr)
+      let Raw.{binding ; body ; _} = e.value in
+      let Raw.{bindings ; lhs_type ; let_rhs ; _} = binding in
+      let%bind variable = patterns_to_var bindings in
+      let%bind ty_opt =
+        bind_map_option
+          (fun (_ , type_expr) -> simpl_type_expression type_expr)
           lhs_type in
-      let%bind rhs = simpl_expression ?te_annot:type_annotation let_rhs in
+      let%bind rhs = simpl_expression let_rhs in
+      let rhs' =
+        match ty_opt with
+        | None -> rhs
+        | Some ty -> e_annotation rhs ty in
       let%bind body = simpl_expression body in
-      return @@ mk_let_in (variable.value , None) rhs body
+      return @@ e_let_in (variable.value , None) rhs' body
     )
   | Raw.EAnnot a -> (
-      let (expr , type_expr) = a.value in
-      match te_annot with
-      | None -> (
-          let%bind te_annot = simpl_type_expression type_expr in
-          let%bind expr' = simpl_expression ~te_annot expr in
-          ok expr'
-        )
-      | Some _ -> simple_fail "no double annotation"
+      let (a , loc) = r_split a in
+      let (expr , type_expr) = a in
+      let%bind expr' = simpl_expression expr in
+      let%bind type_expr' = simpl_type_expression type_expr in
+      return @@ e_annotation ~loc expr' type_expr'
     )
   | EVar c -> (
       let c' = c.value in
       match List.assoc_opt c' constants with
-      | None -> return @@ E_variable c.value
-      | Some s -> return @@ E_constant (s , [])
+      | None -> return @@ e_variable c.value
+      | Some s -> return @@ e_constant s []
     )
   | ECall x -> (
-      let (e1, e2) = x.value in
+      let ((e1 , e2) , loc) = r_split x in
       let%bind args = bind_map_list simpl_expression (nseq_to_list e2) in
       match e1 with
-      | EVar f ->
-          (match List.assoc_opt f.value constants with
-          | None ->
+      | EVar f -> (
+          let (f , f_loc) = r_split f in
+          match List.assoc_opt f constants with
+          | None -> (
               let%bind arg = simpl_tuple_expression (nseq_to_list e2) in
-              return @@ E_application (e_variable f.value, arg)
-          | Some s -> return @@ E_constant (s , args))
-      | e1 ->
-        let%bind e1' = simpl_expression e1 in
-        let%bind arg = simpl_tuple_expression (nseq_to_list e2) in
-        return @@ E_application (e1' , arg)
+              return @@ e_application ~loc (e_variable ~loc:f_loc f) arg
+            )
+          | Some s -> return @@ e_constant ~loc s args
+        )
+      | e1 -> (
+          let%bind e1' = simpl_expression e1 in
+          let%bind arg = simpl_tuple_expression (nseq_to_list e2) in
+          return @@ e_application ~loc e1' arg
+      )
     )
-  | EPar x -> simpl_expression ?te_annot x.value.inside
-  | EUnit _ -> return @@ E_literal Literal_unit
-  | EBytes x -> return @@ E_literal (Literal_bytes (Bytes.of_string @@ fst x.value))
-  | ETuple tpl -> simpl_tuple_expression ?te_annot @@ (npseq_to_list tpl.value)
-  | ERecord r ->
+  | EPar x -> simpl_expression x.value.inside
+  | EUnit reg -> (
+      let (_ , loc) = r_split reg in
+      return @@ e_literal ~loc Literal_unit
+    )
+  | EBytes x -> (
+      let (x , loc) = r_split x in
+      return @@ e_literal ~loc (Literal_bytes (Bytes.of_string @@ fst x))
+    )
+  | ETuple tpl -> simpl_tuple_expression @@ (npseq_to_list tpl.value)
+  | ERecord r -> (
+      let (r , loc) = r_split r in
       let%bind fields = bind_list
         @@ List.map (fun ((k : _ Raw.reg), v) -> let%bind v = simpl_expression v in ok (k.value, v))
         @@ List.map (fun (x:Raw.field_assign Raw.reg) -> (x.value.field_name, x.value.field_expr))
-        @@ pseq_to_list r.value.elements in
-      let aux prev (k, v) = SMap.add k v prev in
-      return @@ E_record (List.fold_left aux SMap.empty fields)
-  | EProj p' -> (
-      let p = p'.value in
-      simpl_projection p
+        @@ pseq_to_list r.elements in
+      let map = SMap.of_list fields in
+      return @@ e_record ~loc map
     )
-  | EConstr c ->
-      let (c, args) = c.value in
+  | EProj p -> simpl_projection p
+  | EConstr c -> (
+      let ((c_name , args) , loc) = r_split c in
+      let (c_name , _c_loc) = r_split c_name in
       let args =
         match args with
           None -> []
         | Some arg -> [arg] in
       let%bind arg = simpl_tuple_expression @@ args in
-      return @@ E_constructor (c.value, arg)
+      return @@ e_constructor ~loc c_name arg
+    )
   | EArith (Add c) ->
-      simpl_binop ?te_annot "ADD" c.value
+      simpl_binop "ADD" c
   | EArith (Sub c) ->
-      simpl_binop ?te_annot "SUB" c.value
+      simpl_binop "SUB" c
   | EArith (Mult c) ->
-      simpl_binop ?te_annot "TIMES" c.value
+      simpl_binop "TIMES" c
   | EArith (Div c) ->
-      simpl_binop ?te_annot "DIV" c.value
+      simpl_binop "DIV" c
   | EArith (Mod c) ->
-      simpl_binop ?te_annot "MOD" c.value
-  | EArith (Int n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_int n)
-  | EArith (Nat n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_nat n)
-  | EArith (Mtz n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_tez n)
+      simpl_binop "MOD" c
+  | EArith (Int n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd @@ n in
+      return @@ e_literal ~loc (Literal_int n)
+    )
+  | EArith (Nat n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd @@ n in
+      return @@ e_literal ~loc (Literal_nat n)
+    )
+  | EArith (Mtz n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd @@ n in
+      return @@ e_literal ~loc (Literal_tez n)
+    )
   | EArith _ -> simple_fail "arith: not supported yet"
-  | EString (String s) ->
+  | EString (String s) -> (
+      let (s , loc) = r_split s in
       let s' =
-        let s = s.value in
+        let s = s in
         String.(sub s 1 ((length s) - 2))
       in
-      return @@ E_literal (Literal_string s')
+      return @@ e_literal ~loc (Literal_string s')
+    )
   | EString _ -> simple_fail "string: not supported yet"
-  | ELogic l -> simpl_logic_expression ?te_annot l
-  | EList l -> simpl_list_expression ?te_annot l
+  | ELogic l -> simpl_logic_expression l
+  | EList l -> simpl_list_expression l
   | ECase c -> (
-      let%bind e = simpl_expression c.value.expr in
+      let (c , loc) = r_split c in
+      let%bind e = simpl_expression c.expr in
       let%bind lst =
         let aux (x : Raw.expr Raw.case_clause) =
           let%bind expr = simpl_expression x.rhs in
@@ -211,10 +262,10 @@ let rec simpl_expression :
         bind_list
         @@ List.map aux
         @@ List.map get_value
-        @@ npseq_to_list c.value.cases.value in
+        @@ npseq_to_list c.cases.value in
       let default_action () =
         let%bind cases = simpl_cases lst in
-        return @@ E_matching (e , cases) in
+        return @@ e_matching ~loc e  cases in
       (* Hack to take care of patterns introduced by `parser/ligodity/Parser.mly` in "norm_fun_expr" *)
       match lst with
       | [ (pattern , rhs) ] -> (
@@ -238,125 +289,127 @@ let rec simpl_expression :
       | _ -> default_action ()
     )
   | EFun lamb -> simpl_fun lamb
-  | ESeq s ->
-      let items : Raw.expr list = pseq_to_list s.value.elements in
+  | ESeq s -> (
+      let (s , loc) = r_split s in
+      let items : Raw.expr list = pseq_to_list s.elements in
       (match items with
-         [] -> return @@ E_skip
+         [] -> return @@ e_skip ~loc ()
        | expr::more ->
           let expr' = simpl_expression expr in
           let apply (e1: Raw.expr) (e2: expression Trace.result) =
             let%bind a = simpl_expression e1 in
             let%bind e2' = e2 in
-            return @@ E_sequence (a, e2')
+            return @@ e_sequence a e2'
           in List.fold_right apply more expr')
-  | ECond c ->
-      let c = c.value in
+    )
+  | ECond c -> (
+      let (c , loc) = r_split c in
       let%bind expr = simpl_expression c.test in
       let%bind match_true = simpl_expression c.ifso in
       let%bind match_false = simpl_expression c.ifnot in
-      return @@ E_matching (expr, (Match_bool {match_true; match_false}))
+      return @@ e_matching ~loc expr (Match_bool {match_true; match_false})
+    )
 
-and simpl_fun lamb : expr result =
+and simpl_fun lamb' : expr result =
   let return x = ok x in
-  let rec aux args body =
-    match body with
-    | Raw.EFun l -> (
-        let l' = l.value in
-        let annot = Option.map snd l'.p_annot in
-        aux (args @ [(l'.param.value , annot)])  l'.body
-      )
-    | _ -> (args , body) in
-  let (args , body) = aux [] (Raw.EFun lamb) in
+  let (lamb , loc) = r_split lamb' in
   let%bind args' =
-    let aux  = fun (name , ty_opt) ->
-      let%bind ty =
-        match ty_opt with
-        | Some ty -> simpl_type_expression ty
-        | None when name = "storage" -> ok (T_variable "storage")
-        | None -> simple_fail "missing type annotation on input"
-      in
-      ok (name , ty)
+    let args = lamb.params in
+    let%bind p_args = bind_map_list pattern_to_typed_var args in
+    let aux ((var : Raw.variable) , ty_opt) =
+      match var.value , ty_opt with
+      | "storage" , None ->
+        ok (var , T_variable "storage")
+      | _ , None ->
+        simple_fail "untyped function parameter"
+      | _ , Some ty -> (
+        let%bind ty' = simpl_type_expression ty in
+        ok (var , ty')
+      )
     in
-    bind_map_list aux args
+    bind_map_list aux p_args
   in
   let arguments_name = "arguments" in
   let (binder , input_type) =
     let type_expression = T_tuple (List.map snd args') in
     (arguments_name , type_expression) in
-  let body, body_type =
-    match body with
-    | EAnnot {value = expr, type_expr} -> expr, Some type_expr
-    | expr -> expr, None in
+  let%bind (body , body_type) = expr_to_typed_expr lamb.body in
   let%bind output_type =
     bind_map_option simpl_type_expression body_type in
   let%bind result = simpl_expression body in
   let wrapped_result =
-    let aux = fun i (name , ty) wrapped ->
-      let accessor = E_accessor (E_variable arguments_name , [ Access_tuple i ]) in
-      e_let_in (name , Some ty) accessor wrapped
+    let aux = fun i ((name : Raw.variable) , ty) wrapped ->
+      let accessor = e_accessor (e_variable arguments_name) [ Access_tuple i ] in
+      e_let_in (name.value , Some ty) accessor wrapped
     in
     let wraps = List.mapi aux args' in
     List.fold_right' (fun x f -> f x) result wraps in
-  let lambda = {binder = (binder , Some input_type); input_type = (Some input_type); output_type; result = wrapped_result}
-  in return @@ E_lambda lambda
+  return @@ e_lambda ~loc binder (Some input_type) output_type wrapped_result
 
 
 and simpl_logic_expression ?te_annot (t:Raw.logic_expr) : expr result =
   let return x = ok @@ make_option_typed x te_annot in
   match t with
-  | BoolExpr (False _) ->
-      return @@ E_literal (Literal_bool false)
-  | BoolExpr (True _) ->
-      return @@ E_literal (Literal_bool true)
+  | BoolExpr (False reg) -> (
+      let loc = Location.lift reg in
+      return @@ e_literal ~loc (Literal_bool false)
+    )
+  | BoolExpr (True reg) -> (
+      let loc = Location.lift reg in
+      return @@ e_literal ~loc (Literal_bool true)
+    )
   | BoolExpr (Or b) ->
-      simpl_binop ?te_annot "OR" b.value
+      simpl_binop "OR" b
   | BoolExpr (And b) ->
-      simpl_binop ?te_annot "AND" b.value
+      simpl_binop "AND" b
   | BoolExpr (Not b) ->
-      simpl_unop ?te_annot "NOT" b.value
+      simpl_unop "NOT" b
   | CompExpr (Lt c) ->
-      simpl_binop ?te_annot "LT" c.value
+      simpl_binop "LT" c
   | CompExpr (Gt c) ->
-      simpl_binop ?te_annot "GT" c.value
+      simpl_binop "GT" c
   | CompExpr (Leq c) ->
-      simpl_binop ?te_annot "LE" c.value
+      simpl_binop "LE" c
   | CompExpr (Geq c) ->
-      simpl_binop ?te_annot "GE" c.value
+      simpl_binop "GE" c
   | CompExpr (Equal c) ->
-      simpl_binop ?te_annot "EQ" c.value
+      simpl_binop "EQ" c
   | CompExpr (Neq c) ->
-      simpl_binop ?te_annot "NEQ" c.value
+      simpl_binop "NEQ" c
 
-and simpl_list_expression ?te_annot (t:Raw.list_expr) : expression result =
-  let return x = ok @@ make_option_typed x te_annot in
+and simpl_list_expression (t:Raw.list_expr) : expression result =
+  let return x = ok @@ x in
   match t with
-  | Cons c ->
-      simpl_binop ?te_annot "CONS" c.value
-  | List lst ->
+  | Cons c -> simpl_binop "CONS" c
+  | List lst -> (
+      let (lst , loc) = r_split lst in
       let%bind lst' =
         bind_map_list simpl_expression @@
-        pseq_to_list lst.value.elements in
-      return @@ E_list lst'
+        pseq_to_list lst.elements in
+      return @@ e_list ~loc lst'
+    )
 
-and simpl_binop ?te_annot (name:string) (t:_ Raw.bin_op) : expression result =
-  let return x = ok @@ make_option_typed x te_annot in
-  let%bind a = simpl_expression t.arg1 in
-  let%bind b = simpl_expression t.arg2 in
-  return @@ E_constant (name, [a;b])
+and simpl_binop (name:string) (t:_ Raw.bin_op Region.reg) : expression result =
+  let return x = ok @@ x in
+  let (args , loc) = r_split t in
+  let%bind a = simpl_expression args.arg1 in
+  let%bind b = simpl_expression args.arg2 in
+  return @@ e_constant ~loc name [ a ; b ]
 
-and simpl_unop ?te_annot (name:string) (t:_ Raw.un_op) : expression result =
-  let return x = ok @@ make_option_typed x te_annot in
+and simpl_unop (name:string) (t:_ Raw.un_op Region.reg) : expression result =
+  let return x = ok @@ x in
+  let (t , loc) = r_split t in
   let%bind a = simpl_expression t.arg in
-  return @@ E_constant (name, [a])
+  return @@ e_constant ~loc name [ a ]
 
-and simpl_tuple_expression ?te_annot (lst:Raw.expr list) : expression result =
-  let return x = ok @@ make_option_typed x te_annot in
+and simpl_tuple_expression ?loc (lst:Raw.expr list) : expression result =
+  let return x = ok @@ x in
   match lst with
-  | [] -> return @@ E_literal Literal_unit
-  | [hd] -> simpl_expression ?te_annot hd
+  | [] -> return @@ e_literal ?loc Literal_unit
+  | [hd] -> simpl_expression hd
   | lst ->
       let%bind lst = bind_list @@ List.map simpl_expression lst in
-      return @@ E_tuple lst
+      return @@ e_tuple ?loc lst
 
 and simpl_declaration : Raw.declaration -> declaration Location.wrap result = fun t ->
   let open! Raw in
@@ -368,14 +421,35 @@ and simpl_declaration : Raw.declaration -> declaration Location.wrap result = fu
       ok @@ loc x @@ Declaration_type (name.value , type_expression)
   | LetEntry x (* -> simple_fail "no entry point yet" *)
   | Let x -> (
-      let _, binding = x.value in
-      let {variable ; lhs_type ; let_rhs} = binding in
-      let%bind type_annotation = bind_map_option
-        (fun (_,type_expr) -> simpl_type_expression type_expr)
-        lhs_type in
-      let%bind rhs = simpl_expression ?te_annot:type_annotation let_rhs in
-      let name = variable.value in
-      ok @@ loc x @@ (Declaration_constant (name , type_annotation , rhs))
+      let _ , binding = x.value in
+      let {bindings ; lhs_type ; let_rhs} = binding in
+      let%bind (var , args) =
+        let%bind (hd , tl) = match bindings with
+          | [] -> simple_fail "let without bindgings"
+          | hd :: tl -> ok (hd , tl)
+        in
+        let%bind var = pattern_to_var hd in
+        ok (var , tl)
+      in
+      match args with
+      | [] -> (
+          let%bind lhs_type' = bind_map_option
+              (fun (_ , te) -> simpl_type_expression te) lhs_type in
+          let%bind rhs' = simpl_expression let_rhs in
+          ok @@ loc x @@ (Declaration_constant (var.value , lhs_type' , rhs'))
+        )
+      | _ -> (
+          let fun_ = {
+            kwd_fun = Region.ghost ;
+            params = args ;
+            p_annot = lhs_type ;
+            arrow = Region.ghost ;
+            body = let_rhs ;
+          } in
+          let rhs = Raw.EFun {region=Region.ghost ; value=fun_} in
+          let%bind rhs' = simpl_expression rhs in
+          ok @@ loc x @@ (Declaration_constant (var.value , None , rhs'))
+        )
     )
 
 and simpl_cases : type a . (Raw.pattern * a) list -> a matching result = fun t ->
diff --git a/src/simplify/pascaligo.ml b/src/simplify/pascaligo.ml
index 038fd4484..c5af5e80c 100644
--- a/src/simplify/pascaligo.ml
+++ b/src/simplify/pascaligo.ml
@@ -16,16 +16,18 @@ let get_value : 'a Raw.reg -> 'a = fun x -> x.value
 
 open Operators.Simplify.Pascaligo
 
+let r_split = Location.r_split
+
 let return expr = ok @@ fun expr'_opt ->
   let expr = expr in
   match expr'_opt with
   | None -> ok @@ expr
   | Some expr' -> ok @@ e_sequence expr expr'
 
-let return_let_in binder rhs = ok @@ fun expr'_opt ->
+let return_let_in ?loc binder rhs = ok @@ fun expr'_opt ->
   match expr'_opt with
   | None -> simple_fail "missing return" (* Hard to explain. Shouldn't happen in prod. *)
-  | Some expr' -> ok @@ e_let_in binder rhs expr'
+  | Some expr' -> ok @@ e_let_in ?loc binder rhs expr'
 
 let rec simpl_type_expression (t:Raw.type_expr) : type_expression result =
   match t with
@@ -88,11 +90,12 @@ and simpl_list_type_expression (lst:Raw.type_expr list) : type_expression result
 
 let rec simpl_expression (t:Raw.expr) : expr result =
   let return x = ok x in
-  let simpl_projection = fun (p:Raw.projection) ->
+  let simpl_projection = fun (p : Raw.projection Region.reg) ->
+    let (p' , loc) = r_split p in
     let var =
-      let name = p.struct_name.value in
+      let name = p'.struct_name.value in
       e_variable name in
-    let path = p.field_path in
+    let path = p'.field_path in
     let path' =
       let aux (s:Raw.selection) =
         match s with
@@ -100,97 +103,112 @@ let rec simpl_expression (t:Raw.expr) : expr result =
         | Component index -> Access_tuple (Z.to_int (snd index.value))
       in
       List.map aux @@ npseq_to_list path in
-    return @@ E_accessor (var, path')
+    return @@ e_accessor ~loc var path'
   in
   match t with
   | EAnnot a -> (
-      let (expr , type_expr) = a.value in
+      let ((expr , type_expr) , loc) = r_split a in
       let%bind expr' = simpl_expression expr in
       let%bind type_expr' = simpl_type_expression type_expr in
-      return @@ e_annotation expr' type_expr'
+      return @@ e_annotation ~loc expr' type_expr'
     )
   | EVar c -> (
-      let c' = c.value in
+      let (c' , loc) = r_split c in
       match List.assoc_opt c' constants with
-      | None -> return @@ E_variable c.value
-      | Some s -> return @@ E_constant (s , [])
+      | None -> return @@ e_variable ~loc c.value
+      | Some s -> return @@ e_constant ~loc s []
     )
   | ECall x -> (
-      let (name, args) = x.value in
-      let f = name.value in
-      let args' = npseq_to_list args.value.inside in
+      let ((name, args) , loc) = r_split x in
+      let (f , f_loc) = r_split name in
+      let (args , args_loc) = r_split args in
+      let args' = npseq_to_list args.inside in
       match List.assoc_opt f constants with
       | None ->
-          let%bind arg = simpl_tuple_expression args' in
-          return @@ E_application (e_variable f, arg)
+          let%bind arg = simpl_tuple_expression ~loc:args_loc args' in
+          return @@ e_application ~loc (e_variable ~loc:f_loc f) arg
       | Some s ->
           let%bind lst = bind_map_list simpl_expression args' in
-          return @@ E_constant (s , lst)
+          return @@ e_constant ~loc s lst
     )
   | EPar x -> simpl_expression x.value.inside
-  | EUnit _ -> return @@ E_literal Literal_unit
-  | EBytes x -> return @@ E_literal (Literal_bytes (Bytes.of_string @@ fst x.value))
+  | EUnit reg ->
+    let loc = Location.lift reg in
+    return @@ e_literal ~loc Literal_unit
+  | EBytes x ->
+    let (x' , loc) = r_split x in
+    return @@ e_literal ~loc (Literal_bytes (Bytes.of_string @@ fst x'))
   | ETuple tpl ->
       let (Raw.TupleInj tpl') = tpl in
-      simpl_tuple_expression
-      @@ npseq_to_list tpl'.value.inside
+      let (tpl' , loc) = r_split tpl' in
+      simpl_tuple_expression ~loc @@ npseq_to_list tpl'.inside
   | ERecord r ->
       let%bind fields = bind_list
         @@ List.map (fun ((k : _ Raw.reg), v) -> let%bind v = simpl_expression v in ok (k.value, v))
         @@ List.map (fun (x:Raw.field_assign Raw.reg) -> (x.value.field_name, x.value.field_expr))
         @@ pseq_to_list r.value.elements in
       let aux prev (k, v) = SMap.add k v prev in
-      return @@ E_record (List.fold_left aux SMap.empty fields)
-  | EProj p' -> (
-      let p = p'.value in
-      simpl_projection p
+      return @@ e_record (List.fold_left aux SMap.empty fields)
+  | EProj p -> simpl_projection p
+  | EConstr (ConstrApp c) -> (
+      let ((c, args) , loc) = r_split c in
+      let (args , args_loc) = r_split args in
+      let%bind arg =
+        simpl_tuple_expression ~loc:args_loc
+        @@ npseq_to_list args.inside in
+      return @@ e_constructor ~loc c.value arg
     )
-  | EConstr (ConstrApp c) ->
-      let (c, args) = c.value in
-      let%bind arg =
-        simpl_tuple_expression
-        @@ npseq_to_list args.value.inside in
-      return @@ E_constructor (c.value, arg)
   | EConstr (SomeApp a) ->
-      let (_, args) = a.value in
+      let ((_, args) , loc) = r_split a in
+      let (args , args_loc) = r_split args in
       let%bind arg =
-        simpl_tuple_expression
-        @@ npseq_to_list args.value.inside in
-      return @@ E_constant ("SOME", [arg])
-  | EConstr (NoneExpr _) ->
-      return @@ E_constant ("NONE" , [])
+        simpl_tuple_expression ~loc:args_loc
+        @@ npseq_to_list args.inside in
+      return @@ e_constant ~loc "SOME" [arg]
+  | EConstr (NoneExpr reg) -> (
+      let loc = Location.lift reg in
+      return @@ e_none ~loc ()
+    )
   | EArith (Add c) ->
-      simpl_binop "ADD" c.value
+      simpl_binop "ADD" c
   | EArith (Sub c) ->
-      simpl_binop "SUB" c.value
+      simpl_binop "SUB" c
   | EArith (Mult c) ->
-      simpl_binop "TIMES" c.value
+      simpl_binop "TIMES" c
   | EArith (Div c) ->
-      simpl_binop "DIV" c.value
+      simpl_binop "DIV" c
   | EArith (Mod c) ->
-      simpl_binop "MOD" c.value
-  | EArith (Int n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_int n)
-  | EArith (Nat n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_nat n)
-  | EArith (Mtz n) ->
-      let n = Z.to_int @@ snd @@ n.value in
-      return @@ E_literal (Literal_tez n)
+      simpl_binop "MOD" c
+  | EArith (Int n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd n in
+      return @@ e_literal ~loc (Literal_int n)
+    )
+  | EArith (Nat n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd @@ n in
+      return @@ e_literal ~loc (Literal_nat n)
+    )
+  | EArith (Mtz n) -> (
+      let (n , loc) = r_split n in
+      let n = Z.to_int @@ snd @@ n in
+      return @@ e_literal ~loc (Literal_tez n)
+    )
   | EArith _ -> simple_fail "arith: not supported yet"
   | EString (String s) ->
+    let (s , loc) = r_split s in
       let s' =
-        let s = s.value in
+        (* S contains quotes *)
         String.(sub s 1 ((length s) - 2))
       in
-      return @@ E_literal (Literal_string s')
+      return @@ e_literal ~loc (Literal_string s')
   | EString _ -> simple_fail "string: not supported yet"
   | ELogic l -> simpl_logic_expression l
   | EList l -> simpl_list_expression l
   | ESet _ -> simple_fail "set: not supported yet"
-  | ECase c ->
-      let%bind e = simpl_expression c.value.expr in
+  | ECase c -> (
+      let (c , loc) = r_split c in
+      let%bind e = simpl_expression c.expr in
       let%bind lst =
         let aux (x : Raw.expr Raw.case_clause) =
           let%bind expr = simpl_expression x.rhs in
@@ -198,84 +216,103 @@ let rec simpl_expression (t:Raw.expr) : expr result =
         bind_list
         @@ List.map aux
         @@ List.map get_value
-        @@ npseq_to_list c.value.cases.value in
+        @@ npseq_to_list c.cases.value in
       let%bind cases = simpl_cases lst in
-      return @@ E_matching (e, cases)
-  | EMap (MapInj mi) ->
+      return @@ e_matching ~loc e cases
+    )
+  | EMap (MapInj mi) -> (
+      let (mi , loc) = r_split mi in
       let%bind lst =
-        let lst = List.map get_value @@ pseq_to_list mi.value.elements in
+        let lst = List.map get_value @@ pseq_to_list mi.elements in
         let aux : Raw.binding -> (expression * expression) result = fun b ->
           let%bind src = simpl_expression b.source in
           let%bind dst = simpl_expression b.image in
           ok (src, dst) in
         bind_map_list aux lst in
-      return (E_map lst)
-  | EMap (MapLookUp lu) ->
-      let%bind path = match lu.value.path with
-        | Name v -> return (E_variable v.value)
-        | Path p -> simpl_projection p.value
+      return @@ e_map ~loc lst
+    )
+  | EMap (MapLookUp lu) -> (
+      let (lu , loc) = r_split lu in
+      let%bind path = match lu.path with
+        | Name v -> (
+            let (v , loc) = r_split v in
+            return @@ e_variable ~loc v
+          )
+        | Path p -> simpl_projection p
       in
-      let%bind index = simpl_expression lu.value.index.value.inside in
-      return (E_look_up (path, index))
+      let%bind index = simpl_expression lu.index.value.inside in
+      return @@ e_look_up ~loc path index
+    )
 
 and simpl_logic_expression (t:Raw.logic_expr) : expression result =
   let return x = ok x in
   match t with
-  | BoolExpr (False _) ->
-      return @@ E_literal (Literal_bool false)
-  | BoolExpr (True _) ->
-      return @@ E_literal (Literal_bool true)
+  | BoolExpr (False reg) -> (
+      let loc = Location.lift reg in
+      return @@ e_literal ~loc (Literal_bool false)
+    )
+  | BoolExpr (True reg) -> (
+      let loc = Location.lift reg in
+      return @@ e_literal ~loc (Literal_bool true)
+    )
   | BoolExpr (Or b) ->
-      simpl_binop "OR" b.value
+      simpl_binop "OR" b
   | BoolExpr (And b) ->
-      simpl_binop "AND" b.value
+      simpl_binop "AND" b
   | BoolExpr (Not b) ->
-      simpl_unop "NOT" b.value
+      simpl_unop "NOT" b
   | CompExpr (Lt c) ->
-      simpl_binop "LT" c.value
+      simpl_binop "LT" c
   | CompExpr (Gt c) ->
-      simpl_binop "GT" c.value
+      simpl_binop "GT" c
   | CompExpr (Leq c) ->
-      simpl_binop "LE" c.value
+      simpl_binop "LE" c
   | CompExpr (Geq c) ->
-      simpl_binop "GE" c.value
+      simpl_binop "GE" c
   | CompExpr (Equal c) ->
-      simpl_binop "EQ" c.value
+      simpl_binop "EQ" c
   | CompExpr (Neq c) ->
-      simpl_binop "NEQ" c.value
+      simpl_binop "NEQ" c
 
 and simpl_list_expression (t:Raw.list_expr) : expression result =
   let return x = ok x in
   match t with
   | Cons c ->
-      simpl_binop "CONS" c.value
-  | List lst ->
+      simpl_binop "CONS" c
+  | List lst -> (
+      let (lst , loc) = r_split lst in
       let%bind lst' =
         bind_map_list simpl_expression @@
-        pseq_to_list lst.value.elements in
-      return @@ E_list lst'
-  | Nil _ ->
-      return @@ E_list []
+        pseq_to_list lst.elements in
+      return @@ e_list ~loc lst'
+    )
+  | Nil reg -> (
+      let loc = Location.lift reg in
+      return @@ e_list ~loc []
+    )
 
-and simpl_binop (name:string) (t:_ Raw.bin_op) : expression result =
+and simpl_binop (name:string) (t:_ Raw.bin_op Region.reg) : expression result =
   let return x = ok x in
+  let (t , loc) = r_split t in
   let%bind a = simpl_expression t.arg1 in
   let%bind b = simpl_expression t.arg2 in
-  return @@ E_constant (name, [a;b])
+  return @@ e_constant ~loc name [ a ; b ]
 
-and simpl_unop (name:string) (t:_ Raw.un_op) : expression result =
+and simpl_unop (name:string) (t:_ Raw.un_op Region.reg) : expression result =
   let return x = ok x in
+  let (t , loc) = r_split t in
   let%bind a = simpl_expression t.arg in
-  return @@ E_constant (name, [a])
+  return @@ e_constant ~loc name [ a ]
 
-and simpl_tuple_expression (lst:Raw.expr list) : expression result =
+and simpl_tuple_expression ?loc (lst:Raw.expr list) : expression result =
   let return x = ok x in
   match lst with
-  | [] -> return @@ E_literal Literal_unit
+  | [] -> return @@ e_literal Literal_unit
   | [hd] -> simpl_expression hd
-  | lst ->
+  | lst -> (
       let%bind lst = bind_list @@ List.map simpl_expression lst in
-      return @@ E_tuple lst
+      return @@ e_tuple ?loc lst
+    )
 
 and simpl_local_declaration : Raw.local_decl -> _ result = fun t ->
   match t with
@@ -284,26 +321,28 @@ and simpl_local_declaration : Raw.local_decl -> _ result = fun t ->
 
 and simpl_lambda_declaration : Raw.lambda_decl -> _ result = fun l ->
   match l with
-  | FunDecl f ->
-      let%bind (name , e) = simpl_fun_declaration (f.value) in
-      return_let_in name e
+  | FunDecl f -> (
+      let (f , loc) = r_split f in
+      let%bind (name , e) = simpl_fun_declaration ~loc f in
+      return_let_in ~loc name e
+    )
   | ProcDecl _ -> simple_fail "no local procedure yet"
   | EntryDecl _ -> simple_fail "no local entry-point yet"
 
 and simpl_data_declaration : Raw.data_decl -> _ result = fun t ->
   match t with
   | LocalVar x ->
-      let x = x.value in
+      let (x , loc) = r_split x in
       let name = x.name.value in
       let%bind t = simpl_type_expression x.var_type in
       let%bind expression = simpl_expression x.init in
-      return_let_in (name , Some t) expression
+      return_let_in ~loc (name , Some t) expression
   | LocalConst x ->
-      let x = x.value in
+      let (x , loc) = r_split x in
       let name = x.name.value in
       let%bind t = simpl_type_expression x.const_type in
       let%bind expression = simpl_expression x.init in
-      return_let_in (name , Some t) expression
+      return_let_in ~loc (name , Some t) expression
 
 and simpl_param : Raw.param_decl -> (type_name * type_expression) result = fun t ->
   match t with
@@ -318,7 +357,7 @@ and simpl_param : Raw.param_decl -> (type_name * type_expression) result = fun t
       let%bind type_expression = simpl_type_expression c.param_type in
       ok (type_name , type_expression)
 
-and simpl_fun_declaration : Raw.fun_decl -> ((name * type_expression option) * expression) result = fun x ->
+and simpl_fun_declaration : loc:_ -> Raw.fun_decl -> ((name * type_expression option) * expression) result = fun ~loc x ->
   let open! Raw in
   let {name;param;ret_type;local_decls;block;return} : fun_decl = x in
   (match npseq_to_list param.value.inside with
@@ -338,12 +377,8 @@ and simpl_fun_declaration : Raw.fun_decl -> ((name * type_expression option) * e
        let%bind result =
          let aux prec cur = cur (Some prec) in
          bind_fold_right_list aux result body in
-       let expression = E_lambda {
-           binder = (binder , Some input_type) ;
-           input_type = Some input_type ;
-           output_type = Some output_type ;
-           result
-         } in
+       let expression : expression = e_lambda ~loc binder (Some input_type)
+           (Some output_type) result in
        let type_annotation = Some (T_function (input_type, output_type)) in
        ok ((name , type_annotation) , expression)
      )
@@ -355,7 +390,7 @@ and simpl_fun_declaration : Raw.fun_decl -> ((name * type_expression option) * e
          (arguments_name , type_expression) in
        let%bind tpl_declarations =
          let aux = fun i x ->
-           let expr = E_accessor (E_variable arguments_name , [ Access_tuple i ]) in
+           let expr = e_accessor (e_variable arguments_name) [ Access_tuple i ] in
            let type_ = Some (snd x) in
            let ass = return_let_in (fst x , type_) expr in
            ass
@@ -372,24 +407,20 @@ and simpl_fun_declaration : Raw.fun_decl -> ((name * type_expression option) * e
        let%bind result =
          let aux prec cur = cur (Some prec) in
          bind_fold_right_list aux result body in
-       let expression = E_lambda {
-           binder = (binder , Some input_type) ;
-           input_type = Some input_type ;
-           output_type = Some output_type ;
-           result
-         } in
+       let expression = e_lambda ~loc binder (Some input_type) (Some output_type) result in
        let type_annotation = Some (T_function (input_type, output_type)) in
        ok ((name.value , type_annotation) , expression)
      )
   )
 and simpl_declaration : Raw.declaration -> declaration Location.wrap result = fun t ->
   let open! Raw in
-  let loc : 'a . 'a Raw.reg -> _ -> _ = fun x v -> Location.wrap ~loc:(File x.region) v in
   match t with
-  | TypeDecl x ->
-      let {name;type_expr} : Raw.type_decl = x.value in
+  | TypeDecl x -> (
+      let (x , loc) = r_split x in
+      let {name;type_expr} : Raw.type_decl = x in
       let%bind type_expression = simpl_type_expression type_expr in
-      ok @@ loc x @@ Declaration_type (name.value , type_expression)
+      ok @@ Location.wrap ~loc (Declaration_type (name.value , type_expression))
+    )
   | ConstDecl x ->
       let simpl_const_decl = fun {name;const_type;init} ->
         let%bind expression = simpl_expression init in
@@ -398,11 +429,11 @@ and simpl_declaration : Raw.declaration -> declaration Location.wrap result = fu
         ok @@ Declaration_constant (name.value , type_annotation , expression)
       in
       bind_map_location simpl_const_decl (Location.lift_region x)
-  | LambdaDecl (FunDecl x) ->
-      let aux f x =
-        let%bind ((name , ty_opt) , expr) = f x in
-        ok @@ Declaration_constant (name , ty_opt , expr) in
-      bind_map_location (aux simpl_fun_declaration) (Location.lift_region x)
+  | LambdaDecl (FunDecl x) -> (
+      let (x , loc) = r_split x in
+      let%bind ((name , ty_opt) , expr) = simpl_fun_declaration ~loc x in
+      ok @@ Location.wrap ~loc (Declaration_constant (name , ty_opt , expr))
+    )
   | LambdaDecl (ProcDecl _) -> simple_fail "no proc declaration yet"
   | LambdaDecl (EntryDecl _)-> simple_fail "no entry point yet"
 
@@ -418,7 +449,10 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
       let%bind expr = simpl_expression e.value.fail_expr in
       return @@ e_failwith expr
     )
-  | Skip _ -> return @@ e_skip
+  | Skip reg -> (
+      let loc = Location.lift reg in
+      return @@ e_skip ~loc ()
+    )
   | Loop (While l) ->
       let l = l.value in
       let%bind cond = simpl_expression l.cond in
@@ -427,8 +461,8 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
       return @@ e_loop cond body
   | Loop (For _) ->
       simple_fail "no for yet"
-  | Cond c ->
-      let c = c.value in
+  | Cond c -> (
+      let (c , loc) = r_split c in
       let%bind expr = simpl_expression c.test in
       let%bind match_true = match c.ifso with
         | ClauseInstr i -> simpl_instruction_block i
@@ -438,9 +472,10 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
         | ClauseBlock b -> simpl_statements @@ fst b.value.inside in
       let%bind match_true = match_true None in
       let%bind match_false = match_false None in
-      return @@ E_matching (expr, (Match_bool {match_true; match_false}))
+      return @@ e_matching expr ~loc (Match_bool {match_true; match_false})
+    )
   | Assign a -> (
-      let a = a.value in
+      let (a , loc) = r_split a in
       let%bind value_expr = match a.rhs with
         | Expr e -> simpl_expression e
         | NoneExpr _ -> simple_fail "no none assignments yet"
@@ -448,7 +483,7 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
       match a.lhs with
         | Path path -> (
             let (name , path') = simpl_path path in
-            return @@ E_assign (name , path' , value_expr)
+            return @@ e_assign ~loc name path' value_expr
           )
         | MapPath v -> (
             let v' = v.value in
@@ -458,11 +493,11 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
             let%bind key_expr = simpl_expression v'.index.value.inside in
             let old_expr = e_variable name.value in
             let expr' = e_map_update key_expr value_expr old_expr in
-            return @@ E_assign (name.value , [] , expr')
+            return @@ e_assign ~loc name.value [] expr'
           )
     )
   | CaseInstr c -> (
-      let c = c.value in
+      let (c , loc) = r_split c in
       let%bind expr = simpl_expression c.expr in
       let%bind cases =
         let aux (x : Raw.instruction Raw.case_clause Raw.reg) =
@@ -473,25 +508,25 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
         @@ List.map aux
         @@ npseq_to_list c.cases.value in
       let%bind m = simpl_cases cases in
-      return @@ E_matching (expr, m)
+      return @@ e_matching ~loc expr m
     )
   | RecordPatch r -> (
       let r = r.value in
       let (name , access_path) = simpl_path r.path in
       let%bind inj = bind_list
-        @@ List.map (fun (x:Raw.field_assign) -> let%bind e = simpl_expression x.field_expr in ok (x.field_name.value, e))
-        @@ List.map (fun (x:_ Raw.reg) -> x.value)
+        @@ List.map (fun (x:Raw.field_assign Region.reg) ->
+            let (x , loc) = r_split x in
+            let%bind e = simpl_expression x.field_expr in ok (x.field_name.value, e , loc)
+          )
         @@ pseq_to_list r.record_inj.value.elements in
       let%bind expr =
-        let aux = fun (access , v) ->
-          E_assign (name , access_path @ [ Access_record access ] , v) in
+        let aux = fun (access , v , loc) ->
+          e_assign ~loc name (access_path @ [ Access_record access ]) v in
         let assigns = List.map aux inj in
         match assigns with
         | [] -> simple_fail "empty record patch"
         | hd :: tl -> (
-            let aux acc cur =
-              e_sequence (acc) (cur)
-            in
+            let aux acc cur = e_sequence (acc) (cur) in
             ok @@ List.fold_left aux hd tl
           )
       in
@@ -499,15 +534,16 @@ and simpl_single_instruction : Raw.single_instr -> (_ -> expression result) resu
     )
   | MapPatch _ -> simple_fail "no map patch yet"
   | SetPatch _ -> simple_fail "no set patch yet"
-  | MapRemove r ->
-      let v = r.value in
+  | MapRemove r -> (
+      let (v , loc) = r_split r in
       let key = v.key in
       let%bind map = match v.map with
         | Name v -> ok v.value
         | _ -> simple_fail "no complex map remove yet" in
       let%bind key' = simpl_expression key in
-      let expr = E_constant ("MAP_REMOVE", [key' ; e_variable map]) in
-      return @@ E_assign (map , [] , expr)
+      let expr = e_constant ~loc "MAP_REMOVE" [key' ; e_variable map] in
+      return @@ e_assign ~loc map [] expr
+    )
   | SetRemove _ -> simple_fail "no set remove yet"
 
 and simpl_path : Raw.path -> string * Ast_simplified.access_path = fun p ->
diff --git a/src/test/coase_tests.ml b/src/test/coase_tests.ml
index e6e086c6c..a0e176a29 100644
--- a/src/test/coase_tests.ml
+++ b/src/test/coase_tests.ml
@@ -33,7 +33,7 @@ let card_ez owner = card (e_address owner)
 
 let make_cards assoc_lst =
   let card_id_ty = t_nat in
-  e_map assoc_lst card_id_ty card_ty
+  e_typed_map assoc_lst card_id_ty card_ty
 
 let card_pattern (coeff , qtt) =
   ez_e_record [
@@ -53,7 +53,7 @@ let card_pattern_ez (coeff , qtt) =
 let make_card_patterns lst =
   let card_pattern_id_ty = t_nat  in
   let assoc_lst = List.mapi (fun i x -> (e_nat i , x)) lst in
-  e_map assoc_lst card_pattern_id_ty card_pattern_ty
+  e_typed_map assoc_lst card_pattern_id_ty card_pattern_ty
 
 let storage cards_patterns cards next_id =
   ez_e_record [
@@ -210,9 +210,9 @@ let sell () =
       e_pair sell_action storage
     in
     let make_expecter : int -> expression -> unit result = fun n result ->
-      let%bind (ops , storage) = get_e_pair result in
+      let%bind (ops , storage) = get_e_pair @@ Location.unwrap result in
       let%bind () =
-        let%bind lst = get_e_list ops in
+        let%bind lst = get_e_list @@ Location.unwrap ops in
         Assert.assert_list_size lst 1 in
       let expected_storage =
         let cards = List.hds @@ cards_ez first_owner n in
diff --git a/src/test/integration_tests.ml b/src/test/integration_tests.ml
index 6f8a947f7..6c8e78eff 100644
--- a/src/test/integration_tests.ml
+++ b/src/test/integration_tests.ml
@@ -253,7 +253,7 @@ let map () : unit result =
   let ez lst =
     let open Ast_simplified.Combinators in
     let lst' = List.map (fun (x, y) -> e_int x, e_int y) lst in
-    e_map lst' t_int t_int
+    e_typed_map lst' t_int t_int
   in
   let%bind () =
     let make_input = fun n -> ez [(23, n) ; (42, 4)] in
diff --git a/src/typer/typer.ml b/src/typer/typer.ml
index 0567be391..65dbc66d2 100644
--- a/src/typer/typer.ml
+++ b/src/typer/typer.ml
@@ -29,7 +29,7 @@ module Errors = struct
   let wrong_arity (n:string) (expected:int) (actual:int) () =
     let title () = "wrong arity" in
     let full () =
-      Format.asprintf "Wrong number of args passed to [%s]. Expected was %d, received was %d."
+      Format.asprintf "Wrong number of args passed to [%s]. Expected was %d, received was %d"
         n expected actual
     in
     error title full ()
@@ -204,13 +204,20 @@ and type_expression : environment -> ?tv_opt:O.type_value -> I.expression -> O.a
       match tv_opt with
       | None -> ok ()
       | Some tv' -> O.assert_type_value_eq (tv' , tv) in
-    ok @@ make_a_e expr tv e in
+    let location = Location.get_location ae in
+    ok @@ make_a_e ~location expr tv e in
   let main_error =
     let title () = "typing expression" in
-    let content () = Format.asprintf "Expression: %a\nLog: %s\n" I.PP.expression ae (L.get()) in
+    let content () =
+      match L.get () with
+      | "" ->
+        Format.asprintf "Expression: %a\n" I.PP.expression ae
+      | l ->
+        Format.asprintf "Expression: %a\nLog: %s\n" I.PP.expression ae l
+    in
     error title content in
   trace main_error @@
-  match ae with
+  match Location.unwrap ae with
   (* Basic *)
   | E_failwith _ -> simple_fail "can't type failwith in isolation"
   | E_variable name ->
@@ -362,9 +369,9 @@ and type_expression : environment -> ?tv_opt:O.type_value -> I.expression -> O.a
           match input_type with
           | Some ty -> ok ty
           | None -> (
-              match result with
+              match Location.unwrap result with
               | I.E_let_in li -> (
-                  match li.rhs with
+                  match Location.unwrap li.rhs with
                   | I.E_variable name when name = (fst binder) -> (
                       match snd li.binder with
                       | Some ty -> ok ty
@@ -409,7 +416,8 @@ and type_expression : environment -> ?tv_opt:O.type_value -> I.expression -> O.a
       let%bind ex' = type_expression e ex in
       match m with
       (* Special case for assert-like failwiths. TODO: CLEAN THIS. *)
-      | I.Match_bool { match_false ; match_true = E_failwith fw } -> (
+      | I.Match_bool { match_false ; match_true } when I.is_e_failwith match_true -> (
+          let%bind fw = I.get_e_failwith match_true in
           let%bind fw' = type_expression e fw in
           let%bind mf' = type_expression e match_false in
           let%bind () =
@@ -541,55 +549,54 @@ let rec untype_expression (e:O.annotated_expression) : (I.expression) result =
   match e.expression with
   | E_literal l ->
       let%bind l = untype_literal l in
-      return (E_literal l)
+      return (e_literal l)
   | E_constant (n, lst) ->
-      let%bind lst' = bind_list
-        @@ List.map untype_expression lst in
-      return (E_constant (n, lst'))
+      let%bind lst' = bind_map_list untype_expression lst in
+      return (e_constant n lst')
   | E_variable n ->
-      return (E_variable n)
+      return (e_variable n)
   | E_application (f, arg) ->
       let%bind f' = untype_expression f in
       let%bind arg' = untype_expression arg in
-      return (E_application (f', arg'))
+      return (e_application f' arg')
   | E_lambda {binder;input_type;output_type;result} ->
       let%bind input_type = untype_type_value input_type in
       let%bind output_type = untype_type_value output_type in
       let%bind result = untype_expression result in
-      return (E_lambda {binder = (binder , Some input_type);input_type = Some input_type;output_type = Some output_type;result})
+      return (e_lambda binder (Some input_type) (Some output_type) result)
   | E_tuple lst ->
       let%bind lst' = bind_list
         @@ List.map untype_expression lst in
-      return (E_tuple lst')
+      return (e_tuple lst')
   | E_tuple_accessor (tpl, ind)  ->
       let%bind tpl' = untype_expression tpl in
-      return (E_accessor (tpl', [Access_tuple ind]))
+      return (e_accessor tpl' [Access_tuple ind])
   | E_constructor (n, p) ->
       let%bind p' = untype_expression p in
-      return (E_constructor (n, p'))
+      return (e_constructor n p')
   | E_record r ->
       let%bind r' = bind_smap
         @@ SMap.map untype_expression r in
-      return (E_record r')
+      return (e_record r')
   | E_record_accessor (r, s) ->
       let%bind r' = untype_expression r in
-      return (E_accessor (r', [Access_record s]))
+      return (e_accessor r' [Access_record s])
   | E_map m ->
       let%bind m' = bind_map_list (bind_map_pair untype_expression) m in
-      return (E_map m')
+      return (e_map m')
   | E_list lst ->
       let%bind lst' = bind_map_list untype_expression lst in
-      return (E_list lst')
+      return (e_list lst')
   | E_look_up dsi ->
-      let%bind dsi' = bind_map_pair untype_expression dsi in
-      return (E_look_up dsi')
+      let%bind (a , b) = bind_map_pair untype_expression dsi in
+      return (e_look_up a b)
   | E_matching (ae, m) ->
       let%bind ae' = untype_expression ae in
       let%bind m' = untype_matching untype_expression m in
-      return (E_matching (ae', m'))
+      return (e_matching ae' m')
   | E_failwith ae ->
       let%bind ae' = untype_expression ae in
-      return (E_failwith ae')
+      return (e_failwith ae')
   | E_sequence _
   | E_loop _
   | E_assign _ -> simple_fail "not possible to untranspile statements yet"
@@ -597,7 +604,7 @@ let rec untype_expression (e:O.annotated_expression) : (I.expression) result =
       let%bind tv = untype_type_value rhs.type_annotation in
       let%bind rhs = untype_expression rhs in
       let%bind result = untype_expression result in
-      return (E_let_in {binder = (binder , Some tv);rhs;result})
+      return (e_let_in (binder , (Some tv)) rhs result)
 
 and untype_matching : type o i . (o -> i result) -> o O.matching -> (i I.matching) result = fun f m ->
   let open I in
diff --git a/vendors/ligo-utils/simple-utils/location.ml b/vendors/ligo-utils/simple-utils/location.ml
index d8a945000..27ecec4f3 100644
--- a/vendors/ligo-utils/simple-utils/location.ml
+++ b/vendors/ligo-utils/simple-utils/location.ml
@@ -22,16 +22,22 @@ let make (start_pos:Lexing.position) (end_pos:Lexing.position) : t =
 
 let virtual_location s = Virtual s
 let dummy = virtual_location "dummy"
+let generated = virtual_location "generated"
 
 type 'a wrap = {
   wrap_content : 'a ;
   location : t ;
 }
 
-let wrap ~loc wrap_content = { wrap_content ; location = loc }
+let wrap ?(loc = generated) wrap_content = { wrap_content ; location = loc }
+let get_location x = x.location
 let unwrap { wrap_content ; _ } = wrap_content
 let map f x = { x with wrap_content = f x.wrap_content }
 let pp_wrap f ppf { wrap_content ; _ } = Format.fprintf ppf "%a" f wrap_content
 
 let lift_region : 'a Region.reg -> 'a wrap = fun x ->
   wrap ~loc:(File x.region) x.value
+let lift : Region.region -> t = fun x -> File x
+
+let r_extract : 'a Region.reg -> t = fun x -> File x.region
+let r_split : 'a Region.reg -> ('a * t) = fun x -> x.value , File x.region
diff --git a/vendors/ligo-utils/simple-utils/trace.ml b/vendors/ligo-utils/simple-utils/trace.ml
index 506ad253b..73dd56366 100644
--- a/vendors/ligo-utils/simple-utils/trace.ml
+++ b/vendors/ligo-utils/simple-utils/trace.ml
@@ -134,7 +134,7 @@ let mk_error
   let message' = X_option.map (fun x -> ("message" , `String (x ()))) message in
   `Assoc (X_option.collapse_list [ error_code' ; title' ; message' ; data' ])
 
-let error title message () = mk_error ~title:(title) ~message:(message) ()
+let error ?data ?error_code title message () = mk_error ?data ?error_code ~title:(title) ~message:(message) ()
 
 (**
    Helpers that ideally shouldn't be used in production.
@@ -470,13 +470,17 @@ let json_of_error = J.to_string
 
 let error_pp out (e : error) =
   let open JSON_string_utils in
-  let message    = e |> member "message"    |> J.to_string in
+  let message =
+    let opt = e |> member "message" |> string in
+    X_option.unopt ~default:"" opt in
   let error_code =
     let error_code = e |> member "error_code" in
     match error_code with
     | `Null -> ""
     | _ -> " (" ^ (J.to_string error_code) ^ ")" in
-  let title      = e |> member "title"      |> J.to_string in
+  let title =
+    let opt = e |> member "title" |> string in
+    X_option.unopt ~default:"" opt in
   let data =
     let data = e |> member "data" in
     match data with
@@ -484,9 +488,6 @@ let error_pp out (e : error) =
     | _ -> J.to_string data in
   Format.fprintf out "%s (%s): %s. %s" title error_code message data
 
-(* let error_pp out (e : error) =
- *   Format.fprintf out "%s" @@ json_of_error e *)
-
 
 let error_pp_short out (e : error) =
   let open JSON_string_utils in