diff --git a/src/bin/expect_tests/typer_error_tests.ml b/src/bin/expect_tests/typer_error_tests.ml
index 55f182c97..51b3f56d6 100644
--- a/src/bin/expect_tests/typer_error_tests.ml
+++ b/src/bin/expect_tests/typer_error_tests.ml
@@ -104,4 +104,5 @@ let%expect_test _ =
     * Open a gitlab issue: https://gitlab.com/ligolang/ligo/issues/new
     * Check the changelog by running 'ligo changelog' |} ] ;
 
-
+  run_ligo_bad [ "compile-contract" ; "../../test/contracts/negative/id.mligo" ; "main" ] ;
+  [%expect {| ligo: in file "id.mligo", line 45, characters 4-51. Expected a different type: Expected the type option but got the type record[profile -> bytes , owner -> address , controller -> address] |}] ;
diff --git a/src/stages/ast_typed/combinators.ml b/src/stages/ast_typed/combinators.ml
index c46e39e21..42ce3118a 100644
--- a/src/stages/ast_typed/combinators.ml
+++ b/src/stages/ast_typed/combinators.ml
@@ -1,6 +1,28 @@
 open Trace
 open Types
 
+module Errors = struct
+  let not_a_x_expression expected_expression actual_expression () =
+    let message () =
+      Format.asprintf "Expected a %s expression but got a %a expression"
+        expected_expression
+        PP.expression actual_expression in
+    error (thunk "Expected a different expression") message
+
+  let not_a_x_type expected_type actual_type () =
+    let message () =
+      Format.asprintf "Expected the type %s but got the type %a"
+        expected_type
+        PP.type_value actual_type in
+    error (thunk "Expected a different type") message
+
+  let declaration_not_found expected_declaration () =
+    let message () =
+      Format.asprintf "Could not find a declaration with the name %s"
+        expected_declaration in
+    error (thunk "No declaration with the given name") message
+end
+
 let make_t type_value' simplified = { type_value' ; simplified }
 let make_a_e ?(location = Location.generated) expression type_annotation environment = {
   expression ;
@@ -61,102 +83,102 @@ let get_expression (x:annotated_expression) = x.expression
 
 let get_lambda e : _ result = match e with
   | E_lambda l -> ok l
-  | _ -> simple_fail "not a lambda"
+  | _ -> fail @@ Errors.not_a_x_expression "lambda" e ()
 
 let get_lambda_with_type e =
   match (e.expression , e.type_annotation.type_value') with
   | E_lambda l , T_arrow (i,o) -> ok (l , (i,o))
-  | _ -> simple_fail "not a lambda with functional type"
+  | _ -> fail @@ Errors.not_a_x_expression "lambda with functional type" e.expression ()
 
 let get_t_bool (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_bool) -> ok ()
-  | _ -> simple_fail "not a bool"
+  | _ -> fail @@ Errors.not_a_x_type "bool" t ()
 
 let get_t_int (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_int) -> ok ()
-  | _ -> simple_fail "not a int"
+  | _ -> fail @@ Errors.not_a_x_type "int" t ()
 
 let get_t_nat (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_nat) -> ok ()
-  | _ -> simple_fail "not a nat"
+  | _ -> fail @@ Errors.not_a_x_type "nat" t ()
 
 let get_t_unit (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_unit) -> ok ()
-  | _ -> simple_fail "not a unit"
+  | _ -> fail @@ Errors.not_a_x_type "unit" t ()
 
 let get_t_mutez (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_mutez) -> ok ()
-  | _ -> simple_fail "not a tez"
+  | _ -> fail @@ Errors.not_a_x_type "tez" t ()
 
 let get_t_bytes (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_bytes) -> ok ()
-  | _ -> simple_fail "not a bytes"
+  | _ -> fail @@ Errors.not_a_x_type "bytes" t ()
 
 let get_t_string (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_string) -> ok ()
-  | _ -> simple_fail "not a string"
+  | _ -> fail @@ Errors.not_a_x_type "string" t ()
 
 let get_t_contract (t:type_value) : type_value result = match t.type_value' with
   | T_operator (TC_contract x) -> ok x
-  | _ -> simple_fail "not a contract"
+  | _ -> fail @@ Errors.not_a_x_type "contract" t ()
 
 let get_t_option (t:type_value) : type_value result = match t.type_value' with
   | T_operator (TC_option o) -> ok o
-  | _ -> simple_fail "not a option"
+  | _ -> fail @@ Errors.not_a_x_type "option" t ()
 
 let get_t_list (t:type_value) : type_value result = match t.type_value' with
   | T_operator (TC_list l) -> ok l
-  | _ -> simple_fail "not a list"
+  | _ -> fail @@ Errors.not_a_x_type "list" t ()
 
 let get_t_set (t:type_value) : type_value result = match t.type_value' with
   | T_operator (TC_set s) -> ok s
-  | _ -> simple_fail "not a set"
+  | _ -> fail @@ Errors.not_a_x_type "set" t ()
 
 let get_t_key (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_key) -> ok ()
-  | _ -> simple_fail "not a key"
+  | _ -> fail @@ Errors.not_a_x_type "key" t ()
 
 let get_t_signature (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_signature) -> ok ()
-  | _ -> simple_fail "not a signature"
+  | _ -> fail @@ Errors.not_a_x_type "signature" t ()
 
 let get_t_key_hash (t:type_value) : unit result = match t.type_value' with
   | T_constant (TC_key_hash) -> ok ()
-  | _ -> simple_fail "not a key_hash"
+  | _ -> fail @@ Errors.not_a_x_type "key_hash" t ()
 
 let get_t_tuple (t:type_value) : type_value list result = match t.type_value' with
   | T_tuple lst -> ok lst
-  | _ -> simple_fail "not a tuple"
+  | _ -> fail @@ Errors.not_a_x_type "tuple" t ()
 
 let get_t_pair (t:type_value) : (type_value * type_value) result = match t.type_value' with
   | T_tuple lst ->
       let%bind () =
-        trace_strong (simple_error "not a pair") @@
+        trace_strong (Errors.not_a_x_type "pair (tuple with two elements)" t ()) @@
         Assert.assert_list_size lst 2 in
       ok List.(nth lst 0 , nth lst 1)
-  | _ -> simple_fail "not a tuple"
+  | _ -> fail @@ Errors.not_a_x_type "pair (tuple with two elements)" t ()
 
 let get_t_function (t:type_value) : (type_value * type_value) result = match t.type_value' with
   | T_arrow (a,r) -> ok (a,r)
-  | _ -> simple_fail "not a function"
+  | _ -> fail @@ Errors.not_a_x_type "function" t ()
 
 let get_t_sum (t:type_value) : type_value constructor_map result = match t.type_value' with
   | T_sum m -> ok m
-  | _ -> simple_fail "not a sum"
+  | _ -> fail @@ Errors.not_a_x_type "sum" t ()
 
 let get_t_record (t:type_value) : type_value label_map result = match t.type_value' with
   | T_record m -> ok m
-  | _ -> simple_fail "not a record type"
+  | _ -> fail @@ Errors.not_a_x_type "record" t ()
 
 let get_t_map (t:type_value) : (type_value * type_value) result =
   match t.type_value' with
   | T_operator (TC_map (k,v)) -> ok (k, v)
-  | _ -> simple_fail "get: not a map"
+  | _ -> fail @@ Errors.not_a_x_type "map" t ()
 
 let get_t_big_map (t:type_value) : (type_value * type_value) result =
   match t.type_value' with
   | T_operator (TC_big_map (k,v)) -> ok (k, v)
-  | _ -> simple_fail "get: not a big_map"
+  | _ -> fail @@ Errors.not_a_x_type "big_map" t ()
 
 let get_t_map_key : type_value -> type_value result = fun t ->
   let%bind (key , _) = get_t_map t in
@@ -303,5 +325,5 @@ let get_declaration_by_name : program -> string -> declaration result = fun p na
     match declaration with
     | Declaration_constant (d , _) -> d.name = Var.of_name name
   in
-  trace_option (simple_error "no declaration with given name") @@
+  trace_option (Errors.declaration_not_found name ()) @@
   List.find_opt aux @@ List.map Location.unwrap p
diff --git a/src/test/contracts/negative/id.mligo b/src/test/contracts/negative/id.mligo
new file mode 100644
index 000000000..d0817f270
--- /dev/null
+++ b/src/test/contracts/negative/id.mligo
@@ -0,0 +1,115 @@
+type id = int
+
+type id_details = {
+  owner: address;
+  controller: address;
+  profile: bytes;
+}
+
+(* The prices kept in storage can be changed by bakers, though they should only be
+   adjusted down over time, not up. *)
+type storage = (id, id_details) big_map * int * (tez * tez)
+
+(** Preliminary thoughts on ids:
+
+I very much like the simplicity of http://gurno.com/adam/mne/.
+5 three letter words means you have a 15 character identity, not actually more
+annoying than an IP address and a lot more memorable than the raw digits. This
+can be stored as a single integer which is then translated into the corresponding
+series of 5 words.
+
+I in general like the idea of having a 'skip' mechanism, but it does need to cost
+something so people don't eat up the address space. 256 ^ 5 means you have a lot
+of address space, but if people troll by skipping a lot that could be eaten up.
+Should probably do some napkin calculations for how expensive skipping needs to
+be to deter people from doing it just to chew up address space.
+*)
+
+let buy (parameter, storage: (bytes * address option) * storage) =
+  let void: unit = assert (amount = storage.2.0) in
+  let profile, initial_controller = parameter in
+  let identities, last_id, prices = storage in
+  let controller: address =
+    match initial_controller with
+    | Some addr -> addr
+    | None -> sender
+  in
+  let new_id: id = last_id + 1 in
+  let new_id_details: id_details = {
+    owner = sender ;
+    controller = controller ;
+    profile = profile ;
+  }
+  in
+  let updated_identities: (id, id_details) big_map =
+    Big_map.update new_id new_id_details identities
+  in
+  ([]: instruction), (updated_identities, new_id, prices)
+
+let update_owner (parameter, storage: (id * address) * storage) =
+  let id, new_owner = parameter in
+  let identities, last_id, prices = storage in
+  let current_id_details = Bip_map.find_opt id identities in
+  let is_allowed: bool =
+    if sender = current_id_details.owner
+    then true
+    else failwith "You are not the owner of the ID " ^ (string_of_int id)
+  in
+  let updated_id_details = {
+    owner = new_owner;
+    controller = current_id_details.controller;
+    profile = current_id_details.profile;
+  }
+  in
+  let updated_identities = Big_map.update id updated_id_details identities in
+  ([]: instruction), (updated_identities, last_id, prices)
+
+let update_details (parameter, storage: (id * bytes option * address option) * storage) =
+  let id, new_profile, new_controller = parameter in
+  let identities, last_id, prices = storage in
+  let current_id_details = Big_map.find_opt id identities in
+  let is_allowed: bool =
+    if
+      match current_id_details with
+      | Some id_details -> (sender = id_details.controller) || (sender = id_details.owner)
+      | None -> failwith ("No such ID " + id)
+    then true
+    else failwith ("You are not the owner or controller of the ID " ^ id)
+  in
+  let owner: address = current_id_details.owner in
+  let profile: bytes =
+    match new_profile with
+    | None -> (* Default *) current_id_details.profile
+    | Some new_profile -> new_profile
+  in
+  let controller: address =
+    match new_controller with
+    | None -> (* Default *) current_id_details.controller
+    | Some new_controller -> new_controller
+  in
+  let updated_id_details = {
+    owner = owner;
+    controller = controller;
+    profile = profile;
+  }
+  in
+  let updated_identities = Big_map.update id updated_id_details identities in
+  ([]: instruction), (updated_identities, last_id, prices)
+
+(* Let someone skip the next identity so nobody has to take one that's undesirable *)
+let skip (p,s: unit * storage) =
+  let void: unit = assert (amount = storage.2.1) in
+  let identities, last_id, prices = storage in
+  ([]: instruction), (identities, last_id + 1, prices)
+
+let whois_id (query, storage: id * storage) =
+  let identities, last_id, _ = storage in
+  let result: (unit -> id_details) =
+    let id_details: id_details =
+      begin
+      match Big_map.find_opt query identities with
+      | Some details -> details
+      | None -> failwith "This ID doesn't exist in the system."
+      end
+    in (fun (x: unit) -> id_details)
+  in ([result]: instruction), storage