All typer errors in ast_typed/misc.ml are covered it seems.

src/bin/expect_tests/typer_error_tests.ml

@@ -16,4 +16,10 @@ let%expect_test _ =
   run_ligo_bad [ "compile-contract" ; "../../test/contracts/negative/error_typer_5.mligo" ; "main" ] ;
   [%expect {| ligo: unbound type variable:  {"variable":"boolean","in":"- E[]\tT[] ]","did_you_mean":"bool"} |} ] ;
 
+  run_ligo_bad [ "compile-contract" ; "../../test/contracts/negative/error_typer_6.mligo" ; "main" ] ;
+  [%expect {| ligo: in file "error_typer_6.mligo", line 1, characters 30-64. different type constructors: Expected these two constant type constructors to be the same, but they're different {"a":"string","b":"bool"} |} ] ;
+
+  run_ligo_bad [ "compile-contract" ; "../../test/contracts/negative/error_typer_7.mligo" ; "main" ] ;
+  [%expect {| ligo: in file "error_typer_7.mligo", line 4, characters 17-56. records have different sizes: Expected these two types to be the same, but they're different (both are records, but with a different number of arguments) {"a":"record[b -> string , a -> int]","b":"record[c -> bool , b -> string , a -> int]"} |} ] ;
+
 

src/stages/ast_typed/misc.ml

@@ -56,7 +56,7 @@ module Errors = struct
 
   let different_types name a b () =
     let title () = name ^ " are different" in
-    let message () = "" in
+    let message () = "Expected these two types to be the same, but they're different" in
     let data = [
       ("a" , fun () -> Format.asprintf "%a" PP.type_value a) ;
       ("b" , fun () -> Format.asprintf "%a" PP.type_value b )
@@ -321,7 +321,7 @@ let rec assert_type_value_eq (a, b: (type_value * type_value)) : unit result = m
       | TC_big_map (ka,va), TC_big_map (kb,vb) -> ok @@ ([ka;va] ,[kb;vb]) 
       | _,_ -> fail @@ different_operators opa opb
       in
-    trace (different_types "constant sub-expression" a b)
+    trace (different_types "arguments to type operators" a b)
       @@ bind_list_iter (fun (a,b) -> assert_type_value_eq (a,b) )(List.combine lsta lstb)
   )
   | T_operator _, _ -> fail @@ different_kinds a b

src/test/contracts/negative/error_typer_6.mligo

@@ -0,0 +1,3 @@
+let foo : (int, string) map = (Map.literal [] : (int, bool) map)
+let main (p:int) (storage : int) =
+  (([] : operation list) , p)

src/test/contracts/negative/error_typer_7.mligo

@@ -0,0 +1,7 @@
+type toto = { a : int ; b : string }
+type tata = { a : int ; }
+
+let foo : tata = ({a = 1 ; b = "foo" ; c = true} : toto)
+
+let main (p:int) (storage : int) =
+  (([] : operation list) , p + foo.a)