fix UTop.check_phrase

The [get_ocaml_error_message] was done after the [Btype.backtrack] in
case of error, causing the type to be displayed incorrectly.

src/lib/uTop.ml

@@ -307,16 +307,22 @@ let check_phrase phrase =
         } in
         let check_phrase = Parsetree.Ptop_def [top_def] in
         try
-          let _ = discard_formatters [Format.err_formatter] (fun () -> Toploop.execute_phrase false null check_phrase) in
+          let _ =
+            discard_formatters [Format.err_formatter] (fun () ->
+#if ocaml_version > (4, 00, 1)
+              Env.reset_cache_toplevel ();
+#endif
+              Toploop.execute_phrase false null check_phrase)
+          in
           (* The phrase is safe. *)
           Toploop.toplevel_env := env;
           Btype.backtrack snap;
           None
         with exn ->
           (* The phrase contains errors. *)
+          let loc, msg = get_ocaml_error_message exn in
           Toploop.toplevel_env := env;
           Btype.backtrack snap;
-          let loc, msg = get_ocaml_error_message exn in
           Some ([loc], msg)
 
 (* +-----------------------------------------------------------------+

src/lib/uTop_main.ml

@@ -538,6 +538,9 @@ let rec loop term =
         let pp = Format.formatter_of_buffer buffer in
         Format.pp_set_margin pp (LTerm.size term).cols;
         (try
+#if ocaml_version > (4, 00, 1)
+           Env.reset_cache_toplevel ();
+#endif
            ignore (Toploop.execute_phrase true pp phrase);
            (* Flush everything. *)
            Format.pp_print_flush Format.std_formatter ();
@@ -742,6 +745,7 @@ module Emacs(M : sig end) = struct
     (* Rewrite toplevel expressions. *)
     let phrase = rewrite phrase in
     try
+      Env.reset_cache_toplevel ();
       ignore (Toploop.execute_phrase true Format.std_formatter phrase);
       true
     with exn ->