remove the spellcheck bolierplate, add a hint for missing type rec …

…in napkin

jscomp/super_errors/super_typetexp.ml

@@ -9,51 +9,33 @@ open Ctype *)
 open Format
 open Printtyp
 
-(* taken from https://github.com/BuckleScript/ocaml/blob/d4144647d1bf9bc7dc3aadc24c25a7efa3a67915/typing/typetexp.ml#L869 *)
-let spellcheck ppf fold env lid =
-  let cutoff =
-    match String.length (Longident.last lid) with
-      | 1 | 2 -> 0
-      | 3 | 4 -> 1
-      | 5 | 6 -> 2
-      | _ -> 3
-  in
-  let compare target head acc =
-    let (best_choice, best_dist) = acc in
-    match Misc.edit_distance target head cutoff with
-      | None -> (best_choice, best_dist)
-      | Some dist ->
-        let choice =
-          if dist < best_dist then [head]
-          else if dist = best_dist then head :: best_choice
-          else best_choice in
-        (choice, min dist best_dist)
-  in
-  let init = ([], max_int) in
-  let handle (choice, _dist) =
-    match List.rev choice with
-      | [] -> ()
-      | last :: rev_rest ->
-        (* the modified part *)
-        fprintf ppf "@[<v 2>@,@,@{<info>Hint: Did you mean %s%s%s?@}@]"
-          (String.concat ", " (List.rev rev_rest))
-          (if rev_rest = [] then "" else " or ")
-          last
-  in
+let did_you_mean ppf choices : bool = 
   (* flush now to get the error report early, in the (unheard of) case
      where the linear search would take a bit of time; in the worst
      case, the user has seen the error, she can interrupt the process
      before the spell-checking terminates. *)
-  fprintf ppf "@?";
+  fprintf ppf "@?";  
+  match choices () with   
+  | [] -> false
+  | last :: rev_rest ->
+    fprintf ppf "@[<v 2>@,@,@{<info>Hint: Did you mean %s%s%s?@}@]"
+      (String.concat ", " (List.rev rev_rest))
+      (if rev_rest = [] then "" else " or ")
+      last;
+    true  
+
+
+let spellcheck ppf fold env lid =
+  let choices path name : string list = 
+    let env : string list = fold (fun x  _ _ xs -> x ::xs ) path env []   in
+    Misc.spellcheck env name in 
   match lid with
-    | Longident.Lapply _ -> ()
+    | Longident.Lapply _ -> false
     | Longident.Lident s ->
-      handle (fold (compare s) None env init)
+      did_you_mean ppf (fun _ -> choices None s)
     | Longident.Ldot (r, s) ->
-      handle (fold (compare s) (Some r) env init)
+      did_you_mean ppf (fun _ -> choices (Some r) s)
 
-let spellcheck ppf fold =
-  spellcheck ppf (fun f -> fold (fun s _ _ x -> f s x))
 
 let fold_descr fold get_name f = fold (fun descr acc -> f (get_name descr) acc)
 let fold_constructors x  = fold_descr Env.fold_constructors (fun d -> d.cstr_name) x
@@ -64,8 +46,10 @@ let fold_labels x = fold_descr Env.fold_labels (fun d -> d.lbl_name) x
 let report_error env ppf = function
   | Typetexp.Unbound_type_constructor lid ->
     (* modified *)
-    fprintf ppf "This type constructor's parameter, `%a`, can't be found. Is it a typo?" longident lid;
-    spellcheck ppf Env.fold_types env lid;
+    fprintf ppf "@[<v>This type constructor, `%a`, can't be found.@ " longident lid;
+    let has_candidate = spellcheck ppf Env.fold_types env lid in
+    if !Js_config.napkin && not has_candidate then 
+      fprintf ppf "For recursive type declaration, you may forget rec in `type rec` ?@]"
   | Unbound_value lid ->
       (* modified *)
       begin
@@ -76,7 +60,7 @@ let report_error env ppf = function
             Printtyp.longident outer;
         | other_ident -> fprintf ppf "The value %a can't be found" Printtyp.longident other_ident
       end;
-      spellcheck ppf Env.fold_values env lid;
+      spellcheck ppf Env.fold_values env lid |> ignore
   | Unbound_module lid ->
       (* modified *)
       begin match lid with
@@ -103,7 +87,7 @@ let report_error env ppf = function
             longident lid
         end
       end;
-      spellcheck ppf Env.fold_modules env lid
+      spellcheck ppf Env.fold_modules env lid |> ignore
   | Unbound_constructor lid ->
       (* modified *)
       fprintf ppf "@[<v>\