bugfix: don't suggest privileged @-names in error messages (#4916)

Author: crusso

src/mo_def/syntax.ml

@@ -305,6 +305,15 @@ open Source
 let anon_id sort at = "@anon-" ^ sort ^ "-" ^ string_of_pos at.left
 let is_anon_id id = Lib.String.chop_prefix "@anon-" id.it <> None
 
+let is_privileged name =
+  String.length name > 0 && name.[0] = '@'
+
+let is_underscored name =
+  String.length name > 0 && name.[0] = '_'
+
+let is_scope name =
+  String.length name > 0 && name.[0] = '$'
+
 (* Types & Scopes *)
 
 let arity t =

src/mo_frontend/suggest.ml

@@ -1,5 +1,6 @@
 
 (* Suggestions *)
+open Mo_def
 open Mo_types
 open Mo_config
 open Type
@@ -9,6 +10,11 @@ let oneof sep lastsep ss =
   ((if rest <> [] then (String.concat sep rest) ^ lastsep else "") ^ last)
 
 let suggest_id desc id ids =
+  let ids =
+      List.filter (fun id ->
+        not (Syntax.is_privileged id))
+      ids
+  in
   if !Flags.ai_errors then
     Printf.sprintf
       "\nThe %s %s is not available. Try something else?"

src/mo_frontend/typing.ml

@@ -139,7 +139,7 @@ let display_obj fmt (s, fs) =
 let display_vals fmt vals =
   if !Flags.ai_errors then
     let tfs = T.Env.fold (fun x (t, _, _, _) acc ->
-      if x = "Prim" || (String.length x >= 0 && x.[0] = '@')
+      if x = "Prim" || Syntax.is_privileged x
       then acc
       else T.{lab = x; src = {depr = None; region = Source.no_region }; typ = t}::acc)
       vals []
@@ -163,7 +163,7 @@ let display_labs fmt labs =
 let display_typs fmt typs =
   if !Flags.ai_errors then
     let tfs = T.Env.fold (fun x c acc ->
-      if (String.length x >= 0 && (x.[0] = '@' || x.[0] = '$')) ||
+      if Syntax.(is_privileged x || is_scope x) ||
         T.(match Cons.kind c with
           | Def ([], Prim _)
           | Def ([], Any)
@@ -271,11 +271,7 @@ let emit_unused_warnings env =
   List.iter emit list
 
 let ignore_warning_for_id id =
-  if String.length id > 0 then
-    let prefix = String.get id 0 in
-    prefix = '_' || prefix = '@'
-  else
-    false
+  Syntax.(is_underscored id || is_privileged id)
 
 let detect_unused env inner_identifiers =
   if not env.pre && env.check_unused then

test/fail/ok/suggest-unprivileged.tc.ok

@@ -0,0 +1 @@
+suggest-unprivileged.mo:5.1-5.7: type error [M0057], unbound variable cycles

test/fail/ok/suggest-unprivileged.tc.ret.ok

@@ -0,0 +1 @@
+Return code 1

test/fail/suggest-unprivileged.mo

@@ -0,0 +1,5 @@
+import Prim "mo:⛔";
+
+// should not suggest @cycles because privileged
+
+cycles;