fix: Redundant type instantiation wrong when return expression

Changelog.md

@@ -4,6 +4,8 @@
 
 * motoko (`moc`)
 
+  * Fix the `M0223` warning check for redundant type instantiations to avoid false positives (#5605).
+
   * Use `self` parameter, not `Self` type, to enable contextual dot notation (#5574).
 
   * Enable parser recovery to gather more syntax errors at once (previously only enabled for `moc.js`) (#5589).

src/lang_utils/diag.ml

@@ -120,3 +120,7 @@ let flush_messages : 'a result -> 'a option = function
 let run r = match flush_messages r with
   | None -> exit 1
   | Some x -> x
+
+type save = messages
+let save_store s = !s
+let load_store s msgs = s := msgs

src/lang_utils/diag.mli

@@ -62,3 +62,7 @@ val is_error_free : msg_store -> bool
 val add_msg : msg_store -> message -> unit
 val add_msgs : msg_store -> messages -> unit
 val with_message_store : ?allow_errors:bool -> (msg_store -> 'a option) -> 'a result
+
+type save
+val save_store : msg_store -> save
+val load_store : msg_store -> save -> unit