Better error message extension (v10.1) (#6057)

* better error message for extension point

* update CHANGELOG.md

Author: aspeddro

CHANGELOG.md

@@ -18,6 +18,10 @@
 #### :rocket: New Feature
 - Add support for toplevel `await` https://github.com/rescript-lang/rescript-compiler/pull/6054
 
+#### :nail_care: Polish
+
+- Better error message for extension point https://github.com/rescript-lang/rescript-compiler/pull/6057
+
 # 10.1.3
 
 #### :rocket: New Feature

jscomp/frontend/ast_exp_handle_external.ml

@@ -69,12 +69,23 @@ let handle_debugger loc (payload : Ast_payload.t) =
       Ast_external_mk.local_external_apply loc ~pval_prim:[ "#debugger" ]
         ~pval_type:(Typ.arrow Nolabel (Typ.any ()) (Ast_literal.type_unit ()))
         [ Ast_literal.val_unit ~loc () ]
-  | _ -> Location.raise_errorf ~loc "bs.debugger does not accept payload"
+  | _ ->
+      Location.raise_errorf ~loc "%%debugger extension doesn't accept arguments"
 
 let handle_raw ~kind loc payload =
   let is_function = ref false in
   match Ast_payload.raw_as_string_exp_exn ~kind ~is_function payload with
-  | None -> Location.raise_errorf ~loc "bs.raw can only be applied to a string"
+  | None -> (
+      match kind with
+      | Raw_re ->
+          Location.raise_errorf ~loc
+            "%%re extension can only be applied to a string"
+      | Raw_exp ->
+          Location.raise_errorf ~loc
+            "%%raw extension can only be applied to a string"
+      | Raw_program ->
+          Location.raise_errorf ~loc
+            "%%%%raw extension can only be applied to a string")
   | Some exp ->
       {
         exp with
@@ -99,4 +110,6 @@ let handle_raw_structure loc payload =
               ~pval_type:(Typ.arrow Nolabel (Typ.any ()) (Typ.any ()))
               [ exp ];
         }
-  | None -> Location.raise_errorf ~loc "bs.raw can only be applied to a string"
+  | None ->
+      Location.raise_errorf ~loc
+        "%%%%raw extension can only be applied to a string"