raise instead of emulating Obj.magic

Author: zth

jscomp/frontend/ast_exp_extension.ml

@@ -27,14 +27,23 @@ let handle_extension e (self : Bs_ast_mapper.mapper)
     (({txt; loc}, payload) : Parsetree.extension) =
   match txt with
   | "todo" ->
-    Location.prerr_warning e.Parsetree.pexp_loc
-      (Bs_todo
-         (match Ast_payload.is_single_string payload with
-         | Some (s, _) -> Some s
-         | None -> None));
+    let todo_message =
+      match Ast_payload.is_single_string payload with
+      | Some (s, _) -> Some s
+      | None -> None
+    in
+    Location.prerr_warning e.Parsetree.pexp_loc (Bs_todo todo_message);
     Exp.apply ~loc
-      (Exp.ident ~loc {txt = Longident.parse "Obj.magic"; loc})
-      [(Nolabel, Exp.construct ~loc {txt = Longident.Lident "()"; loc} None)]
+      (Exp.ident ~loc {txt = Longident.parse "failwith"; loc})
+      [
+        ( Nolabel,
+          Exp.constant ~loc
+            (Pconst_string
+               ( (match todo_message with
+                 | None -> "todo"
+                 | Some msg -> msg),
+                 None )) );
+      ]
   | "ffi" -> Ast_exp_handle_external.handle_ffi ~loc ~payload
   | "bs.raw" | "raw" ->
     Ast_exp_handle_external.handle_raw ~kind:Raw_exp loc payload