Warn instance variable `E`

It is not dumped, as it is a short alias for `:encoding`.

1 files changed, 7 insertions, 1 deletions

diff --git a/marshal.c b/marshal.c
index 5e0c30b54a..b6de65023c 100644
--- a/marshal.c
+++ b/marshal.c
@@ -576,7 +576,13 @@ w_obj_each(st_data_t key, st_data_t val, st_data_t a)
     struct w_ivar_arg *ivarg = (struct w_ivar_arg *)a;
     struct dump_call_arg *arg = ivarg->dump;
 
-    if (to_be_skipped_id(id)) return ST_CONTINUE;
+    if (to_be_skipped_id(id)) {
+        if (id == s_encoding_short) {
+            rb_warn("instance variable `E' on class %"PRIsVALUE" is not dumped",
+                    CLASS_OF(arg->obj));
+        }
+        return ST_CONTINUE;
+    }
     if (!ivarg->num_ivar) {
         rb_raise(rb_eRuntimeError, "instance variable added to %"PRIsVALUE" instance",
                  CLASS_OF(arg->obj));