Fix undef %Foo:: to update subclasses

This is something I think I broke with 80ebaca, which made sure
that isa linearisations were cached on subclasses after calls
to mro_isa_changed_in (so the data could be used to delete
isarev entries).

The result is that hv_undef, which calls mro_isa_changed_in before
deleting everything, was updating the subclasses’ isa caches while its
own @ISA was still visible.

1 files changed, 6 insertions, 1 deletions

diff --git a/hv.c b/hv.c
index e82b74f5df..b43523954a 100644
--- a/hv.c
+++ b/hv.c
@@ -1857,7 +1857,12 @@ Perl_hv_undef(pTHX_ HV *hv)
     xhv = (XPVHV*)SvANY(hv);
 
     if ((name = HvENAME_get(hv)) && !PL_dirty)
-        mro_isa_changed_in(hv);
+    {
+        /* Delete the @ISA element before calling mro_package_moved, so it
+           does not see it. */
+        (void)hv_delete(hv, "ISA", 3, G_DISCARD);
+        mro_package_moved(NULL, hv, NULL, name, HvENAMELEN_get(hv));
+    }
 
     hfreeentries(hv);
     if (name || (name = HvNAME(hv))) {