Fix *ISA = *glob_without_array

I broke this in 5.14 with commit 6624142a.

In trying to make *ISA = *Other::ISA work, I added logic to make
@Other::ISA’s existing magic now point to *ISA’s stash.  I skipped
that logic if *Other::ISA did not contain an array.  But in so
doing, I inadvertently skipped the call to mro_isa_changed_in at the
same time.

1 files changed, 11 insertions, 1 deletions

diff --git a/t/mro/basic.t b/t/mro/basic.t
index 9955b813b6..e1a4dbfddb 100644
--- a/t/mro/basic.t
+++ b/t/mro/basic.t
@@ -3,7 +3,7 @@
 use strict;
 use warnings;
 
-BEGIN { require q(./test.pl); } plan(tests => 52);
+BEGIN { require q(./test.pl); } plan(tests => 53);
 
 require mro;
 
@@ -328,3 +328,13 @@ is(eval { MRO_N->testfunc() }, 123);
     undef %Thwit::;
     ok !Thrext->isa('Sile'), 'undef %package:: updates subclasses';
 }
+
+{
+    # Obliterating @ISA via glob assignment
+    # Broken in 5.14.0; fixed in 5.17.2
+    @Gwythaint::ISA = "Fantastic::Creature";
+    undef *This_glob_haD_better_not_exist; # paranoia; must have no array
+    *Gwythaint::ISA = *This_glob_haD_better_not_exist;
+    ok !Gwythaint->isa("Fantastic::Creature"),
+       'obliterating @ISA via glob assignment';
+}