Revert change #31489.

That change was adding a hook to cope with the case when one was
undef'ining *ISA globs, in order to clean up correctly. However, this
broke the case where one was assiging an array ref to @ISA, which
is likely to be more common.
Conclusion: don't undef *ISA. (or more generally don't undef globs
that contain magical variables)
p4raw-link: @31489 on //depot/perl: 5be5c7a687aa37f2ea9dec7988eb57cad1f1ec24

p4raw-id: //depot/perl@31502

1 files changed, 1 insertions, 42 deletions

diff --git a/t/mro/basic.t b/t/mro/basic.t
index be7e3ddec0..e6792751ee 100644
--- a/t/mro/basic.t
+++ b/t/mro/basic.t
@@ -3,7 +3,7 @@
 use strict;
 use warnings;
 
-require q(./test.pl); plan(tests => 27);
+require q(./test.pl); plan(tests => 21);
 
 {
     package MRO_A;
@@ -147,44 +147,3 @@ is(eval { MRO_N->testfunc() }, 123);
     undef @ISACLEAR::ISA;
     ok(eq_array(mro::get_linear_isa('ISACLEAR'),[qw/ISACLEAR/]));
 }
-
-{
-    {
-        package ISACLEAR2;
-        our @ISA = qw/XX YY ZZ/;
-    }
-
-    # baseline
-    ok(eq_array(mro::get_linear_isa('ISACLEAR2'),[qw/ISACLEAR2 XX YY ZZ/]));
-
-    # delete @ISA
-    delete $ISACLEAR2::{ISA};
-    ok(eq_array(mro::get_linear_isa('ISACLEAR2'),[qw/ISACLEAR2/]));
-}
-
-# another destructive test, undef the ISA glob
-{
-    {
-        package ISACLEAR3;
-        our @ISA = qw/XX YY ZZ/;
-    }
-    # baseline
-    ok(eq_array(mro::get_linear_isa('ISACLEAR3'),[qw/ISACLEAR3 XX YY ZZ/]));
-
-    undef *ISACLEAR3::ISA;
-    ok(eq_array(mro::get_linear_isa('ISACLEAR3'),[qw/ISACLEAR3/]));
-}
-
-# This is how Class::Inner does it
-{
-    {
-        package ISACLEAR4;
-        our @ISA = qw/XX YY ZZ/;
-    }
-    # baseline
-    ok(eq_array(mro::get_linear_isa('ISACLEAR4'),[qw/ISACLEAR4 XX YY ZZ/]));
-
-    delete $ISACLEAR4::{ISA};
-    delete $::{ISACLEAR4::};
-    ok(eq_array(mro::get_linear_isa('ISACLEAR4'),[qw/ISACLEAR4/]));
-}