Stop filetest ops from calling FETCH on parent op’s arg

This is a regression in 5.14.0.

Commit 6f1401dc made ops call get-magic before overloading, but it
ended up making filetest ops call get-magic on the topmost item of the
stack even if the filetest op was not going to use the stack (which
happens for ‘-r bareword’ and plain ‘-r’).

This would affect cases like:

  push @foo, $tied, -r;

1 files changed, 12 insertions, 1 deletions

diff --git a/t/op/filetest.t b/t/op/filetest.t
index a6d62ed320..08380d1c97 100644
--- a/t/op/filetest.t
+++ b/t/op/filetest.t
@@ -10,7 +10,7 @@ BEGIN {
 }
 
 use Config;
-plan(tests => 29 + 27*14);
+plan(tests => 30 + 27*14);
 
 ok( -d 'op' );
 ok( -f 'TEST' );
@@ -204,3 +204,14 @@ for my $op (split //, "rwxoRWXOezsfdlpSbctugkTMBAC") {
  push my @foo, "bar", -l baz;
  is $foo[0], "bar", '-l bareword does not corrupt the stack';
 }
+
+# File test ops should not call get-magic on the topmost SV on the stack if
+# it belongs to another op.
+{
+  my $w;
+  sub oon::TIESCALAR{bless[],'oon'}
+  sub oon::FETCH{$w++}
+  tie my $t, 'oon';
+  push my @a, $t, -t;
+  is $w, 1, 'file test does not call FETCH on stack item not its own';
+}