-T "unreadable file" should set stat info consistently

This was mentioned in ticket #77388.  It turns out to be
related to #4253.

If the file cannot be opened, -T and -B on filenames set the last han-
dle to null and set the last stat type to stat, but leave the actual
stat buffer and success status as they were.

That means that stat(_) will continue to return the previous buffer,
but lstat(_) will no longer work.

This is another of those inconsistent cases where the internal stat
info is only partially set.

Originally, this code would set PL_laststatval (the success status) to
-1.  Commit 25988e07 (the patch in ticket #4253) intentionally changed
this to make -T _ less suprising on read-only files.

But the patch ended up affecting -T with an explicit file name, too.
It also only partially fixed things for -T _, because the last stat
type *was* still being set.

This commit changes it to set all the stat info, for explicit file
names, or no stat info, for _ (if the previous stat was with a
file name).

1 files changed, 9 insertions, 1 deletions

diff --git a/t/op/filetest.t b/t/op/filetest.t
index a0a3cedd37..cdd76ccbcd 100644
--- a/t/op/filetest.t
+++ b/t/op/filetest.t
@@ -10,7 +10,7 @@ BEGIN {
 }
 
 use Config;
-plan(tests => 46 + 27*14);
+plan(tests => 47 + 27*14);
 
 ok( -d 'op' );
 ok( -f 'TEST' );
@@ -320,6 +320,14 @@ SKIP: {
 is runperl(prog => '-T _', switches => ['-w'], stderr => 1), "",
   'no uninit warnings from -T with no preceding stat';
 
+SKIP: {
+    my $rand_file_name = 'filetest-' . rand =~ y/.//cdr;
+    if (-e $rand_file_name) { skip "File $rand_file_name exists", 1 }
+    stat 'test.pl';
+    -T $rand_file_name;
+    ok !stat _, '-T "nonexistent" resets stat success status';
+}
+
 # Unsuccessful filetests on filehandles should leave stat buffers in the
 # same state whether fatal warnings are on or off.
 {