put an experimental warning on lexical topic

diff --git a/lib/warnings.pm b/lib/warnings.pm
index cafda2d..c0c2cc9 100644 (file)
--- a/lib/warnings.pm
+++ b/lib/warnings.pm
@@ -230,11 +230,12 @@ our %Offsets = (
 
     'experimental'     => 102,
     'experimental::lexical_subs'=> 104,
-    'experimental::regex_sets'=> 106,
+    'experimental::lexical_topic'=> 106,
+    'experimental::regex_sets'=> 108,
   );
 
 our %Bits = (
-    'all'              => "\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x05", # [0..53]
+    'all'              => "\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x15", # [0..54]
     'ambiguous'                => "\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00", # [29]
     'bareword'         => "\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00", # [30]
     'closed'           => "\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [6]
@@ -244,9 +245,10 @@ our %Bits = (
     'digit'            => "\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00", # [31]
     'exec'             => "\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [7]
     'exiting'          => "\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [3]
-    'experimental'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x05", # [51..53]
+    'experimental'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x15", # [51..54]
     'experimental::lexical_subs'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01", # [52]
-    'experimental::regex_sets'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04", # [53]
+    'experimental::lexical_topic'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04", # [53]
+    'experimental::regex_sets'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10", # [54]
     'glob'             => "\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [4]
     'illegalproto'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00", # [47]
     'imprecision'      => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00", # [46]
@@ -291,7 +293,7 @@ our %Bits = (
   );
 
 our %DeadBits = (
-    'all'              => "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\x0a", # [0..53]
+    'all'              => "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\x2a", # [0..54]
     'ambiguous'                => "\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00", # [29]
     'bareword'         => "\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00", # [30]
     'closed'           => "\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [6]
@@ -301,9 +303,10 @@ our %DeadBits = (
     'digit'            => "\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00", # [31]
     'exec'             => "\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [7]
     'exiting'          => "\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [3]
-    'experimental'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x0a", # [51..53]
+    'experimental'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x2a", # [51..54]
     'experimental::lexical_subs'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02", # [52]
-    'experimental::regex_sets'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08", # [53]
+    'experimental::lexical_topic'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08", # [53]
+    'experimental::regex_sets'=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20", # [54]
     'glob'             => "\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [4]
     'illegalproto'     => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00", # [47]
     'imprecision'      => "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00", # [46]
@@ -348,8 +351,8 @@ our %DeadBits = (
   );
 
 $NONE     = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
-$DEFAULT  = "\x10\x01\x00\x00\x00\x50\x04\x00\x00\x00\x00\x00\x00\x05", # [2,52,53,4,22,23,25]
-$LAST_BIT = 108 ;
+$DEFAULT  = "\x10\x01\x00\x00\x00\x50\x04\x00\x00\x00\x00\x00\x00\x15", # [2,52..54,4,22,23,25]
+$LAST_BIT = 110 ;
 $BYTES    = 14 ;
 
 $All = "" ; vec($All, $Offsets{'all'}, 2) = 3 ;

diff --git a/op.c b/op.c
index 1d676c4..91b9d5d 100644 (file)
--- a/op.c
+++ b/op.c
@@ -578,6 +578,13 @@ Perl_allocmy(pTHX_ const char *const name, const STRLEN len, const U32 flags)
                              PL_parser->in_my == KEY_state ? "state" : "my"), flags & SVf_UTF8);
        }
     }
+    else if (len == 2 && name[1] == '_' && !is_our)
+       /* diag_listed_as: Use of my $_ is experimental */
+       Perl_ck_warner_d(aTHX_ packWARN(WARN_EXPERIMENTAL__LEXICAL_TOPIC),
+                             "Use of %s $_ is experimental",
+                              PL_parser->in_my == KEY_state
+                                ? "state"
+                                : "my");
 
     /* allocate a spare slot and store the name in that slot */
 

diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index 9443db3..eb7b69c 100644 (file)
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -35,7 +35,8 @@ This release reverts that change.
 
 =head1 Deprecations
 
-The premature deprecation of lexical $_ in 5.17.7 has been reverted.
+The deprecation of lexical C<$_> in 5.17.7 has been commuted.  The feature
+is now marked experimental.
 
 =head2 Deprecated pragma
 

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index 9ec4446..3a76c76 100644 (file)
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -5702,6 +5702,12 @@ old way has bad side effects.
 it already went past any symlink you are presumably trying to look for.
 The operation returned C<undef>.  Use a filename instead.
 
+=item Use of my $_ is experimental
+
+(S experimental::lexical_topic) Lexical $_ is an experimental feature and
+its behavior may change or even be removed in any future release of perl.
+See the explanation under L<perlvar/$_>.
+
 =item Use of %s on a handle without * is deprecated
 
 (D deprecated) You used C<tie>, C<tied> or C<untie> on a scalar but that scalar
@@ -5733,6 +5739,12 @@ C<$array[0+$ref]>.  This warning is not given for overloaded objects,
 however, because you can overload the numification and stringification
 operators and then you presumably know what you are doing.
 
+=item Use of state $_ is experimental
+
+(S experimental::lexical_topic) Lexical $_ is an experimental feature and
+its behavior may change or even be removed in any future release of perl.
+See the explanation under L<perlvar/$_>.
+
 =item Use of tainted arguments in %s is deprecated
 
 (W taint, deprecated) You have supplied C<system()> or C<exec()> with multiple

diff --git a/regen/warnings.pl b/regen/warnings.pl
index 93b26fe..94a9843 100644 (file)
--- a/regen/warnings.pl
+++ b/regen/warnings.pl
@@ -89,6 +89,8 @@ my $tree = {
                                     [ 5.017, DEFAULT_ON ],
                                 'experimental::regex_sets' =>
                                     [ 5.017, DEFAULT_ON ],
+                                'experimental::lexical_topic' =>
+                                    [ 5.017, DEFAULT_ON ],
                         }],
 
                 #'default'     => [ 5.008, DEFAULT_ON ],

diff --git a/t/lib/warnings/9uninit b/t/lib/warnings/9uninit
index fb9a487..f74b7e3 100644 (file)
--- a/t/lib/warnings/9uninit
+++ b/t/lib/warnings/9uninit
@@ -787,7 +787,7 @@ s/$m1/$g1/; undef $_;
 tr/x/y/;       undef $_;
 tr/x/y/r;      undef $_;
 
-
+my $_; 
 /y/;
 /$m1/;
 /$g1/;
@@ -820,6 +820,7 @@ undef $g1;
 $m1 = '$g1';
 $foo =~ s//$m1/ee;
 EXPECT
+Use of my $_ is experimental at - line 16.
 Use of uninitialized value $_ in pattern match (m//) at - line 5.
 Use of uninitialized value $m1 in regexp compilation at - line 6.
 Use of uninitialized value $_ in pattern match (m//) at - line 6.

diff --git a/t/lib/warnings/op b/t/lib/warnings/op
index 3e9ea41..c5cbbc3 100644 (file)
--- a/t/lib/warnings/op
+++ b/t/lib/warnings/op
@@ -1,5 +1,8 @@
   op.c         AOK
 
+     Use of my $_ is experimental
+       my $_ ;
+
      Found = in conditional, should be ==
        1 if $a = 1 ;
 
@@ -104,6 +107,17 @@
     
 __END__
 # op.c
+use warnings 'experimental::lexical_topic' ;
+my $_;
+CORE::state $_;
+no warnings 'experimental::lexical_topic' ;
+my $_;
+CORE::state $_;
+EXPECT
+Use of my $_ is experimental at - line 3.
+Use of state $_ is experimental at - line 4.
+########
+# op.c
 use warnings 'syntax' ;
 1 if $a = 1 ;
 1 if $a

diff --git a/warnings.h b/warnings.h
index 3133df0..d0bf710 100644 (file)
--- a/warnings.h
+++ b/warnings.h
@@ -91,7 +91,8 @@
 
 #define WARN_EXPERIMENTAL       51
 #define WARN_EXPERIMENTAL__LEXICAL_SUBS 52
-#define WARN_EXPERIMENTAL__REGEX_SETS 53
+#define WARN_EXPERIMENTAL__LEXICAL_TOPIC 53
+#define WARN_EXPERIMENTAL__REGEX_SETS 54
 
 #define WARNsize               14
 #define WARN_ALLstring         "\125\125\125\125\125\125\125\125\125\125\125\125\125\125"