Make postfix dereferencing work without the postderef feature

The feature still exists, for compatibility with code that tries to enable
it, but it has no effect. The postderef_qq feature still exists, however.

8 files changed, 52 insertions, 66 deletions

diff --git a/feature.h b/feature.h
index dd98058256..a527e06e84 100644
--- a/feature.h
+++ b/feature.h
@@ -78,9 +78,8 @@
 
 #define FEATURE_POSTDEREF_IS_ENABLED \
     ( \
-	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_523 \
-     || (CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
-	 FEATURE_IS_ENABLED("postderef")) \
+	CURRENT_FEATURE_BUNDLE == FEATURE_BUNDLE_CUSTOM && \
+	 FEATURE_IS_ENABLED("postderef") \
     )
 
 #define FEATURE_ARYBASE_IS_ENABLED \
diff --git a/lib/feature.pm b/lib/feature.pm
index e2076ed8a6..ec9fff7a6d 100644
--- a/lib/feature.pm
+++ b/lib/feature.pm
@@ -29,7 +29,7 @@ our %feature_bundle = (
     "5.10"    => [qw(array_base say state switch)],
     "5.11"    => [qw(array_base say state switch unicode_strings)],
     "5.15"    => [qw(current_sub evalbytes fc say state switch unicode_eval unicode_strings)],
-    "5.23"    => [qw(current_sub evalbytes fc postderef postderef_qq say state switch unicode_eval unicode_strings)],
+    "5.23"    => [qw(current_sub evalbytes fc postderef_qq say state switch unicode_eval unicode_strings)],
     "all"     => [qw(array_base bitwise current_sub evalbytes fc lexical_subs postderef postderef_qq refaliasing say signatures state switch unicode_eval unicode_strings)],
     "default" => [qw(array_base)],
 );
@@ -260,26 +260,31 @@ This feature is available from Perl 5.18 onwards.
 
 =head2 The 'postderef' and 'postderef_qq' features
 
-The 'postderef' feature allows the use of L<postfix dereference
-syntax|perlref/Postfix Dereference Syntax>.  For example, it will make the
-following two statements equivalent:
+The 'postderef_qq' feature extends the applicability of L<postfix
+dereference syntax|perlref/Postfix Dereference Syntax> so that postfix array
+and scalar dereference are available in double-quotish interpolations. For
+example, it makes the following two statements equivalent:
 
-  my @x = @{ $h->{a} };
-  my @x = $h->{a}->@*;
+  my $s = "[@{ $h->{a} }]";
+  my $s = "[$h->{a}->@*]";
 
-The 'postderef_qq' feature extends this, for array and scalar dereference, to
-working inside of double-quotish interpolations.
-
-These features are available from Perl 5.20 onwards. In Perl 5.20 and 5.22,
-they were classed as experimental, and Perl emitted a warning for their
+This feature is available from Perl 5.20 onwards. In Perl 5.20 and 5.22, it
+was classed as experimental, and Perl emitted a warning for its
 usage, except when explicitly disabled:
 
   no warnings "experimental::postderef";
 
-As of Perl 5.24, use of these features no longer triggers a warning, though
+As of Perl 5.24, use of this feature no longer triggers a warning, though
 the C<experimental::postderef> warning category still exists (for
 compatibility with code that disables it).
 
+The 'postderef' feature was used in Perl 5.20 and Perl 5.22 to enable
+postfix dereference syntax outside double-quotish interpolations. In those
+versions, using it triggered the C<experimental::postderef> warning in the
+same way as the 'postderef_qq' feature did. As of Perl 5.24, this syntax is
+not only no longer experimental, but it is enabled for all Perl code,
+regardless of what feature declarations are in scope.
+
 =head2 The 'signatures' feature
 
 B<WARNING>: This feature is still experimental and the implementation may
@@ -375,7 +380,7 @@ The following feature bundles are available:
 
   :5.24     say state switch unicode_strings
             unicode_eval evalbytes current_sub fc
-            postderef postderef_qq
+            postderef_qq
 
 The C<:default> bundle represents the feature set that is enabled before
 any C<use feature> or C<no feature> declaration.
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index ce8768b285..ae26fbb327 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -52,9 +52,12 @@ you could use the C<bigint> pragma.
 
 =head2 Postfix dereferencing is no longer experimental
 
-Using the C<postderef> and C<postderef_qq> features no longer emits a warning.
-Existing code that disables that warning category will continue to work. The
-C<5.24> feature bundle now includes those features.
+Using the C<postderef> and C<postderef_qq> features no longer emits a
+warning. Existing code that disables the C<experimental::postderef> warning
+category that they previously used will continue to work. The C<postderef>
+feature has no effect; all Perl code can use postfix dereferencing,
+regardless of what feature declarations are in scope. The C<5.24> feature
+bundle now includes the C<postderef_qq> feature.
 
 =head1 Security
 
diff --git a/pod/perlref.pod b/pod/perlref.pod
index 8956be5750..e570b72cd3 100644
--- a/pod/perlref.pod
+++ b/pod/perlref.pod
@@ -758,7 +758,9 @@ For example:
     $r = [ 1, [ 2, 3 ], 4 ];
     $r->[1]->@*;  # equivalent to @{ $r->[1] }
 
-This syntax must be enabled with C<use feature 'postderef'>.
+In Perl 5.20 and 5.22, this syntax must be enabled with C<use feature
+'postderef'>. As of Perl 5.24, no feature declarations are required to make
+it available.
 
 Postfix dereference should work in all circumstances where block
 (circumfix) dereference worked, and should be entirely equivalent.  This
@@ -781,7 +783,7 @@ Glob elements can be extracted through the postfix dereferencing feature:
 
 Postfix array and scalar dereferencing I<can> be used in interpolating
 strings (double quotes or the C<qq> operator), but only if the
-additional C<postderef_qq> feature is enabled.
+C<postderef_qq> feature is enabled.
 
 =head2 Postfix Reference Slicing
 
@@ -800,7 +802,7 @@ Slices">, also behaves as expected:
 
 As with postfix array, postfix value slice dereferencing I<can> be used
 in interpolating strings (double quotes or the C<qq> operator), but only
-if the additional C<postderef_qq> L<feature> is enabled.
+if the C<postderef_qq> L<feature> is enabled.
 
 =head1 Assigning to References
 
diff --git a/regen/feature.pl b/regen/feature.pl
index a7b6e5de29..85ab2b034b 100755
--- a/regen/feature.pl
+++ b/regen/feature.pl
@@ -60,7 +60,7 @@ my %feature_bundle = (
     "5.21"   =>	[qw(say state switch unicode_strings unicode_eval
 		    evalbytes current_sub fc)],
     "5.23"   =>	[qw(say state switch unicode_strings unicode_eval
-		    evalbytes current_sub fc postderef postderef_qq)],
+		    evalbytes current_sub fc postderef_qq)],
 );
 
 # not actually used currently
@@ -575,26 +575,31 @@ This feature is available from Perl 5.18 onwards.
 
 =head2 The 'postderef' and 'postderef_qq' features
 
-The 'postderef' feature allows the use of L<postfix dereference
-syntax|perlref/Postfix Dereference Syntax>.  For example, it will make the
-following two statements equivalent:
+The 'postderef_qq' feature extends the applicability of L<postfix
+dereference syntax|perlref/Postfix Dereference Syntax> so that postfix array
+and scalar dereference are available in double-quotish interpolations. For
+example, it makes the following two statements equivalent:
 
-  my @x = @{ $h->{a} };
-  my @x = $h->{a}->@*;
+  my $s = "[@{ $h->{a} }]";
+  my $s = "[$h->{a}->@*]";
 
-The 'postderef_qq' feature extends this, for array and scalar dereference, to
-working inside of double-quotish interpolations.
-
-These features are available from Perl 5.20 onwards. In Perl 5.20 and 5.22,
-they were classed as experimental, and Perl emitted a warning for their
+This feature is available from Perl 5.20 onwards. In Perl 5.20 and 5.22, it
+was classed as experimental, and Perl emitted a warning for its
 usage, except when explicitly disabled:
 
   no warnings "experimental::postderef";
 
-As of Perl 5.24, use of these features no longer triggers a warning, though
+As of Perl 5.24, use of this feature no longer triggers a warning, though
 the C<experimental::postderef> warning category still exists (for
 compatibility with code that disables it).
 
+The 'postderef' feature was used in Perl 5.20 and Perl 5.22 to enable
+postfix dereference syntax outside double-quotish interpolations. In those
+versions, using it triggered the C<experimental::postderef> warning in the
+same way as the 'postderef_qq' feature did. As of Perl 5.24, this syntax is
+not only no longer experimental, but it is enabled for all Perl code,
+regardless of what feature declarations are in scope.
+
 =head2 The 'signatures' feature
 
 B<WARNING>: This feature is still experimental and the implementation may
diff --git a/t/lib/warnings/toke b/t/lib/warnings/toke
index d65467c218..ad0e74b7d1 100644
--- a/t/lib/warnings/toke
+++ b/t/lib/warnings/toke
@@ -1040,10 +1040,9 @@ EXPECT
 Useless use of \E at - line 3.
 ########
 # toke.c
-use feature 'postderef', 'postderef_qq';
+use feature 'postderef_qq';
 (\$_)->$*;
 "$_->$*";
-no warnings 'experimental::postderef';
 (\$_)->$*;
 "$_->$*";
 EXPECT
diff --git a/t/op/postfixderef.t b/t/op/postfixderef.t
index 920bc2db23..77988bfd3c 100644
--- a/t/op/postfixderef.t
+++ b/t/op/postfixderef.t
@@ -16,33 +16,7 @@ BEGIN {
 
 use strict qw(refs subs);
 
-plan(125);
-
-{
-    no warnings qw 'deprecated syntax';
-    eval '[]->$*';
-    like $@, qr/Can't call method/, '->$* outside of feature scope';
-    eval '[]->@*';
-    like $@, qr/syntax error/, '->@* outside of feature scope';
-    eval '[]->@[1]';
-    like $@, qr/syntax error/, '->@[ outside of feature scope';
-    eval '[]->@{1}';
-    like $@, qr/syntax error/, '->@{ outside of feature scope';
-    eval '[]->%*';
-    like $@, qr/syntax error/, '->%* outside of feature scope';
-    eval '[]->%[1]';
-    like $@, qr/syntax error/, '->%[ outside of feature scope';
-    eval '[]->%{1}';
-    like $@, qr/syntax error/, '->%{ outside of feature scope';
-    eval '[]->&*';
-    like $@, qr/syntax error/, '->&* outside of feature scope';
-    eval '[]->**';
-    like $@, qr/syntax error/, '->** outside of feature scope';
-    eval '[]->*{';
-    like $@, qr/syntax error/, '->*{ outside of feature scope';
-}
-
-use feature 'postderef';
+plan(115);
 
 {
     no strict 'refs';
diff --git a/toke.c b/toke.c
index 763baa5eb0..29ebbbfdcc 100644
--- a/toke.c
+++ b/toke.c
@@ -5133,12 +5133,11 @@ Perl_yylex(pTHX)
 	    else if (*s == '>') {
 		s++;
 		s = skipspace(s);
-		if (FEATURE_POSTDEREF_IS_ENABLED && (
-		    ((*s == '$' || *s == '&') && s[1] == '*')
+		if (((*s == '$' || *s == '&') && s[1] == '*')
 		  ||(*s == '$' && s[1] == '#' && s[2] == '*')
 		  ||((*s == '@' || *s == '%') && strchr("*[{", s[1]))
 		  ||(*s == '*' && (s[1] == '*' || s[1] == '{'))
-		 ))
+		 )
 		{
 		    PL_expect = XPOSTDEREF;
 		    TOKEN(ARROW);