add the smartmatch feature

Perl · Feb 16, 2025 · ed1ae14 · ed1ae14
1 parent cd80cda
commit ed1ae14
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Showing 4 changed files with 108 additions and 48 deletions.
diff --git a/feature.h b/feature.h
diff --git a/lib/feature.pm b/lib/feature.pm
diff --git a/regen/feature.pl b/regen/feature.pl
@@ -49,6 +49,7 @@ BEGIN
     apostrophe_as_package_separator => 'apos_as_name_sep',
     any                     => 'any',
     all                     => 'all',
+    smartmatch              => 'smartmatch',
 );
 
 # NOTE: If a feature is ever enabled in a non-contiguous range of Perl
@@ -58,7 +59,7 @@ BEGIN
 # 5.odd implies the next 5.even, but an explicit 5.even can override it.
 
 # features bundles
-use constant V5_9_5 => sort qw{say state switch indirect multidimensional bareword_filehandles apostrophe_as_package_separator};
+use constant V5_9_5 => sort qw{say state switch indirect multidimensional bareword_filehandles apostrophe_as_package_separator smartmatch};
 use constant V5_11  => sort ( +V5_9_5, qw{unicode_strings} );
 use constant V5_15  => sort ( +V5_11, qw{unicode_eval evalbytes current_sub fc} );
 use constant V5_23  => sort ( +V5_15, qw{postderef_qq} );
@@ -72,7 +73,8 @@ BEGIN
 
 use constant V5_39  => sort ( +V5_37, qw{try} );
 use constant V5_41  => sort
-  grep {; $_ ne 'apostrophe_as_package_separator' }
+  grep {; $_ ne 'apostrophe_as_package_separator'
+       && $_ ne 'smartmatch' }
   ( +V5_39 );
 
 #
@@ -81,7 +83,7 @@ BEGIN
 my %feature_bundle = (
     all     => [ sort keys %feature ],
     default => [ qw{indirect multidimensional bareword_filehandles
-                    apostrophe_as_package_separator} ],
+                    apostrophe_as_package_separator smartmatch} ],
     # using 5.9.5 features bundle
     "5.9.5" => [ +V5_9_5 ],
     "5.10"  => [ +V5_9_5 ],
@@ -701,6 +703,23 @@ =head2 The 'state' feature
 
 This feature is available starting with Perl 5.10.
 
+=head2 The 'smartmatch' feature
+
+C<use feature 'smartmatch'> tells the compiler to enable the
+smartmatch operator C<~~>.  It is enabled by default, but can be
+turned off to disallow the C<~~> operator.
+
+This feature is disabled by default in the 5.42 feature bundle
+onwards:
+
+  $x ~~ $y; # fine
+  use v5.42;
+  $x ~~ $y; # error
+
+This has no effect on the implicit smartmatches done by C<when>.
+
+See L<perlop/"Smartmatch Operator"> for details.
+
 =head2 The 'switch' feature
 
 B<WARNING>: This feature is still experimental and the implementation may

diff --git a/t/lib/feature/api b/t/lib/feature/api
@@ -17,10 +17,10 @@ BEGIN {
    print "bundle: ", feature::feature_bundle(0) // "undef", "\n";
 }
 EXPECT
-default: apostrophe_as_package_separator bareword_filehandles indirect multidimensional
+default: apostrophe_as_package_separator bareword_filehandles indirect multidimensional smartmatch
 unicode_strings is not enabled
 bundle: default
-5.12: apostrophe_as_package_separator bareword_filehandles indirect multidimensional say state switch unicode_strings
+5.12: apostrophe_as_package_separator bareword_filehandles indirect multidimensional say smartmatch state switch unicode_strings
 unicode_strings is enabled
 bundle: 5.11
 ########
@@ -40,9 +40,9 @@ BEGIN {
    print "bundle: ", feature::feature_bundle(0) // "undef", "\n";
 }
 EXPECT
-no feature indirect: apostrophe_as_package_separator bareword_filehandles multidimensional
+no feature indirect: apostrophe_as_package_separator bareword_filehandles multidimensional smartmatch
 indirect is not enabled
 bundle: undef
-added unicode_strings: apostrophe_as_package_separator bareword_filehandles multidimensional unicode_strings
+added unicode_strings: apostrophe_as_package_separator bareword_filehandles multidimensional smartmatch unicode_strings
 unicode_strings is enabled
 bundle: undef