disabling bareword filehandles erroneously forbids package method calls

[ilmari]

Description

When the bareworld_filehandles feature is disabled (e.g. under use v5.35;), package method calls are also forbidden where a bareword filehandle would be.

Steps to Reproduce

$ perl -le 'no feature "bareword_filehandles"; sub foo { "foo" } print main->foo'
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at -e line 1.
Execution of -e aborted due to compilation errors.

It seems to be interpreting the bareword const op under the entersub as a bareword filehandle, even though that's actually the argument to method_named:

$ perl -MO=Concise -e 'no feature "bareword_filehandles"; sub foo { "foo" } print main->foo'
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at -e line 1.
-e had compilation errors.
9  <@> leave[1 ref] KP/REFC ->(end)
1     <0> enter ->2
2     <;> nextstate(main 4 -e:1) :us,*,&,{,$,fea=6 ->3
8     <@> print K ->9
3        <0> pushmark ->4
7        <1> entersub[t1] KRS/TARG,STRICT ->8
4           <0> pushmark ->5
5           <$> const(PV "main") s/BARE ->6
6           <.> method_named(PV "foo") ->7

Expected behavior

Same as with the feature enabled:

$ perl -le 'sub foo { "foo" } print main->foo'
foo

Perl configuration

Summary of my perl5 (revision 5 version 35 subversion 10) configuration:
   
  Platform:
    osname=linux
    osvers=5.10.0-12-amd64
    archname=x86_64-linux
    uname='linux ilmari-thinkpad 5.10.0-12-amd64 #1 smp debian 5.10.103-1 (2022-03-07) x86_64 gnulinux '
    config_args='-de -Dprefix=/home/ilmari/perl5/perlbrew/perls/35.10 -Duseshrplib -Dman1dir=none -Dman3dir=none -Dusedevel -Aeval:scriptdir=/home/ilmari/perl5/perlbrew/perls/35.10/bin'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O2'
    cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='10.2.1 20210110'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib
    libs=-lpthread -lnsl -lgdbm -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.31.so
    so=so
    useshrplib=true
    libperl=libperl.so
    gnulibc_version='2.31'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E -Wl,-rpath,/home/ilmari/perl5/perlbrew/perls/35.10/lib/5.35.10/x86_64-linux/CORE'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_DEVEL
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under linux
  Compiled at Mar 24 2022 20:23:54
  %ENV:
    PERL5LIB="/home/ilmari/.perlbrew/libs/35.10@std/lib/perl5"
    PERLBREW_HOME="/home/ilmari/.perlbrew"
    PERLBREW_LIB="std"
    PERLBREW_MANPATH="/home/ilmari/.perlbrew/libs/35.10@std/man:/home/ilmari/perl5/perlbrew/perls/35.10/man"
    PERLBREW_PATH="/home/ilmari/.perlbrew/libs/35.10@std/bin:/home/ilmari/perl5/perlbrew/bin:/home/ilmari/perl5/perlbrew/perls/35.10/bin"
    PERLBREW_PERL="35.10"
    PERLBREW_ROOT="/home/ilmari/perl5/perlbrew"
    PERLBREW_SHELLRC_VERSION="0.82"
    PERLBREW_VERSION="0.91"
    PERL_LOCAL_LIB_ROOT="/home/ilmari/.perlbrew/libs/35.10@std"
    PERL_MB_OPT="--install_base /home/ilmari/.perlbrew/libs/35.10@std"
    PERL_MM_OPT="INSTALL_BASE=/home/ilmari/.perlbrew/libs/35.10@std"
  @INC:
    /home/ilmari/.perlbrew/libs/35.10@std/lib/perl5/x86_64-linux
    /home/ilmari/.perlbrew/libs/35.10@std/lib/perl5
    /home/ilmari/perl5/perlbrew/perls/35.10/lib/site_perl/5.35.10/x86_64-linux
    /home/ilmari/perl5/perlbrew/perls/35.10/lib/site_perl/5.35.10
    /home/ilmari/perl5/perlbrew/perls/35.10/lib/5.35.10/x86_64-linux
    /home/ilmari/perl5/perlbrew/perls/35.10/lib/5.35.10

[ilmari]

Here are some tests that demonstrate the issue:

diff --git a/t/lib/feature/bareword_filehandles b/t/lib/feature/bareword_filehandles
index a3604770d4..fba6a59927 100644
--- a/t/lib/feature/bareword_filehandles
+++ b/t/lib/feature/bareword_filehandles
@@ -496,3 +496,15 @@ say foo;
 -x foo();
 -x foo;
 EXPECT
+########
+# NAME method calls
+use feature "say";
+no feature "bareword_filehandles";
+sub foo {}
+print main->foo();
+print main->foo;
+say main->foo();
+say main->foo;
+-x main->foo();
+-x main->foo;
+EXPECT

Result:

ilmari@ilmari-thinkpad:~/src/perl/t (blead *$%)$ ./TEST ../lib/feature.t 
t/../lib/feature ... FILE: lib/feature/bareword_filehandles ; line 500
PROG: 
use feature "say";
no feature "bareword_filehandles";
sub foo { "" }
print main->foo();
print main->foo;
say main->foo();
say main->foo;
-x main->foo();
-x main->foo;
EXPECTED:

GOT:
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 4.
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 5.
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 6.
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 7.
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 8.
Bareword filehandle "main" not allowed under 'no feature "bareword_filehandles"' at - line 9.
Execution of - aborted due to compilation errors.
# Failed test 26 - method calls at lib/feature/bareword_filehandles line 500
#
# Note: 'run_multiple_progs' run has one or more failures
#        you can consider setting the environment variable
#        PERL_TEST_ABORT_FIRST_FAILURE=1 before running the test
#        to stop on the first error.
#
FAILED at test 26
Failed 1 test out of 1, 0.00% okay.
	../lib/feature.t

[ilmari]

@tonycoz any ideas?

[leonerd]

#19426 may be related

[rjbs]

Oof. We should turn bareword filehandles back on in the bundle for sure, right? I can't see why we wouldn't, at this point.

[leonerd]

Even if a bugfix turned up right now and was trivial and obviously-correct, I think we'd still feel rather nervous about deploying it directly for an RC1. It feels like this feature hasn't really had enough stress-testing yet, if this much of a showstopper turns up quite this late.

I agree with @rjbs - we should back it out and reënable it in the prevailing feature bundle.

[leonerd]

I've begun a PR here - #19705