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Re: [perl #133143] Warning when list assignment RHS is a scalar

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Sawyer X
April 23, 2018 14:57
Re: [perl #133143] Warning when list assignment RHS is a scalar
Message ID:
Considering this is an established pattern for some developers and that
this can fairly easily be written as a Perl Critic policy I don't see
why this should warn.

On 04/23/2018 03:53 PM, Ed Avis (via RT) wrote:
> # New Ticket Created by  "Ed Avis" 
> # Please include the string:  [perl #133143]
> # in the subject line of all future correspondence about this issue. 
> # <URL: >
> This is a bug report for perl from,
> generated with the help of perlbug 1.40 running under perl 5.22.2.
> -----------------------------------------------------------------
> [Please describe your issue here]
> This is probably a mistake:
>     ($foo, $bar) = $baz;
> In my case it usually means that I wanted @{$baz} instead.
> For other programmers there might be some other reason.
> But surely it cannot be intentional.
> A compile-time warning should be given when an assignment statement
> has a list of two or more items on the LHS, and the RHS is a scalar
> variable expression that begins with a $ sign.  So for example
>     ($foo, $bar) = $h{$key};     # warns
>     (undef, $foo) = $$myref;     # warns
>     ($foo, $bar) = some_call();  # no warning: does not begin $
>     ($foo) = $whatever;          # no warning: odd, but OK
>     ($foo, $bar) = $x ? 1 : 2;   # no warning: out of scope for this bug
> [Please do not change anything below this line]
> -----------------------------------------------------------------
> ---
> Flags:
>     category=core
>     severity=wishlist
> ---
> Site configuration information for perl 5.22.2:
> Configured by Red Hat, Inc. at Fri Nov  4 14:35:02 UTC 2016.
> Summary of my perl5 (revision 5 version 22 subversion 2) configuration:
>   Platform:
>     osname=linux, osvers=4.7.9-200.fc24.x86_64, archname=x86_64-linux-thread-multi
>     uname='linux 4.7.9-200.fc24.x86_64 #1 smp thu oct 20 14:26:16 utc 2016 x86_64 x86_64 x86_64 gnulinux '
>     config_args='-des -Doptimize=none -Dccflags=-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches  -m64 -mtune=generic -Dldflags=-Wl,-z,relro  -Dccdlflags=-Wl,--enable-new-dtags -Wl,-z,relro  -Dlddlflags=-shared -Wl,-z,relro  -Dshrpdir=/usr/lib64 -DDEBUGGING=-g -Dversion=5.22.2 -Dmyhostname=localhost -Dperladmin=root@localhost -Dcc=gcc -Dcf_by=Red Hat, Inc. -Dprefix=/usr -Dvendorprefix=/usr -Dsiteprefix=/usr/local -Dsitelib=/usr/local/share/perl5 -Dsitearch=/usr/local/lib64/perl5 -Dprivlib=/usr/share/perl5 -Dvendorlib=/usr/share/perl5/vendor_perl -Darchlib=/usr/lib64/perl5 -Dvendorarch=/usr/lib64/perl5/vendor_perl -Darchname=x86_64-linux-thread-multi -Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Duseshrplib -Dusethreads -Duseithreads -Dusedtrace=/usr/bin/dtrace -Duselargefiles -Dd_semctl_semun -Di_db -Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio -Dinstallu
>  srbinperl=n -Ubincompat5005 -Uversiononly -Dpager=/usr/bin/less -isr -Dd_gethostent_r_proto -Ud_endhostent_r_proto -Ud_sethostent_r_proto -Ud_endprotoent_r_proto -Ud_setprotoent_r_proto -Ud_endservent_r_proto -Ud_setservent_r_proto -Dscriptdir=/usr/bin -Dusesitecustomize'
>     hint=recommended, useposix=true, d_sigaction=define
>     useithreads=define, usemultiplicity=define
>     use64bitint=define, use64bitall=define, uselongdouble=undef
>     usemymalloc=n, bincompat5005=undef
>   Compiler:
>     cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -fwrapv -fno-strict-aliasing -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64',
>     optimize='  -g',
>     cppflags='-D_REENTRANT -D_GNU_SOURCE -O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4 -grecord-gcc-switches -m64 -mtune=generic -fwrapv -fno-strict-aliasing -I/usr/local/include'
>     ccversion='', gccversion='5.3.1 20160406 (Red Hat 5.3.1-6)', 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='gcc', ldflags ='-Wl,-z,relro  -fstack-protector-strong -L/usr/local/lib'
>     libpth=/usr/local/lib64 /lib64 /usr/lib64 /usr/local/lib /usr/lib /lib/../lib64 /usr/lib/../lib64 /lib
>     libs=-lpthread -lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
>     perllibs=-lpthread -lresolv -lnsl -ldl -lm -lcrypt -lutil -lc
>, so=so, useshrplib=true,
>     gnulibc_version='2.22'
>   Dynamic Linking:
>     dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,--enable-new-dtags -Wl,-z,relro '
>     cccdlflags='-fPIC', lddlflags='-shared -Wl,-z,relro  -L/usr/local/lib -fstack-protector-strong'
> Locally applied patches:
>     Fedora Patch1: Removes date check, Fedora/RHEL specific
>     Fedora Patch3: support for libdir64
>     Fedora Patch4: use libresolv instead of libbind
>     Fedora Patch5: USE_MM_LD_RUN_PATH
>     Fedora Patch6: Skip hostname tests, due to builders not being network capable
>     Fedora Patch7: Dont run one io test due to random builder failures
>     Fedora Patch15: Define SONAME for
>     Fedora Patch16: Install to -Dshrpdir value
>     Fedora Patch22: Document Math::BigInt::CalcEmu requires Math::BigInt (CPAN RT#85015)
>     Fedora Patch26: Make *DBM_File desctructors thread-safe (RT#61912)
>     Fedora Patch27: Make PadlistNAMES() lvalue again (CPAN RT#101063)
>     Fedora Patch28: Make magic vtable writable as a work-around for Coro (CPAN RT#101063)
>     Fedora Patch29: Fix duplicating PerlIO::encoding when spawning threads (RT#31923)
>     Fedora Patch30: Do not let XSLoader load relative paths (CVE-2016-6185)
>     Fedora Patch31: Avoid loading optional modules from default . (CVE-2016-1238)
>     Fedora Patch32: Fix a crash in lexical scope warnings (RT#128597)
>     Fedora Patch33: Do not mangle errno from failed socket calls (RT#128316)
>     Fedora Patch34: Fix crash in "evalbytes S" (RT#129196)
>     Fedora Patch35: Fix crash in "evalbytes S" (RT#129196)
>     Fedora Patch36: Fix crash in "evalbytes S" (RT#129196)
>     Fedora Patch37: Fix crash in splice (RT#129164, RT#129166, RT#129167)
>     Fedora Patch38: Fix string overrun in Perl_gv_fetchmethod_pvn_flags (RT#129267)
>     Fedora Patch39: Fix string overrun in Perl_gv_fetchmethod_pvn_flags (RT#129267)
>     Fedora Patch40: Fix string overrun in Perl_gv_fetchmethod_pvn_flags (RT#129267)
>     Fedora Patch41: Fix string overrun in Perl_gv_fetchmethod_pvn_flags (RT#129267)
>     Fedora Patch42: Fix string overrun in Perl_gv_fetchmethod_pvn_flags (RT#129267)
>     Fedora Patch43: Fix crash when matching UTF-8 string with non-UTF-8 substrings (RT#129350)
>     Fedora Patch44: Fix parsing perl options in shell bang line (RT#129336)
>     Fedora Patch45: Fix firstchar bitmap under UTF-8 with prefix optimization (RT#129950)
>     Fedora Patch46: Avoid infinite loop in h2xs tool if enum and type have the same name (RT130001)
>     Fedora Patch47: Fix stack handling when calling chdir without an argument (RT#129130)
>     Fedora Patch200: Link XS modules to with EU::CBuilder on Linux
>     Fedora Patch201: Link XS modules to with EU::MM on Linux
> ---
> @INC for perl 5.22.2:
>     /home/eda/lib64/perl5/
>     /usr/local/lib64/perl5
>     /usr/local/share/perl5
>     /usr/lib64/perl5/vendor_perl
>     /usr/share/perl5/vendor_perl
>     /usr/lib64/perl5
>     /usr/share/perl5
> ---
> Environment for perl 5.22.2:
>     HOME=/home/eda
>     LANG=en_GB.UTF-8
>     LANGUAGE (unset)
>     LC_CTYPE=en_GB.UTF-8
>     LC_NUMERIC=en_GB.UTF-8
>     LC_TIME=en_GB.UTF-8
>     LD_LIBRARY_PATH (unset)
>     LOGDIR (unset)
>     PATH=/home/eda/bin:/home/eda/bin:/usr/local/bin:/usr/bin:/sbin:/usr/sbin:/sbin:/usr/sbin
>     PERL5LIB=/home/eda/lib64/perl5/
>     PERL_BADLANG (unset)
>     SHELL=/bin/bash

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