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[perl #80306] Quoting behaviour of => is too generous

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From:
Ed Avis
Date:
December 6, 2010 07:05
Subject:
[perl #80306] Quoting behaviour of => is too generous
Message ID:
rt-3.6.HEAD-13564-1291645699-1701.80306-75-0@perl.org
# New Ticket Created by  "Ed Avis" 
# Please include the string:  [perl #80306]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=80306 >


This is a bug report for perl from eda@waniasset.com,
generated with the help of perlbug 1.36 running under perl 5.10.0.


-----------------------------------------------------------------
[Please enter your report here]

It is well-documented that the => operator has the effect of quoting
its LHS.  But it goes even further than explicit quoting would, and
lets through some syntatically dubious constructs.

    use warnings;
    use strict;

    # This is a syntax error.
    my $a = 12 -aa;

    # So is this.
    my $a = 12 '-aa';

    # This, with explicit quoting, is a syntax error too.
    my %h = (12 '-aa' => 1);

    # But this sails through the parser and only errors at runtime.
    my %h = (12 -aa => 1);

It is a fairly common style for subroutines to take a hash of 'switches'
which begin with a - character, as foo(-width => 100, -height => 200).
So this failure to warn about a missing comma is quite likely to cause
head-scratching in practice.

I would suggest making the quoting implied by => be equivalent to that
done by '', so that if 'x' => y is a syntax error then x => y must be
too.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
This perlbug was built using Perl 5.10.0 in the Fedora build system.
It is being executed now by Perl 5.10.0 - Tue Oct 12 16:07:05 UTC 2010.

Site configuration information for perl 5.10.0:

Configured by Red Hat, Inc. at Tue Oct 12 16:07:05 UTC 2010.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.6.32-72.el6.bz634452.x86_64,
archname=x86_64-linux-thread-multi
    uname='linux x86-05.phx2.fedoraproject.org
2.6.32-72.el6.bz634452.x86_64 #1 smp fri sep 17 06:52:25 edt 2010 x86_64
x86_64 x86_64 gnulinux '
    config_args='-des -Doptimize=-O2 -g -pipe -Wall
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m64 -mtune=generic
-Accflags=-DPERL_USE_SAFE_PUTENV -Dccdlflags=-Wl,--enable-new-dtags
-Dversion=5.10.0 -Dmyhostname=localhost -Dperladmin=root@localhost
-Dcc=gcc -Dcf_by=Red Hat, Inc. -Dprefix=/usr -Dvendorprefix=/usr
-Dsiteprefix=/usr/local -Dprivlib=/usr/lib/perl5/5.10.0
-Dsitelib=/usr/local/lib/perl5/site_perl/5.10.0
-Dvendorlib=/usr/lib/perl5/vendor_perl/5.10.0
-Darchlib=/usr/lib64/perl5/5.10.0/x86_64-linux-thread-multi
-Dsitearch=/usr/local/lib64/perl5/site_perl/5.10.0/x86_64-linux-thread-m
ulti
-Dvendorarch=/usr/lib64/perl5/vendor_perl/5.10.0/x86_64-linux-thread-mul
ti -Dinc_version_list=none -Darchname=x86_64-linux-thread-multi
-Dlibpth=/usr/local/lib64 /lib64 /usr/lib64 -Duseshrplib -Dusethreads
-Duseithreads -Duselargefiles -Dd_dosuid -Dd_semctl_semun -Di_db
-Ui_ndbm -Di_gdbm -Di_shadow -Di_syslog -Dman3ext=3pm -Duseperlio
-Dinstallusrbinperl=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
-Dotherlibdirs=/usr/lib/perl5/site_perl'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='gcc', ccflags ='-D_REENTRANT -D_GNU_SOURCE
-DPERL_USE_SAFE_PUTENV -DDEBUGGING -fno-strict-aliasing -pipe
-I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
-I/usr/include/gdbm',
    optimize='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions
-fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DPERL_USE_SAFE_PUTENV
-DDEBUGGING -fno-strict-aliasing -pipe -I/usr/local/include
-I/usr/include/gdbm'
    ccversion='', gccversion='4.4.4 20100630 (Red Hat 4.4.4-10)',
gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='gcc', ldflags =''
    libpth=/usr/local/lib64 /lib64 /usr/lib64
    libs=-lresolv -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lpthread
-lc
    perllibs=-lresolv -lnsl -ldl -lm -lcrypt -lutil -lpthread -lc
    libc=, so=so, useshrplib=true, libperl=libperl.so
    gnulibc_version='2.11.2'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef,
ccdlflags='-Wl,--enable-new-dtags
-Wl,-rpath,/usr/lib64/perl5/5.10.0/x86_64-linux-thread-multi/CORE'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -pipe -Wall
-Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector
--param=ssp-buffer-size=4 -m64 -mtune=generic'

Locally applied patches:
    

---
@INC for perl 5.10.0:
    /home/eda/lib/perl5/5.10.0
    /home/eda/lib/perl5/site_perl/5.10.0
    /usr/local/lib64/perl5/site_perl/5.10.0/x86_64-linux-thread-multi
    /usr/local/lib/perl5/site_perl/5.10.0
    /usr/lib64/perl5/vendor_perl/5.10.0/x86_64-linux-thread-multi
    /usr/lib/perl5/vendor_perl/5.10.0
    /usr/lib/perl5/vendor_perl
    /usr/lib64/perl5/5.10.0/x86_64-linux-thread-multi
    /usr/lib/perl5/5.10.0
    /usr/lib/perl5/site_perl/5.10.0
    /usr/lib/perl5/site_perl
    .

---
Environment for perl 5.10.0:
    HOME=/home/eda
    LANG=en_GB.UTF-8
    LANGUAGE (unset)
    LC_COLLATE=C
    LC_CTYPE=en_GB.UTF-8
    LC_MESSAGES=en_GB.UTF-8
    LC_MONETARY=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/lib64/qt-3.3/bin:/usr/kerberos/sbi
n:/usr/kerberos/bin:/usr/lib64/ccache:/usr/local/bin:/bin:/usr/bin:/usr/
local/sbin:/usr/sbin:/sbin:/sbin:/usr/sbin:/home/eda/bin:/sbin:/usr/sbin
 
PERL5LIB=/home/eda/lib/perl5/5.10.0:/home/eda/lib/perl5/site_perl/5.10.0
    PERL_BADLANG (unset)
    SHELL=/bin/bash

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