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[perl #132150] ... (yada-yada) parsing is inconsistent

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From:
l . mai @ web . de
Date:
September 23, 2017 11:40
Subject:
[perl #132150] ... (yada-yada) parsing is inconsistent
Message ID:
rt-4.0.24-11030-1506166789-282.132150-75-0@perl.org
# New Ticket Created by  l.mai@web.de 
# Please include the string:  [perl #132150]
# in the subject line of all future correspondence about this issue. 
# <URL: https://rt.perl.org/Ticket/Display.html?id=132150 >



This is a bug report for perl from l.mai@web.de,
generated with the help of perlbug 1.40 running under perl 5.26.0.


-----------------------------------------------------------------
[Please describe your issue here]

Perl parses '...' as 'die("Unimplemented")':

$ perl -MO=Deparse -e '...'
die 'Unimplemented';
-e syntax OK


But it only does this at the beginning of a statement:

$ perl -MO=Deparse -e '+ ...'
syntax error at -e line 1, near "+ ..."
-e had compilation errors.


However, '...' is not by itself a statement:

$ perl -MO=Deparse -e '... sub foo {}'
syntax error at -e line 1, near "... sub foo "
-e had compilation errors.


In fact, it's an expression:

$ perl -MO=Deparse -e '... . "hello"'
die('Unimplemented') . 'hello';
-e syntax OK

$ perl -MO=Deparse -e '... lt "hello"'
die('Unimplemented') lt 'hello';
-e syntax OK

$ perl -MO=Deparse -e '..., foo()'
die('Unimplemented'), foo();
-e syntax OK


However, it's a naughty expression that doesn't tell the parser that the next
token should be an operator:

$ perl -MO=Deparse -e '... + 0'
syntax error at -e line 1, near "... +"
-e had compilation errors.

Here '+ 0' is parsed as a unary + applied to 0. The syntax error occurs because
you can't have two terms in a row ('...', '+0') without an operator in between.

This is especially noticeable with '/':

$ perl -MO=Deparse -e '... / 1'
Search pattern not terminated at -e line 1.

$ perl -MO=Deparse -e '... / 1 /'
syntax error at -e line 1, near "... / 1 /"
-e had compilation errors.


For consistency, either '...' should be made a statement of its own, or it
should give operator context to the following token.

[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=low
---
Site configuration information for perl 5.26.0:

Configured by mauke at Fri Sep 22 13:28:36 CEST 2017.

Summary of my perl5 (revision 5 version 26 subversion 0) configuration:
   
  Platform:
    osname=linux
    osvers=4.9.41-1-lts
    archname=i686-linux
    uname='linux simplicio 4.9.41-1-lts #1 smp mon aug 7 17:57:02 cest 2017 i686 gnulinux '
    config_args=''
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=undef
    use64bitall=undef
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
    optimize='-O2 -march=native'
    cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='7.2.0'
    gccosandvers=''
    intsize=4
    longsize=4
    ptrsize=4
    doublesize=8
    byteorder=1234
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=12
    longdblkind=3
    ivtype='long'
    ivsize=4
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=4
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags ='-fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/i686-pc-linux-gnu/7.2.0/include-fixed /usr/lib /lib
    libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.26.so
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.26'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -march=native -L/usr/local/lib -fstack-protector-strong'


---
@INC for perl 5.26.0:
    /home/mauke/usr/lib/perl5/site_perl/5.26.0/i686-linux
    /home/mauke/usr/lib/perl5/site_perl/5.26.0
    /home/mauke/usr/lib/perl5/5.26.0/i686-linux
    /home/mauke/usr/lib/perl5/5.26.0

---
Environment for perl 5.26.0:
    HOME=/home/mauke
    LANG=en_US.UTF-8
    LANGUAGE=en_US
    LC_COLLATE=C
    LC_MONETARY=de_DE.UTF-8
    LC_TIME=de_DE.UTF-8
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/mauke/perl5/perlbrew/bin:/home/mauke/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl
    PERLBREW_BASHRC_VERSION=0.73
    PERLBREW_HOME=/home/mauke/.perlbrew
    PERLBREW_ROOT=/home/mauke/perl5/perlbrew
    PERL_BADLANG (unset)
    PERL_UNICODE=SAL
    SHELL=/bin/bash


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