bug#23515: 25.0.93; ruby-mode: regex ending with : fails to terminate

[John Ledbetter]

Description: in ruby-mode, ending a regex with a colon is not parsed as
a complete regular expression, which causes the rest of the buffer to be
font-locked as part of the regular expression.

To reproduce:

add the following to a ruby-mode buffer:

# start snippet
x = /http:/
def test
x
end
# end snippet

Note that all lines following the regular expression are font-locked as
part of the regex and do not indent correctly.


In GNU Emacs 25.0.93.1 (x86_64-apple-darwin15.4.0, NS appkit-1404.46 Version 
10.11.4 (Build 15E65))
of 2016-04-25 built on nix.local
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
'configure --disable-dependency-tracking --disable-silent-rules
--enable-locallisppath=/usr/local/share/emacs/site-lisp
--infodir=/usr/local/Cellar/emacs/25.0.93/share/info/emacs
--prefix=/usr/local/Cellar/emacs/25.0.93 --with-xml2 --without-dbus
--with-gnutls --with-rsvg --with-ns --disable-ns-self-contained'

Configured features:
JPEG RSVG NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
value of $LANG: en_US.UTF-8
locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
tooltip-mode: t
global-eldoc-mode: t
electric-indent-mode: t
mouse-wheel-mode: t
tool-bar-mode: t
menu-bar-mode: t
file-name-shadow-mode: t
global-font-lock-mode: t
font-lock-mode: t
blink-cursor-mode: t
auto-composition-mode: t
auto-encryption-mode: t
auto-compression-mode: t
line-number-mode: t
transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Making completion list...

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message dired format-spec rfc822 mml
mml-sec password-cache epg epg-config gnus-util mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail
rfc2047 rfc2045 ietf-drums mm-util help-fns help-mode easymenu
cl-loaddefs pcase cl-lib mail-prsvr mail-utils time-date mule-util
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel ns-win ucs-normalize term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list newcomment elisp-mode lisp-mode
prog-mode register page menu-bar rfn-eshadow timer select scroll-bar
mouse jit-lock font-lock syntax facemenu font-core frame cl-generic cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese charscript case-table epa-hook
jka-cmpr-hook help simple abbrev minibuffer cl-preloaded nadvice
loaddefs button faces cus-face macroexp files text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 195852 8262)
(symbols 48 19471 0)
(miscs 40 45 220)
(strings 32 14905 5648)
(string-bytes 1 431667)
(vectors 16 32813)
(vector-slots 8 647456 4536)
(floats 8 158 22)
(intervals 56 217 0)
(buffers 976 12))