If backslash was the last symbol in a string literal the parsing error
occured. E.g. after such a line in pascal
code - "const baseDir = 'C:\';", - all following code was faced as string.

You can reproduce the problem this way:
> emacs -Q

C-x b 1 RET
write following text in a buffer "1":
"""
const baseDir = 'C:\';
var x: integer;
"""
M-x opascal-mode RET
C-r var RET
C-u C-x =

in *Help* window you can see the line:
  face                 font-lock-string-face
but must be:
  face                 font-lock-keyword-face​​


I put a patch to resolve the problem (see attachment to this emal message).


In GNU Emacs 24.5.1 (i686-pc-mingw32)
 of 2015-04-11 on LEG570
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/usr --host=i686-pc-mingw32'

Important settings:
  value of $LANG: RUS
  locale-coding-system: cp1251

Major mode: OPascal

Minor modes in effect:
  tooltip-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:
Mark saved where search started
End of buffer
Mark saved where search started

Char: v (118, #o166, #x76) point=18 of 31 (55%) column=0
Mark saved where search started

Char: v (118, #o166, #x76) point=19 of 32 (56%) column=0
Mark saved where search started


Load-path shadows:
None found.

Features:
(shadow sort gnus-util mail-extr emacsbug message format-spec rfc822 mml
mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev
gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util
mail-prsvr mail-utils misearch multi-isearch pp wid-edit cl-loaddefs
cl-lib descr-text help-fns help-mode easymenu crm thingatpt opascal
time-date tooltip electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel dos-w32 ls-lisp w32-common-fns disp-table w32-win w32-vars
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
lisp-mode prog-mode register page menu-bar rfn-eshadow timer select
scroll-bar mouse jit-lock font-lock syntax facemenu font-core frame cham
georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese hebrew greek romanian slovak czech european ethiopic
indian cyrillic chinese case-table epa-hook jka-cmpr-hook help simple
abbrev minibuffer 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 make-network-process
w32notify w32 multi-tty emacs)

Memory information:
((conses 8 83594 6035)
 (symbols 32 27992 0)
 (miscs 32 60 361)
 (strings 16 23831 3448)
 (string-bytes 1 560770)
 (vectors 8 10708)
 (vector-slots 4 406169 5190)
 (floats 8 62 676)
 (intervals 28 416 41)
 (buffers 508 14))