bug#10255: 23.3.1 NT: UAC permission and network drive path problems

[Jari Aalto <jari.aalto@cante.net>]

Package: emacs
Version: 23.3.1
Severity: normal

TEST CASE

    - OS: Windows 7 64 bit
    - Log in as standard user
    - Start Emacs with "run as administrator"
    - Map remote host to a drive letter
    - Try accessing remote drive, like z:/ e.g. with
      C-x d <drive path>[TAB]

    This causes signallling a cryptic error

SUGGESTION

    Improve error condition checks, missing or non accessible location, and
    display more informative error message.

OUTPUT DATA

"GNU Emacs 23.3.1 (i386-mingw-nt6.1.7601) of 2011-03-10 on 3249CTO"

Debugger entered--Lisp error: (args-out-of-range "z:" 0 3)
  signal(args-out-of-range ("z:" 0 3))
  completion--some(#[(style) "\b	\236A@\n\v\f$\207" [style completion-styles-alist string table pred point] 5] (basic partial-completion emacs22))
  completion-try-completion("z:/" read-file-name-internal file-exists-p 3)
  completion--do-completion()
  minibuffer-complete()
  call-interactively(minibuffer-complete nil nil)
  completing-read("Dired (directory): " read-file-name-internal file-exists-p nil "c:\\cygwin\\home\\jaalto/" file-name-history "c:\\cygwin\\home\\jaalto/")
  read-file-name("Dired (directory): " nil "c:\\cygwin\\home\\jaalto/" nil)
  dired-read-dir-and-switches("")
  call-interactively(dired nil nil)