debugger entered when debug-on-error = nil

[Drew Adams]

emacs -Q

M-: (setq 4 5)

The debugger is entered, even though `debug-on-error' is nil (by default):

Debugger entered--Lisp error: (wrong-type-argument symbolp 4)
  (setq 4 5)
  eval((setq 4 5))
  eval-expression((setq 4 5) nil)
  call-interactively(eval-expression)


In GNU Emacs 22.0.50.1 (i386-mingw-nt5.1.2600)
 of 2006-03-20 on W2ONE
X server distributor `Microsoft Corp.', version 5.1.2600
configured using `configure --with-gcc (3.4) --cflags -Id:/g/include'

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: ENU
  locale-coding-system: cp1252
  default-enable-multibyte-characters: t

Major mode: Debugger

Minor modes in effect:
  encoded-kbd-mode: t
  tooltip-mode: t
  auto-compression-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t

Recent input:
<down-mouse-1> <mouse-1> M-: ( s e t q SPC 4 SPC 5
) <return> <help-echo> <help-echo> <help-echo> <help-echo>
<help-echo> <help-echo> <help-echo> <menu-bar> <help-menu>
<report-emacs-bug>

Recent messages:
(C:\Emacs-22-2006-03-20\bin\emacs.exe -q --no-site-file --debug-init
C:\drews-lisp-20)
Loading encoded-kb...done
For information about the GNU Project and its goals, type C-h C-p.
Loading dired...
Loading regexp-opt...done
Loading dired...done
Loading debug...done
Entering debugger...
Loading help-mode...done
Loading emacsbug...done