bug#26624: 26.0.50; Generalized variable `buffer-local-value' does't restore local flag

[Philipp Stephani]

In *scratch*, evaluate:

(defvar foo-test-var nil)
(with-temp-buffer
  (list (list (buffer-local-value 'foo-test-var (current-buffer))
              (local-variable-p 'foo-test-var)
              (local-variable-if-set-p 'foo-test-var))
        (cl-letf (((buffer-local-value 'foo-test-var (current-buffer)) 123))
          (list (buffer-local-value 'foo-test-var (current-buffer))
                (local-variable-p 'foo-test-var)
                (local-variable-if-set-p 'foo-test-var)))
        (list (buffer-local-value 'foo-test-var (current-buffer))
              (local-variable-p 'foo-test-var)
              (local-variable-if-set-p 'foo-test-var))))

The result is:

((nil nil nil) (123 t t) (nil t t))

But expected is:

((nil nil nil) (123 t t) (nil nil nil))

i.e. the local flag of the variable should be reset.



In GNU Emacs 26.0.50 (build 19, x86_64-apple-darwin16.5.0, NS appkit-1504.82 
Version 10.12.4 (Build 16E195))
 of 2017-04-23 built on p
Repository revision: a1f93c1dfa53dbe007faa09ab0c6e913e86e3ffe
Windowing system distributor 'Apple', version 10.3.1504
Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.

Configured using:
 'configure --without-xml2 --with-modules --without-pop --with-mailutils
 --enable-checking --enable-check-lisp-object-type 'CFLAGS=-ggdb3 -O0'
 MAKEINFO=/usr/local/opt/texinfo/bin/makeinfo'

Configured features:
RSVG DBUS NOTIFY ACL GNUTLS ZLIB TOOLKIT_SCROLL_BARS NS MODULES

Important settings:
  value of $LANG: de_DE.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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message subr-x puny seq byte-opt gv
bytecomp byte-compile cconv cl-loaddefs cl-lib dired dired-loaddefs
format-spec rfc822 mml easymenu mml-sec password-cache epa derived epg
epg-config gnus-util rmail rmail-loaddefs mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel term/ns-win
ns-win ucs-normalize mule-util term/common-win tool-bar dnd fontset
image regexp-opt fringe tabulated-list replace newcomment text-mode
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow
isearch timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors 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 composite charscript case-table epa-hook jka-cmpr-hook
help simple abbrev obarray 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 dbusbind kqueue cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 203864 9733)
 (symbols 48 19974 1)
 (miscs 40 57 190)
 (strings 32 18048 4861)
 (string-bytes 1 589547)
 (vectors 16 34976)
 (vector-slots 8 701022 3277)
 (floats 8 52 66)
 (intervals 56 199 0)
 (buffers 976 11))