bug#47391: 27.2; static list return from function and nconc

[Rajeev Narang via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

(defun fn () '(1 2))

(nconc (fn) '(3))
-> (1 2 3)

(nconc (fn) '(3))
-> (1 2 3 3) ? should be (1 2 3)

If this is not a bug, then hfy-invisible, hfy-face-to-style-i may need to be fixed.


In GNU Emacs 27.2 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.24)
 of 2021-03-19 built on hp
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: emacs-27
Windowing system distributor 'The X.Org Foundation', version 11.0.12010000
System Description: Debian GNU/Linux bullseye/sid

Recent messages:
fn
(1 2 3)
(1 2 3 3)
next-line: End of buffer [2 times]
Mark activated
next-line: End of buffer
Making completion list...
Quit
Mark activated
Making completion list...

Configured using:
 'configure --prefix=/home/rajeev/tmp/build/emacs'

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND GPM DBUS GSETTINGS GLIB NOTIFY
INOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT
LIBOTF XFT ZLIB TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS
LIBSYSTEMD JSON PDUMPER LCMS2 GMP

Important settings:
  value of $LC_TIME: en_GB.UTF-8
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  reveal-mode: t
  global-so-long-mode: t
  global-auto-revert-mode: t
  shell-dirtrack-mode: t
  midnight-mode: t
  display-time-mode: t
  tooltip-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  transient-mark-mode: t
  hs-minor-mode: t

Load-path shadows:
/home/rajeev/.config/emacs/elpa/map-3.0/map hides /home/rajeev/tmp/build/emacs/share/emacs/27.2/lisp/emacs-lisp/map

Features:
(shadow emacsbug dired-aux tabify man cal-move sh-script smie
executable smerge-mode diff vc-bzr vc-src vc-sccs vc-svn vc-cvs vc-rcs
vc-dir ewoc vc vc-dispatcher sort gnus-cite gnus-async gnus-bcklg
gnus-ml ob-ditaa ob-plantuml org-clock org-colview org-habit cl-print
debug misearch multi-isearch js eieio-opt speedbar sb-image ezimage
dframe hfy-cmap help-fns radix-tree htmlfontify htmlfontify-loaddefs
cus-edit cus-start cus-load cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs utf-7 nnml mm-archive
network-stream url-http url-gw nsm url-cache url-auth time-stamp
org-duration view mule-util face-remap edmacro kmacro server
cursor-sensor bbdb-gnus nnfolder pcase rx xt-mouse which-func imenu
timeclock spam spam-stat gnus-uu yenc semantic/util-modes
semantic/util semantic semantic/tag semantic/lex semantic/fw
mode-local cedet org-indent reveal mailalias bbdb-message mail-extr
ol-eww eww mm-url thingatpt url-queue ol-rmail ol-mhe ol-irc ol-info
ol-gnus nnir ol-docview doc-view jka-compr image-mode exif ol-bibtex
bibtex ol-bbdb ol-w3m icomplete so-long autorevert filenotify vc-git
diff-mode bbdb-anniv cl-extra tramp tramp-loaddefs trampver
tramp-integration files-x tramp-compat shell ls-lisp hideshow printing
ps-print ps-print-loaddefs ps-def lpr web-server
web-server-status-codes el/web midnight el/cron bbdb-mua backtrace
help-mode qp el/wthr el/av el/hass el/fin el/remote el/script
type-break cal-iso org-id lunar solar cal-dst holidays hol-loaddefs
el/calc el/loc term disp-table ehelp dirtrack dbus parsec plstore pp
gnutls gnus-delay gnus-draft gnus-agent gnus-srvr gnus-score
score-mode nnvirtual nntp gnus-cache gnus-msg nndraft nnmh
gnus-icalendar org-capture gnus-art mm-uu mml2015 mm-view mml-smime
smime dig icalendar sieve sieve-mode sieve-manage sasl sasl-anonymous
sasl-login sasl-plain sendmail time ox-odt rng-loc rng-uri rng-parse
rng-match rng-dt rng-util rng-pttrn nxml-parse nxml-ns nxml-enc xmltok
nxml-util ox-latex ox-icalendar ox-html table ox-ascii ox-publish ox
org-element avl-tree generator org-agenda org-refile org-crypt org ob
ob-tangle ob-ref ob-lob ob-table ob-exp org-macro org-footnote org-src
ob-comint org-pcomplete pcomplete comint ansi-color ring org-list
org-faces org-entities noutline outline easy-mmode org-version
ob-emacs-lisp ob-core ob-eval org-table ol org-keys org-compat advice
org-macs org-loaddefs find-func gnus-sum url url-proxy url-privacy
url-expand url-methods url-history mailcap shr url-cookie url-domsuf
url-util svg xml dom gnus-group gnus-undo gnus-start gnus-cloud nnimap
nnmail mail-source utf7 netrc nnoo parse-time iso8601 gnus-spec
gnus-int gnus-range message rmc puny dired dired-loaddefs format-spec
rfc822 mml mml-sec epa derived epg epg-config mm-decode mm-bodies
mm-encode mail-parse rfc2231 gmm-utils mailheader gnus-win gnus
nnheader gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums
text-property-search time-date mail-utils mm-util mail-prsvr wid-edit
el/org el/doc el/mail el/tools el/shell el/xmpp el/diary timer-list
el/timer el/util bbdb-com crm mailabbrev bbdb bbdb-site timezone
el/bbdb appt diary-lib diary-loaddefs cal-menu calendar cal-loaddefs
el/init wombat-theme info package easymenu browse-url url-handlers
url-parse auth-source cl-seq eieio eieio-core cl-macs eieio-loaddefs
password-cache json subr-x map url-vars seq byte-opt gv bytecomp
byte-compile cconv cl-loaddefs cl-lib tooltip eldoc electric uniquify
ediff-hook vc-hooks lisp-float-type mwheel term/x-win x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode elisp-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame minibuffer 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 charprop case-table
epa-hook jka-cmpr-hook help simple abbrev obarray 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 threads dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting move-toolbar
gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 684512 118274)
 (symbols 48 40819 5)
 (strings 32 175683 17540)
 (string-bytes 1 5739083)
 (vectors 16 77783)
 (vector-slots 8 1527654 184718)
 (floats 8 1239 1715)
 (intervals 56 41435 1244)
 (buffers 1000 118))