bug#44482: 28.0.50; Confusing syntax warning in ELisp mode

[Eli Zaretskii]

  emacs -Q

  Insert into *scratch*:

  (insert (quux (foobar foo)
                this) "\n")

Observe that "\n" and the following parentheses are highlighted in
red -- the font-lock-warning-face.  Move the mouse pointer to the
highlighted text, obserbe the following tooltip:

  Hidden behind deeper element; move to another line?

It took me quite some time to understand what this tries to tell me.
The key problems with this seem to be:

  . "Hidden behind deeper element" is unclear, because neither
    "hidden" nor "deeper" have any immediately obvious relation to the
    code.
  . "Move to another line" is not clear because "another" is the wrong
    word here.  It is also not clear that the question indicates a
    suggestion.  This could perhaps be improved by using something
    like "suggest to re-indent to move it to the next line".

It would be nice to make this warning clearer.  (I personally think
the issue is so minor that it hardly justifies a warning, but if we do
show a warning, let's at least make it clear.)

In GNU Emacs 28.0.50 (build 741, i686-pc-mingw32)
 of 2020-11-06 built on HOME-C4E4A596F7
Repository revision: af6891629d48f348b6458384898a637cc7ce16e7
Repository branch: master
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure -C --prefix=/d/usr --with-wide-int --with-modules
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
XPM JPEG TIFF GIF PNG RSVG SOUND NOTIFY W32NOTIFY ACL GNUTLS LIBXML2
HARFBUZZ ZLIB TOOLKIT_SCROLL_BARS MODULES THREADS JSON PDUMPER LCMS2

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  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 rmc puny dired dired-loaddefs
rfc822 mml easymenu mml-sec epa derived epg epg-config gnus-util rmail
rmail-loaddefs auth-source cl-seq eieio eieio-core cl-macs
eieio-loaddefs password-cache json map text-property-search time-date
subr-x seq byte-opt gv bytecomp byte-compile cconv mm-decode mm-bodies
mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs
cl-lib sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
mwheel dos-w32 ls-lisp disp-table term/w32-win w32-win w32-vars
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 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 button
loaddefs faces cus-face macroexp files window text-properties overlay
sha1 md5 base64 format env code-pages mule custom widget
hashtable-print-readable backquote threads w32notify w32 lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 59084 10220)
 (symbols 48 7910 1)
 (strings 16 21720 2787)
 (string-bytes 1 631708)
 (vectors 16 12458)
 (vector-slots 8 167771 9582)
 (floats 8 24 41)
 (intervals 40 402 207)
 (buffers 888 11))