To reproduce: in emacs invoked with '-Q', in the Scratch buffer, insert the following code: (require 'cl-macs) (cl-flet ((fn ((min max)) (message "%d %d" min max))) (fn '(2 3))) The cl-flet form evaluates fine (e.g. with C-x C-e or C-M-x), which leads me to conclude that this construct is legal. However, attempting to instrument the form with Edebug (C-u C-M-x) results in an enormous backtrace starting with Debugger entered--Lisp error: (invalid-read-syntax "Expected" "lambda") If I get rid of the argument destructuring, Edebug works as expected. For example, I'm able to step through the following code with Edebug just fine: (cl-flet ((fn (min max) (message "%d %d" min max))) (fn 2 3)) => "2 3" I should be able to, for example, instrument the destructuring (buggy) cl-flet form, run through it with 'g', and see the same output. In GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.37, cairo version 1.16.0) of 2023-05-13, modified by Debian built on x86-ubc-01 Windowing system distributor 'The X.Org Foundation', version 11.0.12101007 System Description: Debian GNU/Linux 12 (bookworm) Configured using: 'configure --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/libexec --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --with-libsystemd --with-pop=yes --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/28.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/28.2/site-lisp:/usr/share/emacs/site-lisp --with-sound=alsa --without-gconf --with-mailutils --with-native-compilation --build x86_64-linux-gnu --prefix=/usr --sharedstatedir=/var/lib --libexecdir=/usr/libexec --localstatedir=/var/lib --infodir=/usr/share/info --mandir=/usr/share/man --with-libsystemd --with-pop=yes --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/28.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/28.2/site-lisp:/usr/share/emacs/site-lisp --with-sound=alsa --without-gconf --with-mailutils --with-native-compilation --with-cairo --with-x=yes --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2 -ffile-prefix-map=/build/emacs-mPr7Vr/emacs-28.2+1=. -fstack-protector-strong -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro' Configured features: ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB Important settings: value of $LANG: en_US.UTF-8 locale-coding-system: utf-8-unix Major mode: Lisp Interaction Minor modes in effect: global-git-commit-mode: t magit-auto-revert-mode: t shell-dirtrack-mode: t paredit-mode: t ws-butler-mode: t global-corfu-mode: t corfu-mode: t fido-vertical-mode: t icomplete-vertical-mode: t icomplete-mode: t fido-mode: t electric-pair-mode: t tooltip-mode: t global-eldoc-mode: t eldoc-mode: t show-paren-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 window-divider-mode: t auto-composition-mode: t auto-encryption-mode: t auto-compression-mode: t line-number-mode: t Load-path shadows: /home/demo/.emacs.d/elpa/transient-20230810.1716/transient hides /usr/share/emacs/28.2/lisp/transient /home/demo/.emacs.d/elpa/xref-1.6.3/xref hides /usr/share/emacs/28.2/lisp/progmodes/xref /home/demo/.emacs.d/elpa/project-0.9.8/project hides /usr/share/emacs/28.2/lisp/progmodes/project /home/demo/.emacs.d/elpa/eldoc-1.14.0/eldoc hides /usr/share/emacs/28.2/lisp/emacs-lisp/eldoc Features: (shadow sort mail-extr emacsbug sendmail edebug cl-print help-fns radix-tree org-element avl-tree generator ol-eww eww xdg url-queue mm-url ol-rmail ol-mhe ol-irc ol-info ol-gnus nnselect gnus-search eieio-opt speedbar ezimage dframe gnus-art mm-uu mml2015 mm-view mml-smime smime dig gnus-sum shr kinsoku svg dom gnus-group gnus-undo gnus-start gnus-dbus dbus xml gnus-cloud nnimap nnmail mail-source utf7 netrc nnoo parse-time gnus-spec gnus-int gnus-range gnus-win gnus nnheader ol-docview doc-view image-mode exif ol-bibtex ol-bbdb ol-w3m ol-doi org-link-doi org ob ob-tangle ob-ref ob-lob ob-table ob-exp org-macro org-footnote org-src ob-comint org-pcomplete org-list org-faces org-entities noutline outline org-version ob-emacs-lisp ob-core ob-eval org-table oc-basic bibtex iso8601 ol org-keys oc org-compat org-macs org-loaddefs cal-menu calendar cal-loaddefs ert ewoc debug backtrace find-func movie-data-table rater-table hash-helper csv-helper parse-csv cl-indent misearch multi-isearch magit-ediff git-rebase goto-addr vc-mtn vc-hg vc-git vc-bzr vc-src vc-sccs vc-svn vc-cvs vc-rcs vc vc-dispatcher bug-reference magit-extras face-remap magit-submodule magit-blame magit-stash magit-reflog magit-bisect magit-push magit-pull magit-fetch magit-clone magit-remote magit-commit magit-sequence magit-notes magit-worktree magit-tag magit-merge magit-branch magit-reset magit-files magit-refs magit-status magit magit-repos magit-apply magit-wip magit-log which-func imenu magit-diff smerge-mode diff git-commit log-edit message rmc puny rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util rmail rmail-loaddefs text-property-search time-date mm-decode mm-bodies mm-encode mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums mail-prsvr mailabbrev mail-utils gmm-utils mailheader pcvs-util add-log magit-core magit-autorevert autorevert filenotify magit-margin magit-transient magit-process with-editor shell pcomplete comint server ansi-color magit-mode transient magit-git magit-base magit-section format-spec cursor-sensor crm dash mule-util jka-compr ediff-ptch comp comp-cstr warnings rx cl-extra help-mode diff-mode easy-mmode ediff ediff-merg ediff-mult ediff-wind ediff-diff ediff-help ediff-init ediff-util dired-aux dired dired-loaddefs paredit ws-butler cus-edit cus-start wid-edit macrostep ring pp ffap thingatpt edmacro kmacro web-mode advice disp-table finder-inf wombat-theme corfu compat compat-29 icomplete elec-pair cus-load pcase info package browse-url url url-proxy url-privacy url-expand url-methods url-history url-cookie url-domsuf url-util mailcap 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 iso-transl tooltip eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type elisp-mode 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 lisp-mode prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu timer select scroll-bar mouse jit-lock font-lock syntax 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 emoji-zwj 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 dbusbind inotify lcms2 dynamic-setting system-font-setting font-render-setting cairo move-toolbar gtk x-toolkit x multi-tty make-network-process native-compile emacs) Memory information: ((conses 16 727871 424820) (symbols 48 38766 141) (strings 32 238349 577478) (string-bytes 1 6177910) (vectors 16 81263) (vector-slots 8 1667405 1015905) (floats 8 484 3251) (intervals 56 28782 5018) (buffers 992 35))