Npostavs referenced Bug#35286 and Bug#30891 in his comment.
Note: I do not want to take credit for Noam Postavky's findings. The hard task is to find the bug. I just "copied" his patch here. So, please try the proposed bugfix.
You told us that your
emacs-version is 26.1. That leaves us only with Bug#30891.
There are two indicators that your problem is Bug#30891:
- The problem deals with negative depths.
- The problem is found in Emacs 26.1 and fixed in Emacs 26.2.
This problem should be fixed with the following code in your init file:
(defun lisp-indent-calc-next-patch (state)
"Move to next line and return calculated indent for it.
STATE is updated by side effect, the first state should be
created by `lisp-indent-initial-state'. This function may move
by more than one line to cross a string literal."
(pcase-let* (((cl-struct lisp-indent-state
(stack indent-stack) ppss ppss-point)
(indent-depth (car ppss)) ; Corresponding to indent-stack.
;; Parse this line so we can learn the state to indent the
;; next line.
(while (let ((last-sexp (nth 2 ppss)))
(setq ppss (parse-partial-sexp
ppss-point (progn (end-of-line) (point))
nil nil ppss))
;; Preserve last sexp of state (position 2) for
;; `calculate-lisp-indent', if we're at the same depth.
(if (and (not (nth 2 ppss)) (= depth (car ppss)))
(setf (nth 2 ppss) last-sexp)
(setq last-sexp (nth 2 ppss)))
(setq depth (car ppss))
;; Skip over newlines within strings.
(nth 3 ppss))
(let ((string-start (nth 8 ppss)))
(setq ppss (parse-partial-sexp (point) (point-max)
nil nil ppss 'syntax-table))
(setf (nth 2 ppss) string-start) ; Finished a complete string.
(setq depth (car ppss)))
(setq ppss-point (point)))
(setq ppss-point (point))
(let* ((depth-delta (- depth indent-depth)))
(cond ((< depth-delta 0)
(setq indent-stack (nthcdr (- depth-delta) indent-stack)))
((> depth-delta 0)
(setq indent-stack (nconc (make-list depth-delta nil)
(cond ((= (forward-line 1) 1) nil)
;; Negative depth, probably some kind of syntax error.
;; Reset state.
(setq ppss (parse-partial-sexp (point) (point))))
((integerp (setq indent (calculate-lisp-indent ppss)))
(setf (car indent-stack) indent))
((consp indent) ; (COLUMN CONTAINING-SEXP-START)
;; This only happens if we're in a string.
(t (error "This shouldn't happen"))))
(setf (lisp-indent-state-stack state) indent-stack)
(setf (lisp-indent-state-ppss-point state) ppss-point)
(setf (lisp-indent-state-ppss state) ppss))))
(if (version<= "26.2" emacs-version)
(warn "If you exclusively use Emacs >= 26.2 you can remove `lisp-indent-calc-next-patch'")
(advice-add 'lisp-indent-calc-next :override #'lisp-indent-calc-next-patch)))