14 files changed, 59 insertions, 84 deletions

diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index e2d73804eb5..aadfc4c335a 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -4966,9 +4966,9 @@ binding slots have been popped."
           (unless (and c (symbolp c))
             (byte-compile-warn-x
              c "`%S' is not a condition name (in condition-case)" c))
-          ;; In reality, the `error-conditions' property is only required
+          ;; In reality, the `error-conditions' property is required only
           ;; for the argument to `signal', not to `condition-case'.
-          ;;(unless (consp (get c 'error-conditions))
+          ;;(unless (error-type-p c)
           ;;  (byte-compile-warn
           ;;   "`%s' is not a known condition name (in condition-case)"
           ;;   c))
@@ -5778,24 +5778,13 @@ already up-to-date."
         (byte-compile-file file)
       (condition-case err
           (byte-compile-file file)
-        (file-error
-         (message (if (cdr err)
-                      ">>Error occurred processing %s: %s (%s)"
-                    ">>Error occurred processing %s: %s")
-                  file
-                  (get (car err) 'error-message)
-                  (prin1-to-string (cdr err)))
-         (let ((destfile (byte-compile-dest-file file)))
-           (if (file-exists-p destfile)
-               (delete-file destfile)))
-         nil)
         (error
-         (message (if (cdr err)
-                      ">>Error occurred processing %s: %s (%s)"
-                    ">>Error occurred processing %s: %s")
-                  file
-                  (get (car err) 'error-message)
-                  (prin1-to-string (cdr err)))
+         (message ">>Error occurred processing %s: %s"
+                  file (error-message-string err))
+         (when (error-has-type-p err 'file-error)
+           (let ((destfile (byte-compile-dest-file file)))
+             (if (file-exists-p destfile)
+                 (delete-file destfile))))
          nil)))))
 
 (defun byte-compile-refresh-preloaded ()
diff --git a/lisp/emacs-lisp/debug.el b/lisp/emacs-lisp/debug.el
index bcea708c678..3019ada1bbd 100644
--- a/lisp/emacs-lisp/debug.el
+++ b/lisp/emacs-lisp/debug.el
@@ -560,9 +560,7 @@ The environment used is the one when entering the activation frame at point."
                     (condition-case err
                         (backtrace-eval exp nframe base)
                       (error (setq errored
-                                   (format "%s: %s"
-                                           (get (car err) 'error-message)
-                                           (car (cdr err)))))))))
+                                   (error-message-string err)))))))
         (if errored
             (progn
               (message "Error: %s" errored)
diff --git a/lisp/emacs-lisp/edebug.el b/lisp/emacs-lisp/edebug.el
index 5cb781cb39f..3bb12e18842 100644
--- a/lisp/emacs-lisp/edebug.el
+++ b/lisp/emacs-lisp/edebug.el
@@ -3745,9 +3745,7 @@ Return the result of the last expression."
   ;; If there is an error, a string is returned describing the error.
   (condition-case edebug-err
       (edebug-eval expr)
-    (error (edebug-format "%s: %s"  ;; could
-                          (get (car edebug-err) 'error-message)
-                          (car (cdr edebug-err))))))
+    (error (error-message-string edebug-err))))
 
 ;;; Printing
 
@@ -3755,14 +3753,7 @@ Return the result of the last expression."
 (defun edebug-report-error (value)
   ;; Print an error message like command level does.
   ;; This also prints the error name if it has no error-message.
-  (message "%s: %s"
-           (or (get (car value) 'error-message)
-               (format "peculiar error (%s)" (car value)))
-           (mapconcat (lambda (edebug-arg)
-                        ;; continuing after an error may
-                        ;; complain about edebug-arg. why??
-                        (prin1-to-string edebug-arg))
-                      (cdr value) ", ")))
+  (message "%s" (error-message-string value)))
 
 ;; Alternatively, we could change the definition of
 ;; edebug-safe-prin1-to-string to only use these if defined.
@@ -3812,10 +3803,7 @@ this is the prefix key.)"
              (condition-case err
                  (edebug-eval expr)
                (error
-                (setq errored
-                      (format "%s: %s"
-                              (get (car err) 'error-message)
-                              (car (cdr err)))))))))
+                (setq errored (error-message-string err)))))))
          (result
           (unless errored
             (values--store-value value)
diff --git a/lisp/emacs-lisp/ert.el b/lisp/emacs-lisp/ert.el
index d5e0afe3b92..6dacd568c7a 100644
--- a/lisp/emacs-lisp/ert.el
+++ b/lisp/emacs-lisp/ert.el
@@ -396,12 +396,11 @@ Returns nil."
 
 Determines whether CONDITION matches TYPE and EXCLUDE-SUBTYPES,
 and aborts the current test as failed if it doesn't."
-  (let ((signaled-conditions (get (car condition) 'error-conditions))
-        (handled-conditions (pcase-exhaustive type
+  (let ((handled-conditions (pcase-exhaustive type
                               ((pred listp) type)
                               ((pred symbolp) (list type)))))
-    (cl-assert signaled-conditions)
-    (unless (cl-intersection signaled-conditions handled-conditions)
+    (unless (cl-some (lambda (hc) (error-has-type-p condition hc))
+                     handled-conditions)
       (ert-fail (append
                  (funcall form-description-fn)
                  (list
@@ -409,7 +408,7 @@ and aborts the current test as failed if it doesn't."
                   :fail-reason (concat "the error signaled did not"
                                        " have the expected type")))))
     (when exclude-subtypes
-      (unless (member (car condition) handled-conditions)
+      (unless (member (error-type condition) handled-conditions)
         (ert-fail (append
                    (funcall form-description-fn)
                    (list
diff --git a/lisp/epa-file.el b/lisp/epa-file.el
index 9bf6916ff7a..ced54b6eeed 100644
--- a/lisp/epa-file.el
+++ b/lisp/epa-file.el
@@ -117,10 +117,10 @@ encryption is used."
   (let ((error epa-file-error))
     (save-window-excursion
       (kill-buffer))
-    (if (nth 3 error)
-        (user-error "Wrong passphrase: %s" (nth 3 error))
+    (if (error-slot-value error 3)
+        (user-error "Wrong passphrase: %s" (error-slot-value error 3))
       (signal 'file-missing
-              (cons "Opening input file" (cdr error))))))
+              (cons "Opening input file" (error-data error))))))
 
 (defun epa--wrong-password-p (context)
   "Return whether a wrong password caused the error in CONTEXT."
@@ -171,23 +171,25 @@ encryption is used."
              ;; signal that as a non-file error
              ;; so that find-file-noselect-1 won't handle it.
              ;; Borrowed from jka-compr.el.
-             (if (and (memq 'file-error (get (car error) 'error-conditions))
-                      (equal (cadr error) "Searching for program"))
+             (if (and (error-has-type-p error 'file-error)
+                      (equal (error-slot-value error 1)
+                             "Searching for program"))
                  (error "Decryption program `%s' not found"
-                        (nth 3 error)))
+                        (error-slot-value error 3)))
              (let ((exists (file-exists-p local-file)))
                (when exists
                  (if-let* ((wrong-password (epa--wrong-password-p context)))
                      ;; Don't display the *error* buffer if we just
                      ;; have a wrong password; let the later error
                      ;; handler notify the user.
-                     (setq error (append error (list wrong-password)))
+                     (setf (error-data error)
+                           (append (error-data error) (list wrong-password)))
                    (epa-display-error context))
                  ;; When the .gpg file isn't an encrypted file (e.g.,
                  ;; it's a keyring.gpg file instead), then gpg will
                  ;; say "Unexpected exit" as the error message.  In
                  ;; that case, just display the bytes.
-                 (if (equal (caddr error) "Unexpected; Exit")
+                 (if (equal (error-slot-value error 2) "Unexpected; Exit")
                      (setq string (with-temp-buffer
                                     (insert-file-contents-literally local-file)
                                     (buffer-string)))
@@ -197,10 +199,10 @@ encryption is used."
                    ;; `find-file-noselect-1'.
                    (setq-local epa-file-error error)
                    (add-hook 'find-file-not-found-functions
-                             'epa-file--find-file-not-found-function
+                             #'epa-file--find-file-not-found-function
                              nil t)))
                (signal (if exists 'file-error 'file-missing)
-                       (cons "Opening input file" (cdr error))))))
+                       (cons "Opening input file" (error-data error))))))
           (set-buffer buf) ;In case timer/filter changed/killed it (bug#16029)!
           (setq-local epa-file-encrypt-to
                       (mapcar #'car (epg-context-result-for
diff --git a/lisp/jka-compr.el b/lisp/jka-compr.el
index 8258ab32495..c4643fb2d8c 100644
--- a/lisp/jka-compr.el
+++ b/lisp/jka-compr.el
@@ -471,22 +471,21 @@ There should be no more than seven characters after the final `/'."
                    ;; If the file we wanted to uncompress does not exist,
                    ;; handle that according to VISIT as `insert-file-contents'
                    ;; would, maybe signaling the same error it normally would.
-                   (if (and (eq (car error-code) 'file-missing)
-                            (eq (nth 3 error-code) local-file))
+                   (if (and (error-has-type-p error-code 'file-missing)
+                            (eq (error-slot-value error-code 3) local-file))
                        (if visit
                            (setq notfound error-code)
-                         (signal 'file-missing
-                                 (cons "Opening input file"
-                                       (nthcdr 2 error-code))))
+                         (setf (error-slot-value error-code 1)
+                               "Opening input file")
+                         (signal error-code))
                      ;; If the uncompression program can't be found,
                      ;; signal that as a non-file error
                      ;; so that find-file-noselect-1 won't handle it.
-                     (if (and (memq 'file-error (get (car error-code)
-                                                     'error-conditions))
+                     (if (and (error-has-type-p error-code 'file-error)
                               (equal (cadr error-code) "Searching for program"))
                          (error "Uncompression program `%s' not found"
-                                (nth 3 error-code)))
-                     (signal (car error-code) (cdr error-code)))))))
+                                (error-slot-value error-code 3))
+                       (signal error-code)))))))
 
           (and
            local-copy
diff --git a/lisp/net/sasl.el b/lisp/net/sasl.el
index 289e867e672..3f805237683 100644
--- a/lisp/net/sasl.el
+++ b/lisp/net/sasl.el
@@ -50,8 +50,7 @@
 
 (defvar sasl-unique-id-function #'sasl-unique-id-function)
 
-(put 'sasl-error 'error-message "SASL error")
-(put 'sasl-error 'error-conditions '(sasl-error error))
+(define-error 'sasl-error "SASL error")
 
 (defun sasl-error (datum)
   (signal 'sasl-error (list datum)))
diff --git a/lisp/net/soap-client.el b/lisp/net/soap-client.el
index beebe9b4445..f6d2ba229e5 100644
--- a/lisp/net/soap-client.el
+++ b/lisp/net/soap-client.el
@@ -2886,7 +2886,7 @@ decode function to perform the actual decoding."
 
 ;;;; Soap Envelope parsing
 
-(if (fboundp 'define-error)
+(if (fboundp 'define-error)             ;Emacs-24.4
     (define-error 'soap-error "SOAP error")
   ;; Support Emacs<24.4 that do not have define-error, so
   ;; that soap-client can remain unchanged in GNU ELPA.
diff --git a/lisp/net/tramp-compat.el b/lisp/net/tramp-compat.el
index f975457d4df..ecc6fe96855 100644
--- a/lisp/net/tramp-compat.el
+++ b/lisp/net/tramp-compat.el
@@ -102,14 +102,19 @@ Add the extension of F, if existing."
     tramp-temp-name-prefix tramp-compat-temporary-file-directory)
    dir-flag (file-name-extension f t)))
 
+(defalias 'tramp-error-type-p
+  (if (fboundp 'error-type-p)           ;Emacs-31
+      #'error-type-p
+    (lambda (symbol) (get symbol 'error-conditions))))
+
 ;; `permission-denied' is introduced in Emacs 29.1.
 (defconst tramp-permission-denied
-  (if (get 'permission-denied 'error-conditions) 'permission-denied 'file-error)
+  (if (tramp-error-type-p 'permission-denied) 'permission-denied 'file-error)
   "The error symbol for the `permission-denied' error.")
 
 (defsubst tramp-compat-permission-denied (vec file)
   "Emit the `permission-denied' error."
-  (if (get 'permission-denied 'error-conditions)
+  (if (tramp-error-type-p 'permission-denied)
       (tramp-error vec tramp-permission-denied file)
     (tramp-error vec tramp-permission-denied "Permission denied: %s" file)))
 
diff --git a/lisp/net/tramp-message.el b/lisp/net/tramp-message.el
index 7b405061ba8..37628e2f001 100644
--- a/lisp/net/tramp-message.el
+++ b/lisp/net/tramp-message.el
@@ -398,8 +398,12 @@ FMT-STRING and ARGUMENTS."
      vec-or-proc 1 "%s"
      (error-message-string
       (list signal
+            ;; FIXME: Looks redundant since `error-message-string'
+            ;; already uses the `error-message' property of `signal'!
             (get signal 'error-message)
             (apply #'format-message fmt-string arguments))))
+    ;; FIXME: This doesn't look right: ELisp code should be able to rely on
+    ;; the "shape" of the list based on the type of the signal.
     (signal signal (list (substring-no-properties
                           (apply #'format-message fmt-string arguments))))))
 
diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index 946d3ba10be..2773f5e76b0 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -1104,8 +1104,7 @@ functions are annotated with \"<f>\" via the
                     ;; specific completion table in more cases.
                     (is-ignore-error
                      (list t (elisp--completion-local-symbols)
-                           :predicate (lambda (sym)
-                                        (get sym 'error-conditions))))
+                           :predicate #'error-type-p))
                     ((elisp--expect-function-p beg)
                      (list nil (elisp--completion-local-symbols)
                            :predicate
@@ -1179,12 +1178,11 @@ functions are annotated with \"<f>\" via the
                                         (forward-sexp 2)
                                         (< (point) beg)))))
                         (list t (elisp--completion-local-symbols)
-                              :predicate (lambda (sym) (get sym 'error-conditions))))
+                              :predicate #'error-type-p))
                        ;; `ignore-error' with a list CONDITION parameter.
                        ('ignore-error
                         (list t (elisp--completion-local-symbols)
-                              :predicate (lambda (sym)
-                                           (get sym 'error-conditions))))
+                              :predicate #'error-type-p))
                        ((and (or ?\( 'let 'let* 'cond 'cond* 'bind*)
                              (guard (save-excursion
                                       (goto-char (1- beg))
diff --git a/lisp/simple.el b/lisp/simple.el
index 99930c3090c..67a4894e315 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -3397,7 +3397,7 @@ Go to the history element by the absolute history position HIST-POS."
 The same as `command-error-default-function' but display error messages
 at the end of the minibuffer using `minibuffer-message' to not obscure
 the minibuffer contents."
-  (if (memq 'minibuffer-quit (get (car data) 'error-conditions))
+  (if (error-has-type-p data 'minibuffer-quit)
       (ding t)
     (discard-input)
     (ding))
diff --git a/lisp/startup.el b/lisp/startup.el
index 9c1eafdae07..5b8f90a81c4 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -1123,15 +1123,12 @@ init-file, or to a default value if loading is not possible."
          (display-warning
           'initialization
           (format-message "\
-An error occurred while loading `%s':\n\n%s%s%s\n\n\
+An error occurred while loading `%s':\n\n%s\n\n\
 To ensure normal operation, you should investigate and remove the
 cause of the error in your initialization file.  Start Emacs with
 the `--debug-init' option to view a complete error backtrace."
                           user-init-file
-                          (get (car error) 'error-message)
-                          (if (cdr error) ": " "")
-                          (mapconcat (lambda (s) (prin1-to-string s t))
-                                     (cdr error) ", "))
+                          (error-message-string error))
           :warning)
          (setq init-file-had-error t))))))
 
@@ -1593,15 +1590,12 @@ please check its value")
      (princ
       (if (eq (car error) 'error)
           (apply #'concat (cdr error))
-        (if (memq 'file-error (get (car error) 'error-conditions))
+        (if (error-has-type-p error 'file-error)
             (format "%s: %s"
                     (nth 1 error)
                     (mapconcat (lambda (obj) (prin1-to-string obj t))
                                (cdr (cdr error)) ", "))
-          (format "%s: %s"
-                  (get (car error) 'error-message)
-                  (mapconcat (lambda (obj) (prin1-to-string obj t))
-                             (cdr error) ", "))))
+          (error-message-string error)))
       'external-debugging-output)
      (terpri 'external-debugging-output)
      (setq initial-window-system nil)
diff --git a/lisp/type-break.el b/lisp/type-break.el
index 440a7136f1d..d71b41da531 100644
--- a/lisp/type-break.el
+++ b/lisp/type-break.el
@@ -1025,7 +1025,7 @@ With optional non-nil ALL, force redisplay of all mode-lines."
       (setq continue nil)
       (and (get-buffer "*Life*")
            (kill-buffer "*Life*"))
-      (condition-case ()
+      (condition-case err
           (progn
             (life 3)
             ;; wait for user to return
@@ -1033,7 +1033,7 @@ With optional non-nil ALL, force redisplay of all mode-lines."
             (type-break-catch-up-event)
             (kill-buffer "*Life*"))
         (life-extinct
-         (message "%s" (get 'life-extinct 'error-message))
+         (message "%s" (error-message-string err))
          ;; restart demo
          (setq continue t))
         (quit