Make warning about unescaped character literals more helpful.

See Bug#31676.

* lisp/emacs-lisp/byte-run.el
(byte-run--unescaped-character-literals-warning): New defun.

* src/lread.c (load_warn_unescaped_character_literals): Use new defun.
(syms_of_lread): Define symbol for new defun.

* lisp/emacs-lisp/bytecomp.el (byte-compile-from-buffer): Use new
defun.

* test/src/lread-tests.el (lread-tests--unescaped-char-literals):
test/lisp/emacs-lisp/bytecomp-tests.el
(bytecomp-tests--unescaped-char-literals): Adapt unit tests.

2 files changed, 6 insertions, 2 deletions

diff --git a/test/lisp/emacs-lisp/bytecomp-tests.el b/test/lisp/emacs-lisp/bytecomp-tests.el
index f66a06bc1bc..5fb64ff2881 100644
--- a/test/lisp/emacs-lisp/bytecomp-tests.el
+++ b/test/lisp/emacs-lisp/bytecomp-tests.el
@@ -540,7 +540,9 @@ literals (Bug#20852)."
         (should (equal (cdr err)
                        (list (concat "unescaped character literals "
                                      "`?\"', `?(', `?)', `?;', `?[', `?]' "
-                                     "detected!"))))))))
+                                     "detected, "
+                                     "`?\\\"', `?\\(', `?\\)', `?\\;', `?\\[', "
+                                     "`?\\]' expected!"))))))))
 
 (ert-deftest bytecomp-tests--old-style-backquotes ()
   "Check that byte compiling warns about old-style backquotes."
diff --git a/test/src/lread-tests.el b/test/src/lread-tests.el
index ae918f03120..82b75b195ca 100644
--- a/test/src/lread-tests.el
+++ b/test/src/lread-tests.el
@@ -140,7 +140,9 @@ literals (Bug#20852)."
     (should (equal (lread-tests--last-message)
                    (concat (format-message "Loading `%s': " file-name)
                            "unescaped character literals "
-                           "`?\"', `?(', `?)', `?;', `?[', `?]' detected!")))))
+                           "`?\"', `?(', `?)', `?;', `?[', `?]' detected, "
+                           "`?\\\"', `?\\(', `?\\)', `?\\;', `?\\[', `?\\]' "
+                           "expected!")))))
 
 (ert-deftest lread-tests--funny-quote-symbols ()
   "Check that 'smart quotes' or similar trigger errors in symbol names."