Raise an error when detecting old-style backquotes.

They have been deprecated for a decade now.

* src/lread.c (Fload): Don't use record_unwind_protect to warn about
old-style backquotes any more.  They now generate a hard error.
(read1): Signal an error when detecting old-style backquotes.  Remove
unused label.
(syms_of_lread): Remove unused internal variable
'lread--old-style-backquotes'.
(load_error_old_style_backquotes): Rename from
'load_warn_oldstyle_backquotes'.  Signal an error.

* lisp/emacs-lisp/bytecomp.el (byte-compile-from-buffer): Remove check
from byte compiler.  It isn't triggered any more.

* test/src/lread-tests.el (lread-tests--old-style-backquotes): Adapt
unit test.

* test/lisp/emacs-lisp/bytecomp-tests.el
(bytecomp-tests--old-style-backquotes)
(bytecomp-tests-function-put): Adapt unit tests.

* etc/NEWS: Document change.

2 files changed, 8 insertions, 13 deletions

diff --git a/test/lisp/emacs-lisp/bytecomp-tests.el b/test/lisp/emacs-lisp/bytecomp-tests.el
index 30d2a4753cf..1f85c269780 100644
--- a/test/lisp/emacs-lisp/bytecomp-tests.el
+++ b/test/lisp/emacs-lisp/bytecomp-tests.el
@@ -534,23 +534,18 @@ literals (Bug#20852)."
 
 (ert-deftest bytecomp-tests--old-style-backquotes ()
   "Check that byte compiling warns about old-style backquotes."
-  (should (boundp 'lread--old-style-backquotes))
   (bytecomp-tests--with-temp-file source
     (write-region "(` (a b))" nil source)
     (bytecomp-tests--with-temp-file destination
       (let* ((byte-compile-dest-file-function (lambda (_) destination))
-            (byte-compile-error-on-warn t)
-            (byte-compile-debug t)
-            (err (should-error (byte-compile-file source))))
+             (byte-compile-debug t)
+             (err (should-error (byte-compile-file source))))
         (should (equal (cdr err)
-                       (list "!! The file uses old-style backquotes !!
-This functionality has been obsolete for more than 10 years already
-and will be removed soon.  See (elisp)Backquote in the manual.")))))))
+                       '("Loading `nil': old-style backquotes detected!")))))))
 
 
 (ert-deftest bytecomp-tests-function-put ()
   "Check `function-put' operates during compilation."
-  (should (boundp 'lread--old-style-backquotes))
   (bytecomp-tests--with-temp-file source
     (dolist (form '((function-put 'bytecomp-tests--foo 'foo 1)
                     (function-put 'bytecomp-tests--foo 'bar 2)
diff --git a/test/src/lread-tests.el b/test/src/lread-tests.el
index ac730b4f005..3f41982eba1 100644
--- a/test/src/lread-tests.el
+++ b/test/src/lread-tests.el
@@ -173,13 +173,13 @@ literals (Bug#20852)."
     (should (string-suffix-p "/somelib.el" (caar load-history)))))
 
 (ert-deftest lread-tests--old-style-backquotes ()
-  "Check that loading warns about old-style backquotes."
+  "Check that loading doesn't accept old-style backquotes."
   (lread-tests--with-temp-file file-name
     (write-region "(` (a b))" nil file-name)
-    (should (equal (load file-name nil :nomessage :nosuffix) t))
-    (should (equal (lread-tests--last-message)
-                   (concat (format-message "Loading `%s': " file-name)
-                           "old-style backquotes detected!")))))
+    (let ((data (should-error (load file-name nil :nomessage :nosuffix))))
+      (should (equal (cdr data)
+                     (list (concat (format-message "Loading `%s': " file-name)
+                                   "old-style backquotes detected!")))))))
 
 (ert-deftest lread-lread--substitute-object-in-subtree ()
   (let ((x (cons 0 1)))