Old-style backquotes

Old-style backquotes

[Philipp Stephani]

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Hi,

old-style backquotes were deprecated ten years ago
(1d06469794a66d6c8b424e6f17da029ebc5bb295). Is it time to finally turn them
into errors for Emacs 26, and remove them in Emacs 27?

Philipp

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Re: Old-style backquotes

[Paul Eggert]

On 10/03/2017 06:51 AM, Philipp Stephani wrote:
> old-style backquotes were deprecated ten years ago 
> (1d06469794a66d6c8b424e6f17da029ebc5bb295). Is it time to finally turn 
> them into errors for Emacs 26, and remove them in Emacs 27?

Ten years is long enough, so I'd say it's time.

[PATCH] Raise an error when detecting old-style backquotes.

[Philipp Stephani]

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.

* test/src/lread-tests.el (lread-tests--old-style-backquotes): Adapt
unit test.
---
 src/lread.c             | 32 ++++++--------------------------
 test/src/lread-tests.el | 10 +++++-----
 2 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/src/lread.c b/src/lread.c
index 6bc93b1481..44953baa77 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1003,14 +1003,11 @@ load_error_handler (Lisp_Object data)
   return Qnil;
 }
 
-static void
-load_warn_old_style_backquotes (Lisp_Object file)
+static _Noreturn void
+load_error_old_style_backquotes (void)
 {
-  if (!NILP (Vlread_old_style_backquotes))
-    {
-      AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
-      CALLN (Fmessage, format, file);
-    }
+  AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
+  xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
 }
 
 static void
@@ -1282,10 +1279,6 @@ Return t if the file exists and loads successfully.  */)
 
   version = -1;
 
-  /* Check for the presence of old-style quotes and warn about them.  */
-  specbind (Qlread_old_style_backquotes, Qnil);
-  record_unwind_protect (load_warn_old_style_backquotes, file);
-
   /* Check for the presence of unescaped character literals and warn
      about them. */
   specbind (Qlread_unescaped_character_literals, Qnil);
@@ -3178,10 +3171,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	   first_in_list exception (old-style can still be obtained via
 	   "(\`" anyway).  */
 	if (!new_backquote_flag && first_in_list && next_char == ' ')
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+          load_error_old_style_backquotes ();
 	else
 	  {
 	    Lisp_Object value;
@@ -3232,10 +3222,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    return list2 (comma_type, value);
 	  }
 	else
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+          load_error_old_style_backquotes ();
       }
     case '?':
       {
@@ -3423,7 +3410,6 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	 row.  */
       FALLTHROUGH;
     default:
-    default_label:
       if (c <= 040) goto retry;
       if (c == NO_BREAK_SPACE)
 	goto retry;
@@ -4996,12 +4982,6 @@ variables, this must be set in the first line of a file.  */);
 	       doc: /* List of buffers being read from by calls to `eval-buffer' and `eval-region'.  */);
   Veval_buffer_list = Qnil;
 
-  DEFVAR_LISP ("lread--old-style-backquotes", Vlread_old_style_backquotes,
-	       doc: /* Set to non-nil when `read' encounters an old-style backquote.
-For internal use only.  */);
-  Vlread_old_style_backquotes = Qnil;
-  DEFSYM (Qlread_old_style_backquotes, "lread--old-style-backquotes");
-
   DEFVAR_LISP ("lread--unescaped-character-literals",
                Vlread_unescaped_character_literals,
                doc: /* List of deprecated unescaped character literals encountered by `read'.
diff --git a/test/src/lread-tests.el b/test/src/lread-tests.el
index ac730b4f00..241cebb6b1 100644
--- a/test/src/lread-tests.el
+++ b/test/src/lread-tests.el
@@ -173,13 +173,13 @@ lread-tests--last-message
     (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)))
-- 
2.14.2

Re: Old-style backquotes

[Eli Zaretskii]

> From: Paul Eggert <eggert@cs.ucla.edu>
> Date: Tue, 3 Oct 2017 07:12:25 -0700
> 
> On 10/03/2017 06:51 AM, Philipp Stephani wrote:
> > old-style backquotes were deprecated ten years ago 
> > (1d06469794a66d6c8b424e6f17da029ebc5bb295). Is it time to finally turn 
> > them into errors for Emacs 26, and remove them in Emacs 27?
> 
> Ten years is long enough, so I'd say it's time.

On master, please (unless there are objections).

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Stefan Monnier]

> * src/lread.c (Fload): Don’t use record_unwind_protect to warn about
> old-style backquotes any more.  They now generate a hard error.

Not sure what's the benefit of raising a hard error, over just removing
the obsolete feature altogether.


        Stefan

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Philipp Stephani]

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Stefan Monnier <monnier@iro.umontreal.ca> schrieb am Di., 3. Okt. 2017 um
19:44 Uhr:

> > * src/lread.c (Fload): Don’t use record_unwind_protect to warn about
> > old-style backquotes any more.  They now generate a hard error.
>
> Not sure what's the benefit of raising a hard error, over just removing
> the obsolete feature altogether.
>
>
Removing the special treatment would change the behavior. I'd rather have a
time span where developers would get hard errors instead of subtle behavior
changes.

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Re: [PATCH] Raise an error when detecting old-style backquotes.

[Stefan Monnier]

> Removing the special treatment would change the behavior.  I'd rather have a
> time span where developers would get hard errors instead of subtle behavior
> changes.

I don't think it'll make any real difference: in both cases the old code
won't work anymore: I'm hard pressed to think of a scenario where the
"subtle" behavior change is subtle enough not to be detected
fairly quickly.


        Stefan

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > > * src/lread.c (Fload): Don’t use record_unwind_protect to warn about
  > > old-style backquotes any more.  They now generate a hard error.

  > Not sure what's the benefit of raising a hard error, over just removing
  > the obsolete feature altogether.

The hard error could have a specific error message
to inform users of where to look to find out what to change.

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Stefan Monnier]

> The hard error could have a specific error message
> to inform users of where to look to find out what to change.

We've had such a specific warning (instead of error) for the last
10 years.


        Stefan

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > > The hard error could have a specific error message
  > > to inform users of where to look to find out what to change.

  > We've had such a specific warning (instead of error) for the last
  > 10 years.

I suggest a specific error message as the next step in deprecation.

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Stefan Monnier]

>> > The hard error could have a specific error message
>> > to inform users of where to look to find out what to change.
>> We've had such a specific warning (instead of error) for the last
>> 10 years.
> I suggest a specific error message as the next step in deprecation.

We've never done that when removing obsolete features.
Why should this be different?


        Stefan

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Richard Stallman]

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > We've never done that when removing obsolete features.
  > Why should this be different?

I'm not insisting it should be different.

I just think that, given that this was a very general feature that
changed in a grossly incompatible way, it is worth keeping a little
code to make a specific error message.

-- 
Dr Richard Stallman
President, Free Software Foundation (gnu.org, fsf.org)
Internet Hall-of-Famer (internethalloffame.org)
Skype: No way! See stallman.org/skype.html.

Re: Old-style backquotes

[Philipp Stephani]

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Eli Zaretskii <eliz@gnu.org> schrieb am Di., 3. Okt. 2017 um 17:02 Uhr:

> > From: Paul Eggert <eggert@cs.ucla.edu>
> > Date: Tue, 3 Oct 2017 07:12:25 -0700
> >
> > On 10/03/2017 06:51 AM, Philipp Stephani wrote:
> > > old-style backquotes were deprecated ten years ago
> > > (1d06469794a66d6c8b424e6f17da029ebc5bb295). Is it time to finally turn
> > > them into errors for Emacs 26, and remove them in Emacs 27?
> >
> > Ten years is long enough, so I'd say it's time.
>
> On master, please (unless there are objections).
>

OK, here's a patch.

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From 96d9780bf072772f3be289b4c344d741b9ce3249 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Tue, 3 Oct 2017 16:14:54 +0200
Subject: [PATCH] Raise an error when detecting old-style backquotes.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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.

* test/src/lread-tests.el (lread-tests--old-style-backquotes): Adapt
unit test.
---
 src/lread.c             | 32 ++++++--------------------------
 test/src/lread-tests.el | 10 +++++-----
 2 files changed, 11 insertions(+), 31 deletions(-)

diff --git a/src/lread.c b/src/lread.c
index 6bc93b1481..44953baa77 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1003,14 +1003,11 @@ load_error_handler (Lisp_Object data)
   return Qnil;
 }
 
-static void
-load_warn_old_style_backquotes (Lisp_Object file)
+static _Noreturn void
+load_error_old_style_backquotes (void)
 {
-  if (!NILP (Vlread_old_style_backquotes))
-    {
-      AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
-      CALLN (Fmessage, format, file);
-    }
+  AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
+  xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
 }
 
 static void
@@ -1282,10 +1279,6 @@ Return t if the file exists and loads successfully.  */)
 
   version = -1;
 
-  /* Check for the presence of old-style quotes and warn about them.  */
-  specbind (Qlread_old_style_backquotes, Qnil);
-  record_unwind_protect (load_warn_old_style_backquotes, file);
-
   /* Check for the presence of unescaped character literals and warn
      about them. */
   specbind (Qlread_unescaped_character_literals, Qnil);
@@ -3178,10 +3171,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	   first_in_list exception (old-style can still be obtained via
 	   "(\`" anyway).  */
 	if (!new_backquote_flag && first_in_list && next_char == ' ')
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+          load_error_old_style_backquotes ();
 	else
 	  {
 	    Lisp_Object value;
@@ -3232,10 +3222,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    return list2 (comma_type, value);
 	  }
 	else
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+          load_error_old_style_backquotes ();
       }
     case '?':
       {
@@ -3423,7 +3410,6 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	 row.  */
       FALLTHROUGH;
     default:
-    default_label:
       if (c <= 040) goto retry;
       if (c == NO_BREAK_SPACE)
 	goto retry;
@@ -4996,12 +4982,6 @@ variables, this must be set in the first line of a file.  */);
 	       doc: /* List of buffers being read from by calls to `eval-buffer' and `eval-region'.  */);
   Veval_buffer_list = Qnil;
 
-  DEFVAR_LISP ("lread--old-style-backquotes", Vlread_old_style_backquotes,
-	       doc: /* Set to non-nil when `read' encounters an old-style backquote.
-For internal use only.  */);
-  Vlread_old_style_backquotes = Qnil;
-  DEFSYM (Qlread_old_style_backquotes, "lread--old-style-backquotes");
-
   DEFVAR_LISP ("lread--unescaped-character-literals",
                Vlread_unescaped_character_literals,
                doc: /* List of deprecated unescaped character literals encountered by `read'.
diff --git a/test/src/lread-tests.el b/test/src/lread-tests.el
index ac730b4f00..241cebb6b1 100644
--- a/test/src/lread-tests.el
+++ b/test/src/lread-tests.el
@@ -173,13 +173,13 @@ lread-tests--last-message
     (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)))
-- 
2.14.2

Re: [PATCH] Raise an error when detecting old-style backquotes.

[Philipp Stephani]

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Stefan Monnier <monnier@iro.umontreal.ca> schrieb am Di., 3. Okt. 2017 um
20:52 Uhr:

> > Removing the special treatment would change the behavior.  I'd rather
> have a
> > time span where developers would get hard errors instead of subtle
> behavior
> > changes.
>
> I don't think it'll make any real difference: in both cases the old code
> won't work anymore: I'm hard pressed to think of a scenario where the
> "subtle" behavior change is subtle enough not to be detected
> fairly quickly.
>
>
For example, code such as '(` foo) would change behavior. Whether a certain
list is nested or not is definitely subtle enough.

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Re: Old-style backquotes

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sun, 08 Oct 2017 14:58:45 +0000
> Cc: emacs-devel@gnu.org
> 
> OK, here's a patch. 

Thanks, a few minor comments:

> @@ -3178,10 +3171,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
>  	   first_in_list exception (old-style can still be obtained via
>  	   "(\`" anyway).  */
>  	if (!new_backquote_flag && first_in_list && next_char == ' ')
> -	  {
> -	    Vlread_old_style_backquotes = Qt;
> -	    goto default_label;
> -	  }
> +          load_error_old_style_backquotes ();

Here (and elsewhere) the indentation should be fixed to be in line
with our style.

> --- a/test/src/lread-tests.el
> +++ b/test/src/lread-tests.el
> @@ -173,13 +173,13 @@ lread-tests--last-message
>      (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."

Please don't use literal curved quotes in doc strings and message
text, they will be transformed (by default) when displayed.

Re: Old-style backquotes

[Eli Zaretskii]

> Date: Sun, 08 Oct 2017 19:05:53 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
> 
> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Sun, 08 Oct 2017 14:58:45 +0000
> > Cc: emacs-devel@gnu.org
> > 
> > OK, here's a patch. 
> 
> Thanks, a few minor comments:

Oh, and one more: this needs a NEWS entry.

Thanks.

Re: Old-style backquotes

[Philipp Stephani]

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Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:09 Uhr:

> > Date: Sun, 08 Oct 2017 19:05:53 +0300
> > From: Eli Zaretskii <eliz@gnu.org>
> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
> >
> > > From: Philipp Stephani <p.stephani2@gmail.com>
> > > Date: Sun, 08 Oct 2017 14:58:45 +0000
> > > Cc: emacs-devel@gnu.org
> > >
> > > OK, here's a patch.
> >
> > Thanks, a few minor comments:
>
> Oh, and one more: this needs a NEWS entry.
>
>
Here's a new patch that also fixes the byte compiler tests.

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From a651664039cfe7794920abbd20a17dc62d26f1a5 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Tue, 3 Oct 2017 16:14:54 +0200
Subject: [PATCH] Raise an error when detecting old-style backquotes.
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

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                               |  3 +++
 lisp/emacs-lisp/bytecomp.el            |  8 +-------
 src/lread.c                            | 32 ++++++--------------------------
 test/lisp/emacs-lisp/bytecomp-tests.el | 11 +++--------
 test/src/lread-tests.el                | 10 +++++-----
 5 files changed, 18 insertions(+), 46 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index f961928ffd..75a98d1500 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -77,6 +77,9 @@ them through 'format' first.  Even that is discouraged: for ElDoc
 support, you should set 'eldoc-documentation-function' instead of
 calling 'eldoc-message' directly.
 
+** Old-style backquotes now generate an error.  They have been
+generating warnings for a decade.
+
 \f
 * Lisp Changes in Emacs 27.1
 
diff --git a/lisp/emacs-lisp/bytecomp.el b/lisp/emacs-lisp/bytecomp.el
index 590db570c5..45fa188d6c 100644
--- a/lisp/emacs-lisp/bytecomp.el
+++ b/lisp/emacs-lisp/bytecomp.el
@@ -2048,14 +2048,8 @@ byte-compile-from-buffer
 		 (not (eobp)))
 	  (setq byte-compile-read-position (point)
 		byte-compile-last-position byte-compile-read-position)
-	  (let* ((lread--old-style-backquotes nil)
-                 (lread--unescaped-character-literals nil)
+	  (let* ((lread--unescaped-character-literals nil)
                  (form (read inbuffer)))
-            ;; Warn about the use of old-style backquotes.
-            (when lread--old-style-backquotes
-              (byte-compile-warn "!! 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."))
             (when lread--unescaped-character-literals
               (byte-compile-warn
                "unescaped character literals %s detected!"
diff --git a/src/lread.c b/src/lread.c
index 6bc93b1481..c073fc4ce6 100644
--- a/src/lread.c
+++ b/src/lread.c
@@ -1003,14 +1003,11 @@ load_error_handler (Lisp_Object data)
   return Qnil;
 }
 
-static void
-load_warn_old_style_backquotes (Lisp_Object file)
+static _Noreturn void
+load_error_old_style_backquotes (void)
 {
-  if (!NILP (Vlread_old_style_backquotes))
-    {
-      AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
-      CALLN (Fmessage, format, file);
-    }
+  AUTO_STRING (format, "Loading `%s': old-style backquotes detected!");
+  xsignal1 (Qerror, CALLN (Fformat_message, format, Vload_file_name));
 }
 
 static void
@@ -1282,10 +1279,6 @@ Return t if the file exists and loads successfully.  */)
 
   version = -1;
 
-  /* Check for the presence of old-style quotes and warn about them.  */
-  specbind (Qlread_old_style_backquotes, Qnil);
-  record_unwind_protect (load_warn_old_style_backquotes, file);
-
   /* Check for the presence of unescaped character literals and warn
      about them. */
   specbind (Qlread_unescaped_character_literals, Qnil);
@@ -3178,10 +3171,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	   first_in_list exception (old-style can still be obtained via
 	   "(\`" anyway).  */
 	if (!new_backquote_flag && first_in_list && next_char == ' ')
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+	  load_error_old_style_backquotes ();
 	else
 	  {
 	    Lisp_Object value;
@@ -3232,10 +3222,7 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	    return list2 (comma_type, value);
 	  }
 	else
-	  {
-	    Vlread_old_style_backquotes = Qt;
-	    goto default_label;
-	  }
+	  load_error_old_style_backquotes ();
       }
     case '?':
       {
@@ -3423,7 +3410,6 @@ read1 (Lisp_Object readcharfun, int *pch, bool first_in_list)
 	 row.  */
       FALLTHROUGH;
     default:
-    default_label:
       if (c <= 040) goto retry;
       if (c == NO_BREAK_SPACE)
 	goto retry;
@@ -4996,12 +4982,6 @@ variables, this must be set in the first line of a file.  */);
 	       doc: /* List of buffers being read from by calls to `eval-buffer' and `eval-region'.  */);
   Veval_buffer_list = Qnil;
 
-  DEFVAR_LISP ("lread--old-style-backquotes", Vlread_old_style_backquotes,
-	       doc: /* Set to non-nil when `read' encounters an old-style backquote.
-For internal use only.  */);
-  Vlread_old_style_backquotes = Qnil;
-  DEFSYM (Qlread_old_style_backquotes, "lread--old-style-backquotes");
-
   DEFVAR_LISP ("lread--unescaped-character-literals",
                Vlread_unescaped_character_literals,
                doc: /* List of deprecated unescaped character literals encountered by `read'.
diff --git a/test/lisp/emacs-lisp/bytecomp-tests.el b/test/lisp/emacs-lisp/bytecomp-tests.el
index 30d2a4753c..1f85c26978 100644
--- a/test/lisp/emacs-lisp/bytecomp-tests.el
+++ b/test/lisp/emacs-lisp/bytecomp-tests.el
@@ -534,23 +534,18 @@ bytecomp-tests--with-temp-file
 
 (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 ac730b4f00..3f41982eba 100644
--- a/test/src/lread-tests.el
+++ b/test/src/lread-tests.el
@@ -173,13 +173,13 @@ lread-tests--last-message
     (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)))
-- 
2.14.2

Re: Old-style backquotes

[Eli Zaretskii]

> From: Philipp Stephani <p.stephani2@gmail.com>
> Date: Sun, 08 Oct 2017 16:25:44 +0000
> Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
> 
> Here's a new patch that also fixes the byte compiler tests. 

Thanks, LGTM, but please mention the NEWS change in the log message.

Also, the log message should quote 'like this', not ‘like this’.

Re: Old-style backquotes

[Philipp Stephani]

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Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:38 Uhr:

> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Sun, 08 Oct 2017 16:25:44 +0000
> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
> >
> > Here's a new patch that also fixes the byte compiler tests.
>
> Thanks, LGTM, but please mention the NEWS change in the log message.
>
> Also, the log message should quote 'like this', not ‘like this’.
>

Fixed and pushed as 9613690f6e to master.

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Re: [PATCH] Raise an error when detecting old-style backquotes.

[Stefan Monnier]

>> I don't think it'll make any real difference: in both cases the old code
>> won't work anymore: I'm hard pressed to think of a scenario where the
>> "subtle" behavior change is subtle enough not to be detected
>> fairly quickly.
> For example, code such as '(` foo) would change behavior.  Whether a certain
> list is nested or not is definitely subtle enough.

But this is not a complete scenario.  You'd need to give additional
context:
- why is there '(` foo) in the source code (it seems already contrived)?
- How is the result used (it's important that the result be
  used in a way which works differently but without signaling an error
  in both cases)?


        Stefan

Re: Old-style backquotes

[Philipp Stephani]

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Philipp Stephani <p.stephani2@gmail.com> schrieb am So., 8. Okt. 2017 um
18:59 Uhr:

> Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:38 Uhr:
>
>> > From: Philipp Stephani <p.stephani2@gmail.com>
>> > Date: Sun, 08 Oct 2017 16:25:44 +0000
>> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
>> >
>> > Here's a new patch that also fixes the byte compiler tests.
>>
>> Thanks, LGTM, but please mention the NEWS change in the log message.
>>
>> Also, the log message should quote 'like this', not ‘like this’.
>>
>
> Fixed and pushed as 9613690f6e to master.
>

I've now fixed the Bovine issue and re-pushed this commit as 8b8197235f to
master.

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Re: Old-style backquotes

[Alan Mackenzie]

Hello, Philipp.

On Sat, Dec 09, 2017 at 20:44:35 +0000, Philipp Stephani wrote:
> Philipp Stephani <p.stephani2@gmail.com> schrieb am So., 8. Okt. 2017 um
> 18:59 Uhr:

> > Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:38 Uhr:

> >> > From: Philipp Stephani <p.stephani2@gmail.com>
> >> > Date: Sun, 08 Oct 2017 16:25:44 +0000
> >> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org

> >> > Here's a new patch that also fixes the byte compiler tests.

> >> Thanks, LGTM, but please mention the NEWS change in the log message.

> >> Also, the log message should quote 'like this', not ‘like this’.


> > Fixed and pushed as 9613690f6e to master.


> I've now fixed the Bovine issue and re-pushed this commit as 8b8197235f to
> master.

Just as a matter of interest, I think there are still some old style
backquotes in advice.el.  In master:

    find . -name '*.el' | xargs grep -n '(` '

produces:

    ./emacs-lisp/advice.el:1517:;;   (` (list (, x))))
    ./emacs-lisp/advice.el:1550:;;         (` (progn (print (, x))

.  Do these need converting?

-- 
Alan Mackenzie (Nuremberg, Germany).

Re: Old-style backquotes

[Philipp Stephani]

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Alan Mackenzie <acm@muc.de> schrieb am Sa., 9. Dez. 2017 um 21:55 Uhr:

> Hello, Philipp.
>
> On Sat, Dec 09, 2017 at 20:44:35 +0000, Philipp Stephani wrote:
> > Philipp Stephani <p.stephani2@gmail.com> schrieb am So., 8. Okt. 2017 um
> > 18:59 Uhr:
>
> > > Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:38
> Uhr:
>
> > >> > From: Philipp Stephani <p.stephani2@gmail.com>
> > >> > Date: Sun, 08 Oct 2017 16:25:44 +0000
> > >> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
>
> > >> > Here's a new patch that also fixes the byte compiler tests.
>
> > >> Thanks, LGTM, but please mention the NEWS change in the log message.
>
> > >> Also, the log message should quote 'like this', not ‘like this’.
>
>
> > > Fixed and pushed as 9613690f6e to master.
>
>
> > I've now fixed the Bovine issue and re-pushed this commit as 8b8197235f
> to
> > master.
>
> Just as a matter of interest, I think there are still some old style
> backquotes in advice.el.  In master:
>
>     find . -name '*.el' | xargs grep -n '(` '
>
> produces:
>
>     ./emacs-lisp/advice.el:1517:;;   (` (list (, x))))
>     ./emacs-lisp/advice.el:1550:;;         (` (progn (print (, x))
>
> .  Do these need converting?
>
>
Thanks, compiling didn't catch those because they are in comments. Yes,
they should definitely be fixed. Will send a follow-up patch in a second.

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Re: Old-style backquotes

[Philipp Stephani]

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Philipp Stephani <p.stephani2@gmail.com> schrieb am Sa., 9. Dez. 2017 um
21:58 Uhr:

> Alan Mackenzie <acm@muc.de> schrieb am Sa., 9. Dez. 2017 um 21:55 Uhr:
>
>> Hello, Philipp.
>>
>> On Sat, Dec 09, 2017 at 20:44:35 +0000, Philipp Stephani wrote:
>> > Philipp Stephani <p.stephani2@gmail.com> schrieb am So., 8. Okt. 2017
>> um
>> > 18:59 Uhr:
>>
>> > > Eli Zaretskii <eliz@gnu.org> schrieb am So., 8. Okt. 2017 um 18:38
>> Uhr:
>>
>> > >> > From: Philipp Stephani <p.stephani2@gmail.com>
>> > >> > Date: Sun, 08 Oct 2017 16:25:44 +0000
>> > >> > Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org
>>
>> > >> > Here's a new patch that also fixes the byte compiler tests.
>>
>> > >> Thanks, LGTM, but please mention the NEWS change in the log message.
>>
>> > >> Also, the log message should quote 'like this', not ‘like this’.
>>
>>
>> > > Fixed and pushed as 9613690f6e to master.
>>
>>
>> > I've now fixed the Bovine issue and re-pushed this commit as 8b8197235f
>> to
>> > master.
>>
>> Just as a matter of interest, I think there are still some old style
>> backquotes in advice.el.  In master:
>>
>>     find . -name '*.el' | xargs grep -n '(` '
>>
>> produces:
>>
>>     ./emacs-lisp/advice.el:1517:;;   (` (list (, x))))
>>     ./emacs-lisp/advice.el:1550:;;         (` (progn (print (, x))
>>
>> .  Do these need converting?
>>
>>
> Thanks, compiling didn't catch those because they are in comments. Yes,
> they should definitely be fixed. Will send a follow-up patch in a second.
>

Fixed in commit ac6ea59830.

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