bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Michael Heerdegen]

Hello,

having only lexical-binding: t in "thunk.el"'s header is not sufficient:
to make thunks work ok, `thunk-delay' needs lexical-binding when the
expansion is run.

Try e.g. something trivial as

#+begin_src emacs-lisp
(defun my-thunk-test ()
  (thunk-force (thunk-delay (+ 1 2))))
#+end_src

This compiles ok, but executing (my-thunk-test) without lexbind enabled
gives you a meaningless error like "void-variable: forced".

I think we should document (in the file header) that lexical-binding
mode is required when thunks are created with `thunk-delay'.  I think we
could additionally raise an error in the expansion of `thunk-delay' when
lexical-binding -> nil.


TIA,

Michael.




In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.24)
 of 2017-10-25 built on drachen
Repository revision: cb73c70180f57f3fb99fae3aaefbacf0a61cea3f
Windowing system distributor 'The X.Org Foundation', version 11.0.11905000
System Description:	Debian GNU/Linux testing (buster)

bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Michael Heerdegen]

[-- Attachment #1: Type: text/plain, Size: 340 bytes --]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> #+begin_src emacs-lisp
> (defun my-thunk-test ()
>   (thunk-force (thunk-delay (+ 1 2))))
> #+end_src
>
> This compiles ok, but executing (my-thunk-test) without lexbind enabled
> gives you a meaningless error like "void-variable: forced".

Nicolas, Stefan - ok to fix it like that?


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-WIP-Fix-bug-28990.patch --]
[-- Type: text/x-diff, Size: 748 bytes --]

From 45fe6b1bc9573257e59842283fd7da36d760c524 Mon Sep 17 00:00:00 2001
From: Michael Heerdegen <michael_heerdegen@web.de>
Date: Thu, 26 Oct 2017 12:57:55 +0200
Subject: [PATCH] WIP: Fix bug#28990

---
 lisp/emacs-lisp/thunk.el | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lisp/emacs-lisp/thunk.el b/lisp/emacs-lisp/thunk.el
index bb6d277c27..6dc892c44b 100644
--- a/lisp/emacs-lisp/thunk.el
+++ b/lisp/emacs-lisp/thunk.el
@@ -44,9 +44,12 @@
 
 ;;; Code:
 
+(eval-when-compile (require 'cl-macs))
+
 (defmacro thunk-delay (&rest body)
   "Delay the evaluation of BODY."
   (declare (debug t))
+  (cl-assert lexical-binding)
   (let ((forced (make-symbol "forced"))
         (val (make-symbol "val")))
     `(let (,forced ,val)
-- 
2.14.2


[-- Attachment #3: Type: text/plain, Size: 131 bytes --]


I would additionally add a sentence to "thunk.el"'s header saying that
creating thunks requires lexical binding.


TIA,

Michael.

bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Nicolas Petton]

[-- Attachment #1: Type: text/plain, Size: 286 bytes --]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Nicolas, Stefan - ok to fix it like that?

Yes, that's fine with me.

> I would additionally add a sentence to "thunk.el"'s header saying that
> creating thunks requires lexical binding.

That's a good idea, thanks.

Cheers,
Nico

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 487 bytes --]

bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Michael Heerdegen]

Nicolas Petton <nicolas@petton.fr> writes:

> > Nicolas, Stefan - ok to fix it like that?
>
> Yes, that's fine with me.
>
> > I would additionally add a sentence to "thunk.el"'s header saying that
> > creating thunks requires lexical binding.
>
> That's a good idea, thanks.

Done in bbb85eff49.

Michael.

bug#28990: 27.0.50; thunk-delay: running expansion also requires lexical-binding

[Nicolas Petton]

[-- Attachment #1: Type: text/plain, Size: 109 bytes --]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> Done in bbb85eff49.

Great, thank you.

Cheers,
Nico

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 487 bytes --]