* bug#21185: 25.0.50; byte-compiler warn on quote lexical var
@ 2015-08-04 9:17 stephen_leake
2015-08-06 3:28 ` Stefan Monnier
0 siblings, 1 reply; 4+ messages in thread
From: stephen_leake @ 2015-08-04 9:17 UTC (permalink / raw)
To: 21185
This file gives an example where a new byte-compiler warning would be
useful:
;; quote-lexical-var.el -*- lexical-binding: t -*-
(defun display-var (var)
"Display variable value of VAR (a symbol), if any."
(cond
((boundp var)
(message "%s: %s" (symbol-name var) (symbol-value var)))
(t
(message "%s not bound" (symbol-name var)))))
(defun quote-lexical-var ()
(let ((my-var "foo"))
(message "non-quoted my-var: %s" my-var)
(display-var 'my-var)))
(provide 'quote-lexical-var)
;; end of file
To see the problem, execute (in emacs master, -Q):
(add-to-list 'load-path "/home/stephe/Elisp_Work/")
;; path containing above file
(byte-compile-file "/home/stephe/Elisp_Work/quote-lexical-var.el")
(require 'quote-lexical-var)
(display-var 'default-directory)
This gives "default-directory: /home/stephe" as expected.
(quote-lexical-var)
This gives:
non-quoted my-var: foo
my-var: not bound
Quoting lexical variables does not work; there is no symbol available at
run-time.
I've been bitten by this problem when converting code to use lexical
binding; it would be helpful if the byte-compiler warned about it.
In GNU Emacs 25.0.50.4 (x86_64-w64-mingw32)
of 2015-08-02 on TAKVER2
Repository revision: d2c4309d46529bac656f332677d2c5e199577845
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^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#21185: 25.0.50; byte-compiler warn on quote lexical var
2015-08-04 9:17 bug#21185: 25.0.50; byte-compiler warn on quote lexical var stephen_leake
@ 2015-08-06 3:28 ` Stefan Monnier
2015-08-06 7:15 ` Stephen Leake
2021-07-08 14:12 ` Lars Ingebrigtsen
0 siblings, 2 replies; 4+ messages in thread
From: Stefan Monnier @ 2015-08-06 3:28 UTC (permalink / raw)
To: stephen_leake; +Cc: 21185
> I've been bitten by this problem when converting code to use lexical
> binding; it would be helpful if the byte-compiler warned about it.
Agreed, but I haven't figured out how to make this work.
There are two problems:
1- detect not just things like « 'var » but also things like « '(var1
var2 var3) » since such occur in a few places as well.
2- don't swamp the user with false positives.
Problem 2 is by far the biggest. It's very common to have a local
variable `face' and at the same time to use the symbol `face' (quoted),
for example.
I do have such a warning in my local hacks (it outputs a warning for any
'<var> where <var> is a locally bound lexical variable) and find it
unbearable, even though I'm usually considered to tolerate warnings much
better than most.
Stefan
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#21185: 25.0.50; byte-compiler warn on quote lexical var
2015-08-06 3:28 ` Stefan Monnier
@ 2015-08-06 7:15 ` Stephen Leake
2021-07-08 14:12 ` Lars Ingebrigtsen
1 sibling, 0 replies; 4+ messages in thread
From: Stephen Leake @ 2015-08-06 7:15 UTC (permalink / raw)
To: Stefan Monnier; +Cc: 21185
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> I've been bitten by this problem when converting code to use lexical
>> binding; it would be helpful if the byte-compiler warned about it.
>
> Agreed, but I haven't figured out how to make this work.
> There are two problems:
> 1- detect not just things like « 'var » but also things like « '(var1
> var2 var3) » since such occur in a few places as well.
> 2- don't swamp the user with false positives.
>
> Problem 2 is by far the biggest. It's very common to have a local
> variable `face' and at the same time to use the symbol `face' (quoted),
> for example.
>
> I do have such a warning in my local hacks (it outputs a warning for any
> '<var> where <var> is a locally bound lexical variable) and find it
> unbearable, even though I'm usually considered to tolerate warnings much
> better than most.
Ok. Can you post your local hack? That would at least be useful during a
transition to lexical-binding: t; after that, testing should suffice.
--
-- Stephe
^ permalink raw reply [flat|nested] 4+ messages in thread
* bug#21185: 25.0.50; byte-compiler warn on quote lexical var
2015-08-06 3:28 ` Stefan Monnier
2015-08-06 7:15 ` Stephen Leake
@ 2021-07-08 14:12 ` Lars Ingebrigtsen
1 sibling, 0 replies; 4+ messages in thread
From: Lars Ingebrigtsen @ 2021-07-08 14:12 UTC (permalink / raw)
To: Stefan Monnier; +Cc: stephen_leake, 21185
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> I've been bitten by this problem when converting code to use lexical
>> binding; it would be helpful if the byte-compiler warned about it.
>
> Agreed, but I haven't figured out how to make this work.
> There are two problems:
> 1- detect not just things like « 'var » but also things like « '(var1
> var2 var3) » since such occur in a few places as well.
> 2- don't swamp the user with false positives.
>
> Problem 2 is by far the biggest. It's very common to have a local
> variable `face' and at the same time to use the symbol `face' (quoted),
> for example.
So the suggestion is to have code like
(let ((foo "bar"))
(when (zot 'foo)
...))
give a warning (in lexical code)? That does sound useful, especially if
the `zot' here is `bound-and-true-p', which somebody was using in a
different bug report the other week.
But I think that Stefan is totally correct in 2) -- there will be so
many false positives that it won't be useful. So I'm closing this bug
report.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
^ permalink raw reply [flat|nested] 4+ messages in thread
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2015-08-04 9:17 bug#21185: 25.0.50; byte-compiler warn on quote lexical var stephen_leake
2015-08-06 3:28 ` Stefan Monnier
2015-08-06 7:15 ` Stephen Leake
2021-07-08 14:12 ` Lars Ingebrigtsen
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