GNU bug report logs - #26624
26.0.50; Generalized variable `buffer-local-value' does't restore local flag

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From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: 26624 <at> debbugs.gnu.org
Subject: bug#26624: 26.0.50; Generalized variable `buffer-local-value' does't restore local flag
Date: Sat, 17 Jun 2017 13:10:20 +0000

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Philipp Stephani <p.stephani2 <at> gmail.com> schrieb am So., 23. Apr. 2017 um
19:14 Uhr:

>
> In *scratch*, evaluate:
>
> (defvar foo-test-var nil)
> (with-temp-buffer
>   (list (list (buffer-local-value 'foo-test-var (current-buffer))
>               (local-variable-p 'foo-test-var)
>               (local-variable-if-set-p 'foo-test-var))
>         (cl-letf (((buffer-local-value 'foo-test-var (current-buffer))
> 123))
>           (list (buffer-local-value 'foo-test-var (current-buffer))
>                 (local-variable-p 'foo-test-var)
>                 (local-variable-if-set-p 'foo-test-var)))
>         (list (buffer-local-value 'foo-test-var (current-buffer))
>               (local-variable-p 'foo-test-var)
>               (local-variable-if-set-p 'foo-test-var))))
>
> The result is:
>
> ((nil nil nil) (123 t t) (nil t t))
>
> But expected is:
>
> ((nil nil nil) (123 t t) (nil nil nil))
>
> i.e. the local flag of the variable should be reset.
>
>
It's possible to fix this (see attached patch), but at the expense of
breaking other valid use cases such as (cl-incf (buffer-local-value ...)).
Not sure whether the bug can be fixed at all without breaking other stuff.

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