GNU bug report logs - #14883
warning about unused returned value from some ert shoulds

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#14883: closed (warning about unused returned value from some
 ert shoulds)
Date: Thu, 05 Sep 2013 03:07:02 +0000

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Your message dated Wed, 04 Sep 2013 23:06:38 -0400
with message-id <jwv38pk3r39.fsf-monnier+bug#14883 <at> gnu.org>
and subject line Re: bug#14883: warning about unused returned value from some ert shoulds
has caused the debbugs.gnu.org bug report #14883,
regarding warning about unused returned value from some ert shoulds
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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14883: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=14883
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From: Glenn Morris <rgm <at> gnu.org>
To: submit <at> debbugs.gnu.org
Subject: warning about unused returned value from some ert shoulds
Date: Tue, 16 Jul 2013 16:17:05 -0400

Package: emacs
Version: 24.3
Severity: minor

Compiling a file with contents:

    ;; -*- lexical-binding: t; -*-
    (require 'ert)
    (require 'cl-lib)
    (defvar foo-test 1)
    (should foo-test)
    (cl-assert foo-test)

results in a warning (for some reason, only when lexical-binding is t):

   foo.el:5:1:Warning: value returned from (car value-94600) is unused

The warning is from the `should'. Obviously it is a bogus warning
because the whole point of the should is to test the return value.
The similar cl-assert does not trigger a warning, because internally
cl-assert is written differently.

This is the same issue as http://debbugs.gnu.org/10969, for what is now
cl-pop.

byte-optimize-form-code-walker has special handling for the standard
`pop' macro so as not to warn about unused return values from (pop foo).
It would be nice if there was a general way to get the same result for
arbitrary macros (sort of the opposite of side-effect-free?), but I
don't see how.

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Glenn Morris <rgm <at> gnu.org>
Cc: 14883-done <at> debbugs.gnu.org
Subject: Re: bug#14883: warning about unused returned value from some ert
 shoulds
Date: Wed, 04 Sep 2013 23:06:38 -0400

> Compiling a file with contents:
>     ;; -*- lexical-binding: t; -*-
>     (require 'ert)
>     (require 'cl-lib)
>     (defvar foo-test 1)
>     (should foo-test)
>     (cl-assert foo-test)
> results in a warning (for some reason, only when lexical-binding is t):
>    foo.el:5:1:Warning: value returned from (car value-94600) is unused

This `car' came from the closure conversion.  I believe it is now fixed
in the trunk.  Thank you.


        Stefan

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