Easy enough.  Put these in a directory, say ~/emacs-bug-1801 and run the
following command:

emacs -Q --batch -L . --eval             \
     "(progn                                \
       (setq byte-compile-error-on-warn t)  \
       (batch-byte-compile))" *.el


On Emacs 24.3 the following warning will occur:

In toplevel form:
bug.el:10:1:Warning: Unused lexical argument `key' *<<--- Incorrect; key is
a used lexical argument*
Wrote e:/EmacsPortable.App/Data/src/ergoemacs-mode/bug.elc
In toplevel form:
bug2.el:10:1:Warning: argument `_key' not left unused
*<<--- Correct; _key is a used lexical argument*Wrote
e:/EmacsPortable.App/Data/src/ergoemacs-mode/bug2.elc

Also on emacs 24.3, even though batch-byte-compile-error-on-warn is set to
t, it will ignore the errors, which is not what I expect when I set this
option.
On Emacs trunk (24.4) it will not ignore the error but cause the make to
fail.

Matt



Type the following




On Mon, Jul 14, 2014 at 11:18 AM, Eli Zaretskii <eliz@gnu.org> wrote:

> > Date: Mon, 14 Jul 2014 11:01:12 -0500
> > From: Matthew Fidler <matthew.fidler@gmail.com>
> > Cc: 18014@debbugs.gnu.org
> >
> > You probably downloaded the version with lexical binding disabled.
> >
> > Sorry, I should have linked to the version with lexical binding enabled.
>
> So how about posting a complete, self-contained recipe that could be
> used to reproduce the problem?
>
> TIA
>