bug#18163: 24.4.50; REGRESSION, font-lock in `emacs-lisp-mode': spurious `font-lock-warning-face'

bug#18163: 24.4.50; REGRESSION, font-lock in `emacs-lisp-mode': spurious `font-lock-warning-face'

[Drew Adams]

Recipe from emacs -Q: Type this into an Emacs-Lisp mode buffer:

(defun foo ()
  (condition-case nil
      (let ((toto (lambda (cand)
		     (foo)) bar)))
    (quit (tutu))))

The text "bar)))" is highlighted erroneously, with face
`font-lock-warning-face'.  It should not be highlighted at all.

If you add more right-parens, or any other text, at the end of the same
line as the warning-highlighted text, it too has that red face.  It
does not seem to matter what text you add.  You can remove all of the
warning-face text except the `b' (or any other char in place of `b'),
and it is still highlighted.  You can remove the SPC before the `b'
and it remains highlighted.  If you remove the whitespace before
"(foo..." on the same line, the highlighting remains.

If you remove the newline before the "(foo..." line then the
highlighting goes away.

The first build where I see this regression is this one:

In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-04-25 on ODIEONE
Repository revision: 117024 monnier@iro.umontreal.ca-20140425192226-frpjpmgs0r8ad9wc
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

The last build I have where there is not this regression is this one:

In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-04-21 on ODIEONE
Repository revision: 117005 dancol@dancol.org-20140421180019-po4wdeg7gqvvlh5d
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

This is the build I'm sending this report from:

In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-06-28 on ODIEONE
Bzr revision: 117431 rgm@gnu.org-20140628015517-eku6hj8mpgcvfnso
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

bug#18163: 24.4.50; REGRESSION, font-lock in `emacs-lisp-mode': spurious `font-lock-warning-face'

[Stefan Monnier]

tags 18163 notabug
thanks

> The text "bar)))" is highlighted erroneously, with face
> `font-lock-warning-face'.

It's no error.  There's even a help-text explaining why it's highlighted
this way (if you hover your mouse above the highlighted text).


        Stefan

bug#18163: 24.4.50; REGRESSION, font-lock in `emacs-lisp-mode': spurious `font-lock-warning-face'

[Drew Adams]

> It's no error.  There's even a help-text explaining why it's highlighted
> this way (if you hover your mouse above the highlighted text).

I see.  Yes, I can see that that can be helpful.

It's unfortunate that the same face is used for this kind of warning
and for things like `error' and `user-error', which are not something
to be warned about.  It is handy to highlight those too (specially),
but they should not use a "warning" face, if that face is really
starting to be used to warn.

IOW using `font-lock-warning-face' to warn uncovers an (effectively
new) bug: its use for non-warnings is inappropriate.  It could
arguably have been considered appropriate (though poorly named) as
long as none of the uses involved warning.  There is no longer any
such justification.

bug#18163: 24.4.50; REGRESSION, font-lock in `emacs-lisp-mode': spurious `font-lock-warning-face'

[Leo Liu]

On 2014-08-06 13:15 -0400, Stefan Monnier wrote:
> It's no error.  There's even a help-text explaining why it's highlighted
> this way (if you hover your mouse above the highlighted text).

Maybe the face can be tweaked to improve usability, for example,
underwave/line it.

Leo