Frank Terbeck <ft@bewatermyfriend.org> writes:

> The manual says this:
>
>   ‘default’
>        This element of SPEC doesn’t match any terminal; instead, it
>        specifies defaults that apply to all terminals. This element, if
>        used, must be the first element of SPEC. Each of the following
>        elements can override any or all of these defaults.
>
> I tried using that in a theme, but the "override" part didn't work.
>
> So I did this from "emacs -Q" to see if something else in my setup was
> screwing things up for me:
>
> (deftheme foobar "Foobar theme")
> (custom-theme-set-faces 'foobar
>   '(default ((default :slant normal
>                       :weight bold
>                       :foreground "white"
>                       :background "black")
>              (t :foreground "blue"))))
>
> What I would expect is the `blue' foreground definition from the `t'
> clause to override the `white' foreground definition from the `default'
> clause. But alas, it doesn't work, the foreground remains white.

I can reproduce this in Emacs 27, but not with current master.

It looks like this was fixed in:
commit 05d365d3105371ec956f31f109a2de14c5cf67df
Author: Eli Zaretskii <eliz@gnu.org>
Date:   Sat Apr 4 09:59:16 2020 +0300

    Fix face spec handling for 'default' "terminal class"

    * lisp/faces.el (face-spec-choose): Reverse order of 'defaults'
    and 'result' when generating attribute list, so that the spec for
    'default' "terminal class" is indeed overridden by the actual
    class's spec, per the documentation.  (Bug#40336)

CCing Eli, hoping he can confirm.