Subject: bug#45428: 27.1; (quote (quote (quote ...))) unexpectedly works as anonymous face

From: Markus Triska <[email-masked]>
Date: Tue, 29 Dec 2020 17:40:38 +0100

Eli Zaretskii <[email-masked]> writes:

> If you follow the cross-reference to "Special Properties", you will
> find that the value of the 'face' property can be one of the
> following:
>
>   . a face symbol
>   . a property list of attribute/value pairs
>   . a cons cell of the form (foreground-color . COLOR)
>   . a cons cell of the form (background-color . COLOR)
>   . a list of faces, each one given by any of the above forms
>   . a cons cell of the form (:filtered FILTER FACE-SPEC), where
>     FACE-SPEC is one of the above forms
>
> And now you should recognize that the strange format of the property
> value, which prompted the original bug report, fits the "list of
> faces" format as described by the 5th item in the above list.

In the original bug report, the property value has the form:

    (quote (quote (quote ...)))

I recognize that it is a list. However, I do not recognize that each of
its elements is given "by any of the above forms", i.e., by any of:

>   . a face symbol
>   . a property list of attribute/value pairs
>   . a cons cell of the form (foreground-color . COLOR)
>   . a cons cell of the form (background-color . COLOR)

Could you please clarify which of these forms match (quote (quote ...)) ?

Thank you a lot!
Markus