Subject: bug#20977: 24.5; Hi Lock Mode fails with "Invalid pattern list expression"

From: Michael Heerdegen <[email-masked]>
Date: Sat, 04 Jul 2015 16:46:27 +0200

Raffaele Ricciardi <[email-masked]> writes:

> emacs -Q
> C-h f hi-lock-mode RET
> C-x b *Help* RET
> M-x hi-lock-mode RET
>
> Emacs says:
>
> Invalid pattern list expression at 60

AFAIK this is not an error, just a message (that you can safely ignore).
The mode is enabled nonetheless and should work as expected.

Background: There is a feature that hi-lock-mode searches for pattern
specifications of the kind

  Hi-lock: FOO

that define initial highlightings.

Since the help buffer of `hi-lock-mode' explains this feature, it
contains a match for the regexp searched for (namely "Hi-lock: FOO") but
hi-lock-mode discards it because it is invalid (thus the message).  So
this issue is only a coincidence appearing only in the help buffer of
`hi-lock-mode'.  FWIW I can live with this message in this special case,
though I agree that it is confusing.

Michael.