Re: Default lexical-binding to t

[Stefan Kangas <stefankangas@gmail.com>]

Jim Porter <jporterbugs@gmail.com> writes:

> As for warning about a missing 'lexical-binding' cookie, maybe we could
> check the "Package-Requires" metadata and warn if the "emacs"
> requirement is less than 31, but there's no 'lexical-binding' cookie? If
> you write a package that supports older Emacsen, then you still need the
> cookie. For packages with a minimum Emacs of 31, no-cookie is fine.
>
> (For files that don't report the minimum Emacs, maybe we can make a
> guess that the minimum is "current-emacs - 2", or some other number? I'm
> not sure about the specifics here, but this would give us a warning that
> eventually goes away after a couple of Emacs versions.)

I think disabling the byte compiler and mode line warnings for packages
that explicitly declare support only for Emacs 31 or later makes sense.

While we're at it, we could also disable the warning for built-in and
non-:core libraries.  That would let us remove the cookie from most
files in emacs.git, if we wanted to.