Re: Most of Elisp lacks lexical-binding: t

[phillip.lord@russet.org.uk (Phillip Lord)]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> And that's not just for Emacs core -- there is a massive quantity of
>> Elisp in the ecosystem at large which was not written for lexical
>> binding, and still works absolutely fine in current versions of Emacs.
>> Such libraries might well no longer have a maintainer (but at present
>> not be in any need of one).
>
> Yup.  The path to getting rid of lexical-binding=nil will be long.

Longer still if it is not started.

> Also, in my experience, the older the package the more likely it is to
> rely in tricky ways on dynamic scoping (by which I mean that some uses
> won't be caught by the compiler warnings).

Put code in so that if copyright year < 2018 then use dynamic by
default, otherwise use lexical?

(This is not a serious suggestion, just in case there is any doubt).

> This needs to be done step by step and there will be many steps.
> I proposed some steps a year ago, BTW.  See bug#30078.
>
>> The risk seems rather high to me.  I'm not sure the reward would be
>> worth it?  (When the reward would seem to be nothing more than library
>> authors being able to omit -*- lexical-binding: t; -*- which, even if
>> it looks untidy, isn't exactly an onerous requirement).
>
> For me the issue is that those two settings define two slightly
> different languages, and that increases complexity for newcomers (and
> for old hats as well: I still regularly find myself writing code that
> assumes lexical-binding is non-nil and using it in a context where that
> assumption is not valid).

I think it also limits the uptake of lexical-binding and the ability to
depend on it, because it requires some additional work.

It will break things, no doubt about it. I suspect it will break things
whenever it happens, though, so this isn't a reason for not doing it.

Phil