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To: Nikita Popov <nikita.ppv@gmail.com>,
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Date: Sat, 27 Jul 2019 20:17:07 -0700
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Subject: Re: [PHP-DEV] Re: [RFC] Namespace-scoped declares, again
From: smalyshev@gmail.com (Stanislav Malyshev)

Hi!

> I plan to pick up this proposal again. I think the motivation here has
> become more pressing in the meantime. The strict_operators proposal is
> under discussion, and Rowan's "locked classes" essentially concluded with
> "doing this with a declare is better". I also think that this proposal will
> be helpful for the explicit call-site by-reference passing RFC.

I think it's a wrong way to make semantics of the language to be
different in different libraries. We add one option, than another, than
another, and soon we have 512 variants of the language, all slightly
different, and you have to keep track which one you are dealing with on
each file, and God forbid you move a piece of code from one library to
another, you have to rewrite half of it because it was written in PHP
#243 but this library is actually PHP #116.

I know there is not a consensus about usage of some newly proposed
language features. I think introducing this kind of fragmentation to
deal with it is exactly wrong way to deal with it. It leads to code from
different codebases being incompatible with each other on source level
(even if they work together at runtime). We've decided not to do INI
options to change language behavior, and I think we should also not make
declare() options to change language behavior, because they are -
especially when applying to more than local file - essentially low-grade
INI options. They create non-local context that changes behavior of the
language, and they make it impossible, reading the local code, to know
what it actually means and what would happen if you run it.
I think it's much better for the language not to have some features than
to fragment the language and make it incompatible with itself.

> Based on the received feedback, I plan to change this proposal from being
> "namespace-scoped" to being "directory-scoped" instead. This should both

I don't think it improves much, in my opinion, and it also introduces
hard dependency in the language on specific placing of files and
directories - i.e. if you move file on the filesystem, it can actually
work differently, which was never the case before. Having concepts like
filenames change the core functionality of the language looks to me like
an example of leaky abstraction and a hack which may solve a particular
problem now but at the cost of making the whole design more messy and
introducing more problems in the future.
I said before that moving code between libraries in this setup could
break it - but with this change, even copying a file to a different
directory may break it! Moreover, change in one part of project,
changing some behavioral option, would propagate and influence code
about which the changer may not even know (e.g. if parts of the project
are developed and tested separately and only deployed in final form on a
production filesystem).
This looks like potential to create an environment that is very hard to
navigate and keep straight which of the options is in play for each
peace of code.
-- 
Stas Malyshev
smalyshev@gmail.com