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To: Nikita Popov <nikita.ppv@gmail.com>
CC: Claude Pache <claude.pache@gmail.com>, Nicolas Grekas
	<nicolas.grekas+php@gmail.com>, Mark Randall <marandall@php.net>,
	"internals@lists.php.net" <internals@lists.php.net>
Thread-Topic: [PHP-DEV] [RFC] "use global functions/consts" statement
Thread-Index: AQHV1IfBuqjWnIu9lEWrxlRKvYFij6f9dXecgADKhQCAAFMdqA==
Date: Mon, 27 Jan 2020 14:43:21 +0000
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Subject: Re: [PHP-DEV] [RFC] "use global functions/consts" statement
From: tysonandre775@hotmail.com (tyson andre)

> This would be a compile error right now though, because we don't allow "u=
se"d symbols and declarations to clash.=0A=
=0A=
As I surprisingly discovered when implementing the RFC, they don't clash.=
=0A=
The PHP interpreter has a special case where it doesn't warn or throw about=
 the name being in use=0A=
if the resolved (namespaced) name in use is the same as the element being d=
eclared.=0A=
See https://3v4l.org/RtPKv - the below example works.=0A=
=0A=
```=0A=
<?php=0A=
=0A=
namespace NS;=0A=
use function NS\foo;=0A=
use const NS\BAR;=0A=
=0A=
function foo() { echo BAR; }=0A=
const BAR =3D 3;=0A=
foo();=0A=
```=0A=
=0A=
> While I was the one who originally suggested to allow this kind of code, =
=0A=
> I think it might be better to just unconditionally make it a compile erro=
r,=0A=
> and require the use of declare(function_and_const_lookup=3D'default')=0A=
> if you want to declare namespaced constants or functions. =0A=
>The main motivation for allowing it is interoperability with namespace-sco=
ped declares,=0A=
> but as those don't exist yet (and would still allow a per-file opt-out), =
we can delay this issue.=0A=
> =0A=
> I think that principally, the correct behavior here is to bring the symbo=
l into scope as it is declared,=0A=
> but as you already pointed out, this leads to unclear semantics when cond=
itional function declarations are involved.=0A=
=0A=
The subset of code that can be written requiring "use function NS\foo;" and=
 "use function NS\MY_CONST;"=0A=
with function_and_const_lookup=3D'default' is larger than forbidding it com=
pletely, while still avoiding ambiguity.=0A=
=0A=
> As a minor note, rather than using 'default' as one of the values,=0A=
> I think it would be better to use 'fallback' to make it robust against a =
potential future change of defaults.=0A=
=0A=
I'd rather have that done when the future change of defaults is being propo=
sed.=0A=
Supporting 'fallback' might cause confusion and extra work if the name reso=
lution defaults ever change in a different way.=0A=
At the point where they do change, we either do or don't want a way to supp=
ort the old 'fallback',=0A=
but we will want to support the new 'default'.=0A=
=0A=
Right now, it's deliberately intended to be the same as just leaving the se=
tting off for that file.=