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To: Derick Rethans <derick@php.net>
CC: Benas IML <benas.molis.iml@gmail.com>, Rowan Tommins
	<rowan.collins@gmail.com>, PHP Internals List <internals@lists.php.net>
Thread-Topic: [PHP-DEV] [RFC] Shorter Attribute Syntax Change RFC 0.2
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Date: Fri, 7 Aug 2020 21:50:00 +0000
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Subject: Re: [PHP-DEV] [RFC] Shorter Attribute Syntax Change RFC 0.2
From: theodorejb@outlook.com (Theodore Brown)

On Fri, Aug 7, 2020 at 6:03 AM Derick Rethans <derick@php.net> wrote:=0A=
=0A=
> On Fri, 7 Aug 2020, Theodore Brown wrote:=0A=
> =0A=
> > Even if we assume the implementation is only about 30 lines, it's=0A=
> > still extra complexity that I don't understand the benefit of. I=0A=
> > sincerely would like to know what advantage there is of grouped=0A=
> > attributes over the `@@` syntax.=0A=
> =0A=
> It was very *specifically* voted for:=0A=
> https://wiki.php.net/rfc/attribute_amendments#group_statement_for_attribu=
tes=0A=
=0A=
Hi Derick,=0A=
=0A=
It was specifically voted for the `<<>>` syntax, with the explicit=0A=
qualification that "This feature would be superseded by any other RFC=0A=
getting accepted that changes the syntax." This is exactly what=0A=
happened when the Shorter Attribute Syntax RFC was accepted.=0A=
=0A=
> You still haven't addressed any of the deficiencies that the other=0A=
> alternatives don't have:=0A=
> https://wiki.php.net/rfc/shorter_attribute_syntax_change#proposal=0A=
=0A=
I'm not sure which deficiencies you mean, but let's briefly go=0A=
through the table in the RFC to make sure nothing has been missed:=0A=
=0A=
- Number of required Characters:=0A=
    - `@@` has the advantage here.=0A=
=0A=
- Has End Delimiter:=0A=
    - This isn't clearly a pro or a con in itself.=0A=
=0A=
- Allows Grouping:=0A=
    - As discussed before, `@@` has the advantage of being equally=0A=
    concise without this added complexity.=0A=
=0A=
- Forward Compatibility in PHP 7:=0A=
    - This is at best a temporary benefit of `#[]` which will be=0A=
    irrelevant in a few years, at worst a source of confusion and bugs=0A=
    when code intended for PHP 8 runs on PHP 7 with different results.=0A=
=0A=
- Breaks BC of valid PHP 7 code:=0A=
    - All syntaxes but `<<>>` technically have a BC break. There really=0A=
    should be a separate line in the table for "Breaks useful syntax",=0A=
    since `#[]` and `@[]` have this deficiency, but `@@` does not.=0A=
=0A=
- Used by other language:=0A=
    - This is listed as an advantage for `#[]` and `<<>>`. However, the tab=
le=0A=
    fails to point out that Hack is migrating away from `<<>>` to `@Attr`.=
=0A=
    Furthermore, while `#[]` has the same start/end symbols as Rust, the re=
st=0A=
    of the grammar/semantics vary significantly. E.g. these are valid Rust=
=0A=
    attributes (see https://doc.rust-lang.org/reference/attributes.html):=
=0A=
=0A=
          #[rustfmt::skip]=0A=
          struct S {}=0A=
=0A=
          #[clippy::cyclomatic_complexity =3D "100"]=0A=
          pub fn f() {}=0A=
=0A=
    This is quite different from PHP's semantics, so it's not clear that=0A=
    copying the same start/end symbol would really be a benefit for us.=0A=
    Also note that unlike PHP, `#` does not start a comment in Rust.=0A=
=0A=
- Familiar with Docblock Usage:=0A=
    - `@@` has the advantage here once more.=0A=
=0A=
- Tokens used:=0A=
    - This isn't clearly a pro or con in itself.=0A=
=0A=
- Changes the lexing of **remaining** tokens:=0A=
    - This is apparently a con for `#[]`.=0A=
=0A=
=0A=
Ultimately I think `@@` does the best job balancing a very small BC=0A=
break with concise, familiar syntax that can cleanly support nested=0A=
attributes in the future. And since it avoids the need for attribute=0A=
grouping it also has the simplest implementation.=0A=
=0A=
Kind regards,  =0A=
Theodore=