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Date: Thu, 25 Mar 2021 11:02:39 -0400
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To: Rowan Tommins <rowan.collins@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Auto-capture multi-line closures and
 shortfunctions take 2
From: mike@newclarity.net (Mike Schinkel)



> On Mar 25, 2021, at 10:41 AM, Rowan Tommins <rowan.collins@gmail.com> =
wrote:
>=20
> On 25/03/2021 12:31, Nuno Maduro wrote:
>=20
>> The reason why we believe the vast majority of PHP Developers are =
going to
>> appreciate this RFC is because multi-line short closures (aka
>> Auto-capturing multi-statement closures) *are more simple, shorter to
>> write, and prettier to read *=E2=80=94 and the community love these =
changes as
>> proven on "property promotions", "one-line short closures", etc.
>=20
>=20
> My main point was that the RFC needs to spell out this argument, =
rather than taking it for granted that everyone agrees on "those =
situations where that is warranted".
>=20
> Most of the current text should be summarised in a "syntax choices" =
section somewhere near the end. I would like to see much more space =
devoted to:
>=20
> * Why we need this feature. What has changed since it was left out of =
the arrow functions RFC? What problems is it addressing? Why do you =
think it is the best approach to those problems?
> * The exact semantics proposed: How will the variables to be captured =
be determined? Will it distinguish variables which are written before =
they're read, and if so how is that defined? Can auto-capturing closures =
be nested, i.e. will "fn() { return fn() { echo $a; } }" capture $a from =
the outermost scope? And so on...
>=20
>=20
>> Besides, one advantage of this RFC is that it is consistent with the
>> current syntax of the language and with the short-functions RFC[2]. =
For
>> example, by proposing that "fn" keyword indicates a function will
>> auto-capture variables, by value.
>=20
>=20
> While it's a cute rationalisation, there's no intuitive reason why =
"fn" should have that meaning; we could pick any aspect of the current =
arrow function syntax and say "the 'fn' keyword means that".
>=20
>=20
>=20
>> On the other hand "use (*)" has no usages / or current meaning in the
>> language.
>=20
>=20
> This is a straw man argument. I could equally say that "fn() { } has =
no usages or current meaning in the language" - of course it doesn't, we =
haven't added it yet!
>=20
> The "function use() {}" part of "function use(*) {}" has a =
well-established meaning, and "*" to mean "everything" is a notation =
developers are likely to be very familiar with.
>=20
> The two disadvantages I see with using "fn" as proposed are:
>=20
> * Because it's shorter, people will decide it's the "better" version, =
when they don't actually need any variable capture. An explicit syntax =
like "use(*)" instead makes this a deliberate choice.

And yet adding " use (*)" makes the syntax longer, which goes against =
one of the goals many people have for it: to be shorter.

> * There is no obvious way to expand it to support any by-reference =
capture, which is something people have previously expressed a desire =
for.

Can you please clarify why "function(...) use(...) {...}" can't be their =
solution when someone needs by-reference capture?

-Mike

P.S. BTW, if we *had* to enable by-ref for "fn(...)" then I would argue =
it should be a terse syntax, e.g.:

$callable =3D fn()(&$foo) =3D> $foo=3D bar();