Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:109045
User-Agent: Cyrus-JMAP/3.1.7-991-g5a577d3-fmstable-20200305v3
Mime-Version: 1.0
Message-ID: <421993bf-821c-4ebf-802a-be9814b30b90@www.fastmail.com>
In-Reply-To: 
 <CAH5C8xXp0ZNKsOP7CCWeRo7N9Xeu2SqxBOYCY--bVHVPw6s16g@mail.gmail.com>
References: 
 <CAH5C8xVYFkgyW88332ei8coMOijuynHXg3A2dL50XU4HP5Vpyw@mail.gmail.com>
 <CAKuGYLTsK2h_Yeo1vMju867hhmzyHt+GwoGStcQtiYMi2VB1tg@mail.gmail.com>
 <CAF+90c9RKf5PUQY0XHf=8QVVMw8jiJ=7eWfY5TTANEYt-a-ZAA@mail.gmail.com>
 <8545d15e-ddd5-42be-8405-09697a077234@www.fastmail.com>
 <CAH5C8xWgkUCAJguwnP69VqWXUaR+QtJRPMyBdv7B5vcnQjTD1g@mail.gmail.com>
 <4d9688fe-cc57-44af-903e-05f4cbb1bbcc@www.fastmail.com>
 <CALKiJKpt+xBwyEn-yVY6h_DT-c+T6nUGgye6Ocxjdcpc4fOobg@mail.gmail.com>
 <6bcbf0a5-92d8-4cfa-a00f-e0e967fc037e@www.fastmail.com>
 <CAOWwgpm6VJAphpdkqTo21=S6xXW=6q26v=C=H=KCF=SS0h7BoA@mail.gmail.com>
 <CAH5C8xVpHYW7woD-Fw_o2HvbDpsjGN0fE6Z+S3n0UxcTRBhySQ@mail.gmail.com>
 <CAH5C8xVm5mX6tiLBnBcGTDR0XmumWxfc2q=p5a9qqtisDM-jiQ@mail.gmail.com>
 <CAH5C8xXZKvi20ST1JLPWxuo+7Hpp933_L0WnDNqX8Dum3ukRHA@mail.gmail.com>
 <700327df-45d5-47ca-8828-d7ad9c9bee2e@www.fastmail.com>
 <CAH5C8xWRevvdHyNx01Eg4b_qYAESniYZdkGWfdgiPO81cL4ziQ@mail.gmail.com>
 <CADyq6sKrwur9w+AvJ-hFx28=KZcDU7+2kwuGe+B_YVtKwzAo_g@mail.gmail.com>
 <CAH5C8xVQ-=qzLBCaq5NcU+dbzSpFEPF5Qv0n+W+uwyEdNjhzKg@mail.gmail.com>
 <CADyq6sLkWoCBqY+75xBLEun8xiAFhrY9BHJ9YjhLCXuECqha=A@mail.gmail.com>
 <6f2e7718-5d78-4c57-8da9-f8dd44cc9e7b@www.fastmail.com>
 <CAH5C8xXp0ZNKsOP7CCWeRo7N9Xeu2SqxBOYCY--bVHVPw6s16g@mail.gmail.com>
Date: Sun, 15 Mar 2020 18:22:53 -0500
To: "php internals" <internals@lists.php.net>
Content-Type: text/plain;charset=utf-8
Content-Transfer-Encoding: quoted-printable
Subject: Re: [PHP-DEV] [RFC] [DISCUSSION] Immutable/final/readonly properties
From: larry@garfieldtech.com ("Larry Garfield")

On Sun, Mar 15, 2020, at 4:44 PM, M=C3=A1t=C3=A9 Kocsis wrote:
> >
> > Avoiding that confusion will save the industry millions of dollars.
> >
>=20
> On the one hand, you are right, because currently it's not very useful=
 to
> effectively provide two
> ways of declaring a constant. On the other hand however, if we also
> consider a longer term
> aim of adding support for object default values (just like what Marco
> mentioned):
> public read-only DateTimeImmutable $startupTime =3D new DateTimeImmuta=
ble();
> then allowing default values for "write-once" properties seems much mo=
re
> sensible. At this point,
> the "million dollar mistake" label doesn't hold anymore since class
> constants and "write-once"
> properties with default values will actually be two different things. =
But
> we've just ended up at
> Marco's suggestion:

I'll be honest, I really have no idea how default object values is at al=
l related here.  I mean, those would be nice to have as well for various=
 reasons, but I don't see how it's related to read-only properties.

> >  1. Prevent the parser from accepting default values on write-once
> > properties (parser error)
> >  2. Re-introduce them once we know what we want to do with default v=
alues
> > (and it makes sense)
>=20
> Yes, this scenario definitely makes sense. I'm just not yet sold that =
it
> will have any negative effects
> if we don't restrict the usage of default values now. I understand tha=
t
> it's usually advantageous to be
> conservative with adding new features - especially when groping in the=
 dark
> - since we are the ones
> who have to support and fix them later. That's why I was hesitant to a=
dd
> property covariance to the
> proposal.

The negative effect is if we later decide that it's too much of a proble=
m to have default values, because they're just too confusing (people deb=
ating if they should be a constant, people expecting them to be overwrit=
eable, etc.), we can't simply remove them.  That would be a large breaki=
ng change and not allowed, so we're stuck with 'em.

Whereas if we don't add it now, we can see if people are really clammori=
ng for it and in what situations.  We let the PHP-using masses do the re=
search for us to determine how read-only-default would actually be usefu=
l, or if it would be useful at all.  Then we can add it later in a way t=
hat would actually be useful, or decide not to do it at all.

--Larry Garfield