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Date: Sun, 14 Sep 2014 16:09:31 +0100
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To: Andrey Andreev <narf@devilix.net>
Subject: Re: [PHP-DEV] [VOTE][RFC] Scalar Type Hinting with Cast
From: ajf@ajf.me (Andrea Faulds)


On 14 Sep 2014, at 15:56, Andrey Andreev <narf@devilix.net> wrote:

> It seems a bit political ... A lot of people want either strict type
> hints or type casting hints, but because the people on this list can't
> get to agree on any of the two, this RFC tries to make a compromise
> that, IMO, satisfies nobody. It's done not for the benefit of
> everybody, but just so we can say that PHP has "scalar type hints".
> I've said this in the RFC discussion thread: In order to satisfy both
> sides, instead of arguing which is the one and true way, just
> implement both.

I=92m not sure it satisfies nobody. I realise a lot of people would =
prefer strict types, but plenty are still in favour of this as a =
compromise:

http://strawpoll.me/2463199/r - Might not be representative, but I held =
a poll on Twitter and StackOverflow. There are the results. 67 would =
vote in favour of strict hints (=E0 la Hack), and 36 would vote in =
favour of this RFC, with only 5 willing to vote against it, versus 10 =
voting against strict hints. Note that the options aren=92t mutually =
exclusive.=20

> That is also why I suggested altering the proposed syntax here from:
>=20
>    function foo(int $bar)
>=20
> to:
>=20
>    function foo((int) $bar)

But it=92s not a cast. Such a syntax would be misleading. You would =
reasonably expect the following two functions to be equivalent:

    function foo($bar) { $bar =3D (int)$bar; }
    function foo((int) $bar) { }

Yet they are not equivalent at all.=20

> Whether it applies more strict rules or not, this RFC is clearly about
> type _casting_ hints, while the used syntax has so far only been used
> for strict type hints.

Well, we haven=92t had any scalar hints so far. It=92s also worth noting =
that the documentation for PHP uses this style even though internal =
functions are not strict. Furthermore, scalar types in PHP are =
fundamentally different from non-scalar types. We do not have weak =
typing for non-scalars: there are no implicit casts between non-scalar =
types. However, we implicitly convert and juggle the scalar types all =
the time.

> I know some would argue that this is a side
> effect because you can't cast to a specific class type, but that's not
> the point - the result is a strict type hint and that's what people
> are used to. This is both inconsistent AND prevents PHP from having
> strict scalar type hints in the future (because of the used syntax).

Strict hints would still be possible with different syntax. However, I=92m=
 not sure they=92re a good idea. Strict hints would be abandoning PHP=92s =
weakly-typed nature, and would segregate userland functions into two =
kinds: strict and non-strict. I also don=92t expect that would pass =
internals anyway.

I don=92t think permitting multiple options is really the way forward, =
that sounds like the worst of both worlds.=20

--
Andrea Faulds
http://ajf.me/