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Date: Thu, 28 Apr 2016 17:49:44 +0200
CC: Josh Di Fabio <joshdifabio@gmail.com>,
 Levi Morrison <levim@php.net>,
 internals <internals@lists.php.net>
References: <CAFMT4Nozvf=9yEbaBpe6Zjd1pidnOAH=FjVNNLVzoB6gTz-POg@mail.gmail.com> <CAKiSzdC3JmevOGfTYBcRgMbsCrMEB7POU8WrkBRNM1Nhq8-TDw@mail.gmail.com> <CAFp73XtzXMy1C3G5iYkN2R0-nrg_6a9wPatHVODh8korTGk+SQ@mail.gmail.com>
To: "guilhermeblanco@gmail.com" <guilhermeblanco@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Intersection Types
From: bobwei9@hotmail.com (Bob Weinand)

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> Am 28.4.2016 um 17:11 schrieb guilhermeblanco@gmail.com:
>=20
> Nice!
>=20
> I've read the RFC and there's only one missing thing that is either
> undocumented or missed during patch creation: instanceof.
> I'd be amazing if we could do: $foo instanceof Foo & Bar
>=20
> Cheers,
>=20
> On Thu, Apr 28, 2016 at 5:00 AM, Josh Di Fabio <joshdifabio@gmail.com>
> wrote:
>=20
>> On Thu, Apr 28, 2016 at 4:54 AM, Levi Morrison <levim@php.net> wrote:
>>> Internals,
>>>=20
>>> As alluded to last week I have another RFC for improving the type
>>> system: [intersection types][1].
>>>=20
>>> It allows parameters to define multiple type constraints that must =
be
>>> satisfied. Common combinations of our built-in types include
>>> `ArrayAccess & Traversable & Countable` and `Countable & Iterator`.
>>>=20
>>> Some people have suggest I merge this and union types into one RFC.
>>> For now I'll just proceed with them separately to gain feedback.
>>>=20
>>>  [1]: http://wiki.php.net/rfc/intersection_types
>>>=20
>>> --
>>> PHP Internals - PHP Runtime Development Mailing List
>>> To unsubscribe, visit: http://www.php.net/unsub.php
>>>=20
>>=20
>> To me, it seems that intersection types are more useful than union
>> types (other than the obvious null|Foo and array|Traversable cases) =
as
>> they'd allow us to write smaller interfaces and better follow ISP in
>> userland, with interfaces becoming much more convenient for
>> documenting the requirements of a parameter.
>>=20
>> At present we tend to have incomplete implementations of interfaces
>> (e.g. throw OperationNotSupportedException). Union types would allow
>> us to create more, smaller interfaces and avoid situations where the
>> type of a parameter doesn't accurately reflect the method's true
>> requirements, or where concretions are incomplete implementations of
>> an interface.
>>=20
>> Thanks for your efforts, Levi, I'm excited about this one!
>=20
> --=20
> Guilherme Blanco
> Lead Architect at E-Block

Who=E2=80=99s top-posting here? ;-)

Regarding your suggestion, $foo instanceof Foo & Bar is conflicting with =
bitwise and here. Anyway, you already can $foo instanceof Foo && $foo =
instanceof Bar. Which is IMO just as easy, not conflicting and more =
flexible.
Also, instanceof would not (at least not currently) work with scalar =
types, array or callable. (i.e. $foo instanceof string doesn=E2=80=99t =
work). And thus $foo instanceof Foo & callable doesn=E2=80=99t either. =
Which is quite a difference to intersection/union types.

Bob





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