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Date: Fri, 22 Apr 2016 09:56:13 -0500
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To: Levi Morrison <levim@php.net>
Subject: Re: [PHP-DEV][RFC] Callable Types
From: aaron@icicle.io (Aaron Piotrowski)

Hi!

> On Apr 22, 2016, at 9:39 AM, Levi Morrison <levim@php.net> wrote:
>=20
>> Not much else to say, the syntax reads a bit weird/heavy being all =
in-line
>> with the function signature but at the same time I can't imagine how =
else it
>> would work that would be any better.
>=20
> As mentioned on Reddit and in the future scope section of union types,
> we may want to introduce named type expressions:
>=20
>    type IntReducer =3D callable(int, int): int;
>=20
> Which would also allow unions (if passed, of course):
>=20
>    type Iterable =3D Array | Traversable;
>=20
> It would also allow for a general type-aliasing mechanism for single
> names. This feature has been asked for in the past but I can't
> remember the use-cases so this example is not very good:
>=20
>    type Foo =3D SomeFoo;
>=20
> Then we just use the names where we would have put the expressions:
>=20
>    function reduce(int $a, int $b, IntReducer $reducer): int {
>        return $reducer($a, $b);
>    }
>=20
> --=20
> PHP Internals - PHP Runtime Development Mailing List
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>=20

While this is somewhat off-topic of this particular RFC, since we can =
already do general type-aliasing with `use`,

use SomeFoo as Foo;

perhaps similar syntax could be used for type expressions, eliminating =
the need for a new keyword.

use callable(int, int): int as IntReducer;

use array | Traversable as Iterable;

Cheers!

Aaron Piotrowski
@trowski2002
trowski.com=