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To: Stanislav Malyshev <smalyshev@gmail.com>, internals@lists.php.net
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Date: Thu, 14 Apr 2016 21:27:46 +0200
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Subject: Re: [PHP-DEV] Re: Improving PHP's type system
From: php@fleshgrinder.com (Fleshgrinder)

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From: Fleshgrinder <php@fleshgrinder.com>
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To: Stanislav Malyshev <smalyshev@gmail.com>, internals@lists.php.net
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Subject: Re: [PHP-DEV] Re: Improving PHP's type system
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On 4/14/2016 9:25 PM, Fleshgrinder wrote:
> On 4/14/2016 8:59 PM, Stanislav Malyshev wrote:
>> Hi!
>>
>>> I don't know what is complicated about "string|Stringable" or "Foo|Ba=
r"
>>> since it is super self-explanatory. However, I find myself checking t=
he
>>
>> It may be self-explanatory for you. It's much less self-explanatory fo=
r
>> somebody just starting to learn. It is also very dangerous - if it's
>> either Foo or Bar, can you call Foo::stuff on it or not? If it's strin=
g
>> or not string, can you call strlen on it? Etc., etc. It adds a lot of
>> cognitive load and complicates the whole picture. You may have a
>> specific use case where it is useful (which we have yet to see btw) bu=
t
>> please remember it's a language with literally millions of use cases a=
nd
>> users.
>>
>=20
> Reduce assertions*, enhance self-documentation, making code more robust=
,
> perform checks in the VM and not in userland, ...
>=20
> function fn($arg) {
>     assert('is_string($arg) || method_exists($arg, "__toString")');
> }
>=20
> interface Stringable {
>     function __toString(): string;
> }
>=20
> function fn(string|Stringable $arg) {
>     // :)
> }
>=20
> You can find more information on the topic here:
>=20
> https://en.wikipedia.org/wiki/Tagged_union
>=20
> * Assertions in PHP are very error prone if combined with refactoring
> due to the fact that one should enclose the actual assertion in a strin=
g.
>=20

Oh oh oh, I forgot the very important unions *int|string* and
*float|string* for overflows as one can encounter them from time to
time; even in native code.

--=20
Richard "Fleshgrinder" Fussenegger


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