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Date: Thu, 26 Oct 2023 20:50:07 -0300
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To: Deleu <deleugyn@gmail.com>
Cc: Larry Garfield <larry@garfieldtech.com>, php internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="0000000000007693c50608a73dcf"
Subject: Re: [PHP-DEV] Basic Type Alias
From: ericklima.comp@gmail.com (Erick de Azevedo Lima)

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I'll use it a lot if they'll be namespaced. It avoids name-collision using
the existing ecosystem and we already use lots of "uses" in our codes.
When Enums came to the party, they came namespaced as traits, classes and
interfaces. The last 2 represent types, concrete and abstract.
User defined types are nothing more than types, so I think the way to gois
to keep it namespaced as well.

About the type compatibility, covariance and contravariance, let's say I
define some type inside my package:

// File: C1.php =>  My package code

namespace N1;

typedef MyString = string|Stringable|\Symfony\Component\String\UnicodeString
;
typedef MyBool = null|bool;
typedef BigNumeric = int|float|\Brick\Math\BigNumber;

class C1
{
    protected function myQuestionableFunction(MyString $str1): MyBool
    {
        //...
    }

    protected function myQuestionableFunction2(null|C1 $str1): ScalarNumeric
    {
        //...
    }
}

// File: C2.php => On the project of those who are using my package

namespace N2;

typedef ScalarNumeric = int|float;
typedef Falsy = null|false;

class C1 extends C2
{
    protected function
myQuestionableFunction(string|Stringable|\Symfony\Component\String\UnicodeString
$str1): Falsy
    {
        //...
    }

    protected function myQuestionableFunction2(Falsy|C1 $str1):
ScalarNumeric
    {
        //...
    }
}

I propose that this code should be valid code, because, in the end, these
*typedef's*, are just synonyms.

*Note:* By the way, I propose to use the C/C++ keyword, which is *typedef* and
dropping the syntax* "type MyType = [string, null];",*
which differs too from how typehints are used and do not add any benefits
*.*

--
Erick

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