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Date: Fri, 26 May 2017 10:10:29 -0600
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To: "lists@rhsoft.net" <lists@rhsoft.net>
Cc: "internals@lists.php.net" <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="001a1141c7e283297805506f93e8"
Subject: Re: [PHP-DEV] Parameter type widening RFC
From: derokorian@gmail.com (Ryan Pallas)

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On Fri, May 26, 2017 at 9:01 AM, lists@rhsoft.net <lists@rhsoft.net> wrote:

>
>
> Am 26.05.2017 um 16:26 schrieb Dan Ackroyd:
>
>> On 26 May 2017 at 13:23, lists@rhsoft.net <lists@rhsoft.net> wrote:
>>
>>> does that also fix the issue https://bugs.php.net/bug.php?id=74394
>>>
>>
>>
>> Dear Anonymous,
>>
>> That "issue" is actually 3 issues.
>>
>> case 1
>>
>> class A {
>>    public function test($a) {}
>> }
>> class B extends A {
>>    public function test(string $a) { }
>> }
>>
>> This breaks LSP - because B::test doesn't accept all the things that
>> A::test can accept and so is unlikely to ever be supported.
>>
>
> and how is that a problem?
>
> A accepts anything
> B limits it's inut to a *subset* of "anything"
>
> Because, if I have a function foo(A $a) { $a->test(new Bar()) } that I
cannot pass B into this function, even though it is a subclass of A. You
should be able to pass any subclass where its parent is expected, allowing
parameter narrowing (covariance) would break this.

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