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Date: Thu, 5 Feb 2015 22:34:49 +0000
Message-ID: <CA+kxMuTP42aQQFxFxPy9KSnab-4v1PFN8YRFM1XumNApmRBC1w@mail.gmail.com>
To: Levi Morrison <levim@php.net>
Cc: Andrea Faulds <ajf@ajf.me>, Julien Pauli <jpauli@php.net>, 
	Hannes Magnusson <hannes.magnusson@gmail.com>, Nikita Popov <nikita.ppv@gmail.com>, 
	PHP internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] Allow dropping typehints during inheritance
From: danack@basereality.com (Dan Ackroyd)

On 5 February 2015 at 21:52, Levi Morrison <levim@php.net> wrote:
> To chime in regarding allowing contravariant parameter types: I
> struggle to find use cases for it.

Theoretically it would allow a class to implement two separate
interfaces that would otherwise be incompatible:

interface A {
    function foo();
}

interface B implements A {
    function bar(B $b);
}

interface C implements A {
    function bar(C $c);
};

class D implements B, C {
    // Any object that implements B or C must also
    // implement A, but only the methods from interface A
    // are safe to call inside the method.
    function bar(A $a){
        $a->foo();
    }

    function foo(){...}
}


But I agree, the number of times I've wanted to do this is low.

cheers
Dan