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Date: Mon, 4 Feb 2019 14:10:17 +0100
Message-ID: <CAFPFaM+p8DHi7qaTuctbVcfQRMFobAH-AOmBr8=GdL7VOdndWA@mail.gmail.com>
To: Wes <netmo.php@gmail.com>
Cc: Claude Pache <claude.pache@gmail.com>, PHP Internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="00000000000096d8790581113795"
Subject: Re: [PHP-DEV][RFC] Allow void return type variance
From: george.banyard@gmail.com (Girgias)

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On Mon, 4 Feb 2019 at 13:28, Wes <netmo.php@gmail.com> wrote:

> I know this too. I am often in touch with Levi and void variance is not
> covered by his RFC
> As a matter of fact, if you try to compile that PR void will behave exactly
> like it does now
>

First of all, apologies as I needed a brush up on the difference between
general variance and covariance.
In fact, the RFC linked does not cover the variance of the void type.


> My RFC targets 7.2 and 7.3 other than 7.4
>

Secondly, I am nearly certain, but I would love to be proven wrong, that
new features aren't backported to older PHP releases.
So even then I don't think this will land in PHP 7.2/7.3

Now back to the proposal of the variance of void type.
I'm not sure I see the point of it?
Let me explain: if I define a method as void it means that it does stuff
which doesn't/can't return a sensible value.
Also, I am defining behavior and changing the return type, at least to me,
is a change in behavior.
Because a function/method which clearly is not intended to be used as a
value can now under your proposal become one.
Sure you can say that the return value may be only used by the child class
but if I want to change my parent class to this child class
I can't be sure that it will behave as before because *maybe* the child
class needs the return value of this previously void method.

Maybe I am just overthinking this however in my opinion if a return type
needs to be changed from void to something you are trying to
add behavior to a method which *probably* should go into its own method.

Best regards

George P. Banyard

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