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Date: Sun, 28 May 2017 12:30:34 +0200
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To: Dan Ackroyd <danack@basereality.com>
Cc: Niklas Keller <me@kelunik.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Parameter type widening RFC
From: rasmus@mindplay.dk (Rasmus Schultz)

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> > So this breaks the expected behavior of interfaces.
>
> No it doesn't. It allows interfaces to use contravariance within PHP's
> type system, which is different from before, but it doesn't break
> anything.

The RFC explicitly states that this is *not* contravariance.

And if it's not clear, what I mean by "breaks the expected behavior", is,
as far as I understand, what this RFC actually does is it *removes*
expected behavior.

Correct me if I'm wrong, but really all this RFC does, is remove the
requirement that and implementation of an interface be type-hinted?

To me, that's "broken".

You're favorizing a very, very small number of isolated, valid use-cases -
by removing the normal, natural, expected constraint that an implementation
be type-hinted as specified by the interface. It's part of the reason
interfaces even exist - and this simply ignores that and removes these
checks.

In my opinion, this will very likely lead to a large number of accidental
type-hint omissions - and a very, very small number of actually useful
solutions to real problems.

In my opinion, we can do much better than that, by adding a mixed
type-hint, which will ensure people aren't just accidentally omitting
type-hints and instead explicitly opting out of it to achieve parameter
widening. Solving this from the start also ensures we can have a clean
implementation of real contravariance in the future, without that being a
break change.

> Rasmus, not answering people's questions and instead saying emotional
> stuff suggesting other people have made historically bad decisions
> isn't a productive way to conduct a conversation.

Okay, I'm emotional, sorry about that.

But I think I'm pointing out a real problem and a real possible solution
that doesn't make the trade-offs of the current solution.

That is, I'm fine with introducing this simplified type of contravariance,
but I think it needs to be made explicit - simply omitting a type-hint does
not indicate the desired behavior; it doesn't indicate anything, and
thereby creates a new problem case of accidental type-hint omission.

Is there a very good reason we shouldn't address that, if it's at all
possible?


On Thu, May 25, 2017 at 12:32 PM, Dan Ackroyd <danack@basereality.com>
wrote:

> On 25 May 2017 at 10:21, Rasmus Schultz <rasmus@mindplay.dk> wrote:
>
> > So this breaks the expected behavior of interfaces.
>
> No it doesn't. It allows interfaces to use contravariance within PHP's
> type system, which is different from before, but it doesn't break
> anything.
>
> Niklas Keller wrote:
> > The interface will just work correctly, what's the actual problem you're
> seeing?
>
> Rasmus, not answering people's questions and instead saying emotional
> stuff suggesting other people have made historically bad decisions
> isn't a productive way to conduct a conversation.
>
> cheers
> Dan
>

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