Yes, function/method arguments should be contravariant. I'm sorry I haven't got caught anyone to review after Joe's patch.
I promise to remember about that next time. 2016-11-14 10:20 GMT+01:00 Josh Di Fabio <joshdifa...@gmail.com>: > On Mon, Nov 14, 2016 at 8:54 AM Michał Brzuchalski <mic...@brzuchalski.com> > wrote: > >> Hi All, >> >> Id' like to anounce voting reset - will end in two weeks on 28.11.2016 at >> midnight and requires 2/3 majority as previously. >> >> There were improvements suggested by Joe Watkins and earlier by Nikita >> Popov to the patch. >> >> Those improvements are described on RFC under "Covariance" section >> https://wiki.php.net/rfc/object-typehint#covariance > > This section describes covariance of method arguments. Is this a mistake? > Should this be contravariance? Covariant arguments go against LSP. > >> >> It means any `object` typehint or return type can be narrowed to more >> specified type (class name) similar to `iterable` pseudo-type but behaves >> covariant (more general type can be raplaced with narrowed one). >> >> P.S. I hope this improvement will bring more positive votes. >> >> regards, >> -- >> Michał >> >> 2016-11-10 13:30 GMT+01:00 Joe Watkins <pthre...@pthreads.org>: >> >> > Levi, >> > >> > You are assuming it would *need* to be removed :) >> > >> > Future RFC's must deal with the engine as they find it, as this RFC >> > has done. >> > >> > If it is true that this would prohibit enums being non-objects, and >> > I'm not certain that it does, then enums would have to be objects, if >> > that's how they find the engine. >> > >> > If your only concern is about a non-existent feature, then maybe >> > you're concern can be alleviated by the non-existent JIT (which does >> > partially exist): With a JIT, it doesn't much matter what represents >> enums >> > anyway. >> > >> > These are problems for the future, not today. >> > >> > Cheers >> > Joe >> > >> > On Thu, Nov 10, 2016 at 12:20 PM, Levi Morrison <le...@php.net> wrote: >> > >> >> On Thu, Nov 10, 2016 at 5:18 AM, Joe Watkins <pthre...@pthreads.org> >> >> wrote: >> >> > Morning Levi, >> >> > >> >> >> There is a future compatibility issue of this same type with >> `object`: >> >> > >> >> > If that is an issue, it is for future RFC's to deal with. >> >> > >> >> > Cheers >> >> > Joe >> >> > >> >> > >> >> > On Thu, Nov 10, 2016 at 12:12 PM, Levi Morrison <le...@php.net> >> wrote: >> >> >> >> >> >> On Thu, Nov 10, 2016 at 2:11 AM, Niklas Keller <m...@kelunik.com> >> wrote: >> >> >> > 2016-11-09 21:53 GMT+01:00 Christoph M. Becker <cmbecke...@gmx.de >> >: >> >> >> > >> >> >> >> On 09.11.2016 at 17:28, Joe Watkins wrote: >> >> >> >> >> >> >> >> > I want to explain why I voted no on this: >> >> >> >> > >> >> >> >> > I think it's significantly less useful without variance, >> >> variance >> >> >> >> > is >> >> >> >> > something that is usually difficult to achieve in PHP, but not >> for >> >> >> >> > this >> >> >> >> > feature in particular. >> >> >> >> >> >> >> >> Can you please elaborate what you mean with variance? I see some >> >> >> >> practical use cases for covariance of a method with return type >> >> object, >> >> >> >> but I don't see how contravariance could be achieved for >> parameters >> >> of >> >> >> >> type object. >> >> >> >> >> >> >> >> If your suggestion is only about invariance of object return >> types, >> >> I'm >> >> >> >> not sure if this very special case would make sense (for >> consistency >> >> >> >> reasons). >> >> >> >> >> >> >> > >> >> >> > We already have it for iterable -> array. We would have it for all >> >> other >> >> >> > types if there wouldn't be an implementation issue. >> >> >> > >> >> >> > Regards, Niklas >> >> >> > >> >> >> > Cheers, >> >> >> >> Christoph >> >> >> >> >> >> >> >> > I absolutely want it, but I want it to be properly useful. >> >> >> >> > >> >> >> >> > If the RFC were halted and patched to include variance, >> I'd +1 >> >> >> >> > it. >> >> >> >> > >> >> >> >> > Cheers >> >> >> >> > Joe >> >> >> >> > >> >> >> >> > On Sun, Nov 6, 2016 at 5:28 PM, Michał Brzuchalski >> >> >> >> > <michal@brzuchalski. >> >> >> >> .com> >> >> >> >> > wrote: >> >> >> >> > >> >> >> >> >> Hi everyone, >> >> >> >> >> >> >> >> >> >> Two weeks have passed since this RFC was put to discussion >> here. >> >> >> >> >> >> >> >> >> >> Therefore, I'm going to put it to a vote for inclusion in PHP >> >> 7.2. >> >> >> >> >> >> >> >> >> >> Voting starts today, 2016-11-06, and will close after two >> weeks >> >> on >> >> >> >> >> the >> >> >> >> >> Sunday 2016-11-20 at midnight. >> >> >> >> >> >> >> >> >> >> The RFC and voting widget can be found here: >> >> >> >> >> https://wiki.php.net/rfc/object-typehint >> >> >> >> >> >> >> >> >> >> It's a normal 2/3 majority required vote. >> >> >> >> >> >> >> >> >> >> Thanks! >> >> >> >> >> -- >> >> >> >> >> regards / pozdrawiam, >> >> >> >> >> -- >> >> >> >> >> Michał Brzuchalski >> >> >> >> >> about.me/brzuchal >> >> >> >> >> brzuchalski.com >> >> >> >> >> >> >> >> >> > >> >> >> >> >> >> >> >> >> >> >> >> -- >> >> >> >> PHP Internals - PHP Runtime Development Mailing List >> >> >> >> To unsubscribe, visit: http://www.php.net/unsub.php >> >> >> >> >> >> >> >> >> >> >> >> >> >> In a return type context `iterable` can be changed to `Traversable` >> or >> >> >> `array`; it cannot be changed to `Collection` as we cannot guarantee >> >> >> at compile-time that `Collection` implements Traversable. >> >> >> >> >> >> There is a future compatibility issue of this same type with >> `object`: >> >> >> right now the only user-definable types are objects. However, enums >> >> >> are an often requested feature and they may not be objects. Thus we >> >> >> wouldn't be able to guarantee that `Foo` is an object. There is a >> >> >> draft RFC with a patch for enums and expect it will come to a >> >> >> discussion soon, so I don't think we'll have to wait very long to >> know >> >> >> the answer here. >> >> > >> >> > >> >> >> >> I strongly disagree here; once we add `object` return type covariance >> >> it cannot easily be removed. >> >> >> > >> > >> >> >> -- >> regards / pozdrawiam, >> -- >> Michał Brzuchalski >> about.me/brzuchal >> brzuchalski.com > > > P.S. Apologies for the non-plaintext email. > -- regards / pozdrawiam, -- Michał Brzuchalski about.me/brzuchal brzuchalski.com
