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Date: Wed, 20 Apr 2016 11:42:54 +0200
Message-ID: <CAKrrN66QkEutsrOd9+6dWXf=HRa+TKbcM9YmkZMp5seY+Ev0yQ@mail.gmail.com>
To: Dominic Grostate <codekestrel@googlemail.com>
Cc: Mathieu Rochette <mathieu@rochette.cc>, "Ben Scholzen 'DASPRiD'" <mail@dasprids.de>, 
	Josh Di Fabio <joshdifabio@gmail.com>, Mathieu Rochette <mathieu@texthtml.net>, 
	Sara Golemon <pollita@php.net>, PHP internals <internals@lists.php.net>, 
	Rasmus Schultz <rasmus@mindplay.dk>
Content-Type: multipart/alternative; boundary=089e0111e15a30d3bb0530e76ce0
Subject: Re: [PHP-DEV] [RFC:generics]
From: quim@kalpe.com (Quim Calpe)

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On Wed, Apr 20, 2016 at 11:10 AM, Dominic Grostate <
codekestrel@googlemail.com> wrote:

> I've made an amendment to the RFC to clarify on the Nested Types, which is
> indeed supposed to be part of the feature.  Rasmus may want to reword it if
> it isn't very clear.
>
> Regarding union and intersections for upper (and maybe lower) bounds.
> Would it be appropriate to exclude these from type parameters until their
> respective RFCs are approved?  As including them in generics but not in
> standard type hints may create an inconsistency.
>
> In short, perhaps a generics implementation should incorporate unions (and
> any future type constraints) as existing features only.  This would help
> RFC Generics to focus on: Type aliasing, Introspection and Reflection.
>

That would be a wise move, there are currently some RFCs with similar areas
of contention


> On 20 Apr 2016 9:05 a.m., "Mathieu Rochette" <mathieu@rochette.cc> wrote:
>
> >
> >
> > On 20/04/2016 00:22, Sara Golemon wrote:
> >
> >> On Tue, Apr 19, 2016 at 1:16 PM, Mathieu Rochette <mathieu@texthtml.net
> >
> >> wrote:
> >>
> >>> about the upper bounds, have you consider another way of describing the
> >>> constraints, eg:
> >>>
> >>> class Box<T> where T is Boxable
> >>>
> >>> this would allow multiple constraints, eg:
> >>>
> >>> class Collection<T> where T is Traversable, T is Countable
> >>>
> >>> IMO, this sort of problem should be solved by combining this feature
> >> with union types, so you could have something like:
> >>
> >> class Collection<T as (Traversable | Countable)> {...
> >>
> >> And merely inherit the logic rules from that feature rather than
> >> inventing yet another one.
> >>
> > obviously if the union type rfc passes we don't need another way of
> > expressing this.
> > that was only in the case it does not, I think having a way to have at
> > least types intersection
> > is useful here (and I didn't event think about <T is A & B>)
> >
> >>
> >> can generic types be nested ?
> >>>
> >>> class Stuff<A, B is Something<A, string>>
> >>>
> >>> I can't imagine why not...
> >>
> > just to be clear, it's not just nested generic. the A type have to be
> same
> > in both "subtypes"
> >
> >>
> >> For my part, I love the concept overall.  Generics are an important
> >> part of moving PHP towards comprehensive type-safety.  But then, you
> >> know how I feel about Hack. :)
> >>
> >> -Sara
> >>
> >>
> >
>

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