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Date: Fri, 26 Jan 2018 15:29:30 +0000
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To: PHP Internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV][RFC][DISCUSSION] Collection Inspection
From: rowan.collins@gmail.com (Rowan Collins)

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On 26 January 2018 at 14:20, Michael Morris <tendoaki@gmail.com> wrote:

> On Thu, Jan 25, 2018 at 11:59 PM, Niklas Keller <me@kelunik.com> wrote:
> >> >> $b instanceof SomeClass<string>
> >> >>
> >> >> Returns true if SomeClass can be iterated and contains only strings.
> >> >>
> >> >
> >> > This would block generics with that syntax then.
> >> >
> >>
> >> I don't understand this comment.
> >>
> >
> > You restrict these type parameters to iterators, but generics are useful
> > in a lot more places.
> >
>
> iterABLE --- not iterATOR.  Two different things.
>
> [...]
>
> The similarity of the names is regrettable, but it's already in place and
> can't be changed at this point.
>


I think you misunderstood Niklas's point. Your example showed the syntax
"SomeClass<string>" with an iterator/iterable specific meaning, which would
mean we couldn't later use this syntax for generics. With generics, "$b
instanceof SomeClass<string>" would mean "is the class of $b, or one of its
parents or interfaces, a generic template SomeClass<T> specialised on the
type string"; that would be incompatible with your proposed meaning of "$b can
be iterated and contains only strings".

The plain form "iterable<string>" would co-exist fine with generics, and
"Iterator<string>" could be kept compatible if a generic interface
"Iterator<T>" was added when generics came along, so we wouldn't be tying
our hands by adding those.

Regards,
-- 
Rowan Collins
[IMSoP]

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