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Date: Tue, 22 Nov 2016 18:25:03 -0700
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To: Dan Ackroyd <danack@basereality.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC][DISCUSSION] Object type hint, now with added variance
From: levim@php.net (Levi Morrison)

On Tue, Nov 22, 2016 at 5:52 PM, Dan Ackroyd <danack@basereality.com> wrote:
> Hi,
>
> This is the reintroduction of the Object Type RFC for discussion.
>
> There was previously strong feedback from people who would prefer that
> the inheritance checks for methods that use object types should be
> co/contravariant. This has been added to the RFC.
>
> https://wiki.php.net/rfc/object-typehint
>
> cheers
> Dan
> Ack
>
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I strongly oppose this additional variance on the grounds that it
assumes that all types that are not statically known to the engine are
objects. This is a restrictive future compatibility concern. For
instance enumerations (or enums) are one possible type I can see us
adding that may not be objects. Additionally if we ever add named
aliases for types and union types then those types are not necessarily
objects either. Giving up these options for the sake of object
variance is definitely not prudent in my opinion.