On Mon, Nov 26, 2018 at 2:25 PM Levi Morrison <le...@php.net> wrote:
>
> I am happy to announce my latest RFC, [Covariant Returns and
> Contravariant Parameters][1], is open for discussion. If you do not
> recognize those terms then hopefully the introduction coupled with the
> [examples][2] will help. Here is one snippet that demonstrates
> covariant return types:
>
> <?php
> interface Repository {
> function fetch(int $id): ?Entity;
> }
>
> class UserFactory implements Repository {
> function fetch(int $id): ?UserEntity {
> /* Since UserEntity is an Entity, this is now allowed */
> /* ... implementation ... */
> }
> }
> ?>
>
> Covariant return types and contravariant parameter types are highly
> requested features; here are a few of the bug reports:
>
> * https://bugs.php.net/bug.php?id=71825
> * https://bugs.php.net/bug.php?id=72442
> * https://bugs.php.net/bug.php?id=75385
> * https://bugs.php.net/bug.php?id=75823
>
> There is a [preliminary implementation][3] that is available. It will
> not be rebased during discussion to allow people to check out the code
> and get updates without worrying about it breaking. The code quality
> can definitely be improved, and there are still a few todo comments in
> the code.
>
> Please do not discuss the items found in [Future Scope][4] as part of
> this thread, which includes discussing types such as `mixed`,
> `scalar`, `numeric`, etc.
>
> I look forward to your feedback, and especially with your
> experimentation with the implementation.
>
> Levi Morrison
>
> [1]: https://wiki.php.net/rfc/covariant-returns-and-contravariant-parameters
> [2]:
> https://wiki.php.net/rfc/covariant-returns-and-contravariant-parameters#examples
> [3]: https://github.com/php/php-src/compare/master...morrisonlevi:variance2
> [4]:
> https://wiki.php.net/rfc/covariant-returns-and-contravariant-parameters#future_scope
Our existing engine doesn't always resolve "parent" at compile time
when possible. As part of this patch "parent" is resolved at
compile-time when possible and warnings and/or errors are emitted in
certain cases where there were none before. For instance, this would
only cause an error only if the method `C::m` were to be used:
<?php
class C {
static function m(parent $m) {}
}
?>
This now emits an E_DEPRECATED warning when C is compiled. In 8.0 this
should be elevated to a COMPILE_ERROR.
The current edition of the RFC fails to mention this.
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