On Wed, May 8, 2019 at 6:51 PM Levi Morrison <le...@php.net> wrote: > On Wed, May 8, 2019 at 2:06 AM Nikita Popov <nikita....@gmail.com> wrote: > > > > On Tue, Jan 22, 2019 at 6:59 PM Levi Morrison <le...@php.net> wrote: > >> > >> On Tue, Jan 15, 2019 at 1:27 PM Christoph M. Becker <cmbecke...@gmx.de> > wrote: > >> > > >> > On 04.01.2019 at 20:17, Levi Morrison wrote: > >> > > >> > > I intend to close the vote in a day or two, unless I hear of new> > issues from Dmitry or others. > >> > Any news here? > >> > > >> > -- > >> > Christoph M. Becker > >> > >> I sent this a week ago to Christoph only; oops. > >> > >> I have not heard any news. The vote is now closed. The RFC passes 39 > >> in favor to 1 against. > >> > >> Special thanks to Nikita and Dmitry who have helped find issues and > >> review the patch. It will not be merged until the implementation > >> quality is satisfactory. > > > > > > As we're moving steadily towards 7.4 feature freeze, I'd like to discuss > what we want to do with this RFC... The current implementation doesn't work > correctly (I've done some more work in > https://github.com/nikic/php-src/commits/variance-7.4, but it's also > incomplete) and I have some doubts about how we're approaching this in > general. > > > > This RFC really has two parts: > > 1. The actual variance change. This is a very straightforward change and > there are no issues here. > > 2. The ability to check variance across multiple consecutive class > definitions. This allows type declarations to reference classes that are > declared later in the same file (but within one "block" of declarations). > > > > The second part is technically more dicey and somewhat arbitrary when > seen in the wider scope of how class hoisting and early binding work in > PHP: While PHP supports declaring classes "out of order" in some very > simple cases like this... > > > > class B extends A {} > > class A {} > > > > ...it will not work for anything more involved than that, for example > > > > class C extends B {} > > class B extends A {} > > class A {} > > > > will already generate a "class not found" error. > > > > Now the variance RFC tackles one very specific part of this > long-standing issue: The types referenced in parameter and return types may > be declared later in the file (even if used variantly), but all other uses > of the types still need to respect the declaration order. > > > > I think that we should be separating these two issues (variance and > declaration order), and land the simple variance support in 7.4, while > tackling the declaration order problem *in full* separately (in PHP 8, > because I think we may want to make some BC breaking changes, in particular > by making the class hoisting unconditional.) > > > > Thoughts on this approach? > > > > Nikita > > I fully support this approach. I will prepare a patch for simple > variance in PHP 7.4. I intend to leave the existing test cases that > will fail without supporting consecutive declarations, but marked as > expected failures. > > I think in PHP 8 we can already benefit from the [always generate > fatal error for incompatible method signatures RFC][1]. We might also > be able to make some improvements with compile-time errors on invalid > "parent::" usage (previously done for PHP 7.4 but [backed out][2]), > which might make things a bit more straightforward (it might not -- > turns out parent is not exactly what I thought it was). > > [1]: https://wiki.php.net/rfc/lsp_errors > [2]: > https://github.com/php/php-src/commit/deb44d405eb27a6654ad9a57c1e5f641218b22a4
An update on this: The last part of covariance support has landed [1] a few days ago and is part of 7.4 alpha 1. As already described, full variance is only supported in conjunction with autoloading. When working in a single file or with explicit includes, the requirement that classes need to be declared before being referenced (including reference in variant type declarations) remains. This feature turned out to be a *lot* harder than anticipated. My initial assumption that this would mostly "just work" if we ignore the single file case was very wrong... Nikita [1] https://github.com/php/php-src/commit/8f8fcbbd397370b407dc2552c4bd6ee4ccb0e93b
