[PHP 7.4] Add arrow function

[TomasVotruba]

This PR based on PR to php-src: php/php-src#3941

Current RFC voting is 33:5, so if nothing complicated happens in implementation, this feature will get accepted to PHP 7.4.

I need feedback on this. I'm not sure the ArrowFunction should inherit FunctionLike - because ArrowFunction has exactly 1 statement, not more.

1. Should new interface be created?
2. Should FunctionLike be parrent to the new interface?
3. Should it extend Closure?

I tried to mimic php-src grammar Zend/zend_language_parser.y

[nikic]

I need feedback on this. I'm not sure the ArrowFunction should inherit FunctionLike - because ArrowFunction has exactly 1 statement, not more.

I think it should. We can construct an equivalent statement array for the expression, and code should be able to treat arrow functions just like other functions then.

[TomasVotruba]

Thank you! Ready for 2nd feedback

[TomasVotruba]

On running parser test:

<?php
fn($a) => $a;

with:

vendor/bin/phpunit test/PhpParser/CodeParsingTest.php

I get error:

Syntax error, unexpected T_DOUBLE_ARROW from 2:8 to 2:9

The grammar file is somehow wrong, not sure how.

[TomasVotruba]

I resolved all the comments, ready to review

[TomasVotruba]

What needs to be done here?

I need this feature so I can add and test migration path in Rector.

[nikic]

7.4 and nightly builds are green now. We should update the used php-src archive to make the 7.2 build also pass.

[TomasVotruba]

We should update the used php-src archive to make the 7.2 build also pass

Is that part of test_old? That part of tests is not very clear to me. How should I do that?

[nikic]

@TomasVotruba Yes. https://github.com/nikic/PHP-Parser/blob/master/test_old/run-php-src.sh needs to be changed to fetch a 7.4 archive instead.

[TomasVotruba]

I see, just a sec 👍

Recently I've also noticed "The return keyword can be omitted" in https://stitcher.io/blog/short-closures-in-php

Is that true?

$ids = array_map(fn(Post $post): int => $post->id, $posts);
$ids = array_map(fn(Post $post): return int => $post->id, $posts);

If so, I shall add test case for that

[nikic]

Is that true?

No, adding a return is not allowed there.

[nikic]

Looks good, some final comments...

[TomasVotruba]

I was trying to rebase pull-request to merge the fixup! commits, but I keep failing on so many conflicts.

Could you merge it locally or squash to one commit on merge?

[nikic]

Merged as squash. Thanks for your work on this!

Next up: https://wiki.php.net/rfc/spread_operator_for_array has been accepted :)

[TomasVotruba]

Merged as squash. Thanks for your work on this!

Awesome 👍

Next up: wiki.php.net/rfc/spread_operator_for_array has been accepted :)

Gimme a sec 😆