Assignment from yield reports a processing error

[Nessworthy]

• PHPMD version: 2.8.1 / 2.8.1snapshot202002241446
• PHP Version: 7.4.8 (both)
• Installation type: composer / phar
• Operating System / Distribution & Version: Windows 10

Also tested on 2.8.1 from source at cf8677bbd8c291f7f6ed6437f5c941a49ebc2473

Current Behavior

Running phpmd reports the following processing error:

Unexpected token: }, line: 6, col: 1, file: /path/to/script.php.

Expected Behavior

No processing errors.

Steps To Reproduce:

Using the following script:

<?php declare(strict_types=1);

function test_function(): Generator
{
    $result = yield true;
}

And running phpmd script.php text cleancode

or

php phpmd.phar script.php text cleancode

Checks before submitting

• Be sure that there isn't already an issue about this. See: Issues list
  • Another prior issue around yield, from a previous version reporting and a different error, but it is closed off.
• Be sure that there isn't already a pull request about this. See: Pull requests
• I have added every step to reproduce the bug.
• If possible I added relevant code examples.
• This issue is about 1 bug and nothing more.
• The issue has a descriptive title. For example: "JSON rendering failed on Windows for filenames with space".

[kylekatarnls]

Sure PHPMD should handle it, but as for my personal opinion, having an output (yield) and an assignation ($result =) in the same line of code is a code smell.

A clean code would be:

<?php declare(strict_types=1);

function test_function(): Generator
{
    $result = true;

    yield $result;
}

[Nessworthy]

It's possible to need to make use of both input and output while working with generators, e.g.:

<?php declare(strict_types=1);

function number_addition_generator(int $number): Generator {
    $toAdd = 0;
    while (true) {
        $number += $toAdd;
        $toAdd = yield $number;
    }
}

$generator = number_addition_generator(0);

$generator->current(); // Returns 0
$generator->send(1);   // Returns 1
$generator->send(10);  // Returns 11
$generator->send(100); // Returns 111

Forgive the stupid example 😅

[kylekatarnls]

Indeed, I get the point.

[bug-tape]

Similar problem when using this short cut to stop a generator:

<?php
function some_generator() {
    return yield "last";
}

[wietsewarendorff]

Any progress on this?

[kylekatarnls]

Cause found, you can test the fix with:

composer require "pdepend/pdepend:dev-master as 2.16.0"