Strange generator behaviour

[CiBeRHeMuL]

Description

Hello!

There is so strange behavior of the code when using the generator inside the if branch.

The following code:

<?php

$condition = false;
$func = fn() => $condition ? yield from [] : new \ArrayIterator([1, 2, 3]);
$iterator = $func();
foreach ($iterator as $el) {
    echo "$el\n";
}

Don't print any to the output.
It seems like yield clause is executing anytime despite the code execution (code in example will never enter the if branch).

So, this code should produce this output:

1
2
3

PHP Version

PHP 8.3.14

Operating System

Ubuntu 22.04

[nielsdos]

This is expected.
From the moment you have a yield in your function, even if not executed, your function becomes a generator itself.
So simply having the yield from [] present makes your function a generator.
The new \ArrayIterator([1, 2, 3]) is executed, but no yields happen, so therefore the foreach loop body is never executed.