"The call to ::getIterator is not used" reported right where it's used

[orklah]

Hi,

We got a strange error on phpDocumentor CI:
https://github.com/phpDocumentor/phpDocumentor/runs/790360908?check_suite_focus=true#step:9:18
The error warn of an issue with a getIterator function being unused here:
phpDocumentor/phpDocumentor@337b40d#annotation_257518989

But that's exactly the line where it's actually used, I don't understand what psalm is trying to report here.

I couldn't reproduce the issue locally, but phpDocumentor CI is complex so I don't have the same setup.

The issue was "solved" by changing "findUnusedVariablesAndParams" to false, but it'd be cool to be able to enable this check again.

Do you have an idea what could be the issue here?

[psalm-github-bot]

Hey @orklah, can you reproduce the issue on https://psalm.dev ?

[weirdan]

Call to ... unused actually refers to the return value of a pure function, as calling a pure function without using its result is pointless. It doesn't seem appropriate here though.

[weirdan]

Reproduced with https://psalm.dev/r/6287fdb60c
@orklah is your code similar to that?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/6287fdb60c

<?php
/** @psalm-immutable */
class C implements IteratorAggregate {
    public function getIterator(): Iterator {
        return new ArrayIterator([]);
    }
}

$d = [];
/** @psalm-suppress MixedAssignment */
foreach (new C as $elt) {
    $d[(string)$elt] = $elt;
}

Psalm output (using commit e569f08):

ERROR: UnusedMethodCall - 11:10 - The call to C::getIterator is not used

[orklah]

@orklah is your code similar to that?

Kinda, but there isn't a psalm-immutable annotation in my case. And without it I can't reproduce the issue at all...

[enumag]

Here are my reproducers from #4373 - slightly cleaner as they don't have other problems:

https://psalm.dev/r/dd77299d18
https://psalm.dev/r/ab4bb38b1e

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/dd77299d18

<?php

/**
 * @psalm-immutable
 */
class A implements IteratorAggregate
{
    /**
     * @return Iterator<string>
     */
	public function getIterator() {
    	yield from [];
    }
}

$a = new A;

foreach ($a as $v) {
    echo $v;
}

Psalm output (using commit b904b1d):

ERROR: UnusedMethodCall - 18:10 - The call to A::getIterator is not used

https://psalm.dev/r/ab4bb38b1e

<?php

class A implements IteratorAggregate
{
    /**
     * @return Iterator<string>
     * @psalm-mutation-free
     */
	public function getIterator() {
    	yield from [];
    }
}

$a = new A;

foreach ($a as $v) {
    echo $v;
}

Psalm output (using commit b904b1d):

ERROR: UnusedMethodCall - 16:10 - The call to A::getIterator is not used

[muglug]

Thanks @enumag!