Should Countable::count() be mutation-free?

[enumag]

https://psalm.dev/r/feb35a0874

I'm kinda considering this a bug. Imo count should never change anything inside the data structure. But maybe it's like this on purpose for some reason I can't see?

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/feb35a0874

<?php

/**
 * @psalm-immutable
 */
class A {
	public function test(Countable $x): void {
    	$x->count();
    }
}

Psalm output (using commit ad5a8c2):

ERROR: ImpureMethodCall - 8:10 - Cannot call an possibly-mutating method Countable::count from a mutation-free context

[jsiefer]

Since the implementation of a countable could implement anything, psalm is reporting correctly.

[muglug]

Yup, not a bug