Unnecessary EmptyArrayAccess after checking if key exists

[GeorgeCadwallader]

https://psalm.dev/r/b4217d10dd

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/b4217d10dd

<?php

$testing = [];

if (array_key_exists('a', $testing)) {  
    $a = $testing['a'];
}

Psalm output (using commit 4ac0b64):

ERROR: EmptyArrayAccess - 6:10 - Cannot access value on empty array variable $testing

INFO: MixedAssignment - 6:5 - Unable to determine the type that $a is being assigned to

INFO: UnusedVariable - 6:5 - $a is never referenced or the value is not used

[weirdan]

The code, as presented, is pointless, as if won't be ever entered. Do you have a more realistic example of where you have this issue?

[AdeAttwood]

@weirdan I think there maybe something different with our setup to the playground. The test code we were working with is

<?php

/** @return array<array-key, string> */
function get_array(): array { return []; }
function get_string(): string { return 'a'; }

function get_int(): int {
    /** @psalm-trace $array */
    $array = get_array();
    /** @psalm-trace $counts */
    $counts = array_count_values($array);
    
    if (array_key_exists(get_string(), $counts)) {
        return $counts[get_string()];
    }
    
    return 0;
}

Both environments give the same type for $array of array<array-key, string> however $counts is giving different types the playground is array<array-key, positive-int> however in our environment its array<empty, empty>.

We are on PHP 8.0 and vimeo/psalm v4.15.0. I don't know if the playground is using the master branch or its using a tagged version.

For now we can fix our code by adding a var comment to the differing type and that seems to be a acceptable work around for us.

[weirdan]

Playground is running dev-master. The difference you see is due to #7115 (not yet a part of any release).

[AdeAttwood]

@weirdan thank you, I have run our code on dev-master and that has fixed the issue. This will be resolved in the next release 👍