Psalm does not recognize check on array key existence

[marcosh]

Consider this snippet of code https://psalm.dev/r/a2bb6bbf43

If I remove the checks on $a['baz'], then Psalm detects correctly that $a['foo'] and $a['bar'] are present. With the checks on baz present, it states that $a['foo'] and $a['bar'] could be undefined

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/a2bb6bbf43

<?php

function foo (array $a): void {
    if (!array_key_exists('foo', $a) || !(is_string($a['foo']) || is_null($a['foo'])) ||
    	!array_key_exists('bar', $a) || !(is_string($a['bar']) || is_null($a['bar'])) ||
        !array_key_exists('baz', $a) || !(is_string($a['baz']) || is_null($a['baz']))
    ) {
    	throw new \Exception();
    }
    
	$foo = $a['foo'];
    $bar = $a['bar'];
}

Psalm output (using commit ffe7874):

INFO: PossiblyUndefinedStringArrayOffset - 11:9 - Possibly undefined array offset 'string(foo)' is risky given expected type 'array-key'. Consider using isset beforehand.

INFO: MixedAssignment - 11:2 - Unable to determine the type that $foo is being assigned to

INFO: PossiblyUndefinedStringArrayOffset - 12:12 - Possibly undefined array offset 'string(bar)' is risky given expected type 'array-key'. Consider using isset beforehand.

INFO: MixedAssignment - 12:5 - Unable to determine the type that $bar is being assigned to

INFO: UnusedVariable - 11:2 - Variable $foo is never referenced

INFO: UnusedVariable - 12:5 - Variable $bar is never referenced

[muglug]

OK, more clearly: https://psalm.dev/r/01eae6d98e

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/01eae6d98e

<?php

function two(array $a): void {
    if (!array_key_exists('a', $a) || !(is_string($a['a']) || is_null($a['a'])) ||
    	!array_key_exists('b', $a) || !(is_string($a['b']) || is_null($a['b']))
    ) {
    	throw new \Exception();
    }
    
	echo $a['a'];
    echo $a['b'];
}

function three(array $a): void {
    if (!array_key_exists('a', $a) || !(is_string($a['a']) || is_null($a['a'])) ||
    	!array_key_exists('b', $a) || !(is_string($a['b']) || is_null($a['b'])) ||
        !array_key_exists('c', $a) || !(is_string($a['c']) || is_null($a['c']))
    ) {
    	throw new \Exception();
    }
    
	echo $a['a'];
    echo $a['b'];
}

Psalm output (using commit ffe7874):

INFO: PossiblyUndefinedStringArrayOffset - 22:7 - Possibly undefined array offset 'string(a)' is risky given expected type 'array-key'. Consider using isset beforehand.

INFO: PossiblyUndefinedStringArrayOffset - 23:10 - Possibly undefined array offset 'string(b)' is risky given expected type 'array-key'. Consider using isset beforehand.

[muglug]

Ah, this was just a good ol' combinatorial explosion issue.