??= operator support (PHP 7.4)

[alexeyshockov]

https://psalm.dev/r/97ea41c274 — an example.

Currently Psalm reports EmptyArrayAccess error in the first part of the code above, while the second part is OK.

Bit they are equivalent, the first one just uses short assignment via ??= operator. So no errors should be reported.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/97ea41c274

<?php

/** @var array<array{parcel_id: string, location_id: string}> */
$matches = [];

$bestMatches = [];
foreach ($matches as $match) {
    $bestMatches[$match['parcel_id']] ??= $match['location_id'];
}

foreach ($matches as $match) {
    $bestMatches[$match['parcel_id']] = $bestMatches[$match['parcel_id']] ?? $match['location_id'];
}

Psalm output (using commit 8926f1d):

ERROR: EmptyArrayAccess - 8:5 - Cannot access value on empty array variable $bestMatches

[alexeyshockov]

Thanks a lot!