I'm getting this error only under php 7.4:

$json = \json_decode($json, null, 512, JSON_THROW_ON_ERROR);

phpstan (1.8.2) will report:

 Parameter #2 $assoc of function json_decode expects bool, null given.

It is nullable since php 7.3, but I'm not sure which version resources/functionMap.php is supposed to reflect, and there is no functionMap_php73delta.php file.

I'll create a PR for updating resources/functionMap.php with widened parameter type