I have some PHPStan extensions installed in my project which return errors when I run argtyper.
It looks like currently only 'basic' PHPStan rules are disabled in phpstan-collecting-data.neon
I got it working by disabling all the errors in phpstan-collecting-data.neon manually, but I think it would be good to create an IgnoreErrorExtension (https://phpstan.org/developing-extensions/ignore-error-extensions) to suppress all errors that are not applicate to argtyper.