I've stuck to only doing this in the places where I'm sure we should never get false back. Other places I'm less sure of (and I found more bugs along the way).
this allows CrashDump to be used just to generate data, which will come in useful for non-crash error reporting in the future (e.g. packet decoding errors).
this is not as good as phpstan/phpstan-src#769 (e.g. array_key_first()/array_key_last() aren't covered by this, nor is array_rand()) but it does eliminate the most infuriating cases where this usually crops up.