Bug report

Seems phpstan is bit confused by implementation of offsetSet on ArrayAccess if there is a possibility to set an invalid value.

We have a Message (3rd party object) that says both key and value should be strings, but iconv can return a false|string and the problem was on another place where it was complaining that

Parameter #1 $data of method SomeController::paymentRefund() expects Message, ()|(Message) given. on Line 18 (using value from snippet)

Code snippet that reproduces the problem

https://phpstan.org/r/147b81cf-47f5-4c84-85d0-030583fc673e

Expected output

I would expect the problem to be You cant put false where string is expected on Line 13 (using value from snippet)