The bug I encounter is a little bit hard to explain so this snippet is better than a long text: https://phpstan.org/r/13f4b1df-ce73-4db0-849c-ec6369ac75d9

To me, there are 2 issues, but one is linked to the other.

The first issue is the visible one, that PHPStan yells that a division per 0 may occur while it's not possible thanks to the ternary check.
The second issue is hidden in the fact that doing $int += bool is wrongly interpreted as $int to be 0|1 while it's actually int (type can be narrowed depending on the context).

For instance, if I try with my boolean checks type-casted to (int), there are no more errors: https://phpstan.org/r/ac373a15-f927-43b3-bd3c-101cffb49599

The point is I don't want to add this cast because it shouldn't be mandatory here. PHP Infection could create any mutant that removes the cast and my unit-tests will still pass, without any way for me to kill that mutant and to keep the cast.

I think that solving the wrong interpretation of $int += bool could change the dumpType of it, and it will fix the visible error reported by PHPStan in my first example.