False positive on "Division per 0 error" when dividing by integers incremented by booleans

[niconoe-]

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.

[VincentLanglet]

This seems similar to #8803
I added the bugfix to my PR phpstan/phpstan-src#2209

[phpstan-bot]

@niconoe- After the latest push in 1.10.x, PHPStan now reports different result with your code snippet:

@@ @@
+ 9: Only numeric types are allowed in +, bool given on the right side.
+10: Only numeric types are allowed in +, bool given on the right side.
 13: Dumped type: 0|1
 14: Dumped type: 0|1
 17: Binary operation "/" between 0|1 and 0|1|2 results in an error.

Full report

Line	Error
9	Only numeric types are allowed in +, bool given on the right side.
10	Only numeric types are allowed in +, bool given on the right side.
13	`Dumped type: 0
14	`Dumped type: 0
17	`Binary operation "/" between 0

[ondrejmirtes]

Fixed: phpstan/phpstan-src#2209

[github-actions]

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