Improve specified type in comparisons

[jlherren]

Note that this PR has a side-effect that might need to be addressed, consider this code:

$array = rand() === 0 ? hash_algos() : false;
for ($i = 0; $i < count($array); $i++) {
	echo $array[$i] . "\n"; // <-- this line
}

The change in output is as follows:

- Cannot access offset int on array|false.
+ Cannot access offset int<min, 9223372036854775806> on array|false.

While technically correct, this is not very pretty.

Perhaps this can be fixed by adjusting how IntegerRangeType is represented. Currently, int<0, max> (return value of count()) is internally represented by min=0, max=PHP_INT_MAX, which is technically a bounded interval. If it were to use min=0, max=null instead, then the intended meaning of an open interval can be represented more accurately and the new code in this PR could make use of that information. If this sounds good I'll have a go at it.

[ondrejmirtes]

Yes, please do the min=0, max=null refactoring first. We should honor the usual math rules that INF minus 1 is still INF :) So int<min, 9223372036854775806> should really be just an int.

[jlherren]

I rebased this branch and the issue I mentioned is now fixed.

[ondrejmirtes]

Linking the fixed issue: phpstan/phpstan#577

I'm gonna review this once the time allows, hopefull soon :)

[ondrejmirtes]

Yes, please do. Can you also take a look at #416 - does it make sense to you?

[ondrejmirtes]

Thank you!