string is incorrectly narrowed down in if with and + or conditions

[herndlm]

Bug report

PHPStan seems to be having problems narrowing down types in more complex if statements. In the case I added I use is_string and checks against null and '' to determine that this is a non-empty-string|null type. In a case it is wrongfully detected as string|null though. The example makes more sense than me here I guess :)

Could just be a limitation of PHPStan's capabilities with ifs, feel free to close then.

Code snippet that reproduces the problem

https://phpstan.org/r/ae139617-651e-4a89-8e13-824f9ce1a511

Expected output

No errors

Did PHPStan help you today? Did it make you happy in any way?

Always :)

[ondrejmirtes]

Don't know why it gets lost but it can definitely be solved.

[herndlm]

Feel free to add the info where you are expecting the problem to be, if you think it's easy enough for others to solve :) I can try to take a look at it myself.

[ondrejmirtes]

BooleanOr type narrowing is handled here in TypeSpecifier, sho that's where step debugging should begin: https://github.com/phpstan/phpstan-src/blob/b5e71db32dfd256174290b243d72cefd15768503/src/Analyser/TypeSpecifier.php#L709-L725

[herndlm]

To sum up what I found out in a time-boxed debugging session:
SpecifiedTypes::intersectWith (which is called via TypeSpecifier::specifyTypesInCondition because of the BooleanOr) is ignoring the sureNotType '' which would make the string non-empty. But if I adapt that to basically not ignore it, there are still 2 sure types (string|null) which make problems when combining all of that resulting in string|null & ~''. pretty sure I'm missing something obvious, but maybe this helps somebody.
Maybe I'll continue debugging / working on this

[github-actions]

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