False positive: Comparison operation ">" between 0 and 0 is always false.

[phil-davis]

Bug report

The type of "while strlen" construction in the example was passing phpstan. But now it fails on PHP7 (but looks like it passes on PHP8).

Code snippet that reproduces the problem

https://phpstan.org/r/0694abfa-be7c-47e9-ab0e-d2d6ca7dec80

Expected output

The code should pass phpstan, and was passing with 1.9

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

[phil-davis]

We noticed this in overnight CI that started failing on code here:
https://github.com/owncloud/encryption/blob/master/lib/Crypto/Encryption.php#L321

[phil-davis]

Note: with PHP 7.4 this passes on phpstan 1.9.18 and fails on 1.10.0

[phil-davis]

Is this commit somehow related ?
phpstan/phpstan-src@649eb70

But I don't see an obvious problem with that code, or how it would execute differently on PHP 7.4

[VincentLanglet]

Is this commit somehow related ? phpstan/phpstan-src@649eb70

If you want, you can find the commit who introduce the bug by writing a test case for php 7.4 on phpstan-src and running git bisect.
(or maybe by requiring directly the commit hash from https://github.com/phpstan/phpstan/commits/1.10.x in your composer.json to see if your code works/fail)

[phil-davis]

good idea about using the commit hash, I will try that.

[eigan]

Got similar issue with this snippet

https://phpstan.org/r/b44378ba-632d-4b47-bb04-f8ac420be7a3

Comparison operation ">" between 0 and 31 is always false.

[phil-davis]

Somehow phpstan is thinking that strlen() is going to always return 0 in code like ours.
And it reports:

Because the type is coming from a PHPDoc, you can turn off this check by setting treatPhpDocTypesAsCertain: false in your [configuration file](https://phpstan.org/config-reference).

But I don't see any PHPDoc at all in our code examples, So that message seems to be emitted in error.

[phil-davis]

In my example, I can refactor to:

		$x = strlen($data);
		while ($x > 0) {

and that passes. But having the strlen() call embedded in the while fails on PHP 7.

So there is a silly workaround for my example.

But doing a similar refactoring of @eigan example, it still fails. What is going on?

[ondrejmirtes]

Fixed: phpstan/phpstan-src@f882eff

[github-actions]

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