False positive "Call to function is_array() with mixed will always evaluate to false"

[gilbertsoft]

Bug report

Looks PHPStan is reporting a false positive "Call to function is_array() with mixed will always evaluate to false" in some circumstances.

Code snippet that reproduces the problem

https://phpstan.org/r/f4b7baf4-e5ac-4cb5-9f46-5dabb7296eb7

Expected output

No error.

[brainfoolong]

Hi. Here another one. Since 1.4.8 our tests fail with same code. 1.4.6 works fine.

https://phpstan.org/r/40c172a9-8989-439b-aaa3-3e1aa6d524de

[wolffc]

i stumbled on this issue as well and created an minimal testcase
https://phpstan.org/r/e443e996-53ea-4ce5-beef-ec5502b7e6f6

[stingray-11]

I'm getting a very similar error. The message itself looks like what it's saying can't be correct. The problem might be more general than just is_array(). Call to function is_string() with string|false will always evaluate to false.

[ondrejmirtes]

@lightray22 Please attach a phpstan.org/try example.

[stingray-11]

Here is an example showing both the is_array and is_string errors together.

https://phpstan.org/r/12877267-faa1-4cbc-a025-3ca641b6f53a

[phpstan-bot]

@gilbertsoft After the latest commit in 1.6.x, PHPStan now reports different result with your code snippet:

@@ @@
-47: Call to function is_array() with mixed will always evaluate to false.
+38: Cannot access offset 'gilbertsoft/typo3…' on mixed.
+40: Cannot access offset 'gilbertsoft/typo3…' on mixed.
+46: Cannot access offset 'changes' on mixed.
+47: Call to function is_array() with mixed will always evaluate to false.
+47: Cannot access offset 'applied-changes' on mixed.
+54: Cannot access offset 'preferred-install…' on mixed.

Full report

Line	Error
38	Cannot access offset 'gilbertsoft/typo3…' on mixed.
40	Cannot access offset 'gilbertsoft/typo3…' on mixed.
46	Cannot access offset 'changes' on mixed.
47	Call to function is_array() with mixed will always evaluate to false.
47	Cannot access offset 'applied-changes' on mixed.
54	Cannot access offset 'preferred-install…' on mixed.

[phpstan-bot]

@brainfoolong After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
-16: Call to function is_array() with mixed will always evaluate to false.
+No errors

[github-actions]

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