Foreaching an Iterable<Key, NonNullType> never results in null

[dktapps]

Bug report

Code snippet that reproduces the problem

https://phpstan.org/r/807ccb92-293e-4443-9a37-90d210e75a89 (execution: https://3v4l.org/SWnXd)

Expected output

Zero errors.

[dktapps]

It seems like the foreach type is being inferred from the return type of current() instead of the generic TValue. Since PHPStan doesn't disallow having a non-covariant NamedTag|null return type on an Iterator<int, NamedTag>, I'm not entirely sure where the bug lies -- either null should be allowed and PHPStan should ignore it, or null should be disallowed by covariance rules.

[dktapps]

In line with PHP's own iterators, it's my belief that Iterator->current() should be allowed to return NULL without affecting the iterator's overall type, as per this example: https://3v4l.org/3Flfs

[hrach]

This is IMO not a bug, this is something PHPStan should check. There is no official documentation how current should behave and the internal behaves the way it returns a null in invalid state, but the general logic approach here is to throw (InvalidStateException) in invalid state. Ie. current should return only valid values, otherwise a check via valid() call is needed.

[phpstan-bot]

@dktapps After the latest commit to dev-master, PHPStan now reports different result with your code snippet:

@@ @@
+17: Method Iterable1::current() should return NamedTag|null but returns NamedTag|false.
 49: Cannot call method getValue() on NamedTag|null.

Full report

Line	Error
17	Method Iterable1::current() should return NamedTag
49	Cannot call method getValue() on NamedTag

[phpstan-bot]

@dktapps After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-49: Cannot call method getValue() on NamedTag|null.
+17: Method Iterable1::current() should return NamedTag|null but returns NamedTag|false.

Full report

Line	Error
17	`Method Iterable1::current() should return NamedTag

[ondrejmirtes]

I think this works as expected now.

[github-actions]

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