Failed to infer iterable type when iterating on \Generator<someType>|null

[dktapps]

Bug report

I know that iterating on Generator|null is a bug, but it's not reported until level 7.

When up to level 6, PHPStan does not report a problem and should be able to understand what the iterable type will be in the case where it's not null.

Code snippet that reproduces the problem

https://phpstan.org/r/c9fc2ca5-501f-4fbe-bdcc-cf14a9f12ea9

Expected output

The dumped type should be a union of Block and *ERROR*. It may be an stdClass or it may not be iterable at all.

In addition, an error should be reported on line 18, because neither *ERROR* nor Block has a method called getPos() (definite crash).

Additional notes

I consider this a serious problem because it's an obvious bug that otherwise won't get detected until reaching level 8. This means that reaching level 6 provides a false sense of security while missing problems like this.

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

It's greatly assisted me while updating an old project to a newer API.

[phpstan-bot]

@dktapps After the latest push in 1.11.x, PHPStan now reports different result with your code snippet:

@@ @@
 10: Property HelloWorld::$nullableGenerator is never written, only read.
 13: Property HelloWorld::$regularGenerator is never written, only read.
-17: Dumped type: *ERROR*
+17: Dumped type: Block
+18: Call to an undefined method Block::getPos().
 22: Dumped type: Block
 23: Call to an undefined method Block::getPos().

Full report

Line	Error
10	Property HelloWorld::$nullableGenerator is never written, only read.
13	Property HelloWorld::$regularGenerator is never written, only read.
17	Dumped type: Block
18	Call to an undefined method Block::getPos().
22	Dumped type: Block
23	Call to an undefined method Block::getPos().

[github-actions]

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