The thing that was so curious to me about this issue is that dumpType does infer the correct type in a lot of cases, but the "might not be defined" warning is still emitted (I misunderstood dumpType -- it seems that certainty of the type doesn't guarantee that it's defined).

I have a lot of logic like this in templating code, which can't always be reorganized to circumvent the warning. I'm crossing my fingers for a fix some day from one of our amazing maintainers! ❤️

I'll add my example here, though it is much the same as the original:
https://phpstan.org/r/96490bfa-916f-487b-a915-30c752ef65d3

@hocker1 After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
+ 3: Function test() returns void but does not have any side effects.
 14: If condition is always true.
 14: Variable $x might not be defined.

@hemberger After the latest push in 2.0.x, PHPStan now reports different result with your code snippet:

@@ @@
+ 4: Function test() returns void but does not have any side effects.
 10: Dumped type: 'foo'
 10: Variable $foo might not be defined.