POC: Use SimultaneousTypeTraverser in RuleLevelHelper::transformAcceptedType

[VincentLanglet]

Static analysis is failing because TypeTraverserInstanceofVisitor doesn't support SimultaneousTypeTraverser (not sure it should).

The only current test failing is

16: Function ReturnListNullables\doFoo() should return array<string>|null but returns list<string|null>.

but I feel like we could reproduce more errors because...

UnionType/Intersection types doesn't work well with the SimultaneousTypeTraverser because

• when it's called with A&B&C and A we're not traversing because second type is not an Intersection
• when it's called with A&B&C and A&C we're not traversing because types count are different

The main issue would be, when traversing A&B&C and A&C, to match types in order to

• traverse (A, A)
• traverse (B, Never)
• traverse (C, C)

[ondrejmirtes]

The output from issue-bot is yummy here! https://github.com/phpstan/phpstan-src/actions/runs/16773630245

Please add regression tests for those.

I feel like we could improve IntersectionType::traverseSimultaneously() for all the common pseudotypes like non-empty-string, list etc. represented with IntersectionType.

I feel that even when there's non-empty-string on left side and string on the right side and vice versa, the callback should still be invoked for them.

This needs extensive tests of course.

[ondrejmirtes]

Linking phpstan/phpstan#9096

[VincentLanglet]

The output from issue-bot is yummy here! phpstan/phpstan-src/actions/runs/16773630245

Please add regression tests for those.

Sure, but shouldn't we fix the actual tests first ?

I feel like we could improve IntersectionType::traverseSimultaneously() for all the common pseudotypes like non-empty-string, list etc. represented with IntersectionType.

I feel that even when there's non-empty-string on left side and string on the right side and vice versa, the callback should still be invoked for them.

Yeah, but I dunno how to improve the implementation of the existing traverseSimultaneously, it's not easy :/

[VincentLanglet]

I feel like 6597ef6#r167671380 is helping us.

And maybe same should be done for IntersectionType

[ondrejmirtes]

Yeah, I'm thinking about how to implement it.

[ondrejmirtes]

Right now I have this failing test:

diff --git a/tests/PHPStan/Type/SimultaneousTypeTraverserTest.php b/tests/PHPStan/Type/SimultaneousTypeTraverserTest.php
index 76dc038873..750a7a56bd 100644
--- a/tests/PHPStan/Type/SimultaneousTypeTraverserTest.php
+++ b/tests/PHPStan/Type/SimultaneousTypeTraverserTest.php
@@ -125,6 +125,13 @@ class SimultaneousTypeTraverserTest extends PHPStanTestCase
 			$chooseScalarSubtype,
 			"'aaa'|Foo",
 		];
+
+		yield [
+			'list<string|null>',
+			'array<string>',
+			$chooseScalarSubtype,
+			'list<string>',
+		];
 	}
 
 	/**

[ondrejmirtes]

Alright here's something 0693e5a

But I don't think it works well for constant arrays for example or other situations, but some use cases could be solved now.

[VincentLanglet]

Alright here's something 0693e5a

But I don't think it works well for constant arrays for example or other situations, but some use cases could be solved now.

Isn't it weird to only have the case if ($this->isArray()->yes() && $right->isArray()->yes()) { handled in the IntersectionType::traverseSimultaneously ? I feel like you lost all the other possible intersection like

• string + Accessory
• object like A&B
• ...

[ondrejmirtes]

Well it might not even be needed, depends on how the callback is written. You can send me some failing tests with expectations.

[VincentLanglet]

Current status, 2 errors:

1) PHPStan\Rules\Functions\ReturnTypeRuleTest::testListWithNullablesUnchecked
Failed asserting that two strings are identical.
--- Expected
+++ Actual
@@ @@
-'
+'16: Function ReturnListNullables\doFoo() should return array<string>|null but returns list<string|null>.
 '

/home/runner/work/phpstan-src/phpstan-src/src/Testing/RuleTestCase.php:179
/home/runner/work/phpstan-src/phpstan-src/tests/PHPStan/Rules/Functions/ReturnTypeRuleTest.php:186

2) PHPStan\Rules\Functions\ReturnTypeRuleTest::testBug8846
Failed asserting that two strings are identical.
--- Expected
+++ Actual
@@ @@
-'
+'23: Function Bug8846\test() should return Bug8846\Foo::THREE|Bug8846\Foo::TWO but returns Bug8846\Foo.
 '

First one is maybe an Intersection type with $this->isArray()->yes() (list) but $right->isArray()->maybe() (array|null)...