Union of enum cases accepts the enum class type with negated cases

[takaram]

This PR changes the result of removing an enum case from its class.

enum TestEnum
{
    case A;
    case B;
    case C;
}

function test(TestEnum $enum): void
{
    if ($enum !== TestEnum::A) {
        \PHPStan\dumpType($enum);
    }
}

• Before: TestEnum~TestEnum::A
• After: TestEnum::B|TestEnum::C

Closes phpstan/phpstan#8846

[ondrejmirtes]

Instead of changing what TypeCombinator::remove() does in this case, I'd rather be if you fixed so that Foo::THREE|Foo::TWO accepts Foo~Foo::ONE. You should be able to debug that by looking into what UnionType::accepts() does with ObjectType in this case. Some code that does $type->getEnumCases() and compares them (because both sides will report the same enum cases) should be put somewhere in there.

[takaram]

@ondrejmirtes
Thank you for your suggestion. I'll revise this PR.

[phpstan-bot]

This pull request has been marked as ready for review.

[ondrejmirtes]

It's a bit tricky to mark the rest of the dataProvider as tested only on PHP 8.1. Please reverse the condition and put the enum yields into that condition:

if (PHP_VERSION_ID >= 80100) {
    yield...
}

If PHPCS complains, move one existing yield below the condition.

[takaram]

I reversed the condition and moved some of the existing yields.

[ondrejmirtes]

One more test please:

		yield [
			new UnionType([
				new EnumCaseObjectType('PHPStan\Fixture\TestEnum', 'ONE'),
				new NullType(),
			]),
			new UnionType([
				new ObjectType(
					'PHPStan\Fixture\TestEnum',
					new EnumCaseObjectType('PHPStan\Fixture\TestEnum', 'TWO'),
				),
				new NullType(),
			]),
			TrinaryLogic::createYes(),
		);

[takaram]

I added this test case.

[takaram]

@ondrejmirtes
Thank you for your comments.
Could you check it again?

[ondrejmirtes]

Alright, one more thing: you're trying to fix phpstan/phpstan#8846. Which means we need a regression test in the test class for the rule that reports the false positive. Which means you should write a test in Functions\ReturnTypeRuleTest. And make sure it fails without your changes in src/ :)

[ondrejmirtes]

Perfect, thank you!