Fix get_class return type

[VincentLanglet]

Closes #2350
Closes phpstan/phpstan#4890

[ondrejmirtes]

I feel like a proper solution would be a new Type method. Basically the opposite of getClassStringObjectType. That one goes from class-string<Foo> to Foo.

We need to go from object Foo to class-string<Foo>.

And personally I don't think there's anything wrong with class-string<object{foo: Bar}> because it'd allow for a precise type when doing new on it again.

[VincentLanglet]

Not sure if $this should be intersected with ObjectWithoutClassType here.

With the current implementation, generics.php assertions are not changed.

But we might prefer having

assertType(
		'class-string<object&T (function PHPStan\Generics\FunctionsAssertType\getClassOnTemplateType(), argument)>|false',
		get_class($a)
	);

over

assertType(
		'class-string<T (function PHPStan\Generics\FunctionsAssertType\getClassOnTemplateType(), argument)>|false',
		get_class($a)
	);

If later we're doing new on it. WDYT ?

[VincentLanglet]

I feel like a proper solution would be a new Type method. Basically the opposite of getClassStringObjectType. That one goes from class-string<Foo> to Foo.

We need to go from object Foo to class-string<Foo>.

I introduced getClassStringType(), feel free to challenge the name :)

[phpstan-bot]

This pull request has been marked as ready for review.