Fix phpstan/phpstan#14352: "Cannot re-assign $this." false-positive

[phpstan-bot]

closes phpstan/phpstan#14352

fixes the CI build

[VincentLanglet]

$this = $value should still be reported

[staabm]

$this = $value should still be reported

yes. thats tested via bug-14349.php which was added in the inital implementation

[VincentLanglet]

$this = $value should still be reported

yes. thats tested via bug-14349.php which was added in the inital implementation

I mean $this = $value when $this is an ArrayAccess

[staabm]

I see. added another test showing it still errors

[phpstan-bot]

Pushed successfully. Here's a summary of the changes:

Problem: The original fix checked if the assigned expression's type implements ArrayAccess to suppress the "Cannot re-assign $this" error. But as the reviewer pointed out, $this = $arrayAccessValue should still be reported as an error.

Solution: Added a dimFetch flag to VariableAssignNode that tracks whether the assignment originated from a dimension-fetch expression ($this[$key] = $value) vs a direct assignment ($this = $value). The rule now:

1. Skips the error only when it's a dim-fetch AND $this implements ArrayAccess
2. Still reports $this = $value even when the value implements ArrayAccess
3. Still reports $this[$key] = $value on classes that don't implement ArrayAccess

[VincentLanglet]

I know the case

class TestPlain
{
	public function doFoo(string $key, string $value): void
	{
		$this[$key] = $value;
	}
}

might sometimes works if we extends this class and implement ArrayAccess.

But on the opposide, the code

$t = new TestPlain();

$t->doFoo('', '');

will crash.

IMHO ->yes() should be !->no()
and we will have a behavior similar to https://phpstan.org/r/ae445bd2-da35-4b9f-b0cb-a44c0d1b71e8

[phpstan-bot]

Pushed. Here's a summary of the changes:

Problem: The reviewer pointed out that for non-final classes like TestPlain, $this[$key] = $value should not error because a subclass might implement ArrayAccess. The check should use !->no() instead of ->yes().

Changes:

1. VariableAssignNode — Added dimFetch flag to distinguish $this[$key] = $value (dim-fetch) from $this = $value (direct assignment)

2. AssignHandler — Pass dimFetch: true when creating VariableAssignNode from dim-fetch assignment paths

3. InvalidVariableAssignRule — Changed the check to:

   • Use $node->isDimFetch() to only suppress errors for dim-fetch assignments
   • Check $scope->getType($variable) (the type of $this) instead of the assigned expression type
   • Use !->no() instead of ->yes() — this allows the "maybe" case for non-final classes (line 614 of ObjectType::isSuperTypeOf returns Maybe when checking an interface against a non-final class)

4. Test data — Added TestArrayAccessReassign case to verify $this = $other still errors even when $other implements ArrayAccess

Behavior:

• TestArrayAccess (implements ArrayAccess): $this[$key] = $value → no error, $this = $value → error
• TestArrayAccessReassign: $this = $other → error (even though $other is ArrayAccess)
• FinalTestPlain (final, no ArrayAccess): $this[$key] = $value → error
• TestPlain (non-final, no ArrayAccess): $this[$key] = $value → no error (subclass might implement ArrayAccess)