Feature/undefined expression allowed

[rajyan]

fixes phpstan/phpstan#6107
fixes phpstan/phpstan#5971
fixes phpstan/phpstan#5337
fixes phpstan/phpstan#6899

This PR introduces a new method isUndefinedExpressionAllowed to Scope interface and new property currentlyAllowedUndefinedExpression of MutatingScope.

Currently, access to undefined property is allowed in assign. In Isset_ and Empty_ it is simulating an assign by lookForEnterExpressionAssign to avoid undefined propeties, but it changes from read access to write access which are causing false positives/negatives like issues in above.
The purpose of this feature is to separate isInExpressionAssign and undefined property to avoid those issues.
Also, this feature can make allowing/disallowing undefined expressions much more flexibly like 59d89a5
(this line is added for backwards compatibility that Coalesce doesn't allow dynamic properties)
and may be easier to make strict analysis after #[AllowDynamicProperties] is introduced in PHP 8.2 :)
#1104 (comment)

[rajyan]

memo for failing test https://github.com/pmmp/PocketMine-MP/blob/e0b07ff3087b652407439a29c941f3b66ca92c86/src/pocketmine/Server.php#L2105-L2109

[ondrejmirtes]

I'm blown away by this, it's awesome! Additionally, I love when people start working on a change X (#1104), realize that changeset Y can be contributed separately (#1174) and once it's merged, they go back to implementing X again :)

I'm ready to merge this, I just want to ask you to add regression tests for the linked issues you know this fixes.

[ondrejmirtes]

Also - consider basing this on 1.5.x since it can be considered a bugfix for all those issues.

[rajyan]

I'm blown away by this, it's awesome! Additionally, I love when people start working on a change X (#1104), realize that changeset Y can be contributed separately (#1174) and once it's merged, they go back to implementing X again :)

I'm happy to hear your comments! I think I need two more fixes and can finally complete #1104 :)

[rajyan]

I'm ready to merge this, I just want to ask you to add regression tests for the linked issues you know this fixes.

I'll fix and add tests and do some small refactoring today. I'll mark it ready when it's finished!

[rajyan]

The failing integration test is from json_decode + checkExplicitMixed (property access is not allowed in strict mixed). I'm not sure how to solve this problem as in phpstan/phpstan#1874
but I think this PR #993 may solve the problem.

[rajyan]

Rebased and added some regression tests. This PR is ready for review!
The failing test is related to this PR, but not sure how to fix.
#1174 (comment)

[rajyan]

I'll fix this one next

phpstan-src/tests/PHPStan/Rules/Properties/AccessPropertiesRuleTest.php

Lines 573 to 576 in db78bf5

	[
	'Cannot access property $prop on object|string.', // open issue https://github.com/phpstan/phpstan/issues/3659, https://github.com/phpstan/phpstan/issues/6026
	25,
	],

(this feature makes easier to fix the issue :))
and fix TypeSpecifier for Isset_. Then complete #1104 👍

[ondrejmirtes]

Awesome, thank you!