Infinite loop into out of memory error for class wrongfully extending itself

[FO-nTTaX]

Bug report

When creating a class that extends itself, phpstan will infinitely loop on trying to get the parent class until it is out of memory. I understand this is not valid php code, but I wonder if this might be catch-able and if this could be a normal error with an error message.

Code snippet that reproduces the problem

<?php
class TestClass extends TestClass {}

The share link on phpstan.org does not work because this breaks phpstan pretty badly.

Expected output

This code snippet produces an out of memory error, ideally it should probably create an error message that a class cannot extend itself.

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phpstan helps me all the time telling me when I made stupid typos, this tool is amazing :)

[mergeable]

This bug report is missing a link to reproduction at phpstan.org/try.

It will most likely be closed after manual review.

[herndlm]

This seems to be coming from PHPStan\BetterReflection\Reflection\ReflectionClass::getParentClass() or respectively internally from getInheritanceClassHierarchy. The fix should be simple, but I noticed that the upstream lib and the fork have deviated in general. Shall I try to reproduce it upstream and report/fix there or is another approach preferred?

On the other hand this is indeed invalid PHP code not true (https://3v4l.org/360uT, it just can't find the class), so I'm not sure if Better Reflection "supports" that or if we should rather avoid here that it get so far in the first place. UPDATE: fixing it here might be tricky, e.g. I avoided it in one place, it happened in another one. Most likely that's not the best solution then. I'll later try to reproduce and fix it directly in Better Reflection if that's fine.

Also, the same thing is happening with interfaces as well, e.g. interface Foo extends Foo {}

traceback

1) PHPStan\Analyser\AnalyserIntegrationTest::testBug7787
Error: Xdebug has detected a possible infinite loop, and aborted your script with a stack depth of '256' frames

/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/ReflectionClass.php:1032
/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/ReflectionClass.php:1669
/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/ReflectionClass.php:1672 ---- printed x times ---
/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/ReflectionClass.php:1399
/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/ReflectionClass.php:1563
/home/martin/PhpstormProjects/phpstan-src/vendor/ondrejmirtes/better-reflection/src/Reflection/Adapter/ReflectionClass.php:337
/home/martin/PhpstormProjects/phpstan-src/src/Reflection/ClassReflection.php:758
/home/martin/PhpstormProjects/phpstan-src/src/Reflection/ClassReflection.php:709
/home/martin/PhpstormProjects/phpstan-src/src/Dependency/DependencyResolver.php:229
/home/martin/PhpstormProjects/phpstan-src/src/Dependency/DependencyResolver.php:45
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/FileAnalyser.php:159
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/NodeScopeResolver.php:381
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/NodeScopeResolver.php:284
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/NodeScopeResolver.php:614
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/NodeScopeResolver.php:243
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/FileAnalyser.php:178
/home/martin/PhpstormProjects/phpstan-src/src/Analyser/Analyser.php:70
/home/martin/PhpstormProjects/phpstan-src/tests/PHPStan/Analyser/AnalyserIntegrationTest.php:925
/home/martin/PhpstormProjects/phpstan-src/tests/PHPStan/Analyser/AnalyserIntegrationTest.php:871

[FO-nTTaX]

So I haven't tested it, but something maybe worth looking into is circular extends between multiple classes, as that might lead to the same issue?

[herndlm]

Yes, that's basically the core problem. Circular extends between one or more classes

[ondrejmirtes]

There are many similar problems that are not prevented in PHPStan:

• Circular extends between classes
• Circular extends between interfaces
• Circular uses between traits
• The same problem maybe between the wrong types, like classes extending interfaces

And the same problems will cause infinite recursions in different places in the codebase for generics - where @extends, @implements, @uses are involved.

If the problem can be prevented by throwing an exception in BetterReflection, I'm all for it. I'll then rebase my own fork on top of the latest branch.

[ondrejmirtes]

And while we're at it, there are also constants and class constants whose values can reference themselves in a circular fashion.

In BetterReflection that should be detected and prevented in CompileNodeToValue.

But PHPStan doesn't use that. Here it should be prevented in InitializerExprTypeResolver.

[ondrejmirtes]

This is fixed now thanks to update to BetterReflection 6.0. It will produce this message: "Reflection error: Circular reference to class "Bug7787\TestClass""

[github-actions]

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