I can see the root cause of the different AST now.

in the error case, the file beeing analyzed is not recognized as beeing one of the analyzedFIles in the PathRoutingParser, and therefore will only be parsed with a simple-parser instead of a rich-parser:

Yeah, this usually happens when symlinks are involved, or when a file with exactly the same contents is discovered by PHPStan outside of analysed paths (although I fixed some bugs related to that).

In my case the root problem is, that a custom autoloader builds a "nearly correct" path to the file (which has wrong casing), but the macos filesystem still says
is_file('/Users/m.staab/Documents/GitHub/philipp/lib/CMS/service/CmsImageService.php') -> true

even though in the filesystem the path actually is
/Users/m.staab/Documents/GitHub/philipp/lib/cms/service/CmsImageService.php,

therefore the "wrong" path is required() and php-src remembers this wrong path, and returns it later on in ReflectionClass->getFileName() 💥

The joys of case-insensitive filesystems 😊 Probably not much we can do about that.

I hate our home grown custom autoloader - especially in hybrid with a composer autoloader, which would do a better job when beeing alone.

thanks for the emotional support while crying thru all this shit ;)

Would it be worth to detect a case-insensitive filesystem and compare paths in a insensitive way?

I'm not even sure why an autoloader and a reflection filename have say in this. Would be interesting to see this reproduced here in E2E suite running on windows-latest.

I'm not even sure why an autoloader and a reflection filename have say in this.

➜  repro git:(bug12972) ✗ ls -la   
total 16
drwxr-xr-x@  4 m.staab  staff   128 May 12 16:01 .
drwxr-xr-x@ 42 m.staab  staff  1344 May 12 16:01 ..
-rw-r--r--@  1 m.staab  staff    20 May 12 15:58 OTHER.php
-rw-r--r--@  1 m.staab  staff   123 May 12 15:59 repro.php

➜  phpstan-src git:(bug12972) ✗ cat OTHER.php   
<?php

class Foo {}
➜  phpstan-src git:(bug12972) ✗ cat repro.php
<?php

require __DIR__.'/other.php'; // include file with different case, as a autoloader could do it

$reflection = new ReflectionClass(Foo::class);
var_dump($reflection->getFileName());
➜  phpstan-src git:(bug12972) ✗ php repro.php 
string(53) "/Users/m.staab/Documents/GitHub/phpstan-src/other.php"

see in the last line of the output, that $reflection->getFileName() returns the path, equal to the path used for require, even though in the filesystem the path has a different casing.

Would be interesting to see this reproduced here in E2E suite running on windows-latest.

regression test and fix in phpstan/phpstan-src#3988