Fix ambiguous constant inheritance false positive

[Jean85]

Fixes #7818

Thanks to @orklah for his comment, that allowed me to fix this even without knowing anything about the Psalm codebase!

I've used https://psalm.dev/r/99f7bf3fc4 as a regression test.

[psalm-github-bot]

I found these snippets:

https://psalm.dev/r/99f7bf3fc4

<?php

interface MainInterface {
    final public const TEST = 'test';
}

interface FooInterface extends MainInterface {}
interface BarInterface extends MainInterface {}

class FooBar implements FooInterface, BarInterface {}

Psalm output (using commit 96a7133):

ERROR: AmbiguousConstantInheritance - 4:24 - Ambiguous inheritance of FooBar::TEST from BarInterface and FooInterface

[Jean85]

Ouch, the failing test is highlighting that my fix is too shallow, it swallows the error from the docs snippet. Any pointers?

[orklah]

Thanks for this!

There's 3 variables with a constant storage in that code

$const_storage: it's received as a param. It's the storage of the constant retrieved from the class storage of Baz (it's arbitrarily chosen from the 2 constant storage that exists for Baz::CONSTANT)
$parent_const_storage: it's the constant storage that is retrieved from the interface that we're looking into in the current iteration of the loop
$interface_const_storage: it's the constant storage that was retrieved from the interface we were looking on the previous iteration of the loop

So when everything is ok, we iterate for each interface, we check for the existence of that constant. If it doesn't exists, we continue looping until we found that constant in one interface. When that happens we store the storage for comparison with the next iteration:

psalm/src/Psalm/Internal/Analyzer/Statements/Expression/ClassConstAnalyzer.php

Line 859 in 8c491e9

$interface_const_storage = $parent_const_storage;

So your code compares the arbitrary constant storage with the current constant storage so the result is arbitrary. What you want to do is compare the storage between two interfaces, so between two iterations of the loop (so between $parent_const_storage and $interface_const_storage)

As a note: you should be able to directly compare storages instead of comparing the hash of their location given each instance is should be unique

[orklah]

Thanks!