Fix ReflectionGetAttributesMethodReturnTypeExtension for union types

[janedbal]

Bug

When calling getAttributes() on a union type like ReflectionClass|ReflectionProperty, the ReflectionGetAttributesMethodReturnTypeExtension fails to fire for all members of the union. This causes the return type to fall back to list<ReflectionAttribute<object>> instead of the expected list<ReflectionAttribute<T>>, producing false return.type errors in generic code.

Reproduction:

/** @template T of object */
function get(ReflectionClass|ReflectionProperty $ref, class-string<T> $class): T {
    return $ref->getAttributes($class)[0]->newInstance(); // return.type error: returns object, not T
}

Root cause

isMethodSupported() checked $methodReflection->getDeclaringClass()->getName() === $this->className. When the receiver is a union type, MethodCallReturnTypeHelper iterates per class name in the union, but the $methodReflection passed to isMethodSupported always has the same declaring class (from the first resolved member). So the extension fires for one member but not the others, and the unhandled members fall back to the stub return type.

Fix

Remove the redundant declaring class check from isMethodSupported(). The extension is already registered per-class via getClass() and only dispatched for matching classes by getDynamicMethodReturnTypeExtensionsForClass($className), so the check was unnecessary and actively harmful for union types.

Co-Authored-By: Claude Code

[janedbal]

Looks like duplicate of #5463

[janedbal]

Closing in favor of #5463 which fixes the root cause in MethodCallReturnTypeHelper instead of loosening the extension check.

[VincentLanglet]

Closing in favor of #5463 which fixes the root cause in MethodCallReturnTypeHelper instead of loosening the extension check.

I'll need to rewrite the description cause I changed the strategy by working on ReflectionGetAttributesMethodReturnTypeExtension too