Infer return type from class-string<T> in ClassResolver extensions

[mglaman]

Summary

• When class-string<T> is passed to ClassResolverInterface::getInstanceFromDefinition() or Drupal::classResolver(), PHPStan now infers the return type as T instead of object
• Uses Type::getClassStringObjectType() to extract the generic class type in the no-constant-strings fallback path of DrupalClassResolverReturnType
• Service-ID resolution (e.g. 'service_map.my_service' → MyService) and constant class-name strings (Foo::class) are unchanged

This fills the gap that PR #402 was attempting to address, without replacing the dynamic extensions (which are still needed for service-ID resolution via ServiceMap).

Test plan

• New test_class_string_vars() fixture function covers all four call patterns (ClassResolver, \Drupal::service('class_resolver'), \Drupal::classResolver()->..., \Drupal::classResolver($var)) with class-string<T> variables
• php vendor/bin/phpunit --filter=DrupalContainerDynamicReturnTypeTest — all pass
• php vendor/bin/phpcs src/ — clean

Closes #402

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Improves PHPStan dynamic return type inference for Drupal’s class resolver so that passing a class-string<T> variable to ClassResolverInterface::getInstanceFromDefinition() / \Drupal::classResolver() yields return type T (rather than a generic object), while preserving existing behavior for service-id resolution and constant class-string literals.

Changes:

• Extend DrupalClassResolverReturnType to extract and return the object type from class-string<T> inputs when the argument is not a constant string.
• Add a new type inference fixture covering class-string<T> variables across the four supported call patterns.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Type/DrupalClassResolverReturnType.php	Uses Type::getClassStringObjectType() in the non-constant-string path to return the generic object type for class-string<T> arguments.
tests/src/Type/data/drupal-class-resolver.php	Adds fixture assertions validating inferred return types for class-string<Foo> and class-string<MyService> variables across resolver call patterns.