Deprecation false positive(?): Embeddable reported to require inheritance mapping type

[havvg]

Bug Report

Q	A
Version	2.20.2

Summary

We are currently migrating a project to Doctrine 3 and are encountering the following deprecation.

Entity class 'App\Domain\Value\BoundedTimeframe' is a subclass of the root entity class 'App\Domain\Value\Timeframe', but no inheritance mapping type was declared. This is a misconfiguration and will be an error in Doctrine ORM 3.0. (ClassMetadataFactory.php:165 called by ClassMetadataFactory.php:18, https://github.com/doctrine/orm/pull/10431, package doctrine/orm)

Current behavior

The deprecation about entity inheritance is raised on embeddables.

Expected behavior

There has been no issue within Doctrine 2 using this pattern. As you cannot define inheritance types on embeddables, the deprecation should not be raised for them. In addition, the behavior should work in Doctrine 3, as well. Will it?

How to reproduce

<?xml version="1.0" encoding="utf-8"?>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping https://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
    <embeddable name="App\Domain\Value\Timeframe">
        <field name="from" type="datetime_immutable" column="from" nullable="true" />
        <field name="to" type="datetime_immutable" column="to" nullable="true" />
    </embeddable>
</doctrine-mapping>

<?xml version="1.0" encoding="utf-8"?>
<doctrine-mapping xmlns="http://doctrine-project.org/schemas/orm/doctrine-mapping" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://doctrine-project.org/schemas/orm/doctrine-mapping https://www.doctrine-project.org/schemas/orm/doctrine-mapping.xsd">
    <embeddable name="App\Domain\Value\BoundedTimeframe" />
</doctrine-mapping>

// Simplified

class Timeframe
{
    public function __construct(
        protected readonly \DateTimeImmutable|null $from,
        protected readonly \DateTimeImmutable|null $to,
    ) {
    }
}

class BoundedTimeframe extends Timeframe
{
    public function __construct(\DateTimeImmutable $from, \DateTimeImmutable $to)
    {
        parent::__construct($from, $to);
    }
}