Table per subclass using a discriminator with mapping-by-code

Recently xanatos in a comment to one of my mapping-by-code series post asked how to implement hybrid-mode inheritance with both table per subclass and discriminator columns using mapping-by-code. I think this scenario is quite exotic (why do we need a discriminator column if we have separate tables?), but the documentation explicitly mentions this possibility, so it should be possible with mapping-by-code, too.

Here is the expected XML mapping fragment:

<class name="Payment" table="PAYMENT">
    <id name="Id" type="Int64" column="PAYMENT_ID">
        <generator class="native"/>
    </id>
    <discriminator column="PAYMENT_TYPE" type="string"/>
    <property name="Amount" column="AMOUNT"/>
    ...
    <subclass name="CreditCardPayment" discriminator-value="CREDIT">
        <join table="CREDIT_PAYMENT">
            <key column="PAYMENT_ID"/>
            <property name="CreditCardType" column="CCTYPE"/>
            ...
        </join>
    </subclass>
</class>

And here is how to do it in mapping-by-code:

public class PaymentMap : ClassMapping<Payment>
{
    public PaymentMap()
    {
        Id(x => x.Id, m => m.Generator(Generators.Native));
        Discriminator(d => d.Column("PaymentType"));
        Property(x => x.Amount);
    }
}

public class CreditCardPaymentMap : SubclassMapping<CreditCardPayment>
{
    public CreditCardPaymentMap()
    {
        DiscriminatorValue("CREDIT");
        Join("CreditPayment", j => j.Property(x => x.CreditCardType));
    }
}

I'm impressed again how easily XML mapping can be translated to mapping-by-code syntax.