Next, we determine the [=part=] [=part/name=]. This can be explicitly provided by a "`name`" [=token=] or be automatically assigned. 1. If |name token| is not null, then set |name| to |name token|'s [=token/value=]. 1. Otherwise if |regexp or wildcard token| is not null: - 1. Set |name| to |parser|'s [=pattern parser/next numeric name=]. + 1. Set |name| to |parser|'s [=pattern parser/next numeric name=], [=serialize an integer|serialized=]. 1. Increment |parser|'s [=pattern parser/next numeric name=] by 1. 1. If the result of running [=is a duplicate name=] given |parser| and |name| is true, then throw a {{TypeError}}. 1. Let |encoded prefix| be the result of running |parser|'s [=pattern parser/encoding callback=] given |prefix|.