A possible clarification.
When <constructor spec> is (<constructor name> <field name> ...),
* <field name> can be either one of <field name> in the define-record-type form, or
any of ancestor's field name.
* In the case if the record definition has the same field name as one of ancestor's, it shadows
the ancestor's field name for the purpose of constructor; the constructor's argument initializes
child's slot, and the ancestor's slot of the same name is left uninitialized.
* It is an error if the same identifier appears more than once in <field name> .. of the constructor spec.
These are not explicit in srfi-99's syntactic layer section, but can be derived from
the description of procedural layer description.