You are trying to perform a generic derivation of an expanded base class
with at least one actual generic type parameter which is not `generic-creation-ready'.

`Generic-creation-readiness' states that each actual type parameter either meets his
creation constraint and in case it is itself expanded is recursively `generic-creation-ready'.

As an expanded type is automatically initialized one has to ensure, that all
creation constraints are met.
Consider GENERATOR[G create default_create end]
This generator can create objects of type G. However, it's perfectly valid to
use a type such as GENERATOR[COMPARABLE] as long as one does not try to create
an object of this type directly. For expanded base classes this is not the case,
as they are auto initialized.