The name in a structural_generic_instance_name shall denote a generic
unit that is preelaborated. Note that, unlike in a traditional instantiation,
there are no square brackets around the generic_actual_part in the second
production, which means that it is mandatory and, therefore, that the generic
unit shall have at least one generic formal parameter.
The generic unit shall not take a generic formal object of mode in out.
If the generic unit takes a generic formal object of mode in, then the
corresponding generic actual parameter shall be a static expression.
A structural_generic_instance_name shall not be present in a library
unit if the structural instance is also a library unit and has a semantic
dependence on the former.