Extends support for enum declarations

[dselman]

Extends support for enum declarations

[mttrbrts]

Are you proposing a Liskov substitution semantic, or is this just syntactic sugar for creating a new enum type that shares values with another type?

[dselman]

Closer to the former. The line

o VehicleStatus status

Is saying, "expect an enum value here, coming from the VehicleStatus enum declaration, or any enum declaration that extends VehicleStatus. We would have to add logic to enum declarations to check that they were not redeclaring enum values from a super type...

The implementation could be something like rebuilding EnumDeclaration on top of ConceptDeclaration so we share a lot of the logic for handling super types, decorators etc.

[mttrbrts]

I'm having some déja vu!
#291