DomainConstructor:
    | "FunctionOf"
    | "ListOf"
    | "DictionaryOf"
    | "TupleOf"
    | "Intersection"
    | "Union"
    | "OptArg"
    | "VarArg"
    | "Covariant"
    | "Contravariant"
    | "Bivariant"
    | "Invariant"

A domain constructor is the head of a domain expression.