A contract type ID that may be either a template or an interface ID. A ContractTypeId.ResolvedPkg ID will always be either ContractTypeId.Template or ContractTypeId.Interface; an unresolved ID may be one of those, which indicates an expectation of what the resolved ID will be, or neither, which indicates that resolving what kind of ID this is will be part of the resolution.

Built-in equality is solely determined by the triple of package ID, module name, entity name. This is because there are likely insidious expectations that this be true dating to before contract type IDs were distinguished at all, and we are only interested in distinguishing them statically, which these types do, and by pattern-matching, which does work.

val selector: ContractTypeId[Unit] = Template((), "M", "E")
selector match {
  case ContractTypeId.Unknown(p, m, e) => // this will not match
  case ContractTypeId.Interface(p, m, e) => // this will not match
  case ContractTypeId.Template(p, m, e) => // this will match
}