library we used identifiers such as 'UDEF_CIRCLE' etc.
      instead of the more natural sounding CIRCLE. So with user-defined identifier
      subtypes we have a tradeoff; we need unique identifier names both for our subtype
      identifiers and the v-type for our subtype identifiers so as not to conflict
      with others who might be using identifier subtypes, but those unique names
      might make using macros less "natural" On the other hand, just registering/pre-detecting
      identifiers has no su