There are days I hate the mapping of plain English terms of art over actual in-language effects. Considering sets, if something is, in set terms a specific sub

There are days I hate the mapping of plain English terms of art over actual in-language effects. Considering sets, if something is, in set terms a specific subset with a defining membership or characteristic of a definable superset, representing that at compile time effects a hard constraint which honours the set Venn diagram. If that set/subset constraint doesn't exist then you have to ask yourself if applying a compile time constraint is appropriate.