Not quite. I guess in some ways phantom types achieve the opposite of structural typing. In a language with structural typing, two types are considered equival

Not quite. I guess in some ways phantom types achieve the opposite of structural typing. In a language with structural typing, two types are considered equivalent if they share the same structure. With phantom types we can have a single structure and disambiguate between different uses without touching the underling structure. There's no difference between Id(User) and Id(Post) at runtime, the annotation is purely a compile-time restraint. In fact, because of typescript's structural typing, the only way to use phantom types in ts is to have some dummy field of type `never` that the type system can use to disambiguate between the two [1]. [1]: https://gist.github.com/GoNZooo/243b23702df1fae38c966ae18832c690 https://gist.github.com/GoNZooo/243b23702df1fae38c966ae18832...