But how will it deal with nulls? For example, let's imagine I have a user schema. This schema has 3 fields, username, is_admin and admin_level. I can guarantee using changesets that when is_admin is true, admin_level must be non null. When is_admin is false, it can be null. admin_level would be always treated as nullable by the type system?
The type system _may_ allow the type of a field to be based on the value of another field. I will investigate and, if possible, we would have to figure out a syntax that makes this possible to express.
