checkerForField method
External models, such as REST or I/O, pull type inference data from class constructors. This is to allow for class constructors to process potentially nullable data into non-nullable data by assigning a default at initialization, or to allow a class to process one type into another at construction (eg String myString -> Foo(myString)). Sqlite data, however, is always serialized from dart -- as a result, we don't care about mismatches between the constructor and member fields, and will always use the type defined by the class member.
Implementation
@override
SharedChecker checkerForField(FieldElement field) => checkerForType(field.type);