"Type '{ foo: number; }' is not assignable to type 'B'.
Property 'baz' is missing in type '{ foo: number; }' but required in type '{ foo: number; baz: number; }'."
const e = form.email
^
ERROR: "email" is not in '"name" | "firstname" | "lastname" | "e-mail" | "birthdate" | "password"'