`fun getUserProfile(): Either<OldUser, NewUser&...

# arrow

[pakoito]

fun getUserProfile(): Either<OldUser, NewUser> // a migration

fun getAddresses(): Either<Ipv4, Ipv6> // ad-hoc unions without wrapping

fun <A, B> tailRecM(a: A, f: (A) -> Kind<F, Either<A, B>>): Kind<F, B> // branch in code, reified