# Concerns (questions) with the current implementaion

## There exist alternative `Functor` implementations

See the [relevant subchapter](s01-alternatives.md)

## It might be better to have a per-lifetime trait for `Functor`s

See the [relevant subchapter](s02-lifetimes.md)

## `Stackless` is kind of bad

See the [relevant subchapter](s03-stackless.md)

## `WeakFunctor::F<'a, A>` is not (yet) covariant over the lifetime `'a`

See the [relevant subchapter](s04-covariance.md)

## Can `WeakFunctor` be an associated type of a `Functor` instead of its supertype?