error[E0277]: the trait bound `<T as Base>::Base<C>: Functor<C>` is not satisfied
  --> $DIR/method-chain-gats.rs:18:20
   |
LL |     input.fmap(f1).fmap(f2)
   |                    ^^^^ the trait `Functor<C>` is not implemented for `<T as Base>::Base<C>`
   |
note: the method call chain might not have had the expected associated types
  --> $DIR/method-chain-gats.rs:13:29
   |
LL | fn fmap2<T, A, B, C>(input: T, f1: impl Fn(A) -> B, f2: impl Fn(B) -> C) -> T::Base<C>
   |                             ^ `Base::Base` is `<T as Base>::Base<_>` here
note: required by a bound in `Functor::fmap`
  --> $DIR/method-chain-gats.rs:10:24
   |
LL |     fn fmap<B>(self, f: impl Fn(A) -> B) -> Self::Base<B>
   |        ---- required by a bound in this associated function
LL |     where
LL |         Self::Base<B>: Functor<B>;
   |                        ^^^^^^^^^^ required by this bound in `Functor::fmap`
help: consider further restricting the associated type
   |
LL |     T::Base<B>: Functor<B, Base<C> = T::Base<C>>, <T as Base>::Base<C>: Functor<C>
   |                                                   ++++++++++++++++++++++++++++++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.