class Show (T a) => C a where {
  type T a;
  get :: a -> T a;
}

data D = D;

instance Show D where {
  show _ = "D";
}

instance C D where {
  type T D = D;
  get _ = D;
}

instance C Int where {
  type T Int = Int;
  get i = i;
}

instance C a => C (List a) where {
  type T (List a) = T a;
  get l = case l of
            Nil -> error "list empty";
            Cons x _ -> get x;
          ;
}

data E = E;

instance C E where {
  type T E = Int;
  get _ = 42;
}

test1 = show (get D);
test2 = show (get (Cons 1 (Cons 2 Nil)));
test3 = show (get E);
main = test2;