@@ -24,7 +24,7 @@ data Tree a w = Leaf a
2424 | WithWeight (Tree a w) w
2525 deriving (Show, Eq, Generic)
2626
27−deriving instance Bifunctor (Tree a w)
27+deriving instance Bifunctor Tree
2828
2929mytree :: Tree Int Int
3030mytree = Fork (WithWeight (Leaf 42) 1)