ormolu/data/examples/declaration/class/default-implementations.hs

-- | Foo
class Foo a where
    foo :: a -> a
    foo a = a

-- | Bar
class Bar a where
    bar ::
           a
        -> Int
    bar = const 0

-- | Baz
class Baz a where
    foobar :: a -> a
    foobar a =
        barbaz (bazbar a)
    -- | Bar baz
    barbaz ::
        a -> a
    -- | Baz bar
    bazbar ::
        a ->
        a
    -- First comment
    barbaz a
        = bazbar -- Middle comment
            a
    -- Last comment
    bazbar a
        = barbaz
            a