Ptr a is used as example of representational role but it isn't

Summary

The documentation of role annotations uses this example:

type role Ptr representational
data Ptr a = Ptr Addr#

And it says that this is the disired role of Ptr, but the source code of Ptr tells us:

-- The role of Ptr's parameter is phantom, as there is no relation between
-- the Haskell representation and whatever the user puts at the end of the
-- pointer. And phantom is useful to implement castPtr (see #9163)

-- redundant role annotation checks that this doesn't change
type role Ptr phantom
data Ptr a = Ptr Addr#
  deriving ( Eq  -- ^ @since 2.01
           , Ord -- ^ @since 2.01
           )

Proposed improvements or changes

I propose to find another example or just remove this example and skip straight to the nominal Set example.