drvfail003.hs:16:56: error:
    • No instance for ‘Show (v (v a))’
        arising from the first field of ‘End’ (type ‘v (v a)’)
      Possible fix:
        use a standalone 'deriving instance' declaration,
          so you can specify the instance context yourself
    • When deriving the instance for (Show (Square_ v w a))