Derive static versions of `StandaloneDeriving` instances with `withStatic`

[ABorgna]

Instances declared with StandaloneDeriving are not recognized by withStatic, and they don't get their static version defined. The following program does not compile (missing instance for (Static (Show D))).

{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StaticPointers #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# Language TemplateHaskell #-}

import Control.Distributed.Closure
import Control.Distributed.Closure.TH
import Data.Typeable

data D = D
  deriving (Typeable)

withStatic [d|
  deriving instance Show D
  |]

showC :: forall a. (Typeable a, Static (Show a)) => Closure a -> String
showC a = unclosure $ static (\Dict -> show)
  `cap` (closureDict :: Closure (Dict (Show a)))
  `cap` a

main :: IO ()
main = do
  putStrLn $ showC $ static D

Neither does withStatic work with derived instances

withStatic [d|
  data D = D
    deriving (Typeable, Show)
  |]
-- Static (Show D) doesn't get defined

As a result, there is no way to auto-generate static versions of instances with default implementations.