{- | Low-boilerplate 'Text.PrettyPrint.GenericPretty.Out' instances for
    'Show'ables using @DerivingVia@.

Useful for integrating types that don't work nicely with 'Generic' with
@GenericPretty@. (Really, there should be a class like
'Text.PrettyPrint.GenericPretty.Out' directly in @pretty@, but alas.)

Use as follows:

data EeGadts a where
    C1 :: EeGadts Bool
    C2 :: EeGadts String
deriving stock instance Show (EeGadts a)
deriving via OutShowly (EeGadts a) instance Out (EeGadts a)
-}

{-# LANGUAGE DerivingVia #-}

module Text.PrettyPrint.GenericPretty.ViaShow
  ( module Text.PrettyPrint.GenericPretty.ViaShow
  , Text.PrettyPrint.GenericPretty.Out
  ) where

import Text.PrettyPrint.GenericPretty ( Out(..) )
import qualified Text.PrettyPrint

newtype OutShowly a = OutShowly { forall a. OutShowly a -> a
unOutShowly :: a }

instance Show a => Out (OutShowly a) where
    doc :: OutShowly a -> Doc
doc (OutShowly a
a) = String -> Doc
Text.PrettyPrint.text (String -> Doc) -> String -> Doc
forall a b. (a -> b) -> a -> b
$ a -> String
forall a. Show a => a -> String
show a
a
    docPrec :: Int -> OutShowly a -> Doc
docPrec Int
n (OutShowly a
a) = String -> Doc
Text.PrettyPrint.text (String -> Doc) -> String -> Doc
forall a b. (a -> b) -> a -> b
$ Int -> a -> ShowS
forall a. Show a => Int -> a -> ShowS
showsPrec Int
n a
a String
""