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{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
{-# LANGUAGE TypeOperators #-}
{-# OPTIONS_GHC -ddump-splices -dsuppress-uniques #-}
import Language.Haskell.TH
$([d| data Foo a = Foo a deriving (a ~ a) |])
{-
Note: to debug
~/inplace/bin/ghc-stage2 --interactive
load the following
----------------------------------------
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -ddump-splices -dsuppress-uniques #-}
import Language.Haskell.TH
class (a `C` b) c
main :: IO ()
main
= putStrLn $([d| data Foo a = Foo a deriving (a ~ a) |] >>= stringE . show)
----------------------------------------
Becomes
[DataD [] Foo_0 [PlainTV a_2] Nothing
[NormalC Foo_1 [(Bang NoSourceUnpackedness NoSourceStrictness,VarT a_2)]]
[DerivClause Nothing
[AppT (AppT EqualityT (VarT a_2))
(VarT a_2)]]]
-}
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