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{-# LANGUAGE CPP #-}
{-# LANGUAGE MagicHash #-}
{-# LANGUAGE TemplateHaskell #-}
#if MIN_VERSION_template_haskell(2,16,0)
{-# LANGUAGE UnliftedNewtypes #-}
#endif
module Types (Foo(..)) where
import Language.Haskell.TH.Syntax hiding (newName)
#if MIN_VERSION_template_haskell(2,16,0)
import GHC.Exts (Int#)
import Language.Haskell.TH.Syntax.Compat
#endif
data Foo = MkFoo deriving (Eq, Show)
-- An example of how to use liftTypedFromUntypedSplice to minimize the amount
-- of CPP one has to use when manually defining `liftTyped` in `Lift` instance.
-- This example is contrived, since you could just as well derive this
-- particular `Lift` instance, but the same template will carry over to `Lift`
-- instances that cannot be derived.
instance Lift Foo where
lift MkFoo = [| MkFoo |]
#if MIN_VERSION_template_haskell(2,16,0)
liftTyped = liftTypedFromUntypedSplice
#endif
#if MIN_VERSION_template_haskell(2,16,0)
newtype UN = MkUN Int#
-- An example of how to use unsafeSpliceCoerce to manually define liftTyped
-- for an unlifted type in a backwards-compatible way. This example is
-- contrived, since you could just as well derive this particular `Lift`
-- instance, but the same template will carry over to `Lift` instances that
-- cannot be derived.
instance Lift UN where
lift (MkUN i#) = [| MkUN i# |]
liftTyped x = unsafeSpliceCoerce (lift x)
#endif
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