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NFData(1) instances of Generically(1). #79

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95 changes: 65 additions & 30 deletions Control/DeepSeq.hs
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Original file line number Diff line number Diff line change
@@ -1,14 +1,16 @@
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE CPP #-}
{-# LANGUAGE DefaultSignatures #-}
{-# LANGUAGE EmptyCase #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE InstanceSigs #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE Safe #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE EmptyCase #-}
{-# LANGUAGE UndecidableInstances #-}

#if __GLASGOW_HASKELL__ >= 811 && __GLASGOW_HASKELL__ < 901
-- For the Option instance (https://gitlab.haskell.org/ghc/ghc/issues/15028)
Expand All @@ -19,6 +21,10 @@
-- At the moment of writing GHC source tree has not yet bumped `base` version,
-- so using __GLASGOW_HASKELL__ as a proxy instead of MIN_VERSION_base(4,17,0).

#if MIN_VERSION_base(4,17,0)
#define HAS_GENERICALLY
#endif

-----------------------------------------------------------------------------
-- |
-- Module : Control.DeepSeq
Expand Down Expand Up @@ -260,7 +266,7 @@ f $!! x = x `deepseq` f x
-- > evaluate . force =<< hGetContents h
--
-- @since 1.2.0.0
force :: (NFData a) => a -> a
force :: NFData a => a -> a
force x = x `deepseq` x

-- | Deeply strict version of 'Control.Applicative.<$>'.
Expand Down Expand Up @@ -302,41 +308,41 @@ class NFData a where
--
-- === 'Generic' 'NFData' deriving
--
-- Starting with GHC 7.2, you can automatically derive instances
-- for types possessing a 'Generic' instance.
-- It is possible to derive an instance of 'NFData' for a type @T@
-- possessing a 'Generic' instance via @'GHC.Generics.Generically'
-- T@ (since GHC 9.4).
--
-- Note: 'Generic1' can be auto-derived starting with GHC 7.4
--
-- > {-# LANGUAGE DeriveGeneric #-}
-- > {-# LANGUAGE DeriveAnyClass #-}
-- > {-# LANGUAGE DeriveGeneric #-}
-- > {-# LANGUAGE DerivingStrategies #-}
-- > {-# LANGUAGE DerivingVia #-}
-- >
-- > import GHC.Generics (Generic, Generic1)
-- > import GHC.Generics (Generic, Generic1, Generically(..), Generically1(..))
-- > import Control.DeepSeq
-- >
-- > data Foo a = Foo a String
-- > deriving (Eq, Generic, Generic1)
-- >
-- > instance NFData a => NFData (Foo a)
-- > instance NFData1 Foo
-- > deriving stock (Eq, Generic, Generic1)
-- > deriving NFData via Generically (Foo a)
-- > deriving NFData1 via Generically1 Foo
-- >
-- > data Colour = Red | Green | Blue
-- > deriving Generic
-- >
-- > instance NFData Colour
-- > deriving stock Generic
-- > deriving NFData via Generically Colour
--
-- Starting with GHC 7.10, the example above can be written more
-- concisely by enabling the new @DeriveAnyClass@ extension:
-- It had been possible to derive it with the @DerivingAnyClass@
-- since GHC 7.10 (although at that point the @anyclass@ deriving
-- strategy could not be named).
--
-- > {-# LANGUAGE DeriveGeneric, DeriveAnyClass #-}
-- >
-- > import GHC.Generics (Generic)
-- > import Control.DeepSeq
-- >
-- > data Foo a = Foo a String
-- > deriving (Eq, Generic, Generic1, NFData, NFData1)
-- >
-- > data Colour = Red | Green | Blue
-- > deriving (Generic, NFData)
-- >
-- > deriving anyclass (NFData, NFData1)
-- > deriving anyclass NFData
--
-- @DerivingAnyClass@ is equivalent to writing an empty instance
-- instance declaration which relies on generic default methods
-- (available since GHC 7.2).
--
-- > instance NFData (Foo a)
-- > instance NFData1 Foo
-- > instance NFData Colour
--
-- === Compatibility with previous @deepseq@ versions
--
Expand Down Expand Up @@ -367,20 +373,49 @@ class NFData a where
default rnf :: (Generic a, GNFData Zero (Rep a)) => a -> ()
rnf = grnf RnfArgs0 . from

#ifdef HAS_GENERICALLY
instance (Generic a, GNFData Zero (Rep a)) => NFData (Generically a) where
rnf :: Generically a -> ()
rnf (Generically a) = grnf RnfArgs0 (from a)
#endif

-- | A class of functors that can be fully evaluated.
--
-- It is possible to derive an instance of 'NFData1' for a type
-- constructor @F@ possessing a 'Generic1' instance via
-- @'GHC.Generics.Generically1' F@ (since GHC 9.4).
--
-- > {-# LANGUAGE DeriveAnyClass #-}
-- > {-# LANGUAGE DeriveGeneric #-}
-- > {-# LANGUAGE DerivingStrategies #-}
-- > {-# LANGUAGE DerivingVia #-}
-- >
-- > import GHC.Generics (Generic, Generic1, Generically(..), Generically1(..))
-- > import Control.DeepSeq
-- >
-- > data Foo a = Foo a String
-- > deriving stock (Eq, Generic, Generic1)
-- > deriving NFData via Generically (Foo a)
-- > deriving NFData1 via Generically1 Foo
--
-- @since 1.4.3.0
class NFData1 f where
-- | 'liftRnf' should reduce its argument to normal form (that is, fully
-- evaluate all sub-components), given an argument to reduce @a@ arguments,
-- and then return '()'.
--
-- See 'rnf' for the generic deriving.
-- See 'rnf' for more information on generic deriving.
liftRnf :: (a -> ()) -> f a -> ()

default liftRnf :: (Generic1 f, GNFData One (Rep1 f)) => (a -> ()) -> f a -> ()
liftRnf r = grnf (RnfArgs1 r) . from1

#ifdef HAS_GENERICALLY
instance (Generic1 f, GNFData One (Rep1 f)) => NFData1 (Generically1 f) where
liftRnf :: (a -> ()) -> (Generically1 f a -> ())
liftRnf r (Generically1 as) = grnf (RnfArgs1 r) (from1 as)
#endif

-- | Lift the standard 'rnf' function through the type constructor.
--
-- @since 1.4.3.0
Expand Down
6 changes: 6 additions & 0 deletions changelog.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,11 @@
# Changelog for [`deepseq` package](http://hackage.haskell.org/package/deepseq)

## 1.4.??

* Add instances for `Generically` and `Generically1`. `NFData A`
can now be derived via `Generically A` for `Generic A`.
`NFData1 F` can be derived via `Generically1 F` for `Generic1 F`.

## 1.4.7.0

* Add instances for `Solo` (GHC-9)
Expand Down