Driving.Classes

Derive instances without spelling out "deriving".

Usage

Step 1: add this pragma at the top of the file to load the plugin:

{-# OPTIONS_GHC -fplugin=Driving.Classes #-}

Step 2: enable DerivingStrategies and other relevant extensions as needed (DerivingVia, GeneralizedNewtypeDeriving, DeriveAnyClass):

{-# LANGUAGE DerivingStrategies #-}

Step 3: add an ANN pragma after imports to configure the classes to auto-derive:

{-# ANN module (Driving :: Driving '[ <LIST OF OPTIONS> ]) #-}

Example

This automatically declares instances of Eq, Ord, Show for T, U, V, and disables auto-deriving for MyEndo.

{-# ANN module (Driving :: Driving
  '[ Stock '(Eq, Ord, Show)
   , NoDriving '(Eq MyEndo, Ord MyEndo, Show MyEndo)
   ]) #-}

data T = C1 | C2
data U = D1 | D2
data V = E1 | E2

newtype MyEndo a = MyEndo (a -> a)

Available options:

• Stock
• Anyclass
• Newtype
• Via
• ViaF
• NoDriving

See more examples below.

Options

data Driving :: k -> Type where

Type constructor for configuring the plugin in a source annotation.

Argument: list of types using the constructors below.

Example

{-# ANN module (Driving :: Driving '[ Stock '(Eq, Ord), Newtype Num ]) #-}

Constructors

Driving :: Driving x

Dummy constructor

Instances

(Typeable a, Typeable k) => Data (Driving a)

Defined in Driving.Classes

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Driving a -> c (Driving a)

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Driving a)

toConstr :: Driving a -> Constr

dataTypeOf :: Driving a -> DataType

dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Driving a))

dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Driving a))

gmapT :: (forall b. Data b => b -> b) -> Driving a -> Driving a

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Driving a -> r

gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Driving a -> r

gmapQ :: (forall d. Data d => d -> u) -> Driving a -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> Driving a -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Driving a -> m (Driving a)

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Driving a -> m (Driving a)

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Driving a -> m (Driving a)

data Stock :: k -> Type

Auto-derive classes using the stock deriving strategy.

Argument: a class (of kind k -> Constraint for some k), or a tuple of classes.

Examples

{-# ANN module (Driving :: Driving '[ Stock Show ]) #-}
{-# ANN module (Driving :: Driving '[ Stock '(Eq, Ord) ]) #-}

data Newtype :: k -> Type

Auto-derive classes using the newtype deriving strategy. Enable the extension GeneralizedNewtypeDeriving to use this.

Argument: a class (of kind k -> Constraint for some k), or a tuple of classes.

Examples

{-# ANN module (Driving :: Driving '[ Newtype Num ]) #-}
{-# ANN module (Driving :: Driving '[ Newtype '(Semigroup, Monoid)]) #-}

data Anyclass :: k -> Type

Auto-derive classes using the anyclass deriving strategy. Enable the extension DeriveAnyClass to use this.

Argument: a class (of kind k -> Constraint for some k), or a tuple of classes.

Examples

{-# ANN module (Driving :: Driving '[ Anyclass Binary ]) #-}
{-# ANN module (Driving :: Driving '[ Anyclass '(ToJSON, FromJSON) ]) #-}
-- Classes from the packages binary and aeson

data Via :: k -> l -> Type

Auto-derive classes using the via deriving strategy, for a given via-type. Enable the extension DerivingVia to use this.

Arguments:

1. a class (of kind k -> Constraint for some k), or a tuple of classes;
2. a type.

Examples

{-# ANN module (Driving :: Driving '[ Num `Via` Int ]) #-}
{-# ANN module (Driving :: Driving '[ '(Eq, Ord) `Via` Int ]) #-}

data ViaF :: k -> l -> Type

Auto-derive classes using the via deriving strategy, where the via-type is an application of a given type constructor to each newly declared type. Enable the extension DerivingVia to use this.

Arguments:

1. a class (of kind k -> Constraint for some k), or a tuple of classes;
2. a type constructor.

Examples

{-# ANN module (Driving :: Driving '[ '(Functor, Applicative) `ViaF` WrappedMonad ]) #-}
{-# ANN module (Driving :: Driving '[ '(Semigroup, Monoid) `ViaF` Generically ]) #-}
-- Generically from the package generic-data

data NoDriving :: k -> Type

Cancel auto-deriving for a particular instance.

Argument: an application of a class to a type, or a tuple of those.

Example

Derive Show for all types except MyType:

{-# ANN module (Driving :: Driving '[ Stock Show, NoDriving (Show MyType) ]) #-}

Plugin

plugin :: Plugin

For the compiler.