Data.Constraint.Deriving.ClassDict

Documentation

data ClassDict

A marker to tell the core plugin to replace the implementation of a top-level function by a corresponding class data constructor (wrapped into Dict).

Example:

class BarClass a => FooClass a where
  fooFun1 :: a -> a -> Int
  fooFun2 :: a -> Bool

{-# ANN deriveFooClass ClassDict #-}
deriveFooClass :: forall a . BarClass a
               => (a -> a -> Int)
               -> (a -> Bool)
               -> Dict (FooClass a)
deriveFooClass = deriveFooClass

That is, the plugin replaces the RHS of deriveFooClass function with classDataCon wrapped by bareToDict.

Note:

• The plugin requires you to create a dummy function deriveFooClass and annotate it with ClassDict instead of automatically creating this function for you; this way, the function is visible during type checking: you can use it in the same module (avoiding orphans) and you see its type signature.
• You have to provide a correct signature for deriveFooClass function; the plugin compares this signature against visible classes and their constructors. An incorrect signature will result in a compile-time error.
• The dummy implementation deriveFooClass = deriveFooClass is used here to prevent GHC from inlining the function before the plugin can replace it. But you can implement it in any way you like at your own risk.

Constructors

ClassDict

Instances

Eq ClassDict

Defined in Data.Constraint.Deriving.ClassDict

Methods

(==) :: ClassDict -> ClassDict -> Bool

(/=) :: ClassDict -> ClassDict -> Bool

Data ClassDict

Defined in Data.Constraint.Deriving.ClassDict

Methods

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

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

toConstr :: ClassDict -> Constr

dataTypeOf :: ClassDict -> DataType

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

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

gmapT :: (forall b. Data b => b -> b) -> ClassDict -> ClassDict

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

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

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

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

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

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

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

Read ClassDict

Defined in Data.Constraint.Deriving.ClassDict

Methods

readsPrec :: Int -> ReadS ClassDict

readList :: ReadS [ClassDict]

readPrec :: ReadPrec ClassDict

readListPrec :: ReadPrec [ClassDict]

Show ClassDict

Defined in Data.Constraint.Deriving.ClassDict

Methods

showsPrec :: Int -> ClassDict -> ShowS

show :: ClassDict -> String

showList :: [ClassDict] -> ShowS

classDictPass :: CorePluginEnvRef -> CoreToDo

Run ClassDict plugin pass

type CorePluginEnvRef = IORef CorePluginEnv

Reference to the plugin environment variables.

initCorePluginEnv :: CoreM (IORef CorePluginEnv)

Init the CorePluginM environment and save it to IORef.