{-# LANGUAGE Rank2Types #-}
module Data.Typeable.Lens
( _cast
, _gcast
) where
import Prelude ()
import Control.Lens
import Control.Lens.Internal.Prelude
import Data.Maybe (fromMaybe)
import Data.Typeable
_cast :: (Typeable s, Typeable a) => Traversal' s a
_cast :: forall s a. (Typeable s, Typeable a) => Traversal' s a
_cast a -> f a
f s
s = case forall a b. (Typeable a, Typeable b) => a -> Maybe b
cast s
s of
Just a
a -> forall a. a -> Maybe a -> a
fromMaybe (forall a. HasCallStack => [Char] -> a
error [Char]
"_cast: recast failed") forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall a b. (Typeable a, Typeable b) => a -> Maybe b
cast forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> a -> f a
f a
a
Maybe a
Nothing -> forall (f :: * -> *) a. Applicative f => a -> f a
pure s
s
{-# INLINE _cast #-}
_gcast :: (Typeable s, Typeable a) => Traversal' (c s) (c a)
_gcast :: forall s a (c :: * -> *).
(Typeable s, Typeable a) =>
Traversal' (c s) (c a)
_gcast c a -> f (c a)
f c s
s = case forall {k} (a :: k) (b :: k) (c :: k -> *).
(Typeable a, Typeable b) =>
c a -> Maybe (c b)
gcast c s
s of
Just c a
a -> forall a. a -> Maybe a -> a
fromMaybe (forall a. HasCallStack => [Char] -> a
error [Char]
"_gcast: recast failed") forall b c a. (b -> c) -> (a -> b) -> a -> c
. forall {k} (a :: k) (b :: k) (c :: k -> *).
(Typeable a, Typeable b) =>
c a -> Maybe (c b)
gcast forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> c a -> f (c a)
f c a
a
Maybe (c a)
Nothing -> forall (f :: * -> *) a. Applicative f => a -> f a
pure c s
s
{-# INLINE _gcast #-}