diff options
Diffstat (limited to 'libraries/base/Data/Functor/Compose.hs')
| -rw-r--r-- | libraries/base/Data/Functor/Compose.hs | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/libraries/base/Data/Functor/Compose.hs b/libraries/base/Data/Functor/Compose.hs index d8369ebc05..225d16283b 100644 --- a/libraries/base/Data/Functor/Compose.hs +++ b/libraries/base/Data/Functor/Compose.hs @@ -3,6 +3,7 @@ {-# LANGUAGE GADTs #-} {-# LANGUAGE PolyKinds #-} {-# LANGUAGE ScopedTypeVariables #-} +{-# LANGUAGE StandaloneKindSignatures #-} {-# LANGUAGE Trustworthy #-} {-# LANGUAGE TypeOperators #-} ----------------------------------------------------------------------------- @@ -26,6 +27,7 @@ module Data.Functor.Compose ( import Data.Functor.Classes +import Data.Kind (Type) import Control.Applicative import Data.Coerce (coerce) import Data.Data (Data) @@ -38,6 +40,9 @@ infixr 9 `Compose` -- | Right-to-left composition of functors. -- The composition of applicative functors is always applicative, -- but the composition of monads is not always a monad. +-- +-- Kinds `k2` and `k1` explicitly quantified since 4.15.0.0. +type Compose :: forall k2 k1. (k2 -> Type) -> (k1 -> k2) -> (k1 -> Type) newtype Compose f g a = Compose { getCompose :: f (g a) } deriving ( Data -- ^ @since 4.9.0.0 , Generic -- ^ @since 4.9.0.0 @@ -126,7 +131,7 @@ instance (Alternative f, Applicative g) => Alternative (Compose f g) where -- | The deduction (via generativity) that if @g x :~: g y@ then @x :~: y@. -- -- @since 4.14.0.0 -instance (TestEquality f) => TestEquality (Compose f g) where +instance TestEquality f => TestEquality (Compose f g) where testEquality (Compose x) (Compose y) = case testEquality x y of -- :: Maybe (g x :~: g y) Just Refl -> Just Refl -- :: Maybe (x :~: y) |