Specify kind variables for inferred kinds in base.

14 files changed, 167 insertions, 70 deletions

diff --git a/libraries/base/Control/Arrow.hs b/libraries/base/Control/Arrow.hs
index eec25a3179..56fa82e161 100644
--- a/libraries/base/Control/Arrow.hs
+++ b/libraries/base/Control/Arrow.hs
@@ -1,8 +1,8 @@
-{-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE DeriveFunctor #-}
 {-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE StandaloneDeriving #-}
+{-# LANGUAGE Trustworthy #-}
 {-# OPTIONS_GHC -Wno-inline-rule-shadowing #-}
     -- The RULES for the methods of class Arrow may never fire
     -- e.g. compose/arr;  see #10528
diff --git a/libraries/base/Control/Category.hs b/libraries/base/Control/Category.hs
index c033c7618e..14584bdc0c 100644
--- a/libraries/base/Control/Category.hs
+++ b/libraries/base/Control/Category.hs
@@ -1,7 +1,7 @@
-{-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE Trustworthy #-}
 {-# OPTIONS_GHC -Wno-inline-rule-shadowing #-}
     -- The RULES for the methods of class Category may never fire
     -- e.g. identity/left, identity/right, association;  see #10528
@@ -20,7 +20,7 @@
 
 module Control.Category where
 
-import qualified GHC.Base (id,(.))
+import qualified GHC.Base (id, (.))
 import Data.Type.Coercion
 import Data.Type.Equality
 import Data.Coerce (coerce)
diff --git a/libraries/base/Data/Data.hs b/libraries/base/Data/Data.hs
index a8dfa61115..0ce830742a 100644
--- a/libraries/base/Data/Data.hs
+++ b/libraries/base/Data/Data.hs
@@ -1,10 +1,10 @@
 {-# LANGUAGE BangPatterns #-}
+{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE GADTs #-}
 {-# LANGUAGE NoImplicitPrelude #-}
-{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
diff --git a/libraries/base/Data/Dynamic.hs b/libraries/base/Data/Dynamic.hs
index 5a4f3f9a08..8478f0e680 100644
--- a/libraries/base/Data/Dynamic.hs
+++ b/libraries/base/Data/Dynamic.hs
@@ -1,9 +1,9 @@
-{-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE NoImplicitPrelude #-}
-{-# LANGUAGE GADTs #-}
 {-# LANGUAGE ExplicitForAll #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE PatternSynonyms #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE Trustworthy #-}
 {-# LANGUAGE TypeApplications #-}
 
 -----------------------------------------------------------------------------
diff --git a/libraries/base/Data/Fixed.hs b/libraries/base/Data/Fixed.hs
index 232175a1ab..17e5141b33 100644
--- a/libraries/base/Data/Fixed.hs
+++ b/libraries/base/Data/Fixed.hs
@@ -1,7 +1,9 @@
-{-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE PolyKinds #-}
 {-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
+{-# LANGUAGE Trustworthy #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -41,6 +43,7 @@ module Data.Fixed
 import Data.Data
 import GHC.TypeLits (KnownNat, natVal)
 import GHC.Read
+import Data.Kind (Type, Constraint)
 import Text.ParserCombinators.ReadPrec
 import Text.Read.Lex
 
@@ -61,7 +64,8 @@ mod' n d = n - (fromInteger f) * d where
     f = div' n d
 
 -- | The type parameter should be an instance of 'HasResolution'.
-newtype Fixed (a :: k) = MkFixed Integer
+type    Fixed :: forall k. k -> Type
+newtype Fixed a = MkFixed Integer
         deriving ( Eq  -- ^ @since 2.01
                  , Ord -- ^ @since 2.01
                  )
@@ -80,7 +84,8 @@ instance (Typeable k,Typeable a) => Data (Fixed (a :: k)) where
     dataTypeOf _ = tyFixed
     toConstr _ = conMkFixed
 
-class HasResolution (a :: k) where
+type  HasResolution :: forall k. k -> Constraint
+class HasResolution a where
     resolution :: p a -> Integer
 
 -- | For example, @Fixed 1000@ will give you a 'Fixed' with a resolution of 1000.
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)
diff --git a/libraries/base/Data/Functor/Const.hs b/libraries/base/Data/Functor/Const.hs
index 651041f15b..dd1880e30b 100644
--- a/libraries/base/Data/Functor/Const.hs
+++ b/libraries/base/Data/Functor/Const.hs
@@ -2,7 +2,9 @@
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE NoImplicitPrelude #-}
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
 {-# LANGUAGE Trustworthy #-}
 
 -----------------------------------------------------------------------------
@@ -36,6 +38,9 @@ import GHC.Read (Read(readsPrec), readParen, lex)
 import GHC.Show (Show(showsPrec), showParen, showString)
 
 -- | The 'Const' functor.
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type    Const :: forall k. Type -> k -> Type
 newtype Const a b = Const { getConst :: a }
     deriving ( Bits       -- ^ @since 4.9.0.0
              , Bounded    -- ^ @since 4.9.0.0
diff --git a/libraries/base/Data/Functor/Product.hs b/libraries/base/Data/Functor/Product.hs
index a3678e910e..266a72d75e 100644
--- a/libraries/base/Data/Functor/Product.hs
+++ b/libraries/base/Data/Functor/Product.hs
@@ -1,7 +1,9 @@
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Functor.Product
@@ -26,11 +28,15 @@ import Control.Monad (MonadPlus(..))
 import Control.Monad.Fix (MonadFix(..))
 import Control.Monad.Zip (MonadZip(mzipWith))
 import Data.Data (Data)
+import Data.Kind (Type)
 import Data.Functor.Classes
 import GHC.Generics (Generic, Generic1)
 import Text.Read (Read(..), readListDefault, readListPrecDefault)
 
 -- | Lifted product of functors.
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type Product :: forall k. (k -> Type) -> (k -> Type) -> (k -> Type)
 data Product f g a = Pair (f a) (g a)
   deriving ( Data     -- ^ @since 4.9.0.0
            , Generic  -- ^ @since 4.9.0.0
diff --git a/libraries/base/Data/Functor/Sum.hs b/libraries/base/Data/Functor/Sum.hs
index f7d6178a2b..cca541fe5e 100644
--- a/libraries/base/Data/Functor/Sum.hs
+++ b/libraries/base/Data/Functor/Sum.hs
@@ -1,7 +1,9 @@
 {-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE Safe #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.Functor.Sum
@@ -23,11 +25,15 @@ module Data.Functor.Sum (
 
 import Control.Applicative ((<|>))
 import Data.Data (Data)
+import Data.Kind (Type)
 import Data.Functor.Classes
 import GHC.Generics (Generic, Generic1)
 import Text.Read (Read(..), readListDefault, readListPrecDefault)
 
 -- | Lifted sum of functors.
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type Sum :: forall k. (k -> Type) -> (k -> Type) -> (k -> Type)
 data Sum f g a = InL (f a) | InR (g a)
   deriving ( Data     -- ^ @since 4.9.0.0
            , Generic  -- ^ @since 4.9.0.0
diff --git a/libraries/base/Data/Type/Coercion.hs b/libraries/base/Data/Type/Coercion.hs
index 694bedec01..a3c920d8e4 100644
--- a/libraries/base/Data/Type/Coercion.hs
+++ b/libraries/base/Data/Type/Coercion.hs
@@ -1,14 +1,16 @@
-{-# LANGUAGE DeriveGeneric       #-}
-{-# LANGUAGE TypeOperators       #-}
-{-# LANGUAGE TypeFamilies        #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE GADTs               #-}
-{-# LANGUAGE FlexibleInstances   #-}
-{-# LANGUAGE StandaloneDeriving  #-}
-{-# LANGUAGE NoImplicitPrelude   #-}
-{-# LANGUAGE PolyKinds           #-}
-{-# LANGUAGE RankNTypes          #-}
-{-# LANGUAGE MagicHash           #-}
+{-# LANGUAGE DeriveGeneric            #-}
+{-# LANGUAGE FlexibleInstances        #-}
+{-# LANGUAGE GADTs                    #-}
+{-# LANGUAGE MagicHash                #-}
+{-# LANGUAGE NoImplicitPrelude        #-}
+{-# LANGUAGE PolyKinds                #-}
+{-# LANGUAGE RankNTypes               #-}
+{-# LANGUAGE ScopedTypeVariables      #-}
+{-# LANGUAGE StandaloneDeriving       #-}
+{-# LANGUAGE StandaloneKindSignatures #-}
+{-# LANGUAGE TypeApplications         #-}
+{-# LANGUAGE TypeFamilies             #-}
+{-# LANGUAGE TypeOperators            #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -47,9 +49,10 @@ import GHC.Base
 -- To use this equality in practice, pattern-match on the @Coercion a b@ to get out
 -- the @Coercible a b@ instance, and then use 'coerce' to apply it.
 --
--- @since 4.7.0.0
+-- @since 4.7.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type Coercion :: forall k. k -> k -> Type
 data Coercion a b where
-  Coercion :: Coercible a b => Coercion a b
+  Coercion :: Coercible @k a b => Coercion @k a b
 
 -- with credit to Conal Elliott for 'ty', Erik Hesselink & Martijn van
 -- Steenbergen for 'type-equality', Edward Kmett for 'eq', and Gabor Greif
@@ -78,13 +81,13 @@ repr :: (a Eq.:~: b) -> Coercion a b
 repr Eq.Refl = Coercion
 
 -- | @since 4.7.0.0
-deriving instance Eq   (Coercion a b)
+deriving instance Eq (Coercion a b)
 
 -- | @since 4.7.0.0
 deriving instance Show (Coercion a b)
 
 -- | @since 4.7.0.0
-deriving instance Ord  (Coercion a b)
+deriving instance Ord (Coercion a b)
 
 -- | @since 4.7.0.0
 deriving instance Coercible a b => Read (Coercion a b)
@@ -102,9 +105,13 @@ deriving instance Coercible a b => Bounded (Coercion a b)
 -- | This class contains types where you can learn the equality of two types
 -- from information contained in /terms/. Typically, only singleton types should
 -- inhabit this class.
-class TestCoercion f where
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  TestCoercion :: forall k. (k -> Type) -> Constraint
+class TestCoercion (f :: k -> Type) where
   -- | Conditionally prove the representational equality of @a@ and @b@.
-  testCoercion :: f a -> f b -> Maybe (Coercion a b)
+  testCoercion :: forall (a :: k) (b :: k).
+    f a -> f b -> Maybe (Coercion @k a b)
 
 -- | @since 4.7.0.0
 instance TestCoercion ((Eq.:~:) a) where
diff --git a/libraries/base/Data/Type/Equality.hs b/libraries/base/Data/Type/Equality.hs
index ab321ba011..aa19ae3064 100644
--- a/libraries/base/Data/Type/Equality.hs
+++ b/libraries/base/Data/Type/Equality.hs
@@ -1,19 +1,20 @@
+{-# LANGUAGE DataKinds              #-}
 {-# LANGUAGE DeriveGeneric          #-}
-{-# LANGUAGE TypeOperators          #-}
-{-# LANGUAGE GADTs                  #-}
-{-# LANGUAGE FlexibleInstances      #-}
-{-# LANGUAGE StandaloneDeriving     #-}
-{-# LANGUAGE NoImplicitPrelude      #-}
-{-# LANGUAGE RankNTypes             #-}
-{-# LANGUAGE TypeFamilies           #-}
-{-# LANGUAGE UndecidableInstances   #-}
 {-# LANGUAGE ExplicitNamespaces     #-}
-{-# LANGUAGE MultiParamTypeClasses  #-}
+{-# LANGUAGE FlexibleInstances      #-}
 {-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE DataKinds              #-}
+{-# LANGUAGE GADTs                  #-}
+{-# LANGUAGE MultiParamTypeClasses  #-}
+{-# LANGUAGE NoImplicitPrelude      #-}
 {-# LANGUAGE PolyKinds              #-}
+{-# LANGUAGE RankNTypes             #-}
+{-# LANGUAGE StandaloneDeriving     #-}
 {-# LANGUAGE StandaloneKindSignatures #-}
 {-# LANGUAGE Trustworthy            #-}
+{-# LANGUAGE TypeApplications       #-}
+{-# LANGUAGE TypeFamilies           #-}
+{-# LANGUAGE TypeOperators          #-}
+{-# LANGUAGE UndecidableInstances   #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -61,7 +62,8 @@ infix 4 :~:, :~~:
 -- in practice, pattern-match on the @a :~: b@ to get out the @Refl@ constructor;
 -- in the body of the pattern-match, the compiler knows that @a ~ b@.
 --
--- @since 4.7.0.0
+-- @since 4.7.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type (:~:) :: forall k. k -> k -> Type
 data a :~: b where  -- See Note [The equality types story] in GHC.Builtin.Types.Prim
   Refl :: a :~: a
 
@@ -122,8 +124,9 @@ deriving instance a ~ b => Bounded (a :~: b)
 -- | Kind heterogeneous propositional equality. Like ':~:', @a :~~: b@ is
 -- inhabited by a terminating value if and only if @a@ is the same type as @b@.
 --
--- @since 4.10.0.0
-type (:~~:) :: k1 -> k2 -> Type
+-- @since 4.10.0.0. Kinds `k1` and `k2` explicitly quantified since
+-- 4.15.0.0.
+type (:~~:) :: forall k1 k2. k1 -> k2 -> Type
 data a :~~: b where
    HRefl :: a :~~: a
 
@@ -150,6 +153,9 @@ deriving instance a ~~ b => Bounded (a :~~: b)
 -- | This class contains types where you can learn the equality of two types
 -- from information contained in /terms/. Typically, only singleton types should
 -- inhabit this class.
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  TestEquality :: forall k. (k -> Type) -> Constraint
 class TestEquality f where
   -- | Conditionally prove the equality of @a@ and @b@.
   testEquality :: f a -> f b -> Maybe (a :~: b)
@@ -165,7 +171,7 @@ instance TestEquality ((:~~:) a) where
 infix 4 ==
 
 -- | A type family to compute Boolean equality.
-type (==) :: k -> k -> Bool
+type (==) :: forall k. k -> k -> Bool
 type family a == b where
   f a == g b = f == g && a == b
   a == a = 'True
diff --git a/libraries/base/GHC/Generics.hs b/libraries/base/GHC/Generics.hs
index 56fca9b5a2..6c18844faf 100644
--- a/libraries/base/GHC/Generics.hs
+++ b/libraries/base/GHC/Generics.hs
@@ -11,8 +11,10 @@
 {-# LANGUAGE MagicHash                  #-}
 {-# LANGUAGE NoImplicitPrelude          #-}
 {-# LANGUAGE PolyKinds                  #-}
+{-# LANGUAGE RankNTypes                 #-}
 {-# LANGUAGE ScopedTypeVariables        #-}
 {-# LANGUAGE StandaloneDeriving         #-}
+{-# LANGUAGE StandaloneKindSignatures   #-}
 {-# LANGUAGE Trustworthy                #-}
 {-# LANGUAGE TypeFamilies               #-}
 {-# LANGUAGE TypeOperators              #-}
@@ -754,7 +756,8 @@ import GHC.TypeLits ( KnownSymbol, KnownNat, symbolVal, natVal )
 --------------------------------------------------------------------------------
 
 -- | Void: used for datatypes without constructors
-data V1 (p :: k)
+type V1 :: forall k. k -> Type
+data V1 a
   deriving ( Eq       -- ^ @since 4.9.0.0
            , Ord      -- ^ @since 4.9.0.0
            , Read     -- ^ @since 4.9.0.0
@@ -769,7 +772,8 @@ instance Semigroup (V1 p) where
   v <> _ = v
 
 -- | Unit: used for constructors without arguments
-data U1 (p :: k) = U1
+type U1 :: forall k. k -> Type
+data U1 a = U1
   deriving ( Generic  -- ^ @since 4.7.0.0
            , Generic1 -- ^ @since 4.9.0.0
            )
@@ -820,7 +824,8 @@ instance Monoid (U1 p) where
   mempty = U1
 
 -- | Used for marking occurrences of the parameter
-newtype Par1 p = Par1 { unPar1 :: p }
+type    Par1 :: Type -> Type
+newtype Par1 a = Par1 { unPar1 :: a }
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -848,7 +853,8 @@ deriving instance Monoid p => Monoid (Par1 p)
 
 -- | Recursive calls of kind @* -> *@ (or kind @k -> *@, when @PolyKinds@
 -- is enabled)
-newtype Rec1 (f :: k -> Type) (p :: k) = Rec1 { unRec1 :: f p }
+type    Rec1 :: forall k. (k -> Type) -> (k -> Type)
+newtype Rec1 f a = Rec1 { unRec1 :: f a }
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -878,7 +884,8 @@ deriving instance Semigroup (f p) => Semigroup (Rec1 f p)
 deriving instance Monoid (f p) => Monoid (Rec1 f p)
 
 -- | Constants, additional parameters and recursion of kind @*@
-newtype K1 (i :: Type) c (p :: k) = K1 { unK1 :: c }
+type    K1 :: forall k. Type -> Type -> k -> Type
+newtype K1 i a b = K1 { unK1 :: a }
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -919,8 +926,9 @@ deriving instance Semigroup (f p) => Semigroup (M1 i c f p)
 deriving instance Monoid (f p) => Monoid (M1 i c f p)
 
 -- | Meta-information (constructor names, etc.)
-newtype M1 (i :: Type) (c :: Meta) (f :: k -> Type) (p :: k) =
-    M1 { unM1 :: f p }
+type    M1 :: forall k. Type -> Meta -> (k -> Type) -> (k -> Type)
+newtype M1 i meta f a =
+    M1 { unM1 :: f a }
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -932,7 +940,8 @@ newtype M1 (i :: Type) (c :: Meta) (f :: k -> Type) (p :: k) =
 
 -- | Sums: encode choice between constructors
 infixr 5 :+:
-data (:+:) (f :: k -> Type) (g :: k -> Type) (p :: k) = L1 (f p) | R1 (g p)
+type (:+:) :: forall k. (k -> Type) -> (k -> Type) -> (k -> Type)
+data (f :+: g) a = L1 (f a) | R1 (g a)
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -944,7 +953,8 @@ data (:+:) (f :: k -> Type) (g :: k -> Type) (p :: k) = L1 (f p) | R1 (g p)
 
 -- | Products: encode multiple arguments to constructors
 infixr 6 :*:
-data (:*:) (f :: k -> Type) (g :: k -> Type) (p :: k) = f p :*: g p
+type (:*:) :: forall k. (k -> Type) -> (k -> Type) -> (k -> Type)
+data (f :*: g) a = f a :*: g a
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -985,8 +995,9 @@ instance (Monoid (f p), Monoid (g p)) => Monoid ((f :*: g) p) where
 
 -- | Composition of functors
 infixr 7 :.:
-newtype (:.:) (f :: k2 -> Type) (g :: k1 -> k2) (p :: k1) =
-    Comp1 { unComp1 :: f (g p) }
+type    (:.:) :: forall k2 k1. (k2 -> Type) -> (k1 -> k2) -> (k1 -> Type)
+newtype (f :.: g) a =
+    Comp1 { unComp1 :: f (g a) }
   deriving ( Eq       -- ^ @since 4.7.0.0
            , Ord      -- ^ @since 4.7.0.0
            , Read     -- ^ @since 4.7.0.0
@@ -1017,6 +1028,7 @@ deriving instance Monoid (f (g p)) => Monoid ((f :.: g) p)
 -- | Constants of unlifted kinds
 --
 -- @since 4.9.0.0
+type        URec :: forall k. Type -> k -> Type
 data family URec (a :: Type) (p :: k)
 
 -- | Used for marking occurrences of 'Addr#'
@@ -1090,37 +1102,46 @@ data instance URec Word (p :: k) = UWord { uWord# :: Word# }
 
 -- | Type synonym for @'URec' 'Addr#'@
 --
--- @since 4.9.0.0
-type UAddr   = URec (Ptr ())
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UAddr :: forall k. k -> Type
+type UAddr = URec (Ptr ())
 -- | Type synonym for @'URec' 'Char#'@
 --
--- @since 4.9.0.0
-type UChar   = URec Char
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UChar :: forall k. k -> Type
+type UChar = URec Char
 
 -- | Type synonym for @'URec' 'Double#'@
 --
--- @since 4.9.0.0
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UDouble :: forall k. k -> Type
 type UDouble = URec Double
 
 -- | Type synonym for @'URec' 'Float#'@
 --
--- @since 4.9.0.0
-type UFloat  = URec Float
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UFloat :: forall k. k -> Type
+type UFloat = URec Float
 
 -- | Type synonym for @'URec' 'Int#'@
 --
--- @since 4.9.0.0
-type UInt    = URec Int
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UInt :: forall k. k -> Type
+type UInt = URec Int
 
 -- | Type synonym for @'URec' 'Word#'@
 --
--- @since 4.9.0.0
-type UWord   = URec Word
+-- @since 4.9.0.0. Kind `k` explicitly quantified since 4.15.0.0.
+type UWord :: forall k. k -> Type
+type UWord = URec Word
 
 -- | Tag for K1: recursion (of kind @Type@)
 data R
 
 -- | Type synonym for encoding recursion (of kind @Type@)
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type Rec0 :: forall k. Type -> k -> Type
 type Rec0  = K1 R
 
 -- | Tag for M1: datatype
@@ -1131,15 +1152,27 @@ data C
 data S
 
 -- | Type synonym for encoding meta-information for datatypes
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type D1 :: forall k. Meta -> (k -> Type) -> (k -> Type)
 type D1 = M1 D
 
 -- | Type synonym for encoding meta-information for constructors
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type C1 :: forall k. Meta -> (k -> Type) -> (k -> Type)
 type C1 = M1 C
 
 -- | Type synonym for encoding meta-information for record selectors
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type S1 :: forall k. Meta -> (k -> Type) -> (k -> Type)
 type S1 = M1 S
 
 -- | Class for datatypes that represent datatypes
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  Datatype :: forall k. k -> Constraint
 class Datatype d where
   -- | The name of the datatype (unqualified)
   datatypeName :: t d (f :: k -> Type) (a :: k) -> [Char]
@@ -1164,6 +1197,9 @@ instance (KnownSymbol n, KnownSymbol m, KnownSymbol p, SingI nt)
   isNewtype    _ = fromSing  (sing  :: Sing nt)
 
 -- | Class for datatypes that represent data constructors
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  Constructor :: forall k. k -> Constraint
 class Constructor c where
   -- | The name of the constructor
   conName :: t c (f :: k -> Type) (a :: k) -> [Char]
@@ -1303,6 +1339,9 @@ data DecidedStrictness = DecidedLazy
            )
 
 -- | Class for datatypes that represent records
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  Selector :: forall k. k -> Constraint
 class Selector s where
   -- | The name of the selector
   selName :: t s (f :: k -> Type) (a :: k) -> [Char]
@@ -1355,6 +1394,7 @@ class Generic a where
 -- 'from1' . 'to1' ≡ 'Prelude.id'
 -- 'to1' . 'from1' ≡ 'Prelude.id'
 -- @
+type  Generic1 :: forall k. (k -> Type) -> Constraint
 class Generic1 (f :: k -> Type) where
   -- | Generic representation type
   type Rep1 f :: k -> Type
@@ -1479,10 +1519,16 @@ deriving instance Generic1 Down
 --------------------------------------------------------------------------------
 
 -- | The singleton kind-indexed data family.
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type Sing :: forall k. k -> Type
 data family Sing (a :: k)
 
 -- | A 'SingI' constraint is essentially an implicitly-passed singleton.
-class SingI (a :: k) where
+--
+-- Kind `k` explicitly quantified since 4.15.0.0.
+type  SingI :: forall k. k -> Constraint
+class SingI a where
   -- | Produce the singleton explicitly. You will likely need the @ScopedTypeVariables@
   -- extension to use this method the way you want.
   sing :: Sing a
@@ -1490,6 +1536,7 @@ class SingI (a :: k) where
 -- | The 'SingKind' class is essentially a /kind/ class. It classifies all kinds
 -- for which singletons are defined. The class supports converting between a singleton
 -- type and the base (unrefined) type which it is built from.
+type  SingKind :: Type -> Constraint
 class SingKind k where
   -- | Get a base type from a proxy for the promoted kind. For example,
   -- @DemoteRep Bool@ will be the type @Bool@.
diff --git a/libraries/base/changelog.md b/libraries/base/changelog.md
index c27b4fb1ca..0117815be8 100644
--- a/libraries/base/changelog.md
+++ b/libraries/base/changelog.md
@@ -2,6 +2,14 @@
 
 ## 4.15.0.0 *TBA*
 
+  * `Const` (`Data.Functor.Const`), `Compose` (`Data.Functor.Compose`),
+    `Product` (`Data.Functor.Product`), `Sum` (`Data.Functor.Sum`), `Coercion`
+    and `TestCoercion` (`Data.Type.Coercion`), `(:~:)` and `TestEquality`
+    (`Data.Type.Equality`); `UAddr`, `UChar`, `UDouble` `UFloat`, `UInt`,
+    `UWord`, `Rec0`, `D1`, `C1`, `S1`, `Datatype`, `Constructor`, `Selector`
+    (`GHC.Generics`) now use specified quantification, allowing the use of
+    visible kind application.
+
   * `openFile` now calls the `open` system call with an `interruptible` FFI
     call, ensuring that the call can be interrupted with `SIGINT` on POSIX
     systems.
diff --git a/libraries/ghc-prim/GHC/Types.hs b/libraries/ghc-prim/GHC/Types.hs
index 0a32454149..bdf6c67225 100644
--- a/libraries/ghc-prim/GHC/Types.hs
+++ b/libraries/ghc-prim/GHC/Types.hs
@@ -1,6 +1,6 @@
 {-# LANGUAGE MagicHash, NoImplicitPrelude, TypeFamilies, UnboxedTuples,
              MultiParamTypeClasses, RoleAnnotations, CPP, TypeOperators,
-             PolyKinds #-}
+             PolyKinds, StandaloneKindSignatures, RankNTypes #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  GHC.Types
@@ -226,6 +226,7 @@ inside GHC, to change the kind and type.
 -- about the difference between heterogeneous equality @~~@ and
 -- homogeneous equality @~@, this is printed as @~@ unless
 -- @-fprint-equality-relations@ is set.
+type  (~~) :: forall k1 k2. k1 -> k2 -> Constraint
 class a ~~ b
   -- See also Note [The equality types story] in GHC.Builtin.Types.Prim
 
@@ -282,7 +283,8 @@ class a ~ b
 --      by Joachim Breitner, Richard A. Eisenberg, Simon Peyton Jones and Stephanie Weirich.
 --
 --      @since 4.7.0.0
-class Coercible (a :: k) (b :: k)
+type  Coercible :: forall k. k -> k -> Constraint
+class Coercible a b
   -- See also Note [The equality types story] in GHC.Builtin.Types.Prim
 
 {- *********************************************************************