Enable PolyKinds

Author: ali-abrar

ChangeLog.md

@@ -1,5 +1,9 @@
 # Revision history for patch
 
+## 0.0.4.0
+
+* Enable PolyKinds
+
 ## 0.0.3.2
 
 * Update version bounds

patch.cabal

@@ -1,5 +1,5 @@
 Name: patch
-Version: 0.0.3.2
+Version: 0.0.4.0
 Synopsis: Data structures for describing changes to other data structures.
 Description:
   Data structures for describing changes to other data structures.
@@ -55,6 +55,7 @@ library
                  , Data.Patch.MapWithPatchingMove
 
   ghc-options: -Wall -fwarn-redundant-constraints -fwarn-tabs
+  default-extensions: PolyKinds
 
   if flag(split-these)
     build-depends: these >= 1 && <1.2

src/Data/Patch/Class.hs

@@ -30,7 +30,7 @@ instance Patch (Identity a) where
   apply (Identity a) _ = Just a
 
 -- | 'Proxy' can be used as a 'Patch' that does nothing.
-instance Patch (Proxy a) where
+instance Patch (Proxy (a :: *)) where
   type PatchTarget (Proxy a) = a
   apply ~Proxy _ = Nothing