CoArbitrary and Function for Small

src/Test/QuickCheck/Modifiers.hs

@@ -78,6 +78,7 @@ module Test.QuickCheck.Modifiers
 import Test.QuickCheck.Gen
 import Test.QuickCheck.Arbitrary
 import Test.QuickCheck.Exception
+import Test.QuickCheck.Function
 
 import Data.List
   ( sort
@@ -384,6 +385,12 @@ instance Integral a => Arbitrary (Small a) where
   arbitrary = fmap Small arbitrarySizedIntegral
   shrink (Small x) = map Small (shrinkIntegral x)
 
+instance CoArbitrary a => CoArbitrary (Small a) where
+  coarbitrary (Small a) = coarbitrary a
+
+instance Function a => Function (Small a) where
+  function = functionMap getSmall Small
+
 --------------------------------------------------------------------------
 -- | @Shrink2 x@: allows 2 shrinking steps at the same time when shrinking x
 newtype Shrink2 a = Shrink2 {getShrink2 :: a}