Simplify Arbitrary *DerivedPath again

Turns out, we didn't need the manual stuff, at least not yet.

Author: Ericson2314

hnix-store-tests/src/System/Nix/Arbitrary/DerivedPath.hs

@@ -4,10 +4,11 @@
 module System.Nix.Arbitrary.DerivedPath where
 
 import Data.Set qualified
-import Test.QuickCheck
+import Test.QuickCheck (Arbitrary(..), oneof)
+import Test.QuickCheck.Arbitrary.Generic (GenericArbitrary(..))
 import System.Nix.Arbitrary.OutputName ()
 import System.Nix.Arbitrary.StorePath ()
-import System.Nix.DerivedPath
+import System.Nix.DerivedPath (SingleDerivedPath, DerivedPath, OutputsSpec(..))
 
 instance Arbitrary OutputsSpec where
   arbitrary = oneof
@@ -17,28 +18,8 @@ instance Arbitrary OutputsSpec where
       <$> ((:) <$> arbitrary <*> arbitrary)
     ]
 
-arbitrarySingleDerivedPath :: Word -> Gen SingleDerivedPath
-arbitrarySingleDerivedPath = \case
-  0 -> SingleDerivedPath_Opaque <$> arbitrary
-  depth -> SingleDerivedPath_Built
-    <$> (arbitrarySingleDerivedPath $ depth - 1)
-    <*> arbitrary
+deriving via GenericArbitrary SingleDerivedPath
+  instance Arbitrary SingleDerivedPath
 
-arbitraryDerivedPath :: Word -> Gen DerivedPath
-arbitraryDerivedPath = \case
-  0 -> DerivedPath_Opaque <$> arbitrary
-  depth -> DerivedPath_Built
-    <$> (arbitrarySingleDerivedPath $ depth - 1)
-    <*> arbitrary
-
-instance Arbitrary SingleDerivedPath where
-  arbitrary = do
-    n <- getSize
-    k <- choose (0, n)
-    arbitrarySingleDerivedPath $ fromIntegral k
-
-instance Arbitrary DerivedPath where
-  arbitrary = do
-    n <- getSize
-    k <- choose (0, n)
-    arbitraryDerivedPath $ fromIntegral k
+deriving via GenericArbitrary DerivedPath
+  instance Arbitrary DerivedPath