Import Arbitrary NonEmpty from quickcheck-instances

It was added in QuickCheck-2.9 and dropped in QuickCheck-2.10.
spl · Jul 4, 2017 · 5b41d0d · 5b41d0d
1 parent b2f791a
commit 5b41d0d
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Showing 2 changed files with 14 additions and 4 deletions.
diff --git a/dlist.cabal b/dlist.cabal
@@ -46,9 +46,11 @@ test-suite test
                         base,
                         Cabal,
                         QuickCheck < 2.11
-  if impl(ghc >= 8)
-    -- QuickCheck-2.9 introduced support for Semigroup and NonEmpty in base.
-    -- It is required for testing base >= 4.9 (GHC >= 8).
-    build-depends:      QuickCheck >= 2.9
+  -- Semigroup and NonEmpty were introduced in base-4.9 (ghc-8).
+  -- QuickCheck-2.9 included support. QuickCheck-2.10 dropped support.
+  -- quickcheck-instances-0.3.15 has the Arbitrary NonEmpty instance.
+  if impl(ghc > 8)
+    build-depends:      QuickCheck >= 2.9,
+                        quickcheck-instances >= 0.3.15 && < 0.4
   else
     build-depends:      QuickCheck >= 2.7
diff --git a/tests/Main.hs b/tests/Main.hs
@@ -24,8 +24,16 @@ import Data.DList
 import OverloadedStrings (testOverloadedStrings)
 
 #if MIN_VERSION_base(4,9,0)
+-- base-4.9 introduced Semigroup and NonEmpty.
 import Data.Semigroup (Semigroup(..))
 import Data.List.NonEmpty (NonEmpty(..))
+
+-- QuickCheck-2.10 dropped the Arbitrary NonEmpty instance, so we import it from
+-- quickcheck-instances.
+#if MIN_VERSION_QuickCheck(2,10,0)
+import Test.QuickCheck.Instances ()
+#endif
+
 #endif
 
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