Expand the hashability of NExpr and related structures

src/Nix/Expr/Types.hs

@@ -34,6 +34,7 @@ import           Data.Eq.Deriving
 import           Data.Fix
 import           Data.Functor.Classes
 import           Data.Hashable
+import           Data.Hashable.Lifted
 import           Data.List.NonEmpty (NonEmpty)
 import qualified Data.List.NonEmpty as NE
 import           Data.Monoid
@@ -54,6 +55,8 @@ import qualified Type.Reflection as Reflection
 
 type VarName = Text
 
+instance Hashable1 NonEmpty     -- jww (2018-04-17): an unfortunate orphan
+
 -- | The main nix expression type. This is polymorphic so that it can be made
 -- a functor, which allows us to traverse expressions and map functions over
 -- them. The actual 'NExpr' type is a fixed point of this functor, defined
@@ -100,7 +103,8 @@ data NExprF r
   | NAssert !r !r
   -- ^ Assert that the first returns true before evaluating the second.
   deriving (Ord, Eq, Generic, Generic1, Typeable, Data, Functor,
-            Foldable, Traversable, Show, NFData, NFData1, Serialise, Hashable)
+            Foldable, Traversable, Show, NFData, NFData1, Serialise,
+            Hashable, Hashable1)
 
 -- | We make an `IsString` for expressions, where the string is interpreted
 -- as an identifier. This is the most common use-case...
@@ -113,7 +117,6 @@ instance Lift (Fix NExprF) where
             Just HRefl -> Just [| pack $(liftString $ unpack b) |]
             Nothing -> Nothing
 
-
 -- | The monomorphic expression type is a fixed point of the polymorphic one.
 type NExpr = Fix NExprF
 
@@ -127,7 +130,8 @@ data Binding r
   -- ^ Using a name already in scope, such as @inherit x;@ which is shorthand
   -- for @x = x;@ or @inherit (x) y;@ which means @y = x.y;@.
   deriving (Generic, Generic1, Typeable, Data, Ord, Eq, Functor,
-            Foldable, Traversable, Show, NFData, NFData1, Serialise, Hashable)
+            Foldable, Traversable, Show, NFData, NFData1, Serialise,
+            Hashable, Hashable1)
 
 -- | @Params@ represents all the ways the formal parameters to a
 -- function can be represented.
@@ -139,7 +143,8 @@ data Params r
   -- bind to the set in the function body. The bool indicates whether it is
   -- variadic or not.
   deriving (Ord, Eq, Generic, Generic1, Typeable, Data, Functor, Show,
-            Foldable, Traversable, NFData, NFData1, Serialise, Hashable)
+            Foldable, Traversable, NFData, NFData1, Serialise,
+            Hashable, Hashable1)
 
 -- This uses an association list because nix XML serialization preserves the
 -- order of the param set.
@@ -152,7 +157,16 @@ instance IsString (Params r) where
 -- antiquoted (surrounded by ${...}) or plain (not antiquoted).
 data Antiquoted (v :: *) (r :: *) = Plain !v | EscapedNewline | Antiquoted !r
   deriving (Ord, Eq, Generic, Generic1, Typeable, Data, Functor, Foldable,
-            Traversable, Show, Read, NFData, NFData1, Serialise, Hashable)
+            Traversable, Show, Read, NFData, NFData1, Serialise,
+            Hashable, Hashable1)
+
+instance Hashable2 Antiquoted where
+    liftHashWithSalt2 ha _ salt (Plain a) =
+        ha (salt `hashWithSalt` (0 :: Int)) a
+    liftHashWithSalt2 _ _ salt EscapedNewline =
+        salt `hashWithSalt` (1 :: Int)
+    liftHashWithSalt2 _ hb salt (Antiquoted b) =
+        hb (salt `hashWithSalt` (2 :: Int)) b
 
 -- | An 'NString' is a list of things that are either a plain string
 -- or an antiquoted expression. After the antiquotes have been evaluated,
@@ -166,7 +180,8 @@ data NString r
   --   their indentation will be stripped, but the amount stripped is
   --   remembered.
   deriving (Eq, Ord, Generic, Generic1, Typeable, Data, Functor, Foldable,
-            Traversable, Show, Read, NFData, NFData1, Serialise, Hashable)
+            Traversable, Show, Read, NFData, NFData1, Serialise,
+            Hashable, Hashable1)
 
 -- | For the the 'IsString' instance, we use a plain doublequoted string.
 instance IsString (NString r) where
@@ -232,6 +247,12 @@ instance Eq1 NKeyName where
   liftEq _ (StaticKey a _) (StaticKey b _) = a == b
   liftEq _ _ _ = False
 
+instance Hashable1 NKeyName where
+  liftHashWithSalt h salt (DynamicKey a) =
+      liftHashWithSalt2 (liftHashWithSalt h) h (salt `hashWithSalt` (0 :: Int)) a
+  liftHashWithSalt _ salt (StaticKey n p) =
+      salt `hashWithSalt` (1 :: Int) `hashWithSalt` n `hashWithSalt` p
+
 -- Deriving this instance automatically is not possible because @r@
 -- occurs not only as last argument in @Antiquoted (NString r) r@
 instance Show1 NKeyName where