Add Inject instances for Word types (#112)

src/Dhall.hs

@@ -60,6 +60,7 @@ import Data.Text.Buildable (Buildable(..))
 import Data.Text.Lazy (Text)
 import Data.Typeable (Typeable)
 import Data.Vector (Vector)
+import Data.Word (Word8, Word16, Word32, Word64)
 import Dhall.Core (Expr(..))
 import Dhall.Import (Imported(..))
 import Dhall.Parser (Src(..))
@@ -720,6 +721,34 @@ instance Inject Int where
 
         declared = Integer
 
+instance Inject Word8 where
+    injectWith _ = InputType {..}
+      where
+        embed = IntegerLit . toInteger
+
+        declared = Integer
+
+instance Inject Word16 where
+    injectWith _ = InputType {..}
+      where
+        embed = IntegerLit . toInteger
+
+        declared = Integer
+
+instance Inject Word32 where
+    injectWith _ = InputType {..}
+      where
+        embed = IntegerLit . toInteger
+
+        declared = Integer
+
+instance Inject Word64 where
+    injectWith _ = InputType {..}
+      where
+        embed = IntegerLit . toInteger
+
+        declared = Integer
+
 
 instance Inject Double where
     injectWith _ = InputType {..}