-narrowU :: MachRep -> Integer -> Integer
-narrowU I8 x = fromIntegral (fromIntegral x :: Word8)
-narrowU I16 x = fromIntegral (fromIntegral x :: Word16)
-narrowU I32 x = fromIntegral (fromIntegral x :: Word32)
-narrowU I64 x = fromIntegral (fromIntegral x :: Word64)
+narrowU :: Width -> Integer -> Integer
+narrowU W8 x = fromIntegral (fromIntegral x :: Word8)
+narrowU W16 x = fromIntegral (fromIntegral x :: Word16)
+narrowU W32 x = fromIntegral (fromIntegral x :: Word32)
+narrowU W64 x = fromIntegral (fromIntegral x :: Word64)