Add some hashed operations from classes that cannot be implemented

.travis.yml

@@ -21,8 +21,8 @@ env:
  - CABALVER=1.18 GHCVER=7.6.3
 # - CABALVER=1.18 GHCVER=7.8.1
 # - CABALVER=1.18 GHCVER=7.8.2
- - CABALVER=1.18 GHCVER=7.8.3
- - CABALVER=1.22 GHCVER=7.10.1
+ - CABALVER=1.18 GHCVER=7.8.4
+ - CABALVER=1.22 GHCVER=7.10.3
  - CABALVER=1.24 GHCVER=8.0.1
 # - CABALVER=head GHCVER=head
 # - HPVER=2013.2.0.0
@@ -115,8 +115,9 @@ script:
  # Try to compile tests and benchmarks, run tests
  # For some reason doesn't work with old cabal
  #
- # TODO: don't build tests with cabal 1.24 (ghc 8.0) yet
- - if [ ! $CABALVER = "1.16" -a ! $CABALVER = "1.24" ]; then
+ # Disable tests on GHC 7.6.3 and 7.8.4, as there's something weird happening
+ # because of -inplace and globally installed hashable
+ - if [ ! $CABALVER = "1.16" -a ! $GHCVER = "7.6.3" -a ! $GHCVER = "7.8.4" ]; then
      cabal install HUnit QuickCheck criterion random siphash test-framework test-framework-hunit test-framework-quickcheck2;
      cabal configure -v2 --enable-tests --enable-benchmarks;
      cabal test;

Data/Hashable.hs

@@ -68,6 +68,8 @@ module Data.Hashable
     , Hashed
     , hashed
     , unhashed
+    , mapHashed
+    , traverseHashed
     ) where
 
 import Data.Hashable.Class
@@ -209,4 +211,3 @@ import Data.Hashable.Generic ()
 -- >                                 (1::Int) `hashWithSalt` n
 -- >     hashWithSalt s (Months n) = s `hashWithSalt`
 -- >                                 (2::Int) `hashWithSalt` n
-

Data/Hashable/Class.hs

@@ -1,5 +1,5 @@
 {-# LANGUAGE BangPatterns, CPP, ForeignFunctionInterface, MagicHash,
-             ScopedTypeVariables, UnliftedFFITypes #-}
+             ScopedTypeVariables, UnliftedFFITypes, DeriveDataTypeable #-}
 #ifdef GENERICS
 {-# LANGUAGE DefaultSignatures, FlexibleContexts, GADTs,
     MultiParamTypeClasses, EmptyDataDecls #-}
@@ -50,6 +50,8 @@ module Data.Hashable.Class
     , Hashed
     , hashed
     , unhashed
+    , mapHashed
+    , traverseHashed
     ) where
 
 import Control.Applicative (Const(..))
@@ -66,7 +68,7 @@ import qualified Data.Text as T
 import qualified Data.Text.Array as TA
 import qualified Data.Text.Internal as T
 import qualified Data.Text.Lazy as TL
-import Data.Typeable
+import Data.Typeable (Typeable, TypeRep)
 import Data.Version (Version(..))
 import Data.Word (Word8, Word16, Word32, Word64)
 import Foreign.C (CString)
@@ -80,7 +82,10 @@ import System.IO.Unsafe (unsafePerformIO)
 import System.Mem.StableName
 import Data.Unique (Unique, hashUnique)
 
-#if !(MIN_VERSION_base(4,7,0))
+-- As we use qualified F.Foldable, we don't get warnings with newer base
+import qualified Data.Foldable as F
+
+#if MIN_VERSION_base(4,7,0)
 import Data.Proxy (Proxy)
 #endif
 
@@ -97,10 +102,13 @@ import GHC.Generics
 #endif
 
 #if __GLASGOW_HASKELL__ >= 710
+import Data.Typeable (typeRepFingerprint)
 import GHC.Fingerprint.Type(Fingerprint(..))
 #elif __GLASGOW_HASKELL__ >= 702
-import Data.Typeable.Internal(TypeRep(..))
+import Data.Typeable.Internal (TypeRep (..))
 import GHC.Fingerprint.Type(Fingerprint(..))
+#elif __GLASGOW_HASKELL__ >= 606
+import Data.Typeable (typeRepKey)
 #endif
 
 #if __GLASGOW_HASKELL__ >= 703
@@ -747,12 +755,14 @@ instance Hashable a => Hashable1 (Const a) where
 instance Hashable2 Const where
     liftHashWithSalt2 f _ salt (Const x) = f salt x
 
+#if MIN_VERSION_base(4,7,0)
 instance Hashable (Proxy a) where
     hash _ = 0
     hashWithSalt s _ = s
 
 instance Hashable1 Proxy where
     liftHashWithSalt _ s _ = s
+#endif
 
 -- instances formerly provided by 'semigroups' package
 #if MIN_VERSION_base(4,9,0)
@@ -842,9 +852,17 @@ instance Hashable1 Hashed where
 instance (IsString a, Hashable a) => IsString (Hashed a) where
   fromString s = let r = fromString s in Hashed r (hash r)
 
-instance Foldable Hashed where
+instance F.Foldable Hashed where
   foldr f acc (Hashed a _) = f a acc
 
+-- | 'Hashed' cannot be 'Functor'
+mapHashed :: Hashable b => (a -> b) -> Hashed a -> Hashed b
+mapHashed f (Hashed a _) = hashed (f a)
+
+-- | 'Hashed' cannot be 'Traversable'
+traverseHashed :: (Hashable b, Functor f) => (a -> f b) -> Hashed a -> f (Hashed b)
+traverseHashed f (Hashed a _) = fmap hashed (f a)
+
 -- instances for @Data.Functor.Classes@ higher rank typeclasses
 -- in base-4.9 and onward.
 #if MIN_VERSION_base(4,9,0)