[commit: base] data-proxy: Fix problem with deprecating gcast[12] (ebd99ae)

[Richard Eisenberg]

Repository : http://darcs.haskell.org/ghc.git/

On branch  : data-proxy

http://hackage.haskell.org/trac/ghc/changeset/ebd99ae8e9398b764509e64f526db331856ce235

>---------------------------------------------------------------

commit ebd99ae8e9398b764509e64f526db331856ce235
Author: Richard Eisenberg <eir at cis.upenn.edu>
Date:   Mon Jul 22 17:59:31 2013 +0100

    Fix problem with deprecating gcast[12]

>---------------------------------------------------------------

 Data/Data.hs       |    6 +++---
 Data/Proxy.hs-boot |    2 +-
 Data/Typeable.hs   |   22 +++++++---------------
 3 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/Data/Data.hs b/Data/Data.hs
index 195dc5c..465b30c 100644
--- a/Data/Data.hs
+++ b/Data/Data.hs
@@ -1,5 +1,5 @@
 {-# LANGUAGE Trustworthy #-}
-{-# LANGUAGE CPP, RankNTypes, ScopedTypeVariables #-}
+{-# LANGUAGE CPP, RankNTypes, ScopedTypeVariables, PolyKinds #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -265,7 +265,7 @@ class Typeable a => Data a where
 
   -- | Mediate types and unary type constructors.
   -- In 'Data' instances of the form @T a@, 'dataCast1' should be defined
-  -- as 'gcast1'.
+  -- as 'gcast'.
   --
   -- The default definition is @'const' 'Nothing'@, which is appropriate
   -- for non-unary type constructors.
@@ -276,7 +276,7 @@ class Typeable a => Data a where
 
   -- | Mediate types and binary type constructors.
   -- In 'Data' instances of the form @T a b@, 'dataCast2' should be
-  -- defined as 'gcast2'.
+  -- defined as 'gcast'.
   --
   -- The default definition is @'const' 'Nothing'@, which is appropriate
   -- for non-binary type constructors.
diff --git a/Data/Proxy.hs-boot b/Data/Proxy.hs-boot
index 99d7dcd..3434d99 100644
--- a/Data/Proxy.hs-boot
+++ b/Data/Proxy.hs-boot
@@ -2,4 +2,4 @@
 
 module Data.Proxy ( Proxy(..) ) where
 
-data Proxy t = Proxy
\ No newline at end of file
+data Proxy (t :: k) = Proxy
\ No newline at end of file
diff --git a/Data/Typeable.hs b/Data/Typeable.hs
index 84dba1a..34d777c 100644
--- a/Data/Typeable.hs
+++ b/Data/Typeable.hs
@@ -114,23 +114,15 @@ eqT = if typeRep (Proxy :: Proxy a) == typeRep (Proxy :: Proxy b)
 
 -- | A flexible variation parameterised in a type constructor
 gcast :: forall a b c. (Typeable a, Typeable b) => c a -> Maybe (c b)
-gcast x = case eqT :: Maybe (a :=: b) of
-            Just Refl -> Just x
-            Nothing   -> Nothing
+gcast x = fmap (\Refl -> x) (eqT :: Maybe (a :=: b))
 
-{-# DEPRECATED gcast1, gcast2 "Use eqT or poly-kinded gcast instead" #-}
-
--- | Cast for * -> *
-gcast1 :: forall c t t' a. (Typeable (t :: * -> *), Typeable t')
+-- | Cast over @k1 -> k2@
+gcast1 :: forall c t t' a. (Typeable t, Typeable t')
        => c (t a) -> Maybe (c (t' a)) 
-gcast1 x = if typeRep (Proxy :: Proxy t) == typeRep (Proxy :: Proxy t')
-             then Just $ unsafeCoerce x
-             else Nothing
+gcast1 x = fmap (\Refl -> x) (eqT :: Maybe (t :=: t'))
 
--- | Cast for * -> * -> *
-gcast2 :: forall c t t' a b. (Typeable (t :: * -> * -> *), Typeable t')
+-- | Cast over @k1 -> k2 -> k3@
+gcast2 :: forall c t t' a b. (Typeable t, Typeable t')
        => c (t a b) -> Maybe (c (t' a b)) 
-gcast2 x = if typeRep (Proxy :: Proxy t) == typeRep (Proxy :: Proxy t')
-             then Just $ unsafeCoerce x
-             else Nothing
+gcast2 x = fmap (\Refl -> x) (eqT :: Maybe (t :=: t'))