X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Data%2FTypeable.hs;h=804e853b8de6aec58f024901f498eda4b0b4c127;hb=41e8fba828acbae1751628af50849f5352b27873;hp=c400710b4418e3f3785db2bce03ae48a6622cf87;hpb=d2063b5b0be014545b21819172c87756efcb0b0c;p=ghc-base.git

diff --git a/Data/Typeable.hs b/Data/Typeable.hs
index c400710..804e853 100644
--- a/Data/Typeable.hs
+++ b/Data/Typeable.hs
@@ -1,4 +1,11 @@
-{-# OPTIONS_GHC -XNoImplicitPrelude -XOverlappingInstances -funbox-strict-fields #-}
+{-# LANGUAGE CPP
+           , NoImplicitPrelude
+           , OverlappingInstances
+           , ScopedTypeVariables
+           , ForeignFunctionInterface
+           , FlexibleInstances
+  #-}
+{-# OPTIONS_GHC -funbox-strict-fields #-}
 
 -- The -XOverlappingInstances flag allows the user to over-ride
 -- the instances for Typeable given here.  In particular, we provide an instance
@@ -93,10 +100,10 @@ import GHC.Base
 import GHC.Show         (Show(..), ShowS,
                          shows, showString, showChar, showParen)
 import GHC.Err          (undefined)
-import GHC.Num          (Integer, fromInteger, (+))
+import GHC.Num          (Integer, (+))
 import GHC.Real         ( rem, Ratio )
 import GHC.IORef        (IORef,newIORef)
-import GHC.IO           (IO, unsafePerformIO,block)
+import GHC.IO           (unsafePerformIO,mask_)
 
 -- These imports are so we can define Typeable instances
 -- It'd be better to give Typeable instances in the modules themselves
@@ -302,6 +309,22 @@ showTuple args = showChar '('
 --
 -------------------------------------------------------------
 
+{- Note [Memoising typeOf]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+IMPORTANT: we don't want to recalculate the type-rep once per
+call to the dummy argument.  This is what went wrong in Trac #3245
+So we help GHC by manually keeping the 'rep' *outside* the value 
+lambda, thus
+    
+    typeOfDefault :: forall t a. (Typeable1 t, Typeable a) => t a -> TypeRep
+    typeOfDefault = \_ -> rep
+      where
+        rep = typeOf1 (undefined :: t a) `mkAppTy` 
+              typeOf  (undefined :: a)
+
+Notice the crucial use of scoped type variables here!
+-}
+
 -- | The class 'Typeable' allows a concrete representation of a type to
 -- be calculated.
 class Typeable a where
@@ -315,78 +338,148 @@ class Typeable a where
 class Typeable1 t where
   typeOf1 :: t a -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable' instance from any 'Typeable1' instance.
+typeOfDefault :: forall t a. (Typeable1 t, Typeable a) => t a -> TypeRep
+typeOfDefault = \_ -> rep
+ where
+   rep = typeOf1 (undefined :: t a) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable' instance from any 'Typeable1' instance.
 typeOfDefault :: (Typeable1 t, Typeable a) => t a -> TypeRep
 typeOfDefault x = typeOf1 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 -- | Variant for binary type constructors
 class Typeable2 t where
   typeOf2 :: t a b -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
+typeOf1Default :: forall t a b. (Typeable2 t, Typeable a) => t a b -> TypeRep
+typeOf1Default = \_ -> rep 
+ where
+   rep = typeOf2 (undefined :: t a b) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable1' instance from any 'Typeable2' instance.
 typeOf1Default :: (Typeable2 t, Typeable a) => t a b -> TypeRep
 typeOf1Default x = typeOf2 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 -- | Variant for 3-ary type constructors
 class Typeable3 t where
   typeOf3 :: t a b c -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
+typeOf2Default :: forall t a b c. (Typeable3 t, Typeable a) => t a b c -> TypeRep
+typeOf2Default = \_ -> rep 
+ where
+   rep = typeOf3 (undefined :: t a b c) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable2' instance from any 'Typeable3' instance.
 typeOf2Default :: (Typeable3 t, Typeable a) => t a b c -> TypeRep
 typeOf2Default x = typeOf3 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b c -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 -- | Variant for 4-ary type constructors
 class Typeable4 t where
   typeOf4 :: t a b c d -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
+typeOf3Default :: forall t a b c d. (Typeable4 t, Typeable a) => t a b c d -> TypeRep
+typeOf3Default = \_ -> rep
+ where
+   rep = typeOf4 (undefined :: t a b c d) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable3' instance from any 'Typeable4' instance.
 typeOf3Default :: (Typeable4 t, Typeable a) => t a b c d -> TypeRep
 typeOf3Default x = typeOf4 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b c d -> a
-   argType =  undefined
-
+   argType = undefined
+#endif
+   
 -- | Variant for 5-ary type constructors
 class Typeable5 t where
   typeOf5 :: t a b c d e -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
+typeOf4Default :: forall t a b c d e. (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
+typeOf4Default = \_ -> rep 
+ where
+   rep = typeOf5 (undefined :: t a b c d e) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable4' instance from any 'Typeable5' instance.
 typeOf4Default :: (Typeable5 t, Typeable a) => t a b c d e -> TypeRep
 typeOf4Default x = typeOf5 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b c d e -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 -- | Variant for 6-ary type constructors
 class Typeable6 t where
   typeOf6 :: t a b c d e f -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
+typeOf5Default :: forall t a b c d e f. (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
+typeOf5Default = \_ -> rep
+ where
+   rep = typeOf6 (undefined :: t a b c d e f) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable5' instance from any 'Typeable6' instance.
 typeOf5Default :: (Typeable6 t, Typeable a) => t a b c d e f -> TypeRep
 typeOf5Default x = typeOf6 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b c d e f -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 -- | Variant for 7-ary type constructors
 class Typeable7 t where
   typeOf7 :: t a b c d e f g -> TypeRep
 
+#ifdef __GLASGOW_HASKELL__
+-- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
+typeOf6Default :: forall t a b c d e f g. (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
+typeOf6Default = \_ -> rep
+ where
+   rep = typeOf7 (undefined :: t a b c d e f g) `mkAppTy` 
+         typeOf  (undefined :: a)
+   -- Note [Memoising typeOf]
+#else
 -- | For defining a 'Typeable6' instance from any 'Typeable7' instance.
 typeOf6Default :: (Typeable7 t, Typeable a) => t a b c d e f g -> TypeRep
 typeOf6Default x = typeOf7 x `mkAppTy` typeOf (argType x)
  where
    argType :: t a b c d e f g -> a
-   argType =  undefined
+   argType = undefined
+#endif
 
 #ifdef __GLASGOW_HASKELL__
 -- Given a @Typeable@/n/ instance for an /n/-ary type constructor,
@@ -595,7 +688,7 @@ cache = unsafePerformIO $ do
                                         tc_tbl = empty_tc_tbl, 
                                         ap_tbl = empty_ap_tbl }
 #ifdef __GLASGOW_HASKELL__
-                block $ do
+                mask_ $ do
                         stable_ref <- newStablePtr ret
                         let ref = castStablePtrToPtr stable_ref
                         ref2 <- getOrSetTypeableStore ref