X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=Unsafe%2FCoerce.hs;h=516d7e06b67d231fb8abac514b7032eef2507cfc;hb=2b2397221c29a275630c62d4982caedc2c7cd987;hp=00444bd107ab44d9a055ffd1032af414b904efc2;hpb=42765c1f0758cbe98596ff6f224a16f68e72baf8;p=ghc-base.git

diff --git a/Unsafe/Coerce.hs b/Unsafe/Coerce.hs
index 00444bd..516d7e0 100644
--- a/Unsafe/Coerce.hs
+++ b/Unsafe/Coerce.hs
@@ -1,4 +1,4 @@
-{-# OPTIONS_GHC -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -XNoImplicitPrelude #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Unsafe.Coerce
@@ -14,13 +14,21 @@
 -- it is your responsibility to ensure that the old and new types have
 -- identical internal representations, in order to prevent runtime corruption.
 --
--- 'unsafeCoerce' is just a trivial wrapper for 'unsafeCoerce#';
--- see the latter for important documentation about correct usage.
+-- The types for which 'unsafeCoerce' is representation-safe may differ
+-- from compiler to compiler (and version to version).
+--
+--   * Documentation for correct usage in GHC will be found under
+--     'unsafeCoerce#' in GHC.Base (around which 'unsafeCoerce' is just a
+--     trivial wrapper).
+--
+--   * In nhc98, the only representation-safe coercions are between Enum
+--     types with the same range (e.g. Int, Int32, Char, Word32),
+--     or between a newtype and the type that it wraps.
 
 module Unsafe.Coerce (unsafeCoerce) where
 
 #if defined(__GLASGOW_HASKELL__)
-import GHC.Base (unsafeCoerce#)
+import GHC.Prim (unsafeCoerce#)
 unsafeCoerce :: a -> b
 unsafeCoerce = unsafeCoerce#
 #endif