Improve error messages

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index bbdd9b2..d414c6f 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -654,7 +654,7 @@ cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _)
  | mayDeriveDataTypeable = Nothing
  | otherwise = Just why
   where
  | mayDeriveDataTypeable = Nothing
  | otherwise = Just why
   where

-    why  = ptext SLIT("You need -fglasgow-exts to derive an instance for this class")
+    why  = ptext SLIT("You need -XDeriveDataTypeable to derive an instance for this class")

 
 std_class_via_iso :: Class -> Bool
 std_class_via_iso clas -- These standard classes can be derived for a newtype
 
 std_class_via_iso :: Class -> Bool
 std_class_via_iso clas -- These standard classes can be derived for a newtype