[Slightly more descriptive errors.
Lemmih <lemmih@gmail.com>**20081121032716
 Ignore-this: 9198b58b7e5dfdee31f46b4b4d5fead1
] hunk ./FrontEnd/HsErrors.hs 89
-checkDeriving sl False _ = warn sl "unknown-deriving" "attempt to derive from a non-derivable class"
+checkDeriving sl False xs
+  = let nonDerivable = filter (`notElem` derivableClasses) xs
+    in warn sl "unknown-deriving" ("attempt to derive from a non-derivable class: " ++ unwords (map show nonDerivable))