[produce better error message when presented with an unknown type to load
John Meacham <john@repetae.net>**20060718014556] hunk ./Info/Binary.hs 48
-    b <- Map.lookup ps binTable
-    case b of
-        (Binable (_ :: a)) -> do
+    case Map.lookup ps binTable of
+        Just (Binable (_ :: a)) -> do
hunk ./Info/Binary.hs 52
+        Nothing -> fail $ "getDyn: don't know how to read something of type: " ++ show ps