+\end{code}
+
+Sometimes we need to pick an OccName that has not already been used,
+given a set of in-use OccNames.
+
+\begin{code}
+chooseUniqueOcc :: NameSpace -> String -> OccSet -> OccName
+chooseUniqueOcc ns str set = loop (mkOccName ns str) (0::Int)
+ where
+ loop occ n
+ | occ `elemOccSet` set = loop (mkOccName ns (str ++ show n)) (n+1)
+ | otherwise = occ