usedIn env (LCon v i n args) = let rest = concatMap (usedIn env) args in
                                   case v of
                                      Nothing -> rest
                                      Just (Glob n) -> usedArg env n ++ rest
usedIn env (LCon v i n args) = let rest = concatMap (usedIn env) args in
                                   case v of
                                      Nothing -> rest
                                      Just (Glob n) -> usedArg env n ++ rest
usedIn env (LCon v i n args) = let rest = concatMap (usedIn env) args in
                                   case v of
                                      Nothing -> rest
                                      Just (Glob n) -> usedArg env n ++ rest