Automatic annotations for `for`

automatic.clj

(defn- multi-perm
  "Handles the case when you want the permutations of a list with duplicate items."
  [l]
  (let [f (frequencies l),
        v (vec (distinct l)),
        indices (apply concat
                       (for ^{::t/ann (t/Coll Long)} [^{::t/ann Long} i (range (count v))]
                         (repeat (f (v i)) i)))]
    (map (partial map v) (lex-permutations indices))))