The definition of destructuring-pair? looks like it is missing something in the second clause:

(defn- pair? [x] (and (vector? x) (= 2 (core/count x))))
(defn- destructuring-pair? [x]
  (and (pair? x) (not (or (keyword? x) (= '& x)))))

[Lines 30-32 in current version.]

If pair? x is true, then x is certainly not a keyword or a symbol, so the second clause is automatically true, obviating the need for the function. Should the second clause be replaced with (not (some #(or (keyword? %) (= '& %)) x)), or perhaps (not (or (some keyword? x) (= '& (first x)))) if preferred for your intent?