check-let.clj

(defmacro check-let [bindings & body]
  (assert (vector? bindings))
  (if (not-empty bindings)
    (let [[binding [else & more]] (split-at 2 bindings)]
      `(if-let [~@binding] (check-let [~@more] ~@body) ~else))
    `(do ~@body)))

(check-let (a 1 ::else) ... ) ;; assert vector exception
(check-let [a] ... )          ;; if-let binding count exception
(check-let [a 1 ::else] 5)    ;; 5
(check-let [a nil ::else] 5)  ;; ::else

(check-let [foo (re-find #"foo" "foobar!") ::no-foo
            bar (re-find #"\d+" "12345")   ::no-d+]
  (str foo bar))

;; => "foo12345"

(check-let [foo (re-find #"foo" "bazbar!") ::no-foo
            bar (re-find #"\d+" "12345")   ::no-d+]
  (str foo bar))

;; => :user/no-foo