>defn does not support recursive functions

[julienfantin]

👋 Using >defn on a recursive definition yields a Clojure compiler error.

(>defn walk
  [s u]
  (if-let [[_ v] (find s u)]
    (recur s v)
    u))

1. Caused by java.lang.UnsupportedOperationException
   Can only recur from tail position

The macro-expanded code looks a little something like this, which explains the above error:

(defn walk
  [s u]
  ... input checking ...
  (let [output (do ... body ...)]
    ... output checking ...
    output))

Would it be possible to rewrite the macro to make sure that the user's code remains in tail-position?
Perhaps by moving the output checking to a :post assertion?

[LuisThiamNye]

The :post condition is actually implemented similarly, and so that would not work. I suppose this could be solved by moving the body into an inner fn

(defn myfn [params...]
  ... input checking ...
  (let [f (fn [params...] body...)
        output (f params...)]
    ... output checking ...
    output))

[LuisThiamNye]

Or maybe this:

(defn myfn [params...]
  (let [output (loop [params...]
                 validate-input...
                 body...)]
    validate-output...
    output))