Binding Forms Incompatible with defclass

[superstructor]

Binding forms such as let are incompatible with defclass as such forms only return the value of the last form.

E.g.

(defclass example
   []
   (let [a true]
      {:background (if a :blue :grey)}
      [:h4
        {:color (if a :black :white)}]
      [:&:hover
        {:border [[(px 1) :solid :grey]]}]))

;; will only output
;; [:&:hover
;;        {:border [[(px 1) :solid :grey]]
;; as the first 2 forms are ignored due to the let

The root cause of this is defclass macro return semantics being different to defn / do in that it returns all top level forms, instead of the value of the last form. Its understandable once analyzed that the above let example does what it does in that context, but it is initially surprising behavior for a Clojure(Script) programmer. It certainly caught me out because I was trying to bind a common value with let and it took me awhile to realise why all the styles were not coming through.

I'm not sure how to fix this. Maybe a mitigation such as allowing a single form return style for defclass could work ? E.g.

(defclass example
  []
  [(let ... ])

[dhleong]

Hmm.... I can see now why you would expect that a let form would have the same mechanics as the top-level defclass, but I hadn't considered it before. I suppose when support would also be nice to have here. It may be doable, but my gut is that it will be tricky.

In the meantime, perhaps something like this will work:

(defclass example []
  (let [a true]
    [:& {:background (if a :blue :grey)}
      [:h4 {:color (if a :black :white)}]
      [:&:hover ; etc.
        ]]))