;;;; A mistake in a body a macro spliced is reported where it was written.
;;;;
;;;; do-grid takes the body apart and puts it back inside two dotimes, and
;;;; nothing in it is rewritten on the way. So the (+ mr) below is the very
;;;; form the author wrote, and the line it is reported on is the one it is
;;;; written on -- not the line of the do-grid call, which is where every node
;;;; of an expansion used to land.
(defmacro do-grid [[r rows c cols] & body]
  `(dotimes [~r ~rows]
     (dotimes [~c ~cols]
       ~@body)))

(defn main [] i32
  (let [rows 4
        cols 4
        mr 1]
    (do-grid [br rows bc cols]
      (let [v (+ mr)]
        (set v v))))
  0)