An issue I'm having with typed Clojure

typed clojure issue.clj

(ns greed.coords
  (:require [clojure.core.typed :refer [ann]]))

(ann get-next-coordinate-northeast
     [NonEmptySeqable (Option Number) (Option Number) -> (Option (IPersistentList Number))])
(defn get-next-coordinate-northeast [grid x y]
  (when-not (or (nil? x) (nil? grid) (>= x (- (count (first grid)) 1))
                (nil? y) (<= y 0))
    (list (+ x 1) (- y 1))))

;; greed.coords> (clojure.core.typed/check-ns)
;; Start collecting greed.coords
;; Finished collecting greed.coords
;; Collected 1 namespaces in 22.57 msecs
;; Start checking greed.coords
;; Checked greed.coords in 237.739 msecs
;; Checked 1 namespaces (approx. 72 lines) in 260.809 msecs
;; Type Error (greed/coords.clj:22:54) Polymorphic function clojure.core/first could not be applied to arguments:
;; Polymorphic Variables:
;; 	x
;; 
;; Domains:
;; 	(HVec [x Any *])
;; 	(Option (EmptySeqable x))
;; 	(NonEmptySeqable x)
;; 	(Option (clojure.lang.Seqable x))
;; 
;; Arguments:
;; 	clojure.core.typed/NonEmptySeqable
;; 
;; Ranges:
;; 	x
;; 	nil
;; 	x
;; 	(Option x)
;; 
;; in: (clojure.core/first grid)
;; in: (clojure.lang.Numbers/gte x (clojure.lang.Numbers/minus (clojure.lang.RT/count (clojure.core/first grid)) 1))
;; 
;; 
;; ExceptionInfo Type Checker: Found 1 error  clojure.core/ex-info (core.clj:4327)

Sorry, yes - ignore the <= comment!

I had a look, and List* is available, so:

(ann get-next-coordinate-northeast
     [(NonEmptySeqable (NonEmptySeqable Any)) (Option Number) (Option Number)
      ->
      (Option (List* Number Number))])

FWIW, I can't resist playing while I've got 10 minutes. I'd approach from this angle:

(defn- validate
  [grid [x y :as coords]]
  (when (and grid x y
             (<= 0 x (dec (count (first grid))))
             (<= 0 y (dec (count grid))))
    coords))

(def compass {:north [0 -1]
              :east [1 0]
              :south [0 1]
              :northeast [1 -1]
              ...
              })

(defn offset
  [coords direction]
  (map + coords (compass direction)))

(validate grid (offset [2 5] :east))

(Thoroughly untested..)

Hm. I'll have to investigate this compass idea. Thanks for that. I've been wanting to get a code review, but just haven't asked for one yet. This has been enlightening. Feel free to keep info coming (via any means of communication). :-)

Heterogeneous vectors are much better supported than heterogeneous lists or seqs.