add small test to result.mlish

tapl/tests/mlish/find.mlish

@@ -26,11 +26,25 @@
  : (Option Int)
  -> (None {Int}))
 
+;; args inferred in order, L-to-R, currently no backtracking
 (check-type
  (find (Nil {Int}) (λ ([x : Int]) (<= 2 x)))
  : (Option Int)
  -> (None {Int}))
 
+;; reversing arg order leads to successful inference
+(define (find2 [pred : (→ X Bool)] [lst : (List X)] → (Option X))
+  (match lst with
+   [Nil -> None]
+   [Cons fst rst ->
+         (cond [(pred fst) (Some fst)]
+               [else (find2 pred rst)])]))
+
+(check-type
+ (find2 (λ ([x : Int]) (<= 2 x)) Nil)
+ : (Option Int)
+ -> (None {Int}))
+
 (define (find-min/max [lst : (List X)] [<? : (→ Y Y Bool)] [extract-key : (→ X Y)]
                       → (Option (× X X)))
   (match lst with