;; infer.sx tests — Algorithm W: literals, vars, lambdas, application, let,
;; if, operators, tuples, lists, let-polymorphism.

(define hk-t (fn (src expected)
  (hk-test (str "infer: " src) (hk-infer-type src) expected)))

;; ─── Literals ────────────────────────────────────────────────────────────────
(hk-t "1"          "Int")
(hk-t "3.14"       "Float")
(hk-t "\"hello\""  "String")
(hk-t "'x'"        "Char")
(hk-t "True"       "Bool")
(hk-t "False"      "Bool")

;; ─── Arithmetic and boolean operators ────────────────────────────────────────
(hk-t "1 + 2"      "Int")
(hk-t "3 * 4"      "Int")
(hk-t "10 - 3"     "Int")
(hk-t "True && False" "Bool")
(hk-t "True || False" "Bool")
(hk-t "not True"   "Bool")
(hk-t "1 == 1"     "Bool")
(hk-t "1 < 2"      "Bool")

;; ─── Lambda ───────────────────────────────────────────────────────────────────
;; \x -> x   (identity)  should get t1 -> t1
(hk-test "infer: identity lambda" (hk-infer-type "\\x -> x") "t1 -> t1")

;; \x -> x + 1 : Int -> Int
(hk-test "infer: lambda add" (hk-infer-type "\\x -> x + 1") "Int -> Int")

;; \x -> not x : Bool -> Bool
(hk-test "infer: lambda not" (hk-infer-type "\\x -> not x") "Bool -> Bool")

;; \x y -> x + y : Int -> Int -> Int
(hk-test "infer: two-arg lambda" (hk-infer-type "\\x -> \\y -> x + y") "Int -> Int -> Int")

;; ─── Application ─────────────────────────────────────────────────────────────
(hk-t "not True"    "Bool")
(hk-t "negate 1"    "Int")

;; ─── If-then-else ─────────────────────────────────────────────────────────────
(hk-t "if True then 1 else 2"     "Int")
(hk-t "if 1 == 2 then True else False" "Bool")

;; ─── Let bindings ─────────────────────────────────────────────────────────────
;; let x = 1 in x + 2
(hk-t "let x = 1 in x + 2" "Int")

;; let f x = x + 1 in f 5
(hk-t "let f x = x + 1 in f 5" "Int")

;; let-polymorphism: let id x = x in id 1
(hk-t "let id x = x in id 1" "Int")

;; ─── Tuples ───────────────────────────────────────────────────────────────────
(hk-t "(1, True)"       "(Int, Bool)")
(hk-t "(1, 2, 3)"       "(Int, Int, Int)")

;; ─── Lists ───────────────────────────────────────────────────────────────────
(hk-t "[1, 2, 3]"    "[Int]")
(hk-t "[True, False]" "[Bool]")

;; ─── Polymorphic list functions ───────────────────────────────────────────────
(hk-t "length [1, 2, 3]"   "Int")
(hk-t "null []"             "Bool")
(hk-t "head [1, 2, 3]"     "Int")

{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}