;; class-defaults.sx — Phase 13: class default method implementations.

;; ── Eq default: myNeq derived from myEq via `not (myEq x y)` ──
(define
  hk-myeq-source
  "class MyEq a where\n  myEq :: a -> a -> Bool\n  myNeq :: a -> a -> Bool\n  myNeq x y = not (myEq x y)\ninstance MyEq Int where\n  myEq x y = x == y\n")

(hk-test
  "Eq default: myNeq 3 5 = True (no explicit myNeq in instance)"
  (hk-deep-force (hk-run (str hk-myeq-source "main = myNeq 3 5\n")))
  (list "True"))

(hk-test
  "Eq default: myNeq 3 3 = False"
  (hk-deep-force (hk-run (str hk-myeq-source "main = myNeq 3 3\n")))
  (list "False"))

(hk-test
  "Eq default: myEq still works in same instance"
  (hk-deep-force (hk-run (str hk-myeq-source "main = myEq 7 7\n")))
  (list "True"))

;; ── Override path: instance can still provide the method explicitly. ──
(hk-test
  "Default override: instance-provided beats class default"
  (hk-deep-force
    (hk-run
      "class Hi a where\n  greet :: a -> String\n  greet x = \"default\"\ninstance Hi Bool where\n  greet x = \"override\"\nmain = greet True"))
  "override")

(hk-test
  "Default fallback: empty instance picks default"
  (hk-deep-force
    (hk-run
      "class Hi a where\n  greet :: a -> String\n  greet x = \"default\"\ninstance Hi Bool where\nmain = greet True"))
  "default")

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