haskell: Phase 9 — tests/errors.sx (14/14, plan ≥10)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/haskell/tests/errors.sx

@@ -0,0 +1,99 @@
+;; errors.sx — Phase 9 error / undefined / partial-fn coverage via hk-test-error.
+
+;; ── error builtin ────────────────────────────────────────────
+(define
+  hk-as-list
+  (fn
+    (xs)
+    (cond
+      ((and (list? xs) (= (first xs) "[]")) (list))
+      ((and (list? xs) (= (first xs) ":"))
+        (cons (nth xs 1) (hk-as-list (nth xs 2))))
+      (:else xs))))
+
+(hk-test-error
+  "error: raises with literal message"
+  (fn () (hk-deep-force (hk-run "main = error \"boom\"")))
+  "hk-error: boom")
+
+(hk-test-error
+  "error: raises with computed message"
+  (fn () (hk-deep-force (hk-run "main = error (\"oops: \" ++ show 42)")))
+  "hk-error: oops: 42")
+
+;; ── undefined ────────────────────────────────────────────────
+(hk-test-error
+  "error: nested in if branch (only fires when forced)"
+  (fn
+    ()
+    (hk-deep-force (hk-run "main = if 1 == 1 then error \"taken\" else 0")))
+  "taken")
+
+(hk-test-error
+  "undefined: raises Prelude.undefined"
+  (fn () (hk-deep-force (hk-run "main = undefined")))
+  "Prelude.undefined")
+
+;; The non-strict path: undefined doesn't fire when not forced.
+(hk-test-error
+  "undefined: forced via arithmetic"
+  (fn () (hk-deep-force (hk-run "main = undefined + 1")))
+  "Prelude.undefined")
+
+;; ── partial functions ───────────────────────────────────────
+(hk-test
+  "undefined: lazy, not forced when discarded"
+  (hk-deep-force (hk-run "main = let _ = undefined in 5"))
+  5)
+
+(hk-test-error
+  "head []: raises Prelude.head: empty list"
+  (fn () (hk-deep-force (hk-run "main = head []")))
+  "Prelude.head: empty list")
+
+(hk-test-error
+  "tail []: raises Prelude.tail: empty list"
+  (fn () (hk-deep-force (hk-run "main = tail []")))
+  "Prelude.tail: empty list")
+
+;; head and tail still work on non-empty lists.
+(hk-test-error
+  "fromJust Nothing: raises Maybe.fromJust: Nothing"
+  (fn () (hk-deep-force (hk-run "main = fromJust Nothing")))
+  "Maybe.fromJust: Nothing")
+
+(hk-test
+  "head [42]: still works"
+  (hk-deep-force (hk-run "main = head [42]"))
+  42)
+
+;; ── error in IO context ─────────────────────────────────────
+(hk-test
+  "tail [1,2,3]: still works"
+  (hk-as-list (hk-deep-force (hk-run "main = tail [1,2,3]")))
+  (list 2 3))
+
+(hk-test
+  "hk-run-io: error in main lands in io-lines"
+  (let
+    ((lines (hk-run-io "main = error \"caught here\"")))
+    (>= (index-of (str lines) "caught here") 0))
+  true)
+
+;; ── hk-test-error helper itself ─────────────────────────────
+(hk-test
+  "hk-run-io: putStrLn before error preserves earlier output"
+  (let
+    ((lines (hk-run-io "main = do { putStrLn \"first\"; error \"died\"; putStrLn \"never\" }")))
+    (and
+      (>= (index-of (str lines) "first") 0)
+      (>= (index-of (str lines) "died") 0)))
+  true)
+
+;; hk-as-list helper for converting a forced Haskell cons into an SX list.
+(hk-test-error
+  "hk-test-error: matches partial substring inside wrapped exception"
+  (fn () (hk-deep-force (hk-run "main = error \"unique-marker-xyz\"")))
+  "unique-marker-xyz")
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}