haskell: Phase 9 conformance — partial.hs (7/7), Phase 9 complete

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

lib/haskell/conformance.sh

@@ -20,7 +20,7 @@ if [ ! -x "$SX_SERVER" ]; then
   fi
 fi
 
-PROGRAMS=(fib sieve quicksort nqueens calculator collatz palindrome maybe fizzbuzz anagram roman binary either primes zipwith matrix wordcount powers caesar runlength-str showadt showio)
+PROGRAMS=(fib sieve quicksort nqueens calculator collatz palindrome maybe fizzbuzz anagram roman binary either primes zipwith matrix wordcount powers caesar runlength-str showadt showio partial)
 PASS_COUNTS=()
 FAIL_COUNTS=()
 

lib/haskell/tests/program-partial.sx

@@ -0,0 +1,58 @@
+;; partial.hs — exercises Phase 9 partial functions caught at the top level.
+;;
+;; Each program calls a partial function on bad input; hk-run-io catches the
+;; raise and appends the error message to io-lines so tests can inspect.
+
+(hk-test
+  "partial.hs — main = print (head [])"
+  (let
+    ((lines (hk-run-io "main = print (head [])")))
+    (>= (index-of (str lines) "Prelude.head: empty list") 0))
+  true)
+
+(hk-test
+  "partial.hs — main = print (tail [])"
+  (let
+    ((lines (hk-run-io "main = print (tail [])")))
+    (>= (index-of (str lines) "Prelude.tail: empty list") 0))
+  true)
+
+(hk-test
+  "partial.hs — main = print (fromJust Nothing)"
+  (let
+    ((lines (hk-run-io "main = print (fromJust Nothing)")))
+    (>= (index-of (str lines) "Maybe.fromJust: Nothing") 0))
+  true)
+
+(hk-test
+  "partial.hs — putStrLn before error preserves prior output"
+  (let
+    ((lines (hk-run-io "main = do { putStrLn \"step 1\"; putStrLn (show (head [])); putStrLn \"never\" }")))
+    (and
+      (>= (index-of (str lines) "step 1") 0)
+      (>= (index-of (str lines) "Prelude.head: empty list") 0)
+      (= (index-of (str lines) "never") -1)))
+  true)
+
+(hk-test
+  "partial.hs — undefined as IO action"
+  (let
+    ((lines (hk-run-io "main = print undefined")))
+    (>= (index-of (str lines) "Prelude.undefined") 0))
+  true)
+
+(hk-test
+  "partial.hs — catches error from a user-thrown error"
+  (let
+    ((lines (hk-run-io "main = error \"boom from main\"")))
+    (>= (index-of (str lines) "boom from main") 0))
+  true)
+
+;; Negative case: when no error is raised, io-lines doesn't contain
+;; "Prelude" prefixes from our error path.
+(hk-test
+  "partial.hs — happy path: head [42] succeeds, no error in output"
+  (hk-run-io "main = print (head [42])")
+  (list "42"))
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}

plans/haskell-completeness.md

@@ -138,7 +138,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
   an `hk-error` whose message contains the given substring.
 - [x] Tests in `lib/haskell/tests/errors.sx` (≥ 10 tests: error message
   content, undefined, head/tail/fromJust on bad input, `hk-test-error` helper).
-- [ ] Conformance programs:
+- [x] Conformance programs:
   - `partial.hs` — exercises `head []`, `tail []`, `fromJust Nothing` caught
     at the top level; shows error messages.
 
@@ -293,6 +293,14 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 9 conformance: `partial.hs` (7/7) → Phase 9 complete:
+- New `tests/program-partial.sx` exercising `head []`, `tail []`,
+  `fromJust Nothing`, `undefined`, and user `error` from inside a `do` block;
+  verifies the error message lands in `hk-run-io`'s `io-lines`. Also a happy-
+  path test (`head [42] = 42`) and a "putStrLn before error preserves prior
+  output, never reaches subsequent action" test.
+- Added `partial` to `PROGRAMS` in `conformance.sh`. Phase 9 done.
+
 **2026-05-07** — Phase 9 `tests/errors.sx` (14/14):
 - New file with 14 tests covering: error w/ literal + computed message; error
   in `if` branch (laziness boundary); undefined via direct + forcing-via-