haskell: Phase 8 — tests/show.sx expanded to 26/26 (full audit coverage)

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

lib/haskell/tests/show.sx

@@ -1,9 +1,11 @@
-;; show.sx — tests for the Show class plumbing.
+;; show.sx — tests for the Show / Read class plumbing.
 ;;
-;; Covers:
-;;  - showsPrec / showParen / shows / showString stubs (Phase 8)
-;;  - Eventually expanded to ≥12 tests covering the full audit (Phase 8 ☐).
+;; Covers Phase 8:
+;;  - showsPrec / showParen / shows / showString stubs
+;;  - Read class stubs (reads / readsPrec / read)
+;;  - direct show coverage (Int, Bool, String, list, tuple, Maybe, ADT, ...)
 
+;; ── ShowS / showsPrec / showParen stubs ──────────────────────
 (hk-test
   "shows: prepends show output"
   (hk-deep-force (hk-run "main = shows 5 \"abc\""))
@@ -41,6 +43,7 @@
       "buildJust3 s = showString \"Just \" (shows 3 s)\nmain = showParen True buildJust3 \"\""))
   "(Just 3)")
 
+;; ── Read stubs ───────────────────────────────────────────────
 (hk-test
   "reads: stub returns empty list (null-check)"
   (hk-deep-force (hk-run "main = show (null (reads \"42\"))"))
@@ -56,4 +59,82 @@
   (hk-deep-force (hk-run "main = show (length (reads \"abc\"))"))
   "0")
 
+;; ── Direct `show` audit coverage ─────────────────────────────
+(hk-test "show Int" (hk-deep-force (hk-run "main = show 42")) "42")
+
+(hk-test
+  "show negative Int"
+  (hk-deep-force (hk-run "main = show (negate 5)"))
+  "-5")
+
+(hk-test "show Bool True" (hk-deep-force (hk-run "main = show True")) "True")
+
+(hk-test
+  "show Bool False"
+  (hk-deep-force (hk-run "main = show False"))
+  "False")
+
+(hk-test
+  "show String quotes the value"
+  (hk-deep-force (hk-run "main = show \"hello\""))
+  "\"hello\"")
+
+(hk-test
+  "show list of Int"
+  (hk-deep-force (hk-run "main = show [1,2,3]"))
+  "[1,2,3]")
+
+(hk-test
+  "show empty list"
+  (hk-deep-force (hk-run "main = show (drop 5 [1,2,3])"))
+  "[]")
+
+(hk-test
+  "show pair tuple"
+  (hk-deep-force (hk-run "main = show (1, True)"))
+  "(1,True)")
+
+(hk-test
+  "show triple tuple"
+  (hk-deep-force (hk-run "main = show (1, 2, 3)"))
+  "(1,2,3)")
+
+(hk-test
+  "show Maybe Nothing"
+  (hk-deep-force (hk-run "main = show Nothing"))
+  "Nothing")
+
+(hk-test
+  "show Maybe Just"
+  (hk-deep-force (hk-run "main = show (Just 3)"))
+  "Just 3")
+
+(hk-test
+  "show nested Just wraps inner in parens"
+  (hk-deep-force (hk-run "main = show (Just (Just 3))"))
+  "Just (Just 3)")
+
+(hk-test
+  "show Just (negate 3) wraps negative in parens"
+  (hk-deep-force (hk-run "main = show (Just (negate 3))"))
+  "Just (-3)")
+
+(hk-test
+  "show custom nullary ADT"
+  (hk-deep-force
+    (hk-run "data Day = Mon | Tue | Wed deriving (Show)\nmain = show Tue"))
+  "Tue")
+
+(hk-test
+  "show custom multi-constructor ADT"
+  (hk-deep-force
+    (hk-run
+      "data Shape = Pt | Sq Int | Rect Int Int deriving (Show)\nmain = show (Rect 3 4)"))
+  "Rect 3 4")
+
+(hk-test
+  "show list of Maybe wraps each element"
+  (hk-deep-force (hk-run "main = show [Just 1, Nothing, Just 2]"))
+  "[Just 1,Nothing,Just 2]")
+
 {:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}

plans/haskell-completeness.md

@@ -110,9 +110,11 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 - [x] `showsPrec` / `showParen` stubs so hand-written Show instances compile.
 - [x] `Read` class stub — just enough for `reads :: String -> [(a,String)]` to
   type-check; no real parser needed yet.
-- [ ] Tests in `lib/haskell/tests/show.sx` (≥ 12 tests: show Int, show Bool,
+- [x] Tests in `lib/haskell/tests/show.sx` (≥ 12 tests: show Int, show Bool,
   show Char, show String, show list, show tuple, show Maybe, show custom ADT,
   deriving Show on multi-constructor type, nested constructor parens).
+  _Char tests deferred: Char = Int representation; show on a Char is currently
+  `"97"` not `"'a'"`._
 - [ ] Conformance programs:
   - `showadt.hs` — `data Expr = Lit Int | Add Expr Expr | Mul Expr Expr`
     with `deriving Show`; prints a tree.
@@ -287,6 +289,16 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 8 `tests/show.sx` expanded to full audit coverage (26/26):
+- 16 new direct `show` tests: Int (positive + negative), Bool (T/F), String,
+  list of Int, empty list, pair tuple, triple tuple, Maybe Nothing, Maybe Just,
+  nested Just (paren wrapping), Just (negate 3) (negative wrapping), nullary
+  ADT, multi-constructor ADT with args, list of Maybe.
+- `show ([] :: [Int])` would be the natural empty-list test but our parser
+  doesn't yet support type ascription; used `show (drop 5 [1,2,3])` instead.
+  Char `'a'` → `"'a'"` deferred to Char-tagging design (Char = Int currently
+  yields `"97"`).
+
 **2026-05-07** — Phase 8 `Read` class stub (`reads`, `readsPrec`, `read`):
 - Three lines added to `hk-prelude-src`: `reads s = []`, `readsPrec _ s = reads s`,
   `read s = fst (head (reads s))`. The stubs let user code that mentions