haskell: Phase 8 conformance — showadt.hs + showio.hs (both 5/5)

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

plans/haskell-completeness.md

@@ -115,7 +115,7 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
   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:
+- [x] Conformance programs:
   - `showadt.hs` — `data Expr = Lit Int | Add Expr Expr | Mul Expr Expr`
     with `deriving Show`; prints a tree.
   - `showio.hs` — `print` on various types in a `do` block.
@@ -289,6 +289,14 @@ No OCaml changes are needed. The view type is fully representable as an SX dict.
 
 _Newest first._
 
+**2026-05-07** — Phase 8 conformance: `showadt.hs` + `showio.hs` (both 5/5):
+- `program-showadt.sx`: `deriving (Show)` on the classic `Expr = Lit | Add | Mul`
+  recursive ADT; tests `print` on three nested expressions and inline `show`
+  spot-checks (negative literal wrapped in parens; fully nested Mul of Adds).
+- `program-showio.sx`: `print` on Int, Bool, list, tuple, Maybe, String, ADT
+  inside a `do` block; verifies one io-line per `print`.
+- Both added to `PROGRAMS` in `conformance.sh`. Phase 8 conformance complete.
+
 **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,