haskell: Phase 8 — showsPrec/showParen/shows/showString stubs (+7 tests, 7/7)

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

lib/haskell/tests/show.sx

@@ -0,0 +1,44 @@
+;; show.sx — tests for the Show class plumbing.
+;;
+;; Covers:
+;;  - showsPrec / showParen / shows / showString stubs (Phase 8)
+;;  - Eventually expanded to ≥12 tests covering the full audit (Phase 8 ☐).
+
+(hk-test
+  "shows: prepends show output"
+  (hk-deep-force (hk-run "main = shows 5 \"abc\""))
+  "5abc")
+
+(hk-test
+  "shows: works on True"
+  (hk-deep-force (hk-run "main = shows True \"x\""))
+  "Truex")
+
+(hk-test
+  "showString: prepends literal"
+  (hk-deep-force (hk-run "main = showString \"hello\" \" world\""))
+  "hello world")
+
+(hk-test
+  "showParen True: wraps inner output in parens"
+  (hk-deep-force (hk-run "main = showParen True (showString \"inside\") \"\""))
+  "(inside)")
+
+(hk-test
+  "showParen False: passes through unchanged"
+  (hk-deep-force (hk-run "main = showParen False (showString \"inside\") \"\""))
+  "inside")
+
+(hk-test
+  "showsPrec: prepends show output regardless of prec"
+  (hk-deep-force (hk-run "main = showsPrec 11 42 \"end\""))
+  "42end")
+
+(hk-test
+  "showParen + manual composition: build (Just 3)"
+  (hk-deep-force
+    (hk-run
+      "buildJust3 s = showString \"Just \" (shows 3 s)\nmain = showParen True buildJust3 \"\""))
+  "(Just 3)")
+
+{:fails hk-test-fails :pass hk-test-pass :fail hk-test-fail}