lua: add lua-unwrap-final-return helper (for future use); keep top-level guard

lib/lua/transpile.sx

@@ -532,11 +532,48 @@
 
 (define lua-transpile (fn (src) (lua-tx (lua-parse src))))
 
+(define
+  lua-ret-raise?
+  (fn (x)
+    (and (= (type-of x) "list")
+         (= (len x) 2)
+         (= (first x) (make-symbol "raise"))
+         (= (type-of (nth x 1)) "list")
+         (= (len (nth x 1)) 3)
+         (= (first (nth x 1)) (make-symbol "list"))
+         (= (type-of (nth (nth x 1) 1)) "list")
+         (= (first (nth (nth x 1) 1)) (make-symbol "quote"))
+         (= (nth (nth (nth x 1) 1) 1) (make-symbol "lua-ret")))))
+
+(define
+  lua-ret-value
+  (fn (raise-form) (nth (nth raise-form 1) 2)))
+
+(define
+  lua-unwrap-final-return
+  (fn (sx)
+    (cond
+      ((lua-ret-raise? sx) (lua-ret-value sx))
+      ((and (= (type-of sx) "list") (> (len sx) 0) (= (first sx) (make-symbol "begin")))
+        (let ((items (rest sx)))
+          (cond
+            ((= (len items) 0) sx)
+            (else
+              (let ((last-item (nth items (- (len items) 1))))
+                (cond
+                  ((lua-ret-raise? last-item)
+                    (let ((val (lua-ret-value last-item))
+                          (prefix (lua-init-before items 0 (- (len items) 1))))
+                      (cons (make-symbol "begin") (append prefix (list val)))))
+                  (else sx)))))))
+      (else sx))))
+
 (define
   lua-eval-ast
   (fn (src)
     (let ((sx (lua-transpile src)))
-      (eval-expr (lua-tx-function-guard sx)))))
+      (let ((sx2 (lua-unwrap-final-return sx)))
+        (eval-expr (lua-tx-function-guard sx2))))))
 
 (define
   lua-tx-multi-args

plans/lua-on-sx.md

@@ -82,6 +82,7 @@ Each item: implement → tests → tick box → update progress log.
 
 _Newest first. Agent appends on every commit._
 
+- 2026-04-24: lua: scoreboard iteration — added `lua-unwrap-final-return` (post-processor that rewrites top-level `(raise (list 'lua-ret V))` → `V` so top-level defines leak to SX top and loadstring closures can see them). Tried dropping the function-guard at top level, but too many tests use `if x then return 0 else return err end` at chunk tail, whose returns aren't at the *statement-list* tail — guard still needed. Kept guard + unwrap-as-no-op. Scoreboard unchanged.
 - 2026-04-24: lua: scoreboard iteration — `lua-pat-strip-captures` helper lets patterns with `(...)` capture parens at least match (captures themselves aren't returned yet — match returns whole match). Unblocks common Lua pattern idioms like `(%a+)=(%d+)`. Scoreboard unchanged.
 - 2026-04-24: lua: scoreboard iteration — extended pattern engine to `string.match`/`gmatch`/`gsub`. `gsub` now supports string/function/table replacement modes. 381/381 green (+6 pattern tests).
 - 2026-04-24: lua: scoreboard iteration — **Lua pattern engine (minimal)** for `string.find`. Supports character classes (`%d`/`%a`/`%s`/`%w`/`%p`/`%l`/`%u`/`%c`/`%x` + complements), `.` any, `^`/`$` anchors, quantifiers `*`/`+`/`-`/`?`, literal chars, `%%`. Added `plain` arg pathway. match/gmatch/gsub still literal. Scoreboard unchanged (pattern-using tests still hit other issues downstream).