lua: proper early-return via guard+raise sentinel; fixes if-then-return-end-rest +3 tests

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 — **proper early-return via guard+raise sentinel**. Fixes long-logged limitation: `if cond then return X end ...rest` now exits the enclosing function; `rest` is skipped. `lua-tx-return` raises `(list 'lua-ret value)`; every function body and the top-level chunk + loadstring'd chunks wrap in a guard that catches the sentinel and returns its value. Eliminates "compare incompatible types" from constructs.lua (past line 40). 368/368 green (+3 early-return tests).
 - 2026-04-24: lua: scoreboard iteration — **unary-minus / `^` precedence fix**. Per Lua spec, `^` binds tighter than unary `-`, so `-2^2` should parse as `-(2^2) = -4`, not `(-2)^2 = 4`. My parser recursed into `parse-unary` and then let `^` bind to the already-negated operand. Added `parse-pow-chain` helper and changed the `else` branch of `parse-unary` to parse a primary + `^`-chain before returning; unary operators now wrap the full `^`-chain. Fixed `constructs.lua` past assert #3 (moved to compare-incompatible). 365/365 green (+3 precedence tests).
 - 2026-04-24: lua: scoreboard iteration — `lua-byte-to-char` regression fix. My previous change returned 2-char strings (`"\a"` etc.) for bytes that SX string literals can't express (0, 7, 8, 11, 12, 14–31, 127+), breaking `'a\0a'` length from 3 → 4. Now only 9/10/13 and printable 32-126 produce real bytes; others use a single `"?"` placeholder so `string.len` stays correct. literals.lua back to failing at assert #4 (was regressed to #2).
 - 2026-04-24: lua: scoreboard iteration — **decimal string escapes** `\ddd` (1-3 digits). Tokenizer `read-string` previously fell through to literal for digits, so `"\65"` came out as `"65"` not `"A"`. Added `read-decimal-escape!` consuming up to 3 digits while keeping value ≤255, plus `\a`/`\b`/`\f`/`\v` control escapes and `lua-byte-to-char` ASCII lookup. 362 tests (+2 escape tests).
@@ -133,4 +134,4 @@ _Shared-file issues that need someone else to fix. Minimal repro only._
 - **`string.find`/`match`/`gmatch`/`gsub` patterns are LITERAL only** — no `%d`/`%a`/`.`/`*`/`+`/etc. Implementing Lua patterns is a separate work item; literal search covers the common case.
 - **`string.format`** supports only `%s`, `%d`, `%f`, `%%`. No width/precision flags (`%.2f`, `%5d`).
 - **`string.char`** supports printable ASCII 32–126 plus `\t`/`\n`/`\r`; other codes error.
-- **Early `return` inside nested block** — `if cond then return nil end ...rest` doesn't exit the enclosing function; `rest` runs anyway. Use `if cond then return X else return Y end` instead. Likely needs guard+raise sentinel for proper fix.
+- ~~Early `return` inside nested block~~ — **FIXED 2026-04-24** via guard+raise sentinel (`lua-ret`). All function bodies and the top-level chunk wrap in a guard that catches the return-sentinel; `return` statements raise it.