lua: loadstring returns compiled fn (errors propagate cleanly); parse-fail → (nil, err)

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 — **`loadstring` error propagation**. When `loadstring(s)()` was implemented as `eval-expr ( (let () compiled))`, SX's `eval-expr` wrapped any propagated `raise` as "Unhandled exception: X" — so `error('hi')` inside a loadstring'd chunk came out as that wrapped string instead of the clean `"hi"` Lua expects. Fix: transpile source once into a lambda AST, `eval-expr` it ONCE to get a callable fn value, return that — subsequent calls propagate raises cleanly. Guarded parse-failure path returns `(nil, err)` per Lua convention. vararg.lua now runs past assert #18; errors.lua past parse stage.
 - 2026-04-24: lua: scoreboard iteration — `table.sort` O(n²) insertion-sort → **quicksort** (Lomuto partition). 1000-element sorts finish in ms; but `sort.lua` uses 30k elements and still times out even at 90s (metamethod-heavy interpreter overhead). Correctness verified on 1000/5000 element random arrays.
 - 2026-04-24: lua: scoreboard iteration — `dostring(s)` alias for `loadstring(s)()` (Lua 5.0 compat used by literals.lua). Diagnosed `locals.lua` call-non-fn at call #18 → `getfenv/setfenv` stub-return pattern fails `assert(getfenv(foo("")) == a)` (need real env tracking, deferred). Tokenizer long-string-leading-NL rule verified correct.
 - 2026-04-24: lua: scoreboard iteration — Lua 5.0-style `arg` auto-binding inside vararg functions (some PUC-Rio tests still rely on it). `lua-varargs-arg-table` builds `{1=v1, 2=v2, …, n=count}`; transpile adds `arg` binding alongside `__varargs` when `is-vararg`. Diagnosis done with assert-counter instrumentation — literals.lua fails at #4 (long-string NL rule), vararg.lua was at #2 (arg table — FIXED), attrib.lua at #9, locals.lua now past asserts into call-non-fn. 360 tests.