lua: multi-return + unpack at call sites (+10 tests)

lib/lua/test.sh

@@ -460,6 +460,28 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 561)
 (eval "(lua-eval-ast \"local function sum_to(n) local s = 0 for i = 1, n do s = s + i end return s end return sum_to(10)\")")
 
+;; ── Phase 3: multi-return + unpack ────────────────────────────
+(epoch 570)
+(eval "(lua-eval-ast \"local a, b = (function() return 1, 2 end)() return a + b\")")
+(epoch 571)
+(eval "(lua-eval-ast \"local function two() return 10, 20 end local a, b = two() return b - a\")")
+(epoch 572)
+(eval "(lua-eval-ast \"function swap(a, b) return b, a end local x, y = swap(1, 2) return x * 10 + y\")")
+(epoch 573)
+(eval "(lua-eval-ast \"local function three() return 1, 2, 3 end local a, b = three() return a * 10 + b\")")
+(epoch 574)
+(eval "(lua-eval-ast \"local function two() return 1, 2 end local a, b, c = two() if c == nil then return a + b else return 0 end\")")
+(epoch 575)
+(eval "(lua-eval-ast \"local function two() return 5, 7 end local function outer() return two() end local a, b = outer() return a + b\")")
+(epoch 576)
+(eval "(lua-eval-ast \"local function two() return 9, 9 end local a, b = two(), 5 return a * 10 + b\")")
+(epoch 577)
+(eval "(lua-eval-ast \"local function pair() return 4, 5 end local x = pair() return x + 1\")")
+(epoch 578)
+(eval "(lua-eval-ast \"local function none() return end local a, b = none() if a == nil and b == nil then return 99 else return 0 end\")")
+(epoch 579)
+(eval "(lua-eval-ast \"local a = 0 local b = 0 local function m() return 7, 11 end a, b = m() return a + b\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -710,6 +732,18 @@ check 551 "twice(+1, 5)"                    '7'
 check 560 "max with if"                     '7'
 check 561 "sum_to(10) with for"             '55'
 
+# ── Phase 3: multi-return + unpack ────────────────────────────
+check 570 "anon-fn returns 2, unpack"       '3'
+check 571 "local fn returns 2, unpack"      '10'
+check 572 "swap via multi-return"           '21'
+check 573 "extra returns discarded"         '12'
+check 574 "missing returns nil-padded"      '3'
+check 575 "tail-return passthrough"         '12'
+check 576 "non-last call truncated to 1st"  '95'
+check 577 "single-assign truncates to 1st"  '5'
+check 578 "empty return → all nil"          '99'
+check 579 "multi-assign (non-local)"        '18'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"