lua: method-call binds obj to temp (no more double-eval); chaining works +1 test

lib/lua/test.sh

@@ -954,6 +954,10 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1863)
 (eval "(lua-eval-ast \"local i = 0 repeat i = i + 1 if i >= 3 then break end until false return i\")")
 
+;; ── Method-call chaining (obj evaluated once) ────────────────
+(epoch 1870)
+(eval "(lua-eval-ast \"local a = {x=0} function a:add(x) self.x = self.x+x return self end return a:add(10):add(20):add(30).x\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1443,6 +1447,9 @@ check 1861 "break in for-num"               '55'
 check 1862 "break in for-in"                '30'
 check 1863 "break in repeat"                '3'
 
+# ── Method-call chaining ─────────────────────────────────────
+check 1870 "a:add():add():add().x chain"    '60'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"