lua: if/else/elseif body scoping via (let () …); else-branch leak fixed +3 tests

lib/lua/test.sh

@@ -908,6 +908,14 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 1801)
 (eval "(lua-eval-ast \"do local i = 10 do local i = 100 assert(i == 100) end assert(i == 10) end return \\\"ok\\\"\")")
 
+;; ── if/else/elseif body scoping ──────────────────────────────
+(epoch 1810)
+(eval "(lua-eval-ast \"local x = 10 if true then local x = 99 end return x\")")
+(epoch 1811)
+(eval "(lua-eval-ast \"local x = 10 if false then else local x = 99 end return x\")")
+(epoch 1812)
+(eval "(lua-eval-ast \"local x = 10 if false then elseif true then local x = 99 end return x\")")
+
 EPOCHS
 
 OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -1368,6 +1376,11 @@ check 1705 "f(a, b, ...) mixed"             '783'
 check 1800 "inner do local shadows"         '10'
 check 1801 "nested do scopes"               '"ok"'
 
+# ── if/else/elseif body scoping ──────────────────────────────
+check 1810 "if then local shadows"          '10'
+check 1811 "else local shadows"             '10'
+check 1812 "elseif local shadows"           '10'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "ok $PASS/$TOTAL Lua-on-SX tests passed"