Missing GC barrier in 'luaV_finishset'

testes/gc.lua

@@ -600,6 +600,21 @@ if T then
 end
 
 
+if T then
+  collectgarbage("stop")
+  T.gcstate("pause")
+  local sup = {x = 0}
+  local a = setmetatable({}, {__newindex = sup})
+  T.gcstate("enteratomic")
+  assert(T.gccolor(sup) == "black")
+  a.x = {}   -- should not break the invariant
+  assert(not (T.gccolor(sup) == "black" and T.gccolor(sup.x) == "white"))
+  T.gcstate("pause")  -- complete the GC cycle
+  sup.x.y = 10
+  collectgarbage("restart")
+end
+
+
 if T then
   print("emergency collections")
   collectgarbage()