lua_istable
if (level == 0 || !lua_istable(L, -1))
else if (!lua_istable(L, -1)) { /* field has a non-table value? */
if (!lua_istable(L, -1)) { /* not found? */
if (lua_istable(L, -1)) return 1; /* table already there */
if (lua_gettop(state) == 1 && lua_istable(state, 1)) {