1、He told us all that he had seen.他告诉我们他所看到的一切。(all为直接宾语,that引导定语从句修饰先行词all)
2、He told us all what he had seen.他告诉我们所有的人他看到了什么。(all作间接宾语us的同位语,what引导名词性从句作直接宾语,且在从句中作had seen的宾语)
3、He told us all that he had seen the stoken car.他告诉我们所有的人他看到了那辆被盗的轿车。(all作间接宾语us的同位语,that引导名词性从句作直接宾语,that在从句中不担当成分)