no instance(s) of type variable(s) exist so that String conforms to MM310S02Result inference variable D has incompatible bounds: equality constraints: MM310S02Result lower bounds: String
似乎是没有实例导致的。no instance(s) of type variable(s) exist so that String conforms to MM310S02
传的参数变量MM310S02Result 与定义的变量类型不一致。