enum Size {
            /// its ok. Enum could starts from 0. fixed
            SIZE_SMALL_UNSPECIFIED = 0;
            SIZE_MEDIUM = 1;
            SIZE_LARGE = 2;
} 

enum Size {
            /// its not ok. Rule added
            SIZE_SMALL_UNSPECIFIED = -1;
            SIZE_MEDIUM = 1;
            SIZE_LARGE = 2;
} 

message Size {
            /// its not ok. For messages number should be positive integer. Rule added
            string size = 0;
} 

message Size {
            /// its not ok. For messages number should be positive integer. Rule added
            string size = -1;
}