Function protobuf::reflect::accessor::make_singular_enum_accessor

pub fn make_singular_enum_accessor<M: Message + 'static, E: ProtobufEnum + 'static>(name: &'static str,
                                                                                    has: fn(&M) -> bool,
                                                                                    get: fn(&M) -> E)
                                                                                    -> Box<FieldAccessor + 'static>