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<dyn FieldAccessor + 'static>