#[rlp(..)] does not allow multiple attributes

[Wodann]

If you want to derive both RlpDecodable and RlpEncodable for a struct that has a field that needs to be omitted, it requires both the #[rlp(default)] (for decoding) and #[rlp(skip) (for encoding) attributes.

However, if you combine these two values into a single field annotation, the procedural macro is no longer able to detect the attributes correctly and raises an error. For example:

struct Foo {
  pub bar: u64,
  #[rlp(default, skip)]
  pub cache: OnceLock<u64>,
}

raises the compiler error the trait bound std::sync::OnceLock: access_list::_::alloy_rlp::Decodable is not satisfied.

Instead writing:

struct Foo {
  pub bar: u64,
  #[rlp(default)]
  #[rlp(skip)]
  pub cache: OnceLock<u64>,
}

does compile successfully.