Attribute Macro init_empty

#[init_empty]

This macro takes an fn as the basis of an InitialState implementation for the state type that is returned by the fn (on success).

The fn is expected to build the state type specified as a Path attribute argument without additional input. Example:

pub struct B0 {}

#[hax_lib_protocol_macros::init_empty(B0)]
fn init_b() -> ::hax_lib_protocol::ProtocolResult<B0> {
   Ok(B0 {})
}

// The following is generated by the macro:
#[hax_lib::exclude]
impl InitialState for B0 {
    fn init(prologue: Option<Vec<u8>>) -> ::hax_lib_protocol::ProtocolResult<Self> {
        if let Some(_) = prologue {
            Err(::hax_lib_protocol::ProtocolError::InvalidPrologue)
        } else {
            init_b()
        }
    }
}