Why Initializing the structure with a newtype doesn't work?

help
1

hi, I am working on the parity Ethereum code. However, I faced some weird error when I tried to initialize a structure with newtype. please help me.

here is the troublesome code

    let transaction = Transaction::AssetTransfer {
        network_id: NetworkId([0u8; 2]),
        burns: Vec::new(),
        inputs: Vec::new(),
        outputs: Vec::new(),
        nonce: 0,
    };

and here is compile error

error[E0423]: expected function, found struct `NetworkId`
  --> vm/src/tests/executor.rs:76:21
   |
76 |         network_id: NetworkId([0u8; 2]),
   |                     ^^^^^^^^^ did you mean `NetworkId { /* fields */ }`?

and NetworkId is defined as follow

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub struct NetworkId([u8; 2]);

impl fmt::Display for NetworkId {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        let s = str::from_utf8(&self.0).expect("network_id a valid utf8 string");
        write!(f, "{}", s)
    }
}

impl FromStr for NetworkId {
    type Err = String;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        if s.len() != 2 {
            return Err("Invalid network_id length".to_string())
        }
        let mut network_id = [0u8; 2];
        network_id.copy_from_slice(s.as_bytes());
        Ok(NetworkId(network_id))
    }
}

impl From<&'static str> for NetworkId {
    fn from(s: &'static str) -> Self {
        s.parse().unwrap()
    }
}

impl Default for NetworkId {
    fn default() -> Self {
        "tc".into()
    }
}

and Transaction::AssetTransfer is defined as follow

pub enum Transaction {
  ...
    AssetTransfer {
        network_id: NetworkId,
        burns: Vec<AssetTransferInput>,
        inputs: Vec<AssetTransferInput>,
        outputs: Vec<AssetTransferOutput>,
        nonce: u64,
    },
}

I think it should work..

2

Perhaps your newtype struct is not imported in current scope, and there is a normal struct of the same name NetworkId already defined/imported in the scope.

Tips:

  1. Sometimes the compiler will give you suggestions starting with “help: “, it may resolve your problem.

  2. You can use this to show minimal code for reproduction

3 
use ckey::{sign, KeyPair, Private, Signature, NetworkId};

I already imported NetworkId from module where it is defined and there is no another struct named NetworkId.

and Thank to your tips

4

Is it because the NetworkId field isn't pub?

5

NetworkId field is pub and is declared in key/src/lib.rs as follow

pub use network::NetworkId;

and NetworkId is defined in key/src/network.rs

6

Not in the code you pasted:

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub struct NetworkId([u8; 2]);

NetworkId.0 is not pub. It shouldn't be visible to anyone outside the defining module, which would presumably include the code trying to create it.

Edit: also, "field" means a storage member of a structure. pub use is not a field, it's a public use item. NetworkId is a structure type.

1 Like
7

Additionally i do not know if that helps, troublesome code is test code.


#[test]
fn simple_success() {
    let transaction = Transaction::AssetTransfer {
        network_id: NetworkId([0u8; 2]),
        burns: Vec::new(),
        inputs: Vec::new(),
        outputs: Vec::new(),
        nonce: 0,
    };
    let outpoint = AssetOutPoint {
        transaction_hash: H256::default(),
        index: 0,
        asset_type: H256::default(),
        amount: 0,
    };
    assert_eq!(
        execute(&[], &[], &[Instruction::Push(1)], &transaction, Config::default(), &outpoint),
        Ok(ScriptResult::Unlocked)
    );

    assert_eq!(
        execute(&[], &[], &[Instruction::Success], &transaction, Config::default(), &outpoint),
        Ok(ScriptResult::Unlocked)
    );
}
8

Yes you are right!

After change NetworkId.0 to pub, I could make NetworkId in another module.

and thank to your explanation about filed