基板 frotier rpc 托盤中所需的類型注釋

Question

我正在使用 susbtrate 2.0.1 並嘗試將前沿實現集成到運行時中，這個實現在基板 2.0.0 上運行良好，但現在有一些語法錯誤。

Frontier Dependencies
frontier-consensus = {  default-features = false,git = 'https://github.com/PureStake/frontier.git', branch = 'substrate-v2' }
frontier-rpc = {  default-features = false, git = 'https://github.com/PureStake/frontier.git', branch = 'substrate-v2' }
frontier-rpc-primitives = { default-features = false, git = 'https://github.com/PureStake/frontier.git', branch = 'substrate-v2' }

以下是錯誤：

    error[E0283]: type annotations needed
   --> /Users/dev/Applications/.cargo/git/checkouts/frontier-6f1ff17f29a883b0/c5fe2a6/rpc/src/eth.rs:299:56
    |
299 |         Ok(U256::from(self.client.info().best_number.clone().unique_saturated_into()))
    |                                                              ^^^^^^^^^^^^^^^^^^^^^
    |
    = note: multiple `impl`s satisfying `U256: From<_>` found in the following crates: `core`, `primitive_types`:
            - impl From<&'static str> for U256;
            - impl From<U128> for U256;
            - impl From<[u8; _]> for U256;
            - impl From<i128> for U256;
            and 15 more
help: try using a fully qualified path to specify the expected types
    |
299 |         Ok(U256::from(<<<B as BlockT>::Header as HeaderT>::Number as UniqueSaturatedInto<T>>::unique_saturated_into(self.client.info().best_number.clone())))


type annotations needed
  --> /Users/dev/Applications/.cargo/git/checkouts/frontier-6f1ff17f29a883b0/c5fe2a6/rpc/src/eth_pubsub.rs:88:46
   |
88 |                         self.client.info().best_number.clone().unique_saturated_into() as u32
   |                                                                ^^^^^^^^^^^^^^^^^^^^^
   |
   = note: type must be known at this point
help: try using a fully qualified path to specify the expected types
   |
88 |                         <<<B as BlockT>::Header as HeaderT>::Number as UniqueSaturatedInto<T>>::unique_saturated_into(self.client.info().best_number.clone()) as u32

在這行代碼中出現此錯誤：

fn block_number(&self) -> Result<U256> {
        
        Ok(U256::from(self.client.info().best_number.clone().unique_saturated_into()))
        
    }

native_number = Some(
                        self.client.info().best_number.clone().unique_saturated_into() as u32
);

Answer 1

在這種情況下，編譯器無法從哪個類型（ u64 u32 ...?）中推斷出U256 。

您需要明確地編寫它。

順便說一句，您可以使用saturated_into代替unique_saturated_into ，它支持渦輪魚風格。

例子：

U256::from(self.client.info().best_number.clone().saturated_into::<u32>());

如果您仍然想要unique_saturated_into ：

let bn: u32 = self.client.info().best_number.clone().unique_saturated_into();
U256::from(bn);

---

您能否將此問題遷移到https://substrate.stackexchange.com/questions ？ 那是正確的地方。