rust - 无法在Rust中的程序宏函数声明中打印

Question

我正在使用proc_macro，并希望打印一些详细信息以进行调试。 println!语句不显示任何内容。

这是宏调用:

decl_module! {

    /// The module declaration.
    pub struct Module<T: Trait> for enum Call where origin: T::Origin {
        // A default function for depositing events
        fn deposit_event() = default;

        /// Allow a user to claim ownership of an unclaimed proof
        fn create_claim(origin, proof: Vec<u8>) -> DispatchResult {
            // Verify that the incoming transaction is signed and store who the
            // caller of this function is.
            let sender = ensure_signed(origin)?;
            println!("send is: {}", sender);

            // Verify that the specified proof has not been claimed yet or error with the message
            ensure!(!Proofs::<T>::exists(&proof), "This proof has already been claimed.");

            // Call the `system` pallet to get the current block number
            let current_block = <system::Module<T>>::block_number();

            // Store the proof with the sender and the current block number
            Proofs::<T>::insert(&proof, (sender.clone(), current_block));

            // Emit an event that the claim was created
            Self::deposit_event(RawEvent::ClaimCreated(sender, proof));
            Ok(())
        }

        /// Allow the owner to revoke their claim
        fn revoke_claim(origin, proof: Vec<u8>) -> DispatchResult {
            // Determine who is calling the function
            let sender = ensure_signed(origin)?;

            // Verify that the specified proof has been claimed
            ensure!(Proofs::<T>::exists(&proof), "This proof has not been stored yet.");

            // Get owner of the claim
            let (owner, _) = Proofs::<T>::get(&proof);

            // Verify that sender of the current call is the claim owner
            ensure!(sender == owner, "You must own this claim to revoke it.");

            // Remove claim from storage
            Proofs::<T>::remove(&proof);

            // Emit an event that the claim was erased
            Self::deposit_event(RawEvent::ClaimRevoked(sender, proof));
            Ok(())
        }
    }
}

它取自here。我添加了以下行:

println!("send is: {}", sender);

我正在终端(或任何地方)中运行区块链(Polkadot dApp)，我看不到输出消息。注意:一切正常，但我无法打印。

Answer 1

此宏调用生成包含打印语句的代码。它不会运行该代码。在运行代码并调用create_claim之前，您将看不到打印输出。

如果您想调试宏调用，请参见示例中的几个tools宏，但我不知道它们是否也适用于过程宏或是否具有等效项。