near-bindgen macro: unsupported argument type

Question

I am writing a smart contract promise interface for NEAR blockchain.

I have the following interface:

#[ext_contract(token_receiver)]
pub trait ExtTokenReceiver {

    fn process_token_received(&self, sender_id: AccountId, amount: Balance, message: [u8]) -> Option<String>;
}

However this fails with the following error:

error: Unsupported argument type.
  --> src/token.rs:32:1
   |
32 | #[ext_contract(token_receiver)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: this error originates in an attribute macro (in Nightly builds, run with -Z macro-backtrace for more info)

• How can I debug near-bindgen macro
• What is the Unsupported argument type in this case
• How to fix my interface

Answer 1

I believe the unsupported arguments is [u8]. I have changed the code to use Vec and it works:

use near_sdk::ext_contract;

#[ext_contract(token_receiver)]
pub trait ExtTokenReceiver {
    fn process_token_received(
        &self,
        sender_id: AccountId,
        amount: Balance,
        message: Vec<u8>,
    ) -> Option<String>;
}

    Finished release [optimized] target(s) in 0.05s

What I believe is the issue that the compiler doesn't know the size of the static array at compile time and complains, and Vec as it is a dynamic container that is fine.