require_eq! macro not working

Question

I am trying to use the following code but it isn't working:

require_eq!(self.state,TokenState::Initial,TokenError::NotAtInitialState);

This is error I see when anchor build is run:

require_eq!(game_data.state,TokenState::Initial,TokenError::NotAtInitialState);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `game::TokenState` cannot be formatted with the default formatter

However, the same code works if I use require! macro:

require!(self.state == TokenState::Initial,TokenError::NotAtInitialState);

Is it because I am not using a particular trait required for the custom type? If yes then what is this trait?

Answer 1

game::TokenState cannot be formatted with the default formatter

Deep in the bowels of require_eq!(), to_string() is called on your type TokenState. This method requires that the std::fmt::Display trait be implemented on TokenState.