erc20-token.md

description
An interchain ERC20 token contract

Interchain Token

****ERC20 Token **** app is an interchain ERC20 token contract using the App framework.

The hyperlane-token repo shows an example Interchain Token, an ERC20 that can travel between any Hyperlane chain, also called a HypERC20.

The changes to the vanilla OpenZeppelin ERC20 contract are minimal. It has a transferRemote() function that burns the specified amount of tokens on the sending chain and mints the equivalent amount on the receiving chain.

Contract

Its contract implements a transferRemote method which burns tokens and dispatches corresponding messages.

/**
 * @notice Transfers `_amount` of tokens from `msg.sender` to `_recipient` on the `_destination` chain.
 * @dev Burns `_amount` of tokens from `msg.sender` on the origin chain and dispatches
 *      message to the `destination` chain to mint `_amount` of tokens to `recipient`.
 * @param _destination The identifier of the destination chain.
 * @param _recipient The address of the recipient on the destination chain.
 * @param _amount The amount of tokens to be sent to the remote recipient.
 */
function transferRemote(
    uint32 _destination,
    address _recipient,
    uint256 _amount
) external payable {
    _burn(msg.sender, _amount);
    _dispatchWithGas(
        _destination,
        Message.format(_recipient, _amount),
        gasAmount,
        msg.value,
        msg.sender
    );
}

It also requires a _handle method which mints tokens upon receiving messages.

/**
 * @dev Mints tokens to recipient when router receives transfer message.
 * @param _origin The identifier of the origin chain.
 * @param _message The encoded remote transfer message containing the recipient address and amount.
 */
function _handle(
    uint32 _origin,
    bytes32,
    bytes memory _message
) internal override {
    (address recipient, uint256 amount) = abi.decode(
        _message,
        (address, uint256)
    );
    _mint(recipient, amount);
}