Brainstorming the token standard in eth2

[c-o-l-o-r]

I’ve been thinking more about the approach of extending msg.value to support arbitrary tokens and I’d really like some feedback on the idea:

msg.value is extended to be the following object:

{
  "amount": uint256,
  "token": Address,
}

Now let’s imagine user A wants to send tokens to contract B. User A crafts a transaction using the new msg.value definition and sends it to contract B’s deposit function:

contract B {
  mapping(address => mapping(address => uint256)) deposits;

  function deposit() payable {
    deposits[msg.sender][msg.value.token] += msg.value.amount;
    get_msg_value();
  }
}

The deposit function updates its records and calls get_msg_value(), which is defined as an opcode or EEI host function.

function get_msg_value() {
  token = GenericTransferableTokenInterface(msg.value.token)
  delegatecall(token.transfer(self, msg.value.amount))
}

The msg.sender and msg.value of the call to contract B is forwarded to the token contract using a delegate call and self is the address of the current execution context, contract B in this example. By nature of signing and sending the original transaction, user A approved the transfer to contract B.