Governance Token

Table of Contents

• Overview
  • Hook-based Integration with GovernanceDelegation
  • Token Minting
  • Token Burning
  • Voting Power
    • Queries
  • Delegation

Overview

GovernanceToken is an ERC20 token contract that inherits from ERC20Burnable, ERC20Votes, and Ownable. It allows token holders to delegate their voting power to other addresses, enabling a representative voting system. The contract integrates with the GovernanceDelegation contract through a hook-based approach to support advanced delegation.

Hook-based Integration with GovernanceDelegation

Advanced delegation includes relative and absolute partial delegation, which allow delegators to distribute their voting power among multiple delegates in a fractional manner. The _afterTokenTransfer function in the GovernanceToken is modified to call the afterTokenTransfer function in the GovernanceDelegation contract, allowing the GovernanceDelegation contract to consume the hooks and update its delegation and checkpoint mappings accordingly.

If the call to the GovernanceDelegation's afterTokenTransfer function fails, the token transfer MUST revert. This ensures that the GovernanceDelegation contract remains in sync with the GovernanceToken. Otherwise, the GovernanceToken could be left in an inconsistent state relative to the GovernanceDelegation contract, such as when a token transfer is successful but the delegation state is not updated.

All delegation-related state, including the delegates, checkpoints, and numCheckpoints mappings, is gradually shifted from the GovernanceToken to the GovernanceDelegation contract through transactions that call the GovernanceDelegation's hook (e.g. transfers). In the hook, the GovernanceDelegation contract should check if the to and from addresses have been migrated. If an address hasn't been migrated, the GovernanceDelegation contract should write the data from the GovernanceToken's mappings for that address to its own state. When reading delegation data in the GovernanceDelegation contract for a delegator that hasn't been migrated, the GovernanceDelegation should pull the data from the GovernanceToken's state.

For backwards compatibility, the getter methods in the GovernanceToken MUST check if the data of a given address has been migrated or not. If the data has been migrated, the GovernanceToken MUST forward the call to the GovernanceDelegation contract. Otherwise, the GovernanceToken MUST read from its state.

The delegate and delegateBySig functions in the GovernanceToken MUST forward the calls to the GovernanceDelegation contract, which implements the required delegation logic.

Token Minting

GovernanceToken MUST have a mint(address,uint256) function with external visibility that allows the contract owner to mint an arbitrary number of new tokens to a specific address. This function MUST only be called by the contract owner, the MintManager, as enforced by the onlyOwner modifier inherited from the Ownable contract. When tokens are minted, the voting power of the recipient address MUST be updated accordingly in the GovernanceDelegation contract via the afterTokenTransfer hook. The total token supply is capped to 2^208 - 1 to prevent overflow risks in the voting system. If the total supply exceeds this limit, _mint(address,uint256), as inherited from ERC20Votes, MUST revert.

Token Burning

The contract MUST allow token holders to burn their own tokens using the inherited burn(uint256) or burnFrom(address,uint256) functions inherited from ERC20Burnable. When tokens are burned, the total supply and the holder's voting power MUST be reduced accordingly in the GovernanceDelegation contract via the afterTokenTransfer hook.

Voting Power

Each token corresponds to one unit of voting power. By default, token balance does not account for voting power. To have their voting power counted, token holders MUST delegate their voting power to an address (can be their own address). The contract MUST offer public accessors for querying voting power, as outlined below.

Queries

• The getVotes(address)(uint256) function MUST retrieve the current voting power of an address from the GovernanceDelegation contract.
• The getPastVotes(address,uint256)(uint256) function MUST allow querying the voting power of an address at a specific block number in the past from the GovernanceDelegation contract.
• The getPastTotalSupply(uint256)(uint256) function MUST return the total voting power at a specific block number in the past from the GovernanceDelegation contract.

Delegation

Voting power can be delegated either by calling the delegate(address) function directly (to delegate as the msg.sender) or by providing a signature to be used with function delegateBySig(address,uint256,uint256,uint8,bytes32,bytes32), as inherited from ERC20Votes. These functions are modified to forward the calls to the GovernanceDelegation contract which implements the required logic.

The GovernanceDelegation contract maintains the necessary invariants, such as preventing circular delegation chains, ensuring vote weight consistency, and managing checkpoints. It is incorporated as a predeploy of the OP stack to avoid manual deployments across the Superchain.