Split ERC20Votes and ERC20VotesComp (#2706)
Co-authored-by: Francisco Giordano <frangio.1@gmail.com>
This commit is contained in:
Hadrien Croubois
GitHub
@ -21,7 +21,8 @@ Additionally there are multiple custom extensions, including:
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* {ERC20Snapshot}: efficient storage of past token balances to be later queried at any point in time.
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* {ERC20Permit}: gasless approval of tokens (standardized as ERC2612).
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* {ERC20FlashMint}: token level support for flash loans through the minting and burning of ephemeral tokens (standardized as ERC3156).
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* {ERC20Votes}: support for voting and vote delegation (compatible with Compound's token).
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* {ERC20Votes}: support for voting and vote delegation.
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* {ERC20VotesComp}: support for voting and vote delegation (compatible with Compound's tokenn, with uint96 restrictions).
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Finally, there are some utilities to interact with ERC20 contracts in various ways.
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@ -32,7 +33,6 @@ The following related EIPs are in draft status.
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- {ERC20Permit}
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- {ERC20FlashMint}
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- {ERC20Votes}
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NOTE: This core set of contracts is designed to be unopinionated, allowing developers to access the internal functions in ERC20 (such as <<ERC20-_mint-address-uint256-,`_mint`>>) and expose them as external functions in the way they prefer. On the other hand, xref:ROOT:erc20.adoc#Presets[ERC20 Presets] (such as {ERC20PresetMinterPauser}) are designed using opinionated patterns to provide developers with ready to use, deployable contracts.
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@ -54,6 +54,10 @@ NOTE: This core set of contracts is designed to be unopinionated, allowing devel
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{{ERC20Snapshot}}
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{{ERC20Votes}}
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{{ERC20VotesComp}}
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== Draft EIPs
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The following EIPs are still in Draft status. Due to their nature as drafts, the details of these contracts may change and we cannot guarantee their xref:ROOT:releases-stability.adoc[stability]. Minor releases of OpenZeppelin Contracts may contain breaking changes for the contracts in this directory, which will be duly announced in the https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/CHANGELOG.md[changelog]. The EIPs included here are used by projects in production and this may make them less likely to change significantly.
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@ -62,8 +66,6 @@ The following EIPs are still in Draft status. Due to their nature as drafts, the
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{{ERC20FlashMint}}
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{{ERC20Votes}}
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== Presets
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These contracts are preconfigured combinations of the above features. They can be used through inheritance or as models to copy and paste their source code.
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@ -3,17 +3,19 @@
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pragma solidity ^0.8.0;
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import "./draft-ERC20Permit.sol";
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import "./IERC20Votes.sol";
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import "../../../utils/math/Math.sol";
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import "../../../utils/math/SafeCast.sol";
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import "../../../utils/cryptography/ECDSA.sol";
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/**
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* @dev Extension of the ERC20 token contract to support Compound's voting and delegation.
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* @dev Extension of ERC20 to support Compound-like voting and delegation. This version is more generic than Compound's,
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* and supports token supply up to 2^224^ - 1, while COMP is limited to 2^96^ - 1.
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*
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* This extensions keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
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* NOTE: If exact COMP compatibility is required, use the {ERC20VotesComp} variant of this module.
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*
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* This extension keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
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* by calling the {delegate} function directly, or by providing a signature to be used with {delegateBySig}. Voting
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* power can be queried through the public accessors {getCurrentVotes} and {getPriorVotes}.
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* power can be queried through the public accessors {getVotes} and {getPastVotes}.
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*
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* By default, token balance does not account for voting power. This makes transfers cheaper. The downside is that it
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* requires users to delegate to themselves in order to activate checkpoints and have their voting power tracked.
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@ -22,38 +24,53 @@ import "../../../utils/cryptography/ECDSA.sol";
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*
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* _Available since v4.2._
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*/
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abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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abstract contract ERC20Votes is ERC20Permit {
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struct Checkpoint {
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uint32 fromBlock;
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uint224 votes;
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}
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bytes32 private constant _DELEGATION_TYPEHASH = keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
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mapping (address => address) private _delegates;
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mapping (address => Checkpoint[]) private _checkpoints;
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Checkpoint[] private _totalSupplyCheckpoints;
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/**
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* @dev Emitted when an account changes their delegate.
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*/
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event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
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/**
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* @dev Emitted when a token transfer or delegate change results in changes to an account's voting power.
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*/
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event DelegateVotesChanged(address indexed delegate, uint256 previousBalance, uint256 newBalance);
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/**
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* @dev Get the `pos`-th checkpoint for `account`.
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*/
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function checkpoints(address account, uint32 pos) external view virtual override returns (Checkpoint memory) {
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function checkpoints(address account, uint32 pos) public view virtual returns (Checkpoint memory) {
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return _checkpoints[account][pos];
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}
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/**
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* @dev Get number of checkpoints for `account`.
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*/
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function numCheckpoints(address account) external view virtual override returns (uint32) {
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function numCheckpoints(address account) public view virtual returns (uint32) {
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return SafeCast.toUint32(_checkpoints[account].length);
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}
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/**
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* @dev Get the address `account` is currently delegating to.
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*/
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function delegates(address account) public view virtual override returns (address) {
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function delegates(address account) public view virtual returns (address) {
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return _delegates[account];
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}
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/**
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* @dev Gets the current votes balance for `account`
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*/
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function getCurrentVotes(address account) external view override returns (uint256) {
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function getVotes(address account) public view returns (uint256) {
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uint256 pos = _checkpoints[account].length;
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return pos == 0 ? 0 : _checkpoints[account][pos - 1].votes;
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}
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@ -65,7 +82,7 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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*
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* - `blockNumber` must have been already mined
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*/
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function getPriorVotes(address account, uint256 blockNumber) external view override returns (uint256) {
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function getPastVotes(address account, uint256 blockNumber) public view returns (uint256) {
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require(blockNumber < block.number, "ERC20Votes: block not yet mined");
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return _checkpointsLookup(_checkpoints[account], blockNumber);
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}
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@ -78,7 +95,7 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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*
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* - `blockNumber` must have been already mined
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*/
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function getPriorTotalSupply(uint256 blockNumber) external view override returns (uint256) {
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function getPastTotalSupply(uint256 blockNumber) public view returns (uint256) {
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require(blockNumber < block.number, "ERC20Votes: block not yet mined");
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return _checkpointsLookup(_totalSupplyCheckpoints, blockNumber);
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}
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@ -115,7 +132,7 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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/**
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* @dev Delegate votes from the sender to `delegatee`.
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*/
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function delegate(address delegatee) public virtual override {
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function delegate(address delegatee) public virtual {
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return _delegate(_msgSender(), delegatee);
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}
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@ -123,7 +140,7 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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* @dev Delegates votes from signer to `delegatee`
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*/
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function delegateBySig(address delegatee, uint256 nonce, uint256 expiry, uint8 v, bytes32 r, bytes32 s)
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public virtual override
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public virtual
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{
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require(block.timestamp <= expiry, "ERC20Votes: signature expired");
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address signer = ECDSA.recover(
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@ -140,17 +157,24 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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}
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/**
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* @dev snapshot the totalSupply after it has been increassed.
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* @dev Maximum token supply. Defaults to `type(uint224).max` (2^224^ - 1).
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*/
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function _maxSupply() internal view virtual returns (uint224) {
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return type(uint224).max;
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}
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/**
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* @dev Snapshots the totalSupply after it has been increased.
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*/
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function _mint(address account, uint256 amount) internal virtual override {
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super._mint(account, amount);
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require(totalSupply() <= type(uint224).max, "ERC20Votes: total supply exceeds 2**224");
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require(totalSupply() <= _maxSupply(), "ERC20Votes: total supply risks overflowing votes");
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_writeCheckpoint(_totalSupplyCheckpoints, add, amount);
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}
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/**
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* @dev snapshot the totalSupply after it has been decreased.
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* @dev Snapshots the totalSupply after it has been decreased.
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*/
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function _burn(address account, uint256 amount) internal virtual override {
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super._burn(account, amount);
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@ -159,7 +183,9 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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}
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/**
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* @dev move voting power when tokens are transferred.
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* @dev Move voting power when tokens are transferred.
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*
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* Emits a {DelegateVotesChanged} event.
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*/
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function _beforeTokenTransfer(address from, address to, uint256 amount) internal virtual override {
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_moveVotingPower(delegates(from), delegates(to), amount);
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@ -167,6 +193,8 @@ abstract contract ERC20Votes is IERC20Votes, ERC20Permit {
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/**
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* @dev Change delegation for `delegator` to `delegatee`.
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*
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* Emits events {DelegateChanged} and {DelegateVotesChanged}.
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*/
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function _delegate(address delegator, address delegatee) internal virtual {
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address currentDelegate = delegates(delegator);
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46
contracts/token/ERC20/extensions/ERC20VotesComp.sol
Normal file
46
contracts/token/ERC20/extensions/ERC20VotesComp.sol
Normal file
@ -0,0 +1,46 @@
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// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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import "./ERC20Votes.sol";
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/**
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* @dev Extension of ERC20 to support Compound's voting and delegation. This version exactly matches Compound's
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* interface, with the drawback of only supporting supply up to (2^96^ - 1).
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*
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* NOTE: You should use this contract if you need exact compatibility with COMP (for example in order to use your token
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* with Governor Alpha or Bravo) and if you are sure the supply cap of 2^96^ is enough for you. Otherwise, use the
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* {ERC20Votes} variant of this module.
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*
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* This extensions keeps a history (checkpoints) of each account's vote power. Vote power can be delegated either
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* by calling the {delegate} function directly, or by providing a signature to be used with {delegateBySig}. Voting
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* power can be queried through the public accessors {getCurrentVotes} and {getPriorVotes}.
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*
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* By default, token balance does not account for voting power. This makes transfers cheaper. The downside is that it
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* requires users to delegate to themselves in order to activate checkpoints and have their voting power tracked.
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* Enabling self-delegation can easily be done by overriding the {delegates} function. Keep in mind however that this
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* will significantly increase the base gas cost of transfers.
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*
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* _Available since v4.2._
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*/
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abstract contract ERC20VotesComp is ERC20Votes {
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/**
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* @dev Comp version of the {getVotes} accessor, with `uint96` return type.
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*/
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function getCurrentVotes(address account) external view returns (uint96) {
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return SafeCast.toUint96(getVotes(account));
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}
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/**
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* @dev Comp version of the {getPastVotes} accessor, with `uint96` return type.
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*/
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function getPriorVotes(address account, uint256 blockNumber) external view returns (uint96) {
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return SafeCast.toUint96(getPastVotes(account, blockNumber));
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}
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/**
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* @dev Maximum token supply. Reduced to `type(uint96).max` (2^96^ - 1) to fit COMP interface.
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*/
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function _maxSupply() internal view virtual override returns (uint224) {
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return type(uint96).max;
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}
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}
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@ -1,24 +0,0 @@
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// SPDX-License-Identifier: MIT
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pragma solidity ^0.8.0;
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import "../IERC20.sol";
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interface IERC20Votes is IERC20 {
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struct Checkpoint {
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uint32 fromBlock;
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uint224 votes;
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}
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event DelegateChanged(address indexed delegator, address indexed fromDelegate, address indexed toDelegate);
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event DelegateVotesChanged(address indexed delegate, uint256 previousBalance, uint256 newBalance);
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function delegates(address owner) external view returns (address);
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function checkpoints(address account, uint32 pos) external view returns (Checkpoint memory);
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function numCheckpoints(address account) external view returns (uint32);
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function getCurrentVotes(address account) external view returns (uint256);
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function getPriorVotes(address account, uint256 blockNumber) external view returns (uint256);
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function getPriorTotalSupply(uint256 blockNumber) external view returns(uint256);
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function delegate(address delegatee) external;
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function delegateBySig(address delegatee, uint nonce, uint expiry, uint8 v, bytes32 r, bytes32 s) external;
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}
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