Make ERC20Votes independent from ERC20Permit

CHANGELOG.md

@@ -3,6 +3,8 @@
 ## Unreleased (Breaking)
 
  * `TimelockController`: Changed the role architecture to use `DEFAULT_ADMIN_ROLE` as the admin for all roles, instead of the bespoke `TIMELOCK_ADMIN_ROLE` that was used previously. This aligns with the general recommendation for `AccessControl` and makes the addition of new roles easier. Accordingly, the `admin` parameter and timelock will now be granted `DEFAULT_ADMIN_ROLE` instead of `TIMELOCK_ADMIN_ROLE`. ([#3799](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3799))
+ * `ERC20Votes`: Changed internal vote accounting to reusable `Votes` module previously used by `ERC721Votes`. Removed implicit `ERC20Permit` inheritance. [#3816](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3816)
+ * `Nonces`: Added a new contract to keep track of user nonces. Used for signatures in `ERC20Permit`, `ERC20Votes`, and `ERC721Votes`. ([#3816](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3816))
  * Removed presets in favor of [OpenZeppelin Contracts Wizard](https://wizard.openzeppelin.com/).
  * `TransparentUpgradeableProxy`: Removed `admin` and `implementation` getters, which were only callable by the proxy owner and thus not very useful. ([#3820](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3820))
  * `ProxyAdmin`: Removed `getProxyAdmin` and `getProxyImplementation` getters. ([#3820](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3820))

contracts/governance/utils/Votes.sol

@@ -3,10 +3,11 @@
 pragma solidity ^0.8.0;
 
 import "../../utils/Context.sol";
-import "../../utils/Counters.sol";
+import "../../utils/Nonces.sol";
 import "../../utils/Checkpoints.sol";
 import "../../utils/cryptography/EIP712.sol";
 import "./IVotes.sol";
+import "../../utils/math/SafeCast.sol";
 
 /**
  * @dev This is a base abstract contract that tracks voting units, which are a measure of voting power that can be
@@ -28,9 +29,8 @@ import "./IVotes.sol";
  *
  * _Available since v4.5._
  */
-abstract contract Votes is IVotes, Context, EIP712 {
+abstract contract Votes is IVotes, Context, EIP712, Nonces {
     using Checkpoints for Checkpoints.History;
-    using Counters for Counters.Counter;
 
     bytes32 private constant _DELEGATION_TYPEHASH =
         keccak256("Delegation(address delegatee,uint256 nonce,uint256 expiry)");
@@ -39,8 +39,6 @@ abstract contract Votes is IVotes, Context, EIP712 {
     mapping(address => Checkpoints.History) private _delegateCheckpoints;
     Checkpoints.History private _totalCheckpoints;
 
-    mapping(address => Counters.Counter) private _nonces;
-
     /**
      * @dev Returns the current amount of votes that `account` has.
      */
@@ -170,30 +168,26 @@ abstract contract Votes is IVotes, Context, EIP712 {
         }
     }
 
-    function _add(uint256 a, uint256 b) private pure returns (uint256) {
-        return a + b;
-    }
-
-    function _subtract(uint256 a, uint256 b) private pure returns (uint256) {
-        return a - b;
-    }
-
     /**
-     * @dev Consumes a nonce.
-     *
-     * Returns the current value and increments nonce.
+     * @dev Get number of checkpoints for `account`.
      */
-    function _useNonce(address owner) internal virtual returns (uint256 current) {
-        Counters.Counter storage nonce = _nonces[owner];
-        current = nonce.current();
-        nonce.increment();
+    function _numCheckpoints(address account) internal view virtual returns (uint32) {
+        return SafeCast.toUint32(_delegateCheckpoints[account].length());
     }
 
     /**
-     * @dev Returns an address nonce.
+     * @dev Get the `pos`-th checkpoint for `account`.
      */
-    function nonces(address owner) public view virtual returns (uint256) {
-        return _nonces[owner].current();
+    function _checkpoints(address account, uint32 pos) internal view virtual returns (Checkpoints.Checkpoint memory) {
+        return _delegateCheckpoints[account].getAtPosition(pos);
+    }
+
+    function _add(uint256 a, uint256 b) private pure returns (uint256) {
+        return a + b;
+    }
+
+    function _subtract(uint256 a, uint256 b) private pure returns (uint256) {
+        return a - b;
     }
 
     /**

contracts/mocks/ERC20VotesCompMock.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.0;
 import "../token/ERC20/extensions/ERC20VotesComp.sol";
 
 contract ERC20VotesCompMock is ERC20VotesComp {
-    constructor(string memory name, string memory symbol) ERC20(name, symbol) ERC20Permit(name) {}
+    constructor(string memory name, string memory symbol) ERC20(name, symbol) EIP712(name, "1") {}
 
     function mint(address account, uint256 amount) public {
         _mint(account, amount);

contracts/mocks/ERC20VotesMock.sol

@@ -5,7 +5,7 @@ pragma solidity ^0.8.0;
 import "../token/ERC20/extensions/ERC20Votes.sol";
 
 contract ERC20VotesMock is ERC20Votes {
-    constructor(string memory name, string memory symbol) ERC20(name, symbol) ERC20Permit(name) {}
+    constructor(string memory name, string memory symbol) ERC20(name, symbol) EIP712(name, "1") {}
 
     function mint(address account, uint256 amount) public {
         _mint(account, amount);

contracts/mocks/ERC721VotesMock.sol

@@ -15,7 +15,7 @@ contract ERC721VotesMock is ERC721Votes {
         _mint(account, tokenId);
     }
 
-    function burn(uint256 tokenId) public {
+    function burn(address, uint256 tokenId) public {
         _burn(tokenId);
     }
 

contracts/mocks/NoncesImpl.sol

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+import "../utils/Nonces.sol";
+
+contract NoncesImpl is Nonces {
+    function useNonce(address owner) public {
+        super._useNonce(owner);
+    }
+}

contracts/mocks/VotesMock.sol

@@ -28,7 +28,7 @@ contract VotesMock is Votes {
         _transferVotingUnits(address(0), account, 1);
     }
 
-    function burn(uint256 voteId) external {
+    function burn(address, uint256 voteId) external {
         address owner = _owners[voteId];
         _balances[owner] -= 1;
         _transferVotingUnits(owner, address(0), 1);

contracts/token/ERC20/extensions/ERC20Permit.sol

@@ -7,7 +7,7 @@ import "./IERC20Permit.sol";
 import "../ERC20.sol";
 import "../../../utils/cryptography/ECDSA.sol";
 import "../../../utils/cryptography/EIP712.sol";
-import "../../../utils/Counters.sol";
+import "../../../utils/Nonces.sol";
 
 /**
  * @dev Implementation of the ERC20 Permit extension allowing approvals to be made via signatures, as defined in
@@ -19,11 +19,7 @@ import "../../../utils/Counters.sol";
  *
  * _Available since v3.4._
  */
-abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
-    using Counters for Counters.Counter;
-
-    mapping(address => Counters.Counter) private _nonces;
-
+abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712, Nonces {
     // solhint-disable-next-line var-name-mixedcase
     bytes32 private constant _PERMIT_TYPEHASH =
         keccak256("Permit(address owner,address spender,uint256 value,uint256 nonce,uint256 deadline)");
@@ -70,8 +66,8 @@ abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
     /**
      * @dev See {IERC20Permit-nonces}.
      */
-    function nonces(address owner) public view virtual override returns (uint256) {
-        return _nonces[owner].current();
+    function nonces(address owner) public view virtual override(IERC20Permit, Nonces) returns (uint256) {
+        return super.nonces(owner);
     }
 
     /**
@@ -81,15 +77,4 @@ abstract contract ERC20Permit is ERC20, IERC20Permit, EIP712 {
     function DOMAIN_SEPARATOR() external view override returns (bytes32) {
         return _domainSeparatorV4();
     }
-
-    /**
-     * @dev "Consume a nonce": return the current value and increment.
-     *
-     * _Available since v4.1._
-     */
-    function _useNonce(address owner) internal virtual returns (uint256 current) {
-        Counters.Counter storage nonce = _nonces[owner];
-        current = nonce.current();
-        nonce.increment();
-    }
 }