feat(protocol): remove ERC20SnapshotUpgradeable from TaikoToken and BrigedERC20 tokens

packages/protocol/contracts/L1/TaikoToken.sol

@@ -2,18 +2,25 @@
 pragma solidity 0.8.24;
 
 import "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
-import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20SnapshotUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20VotesUpgradeable.sol";
 import "../common/EssentialContract.sol";
 import "../common/LibStrings.sol";
 
+/// @notice TaikoToken was `EssentialContract, ERC20SnapshotUpgradeable, ERC20VotesUpgradeable`.
+/// We use this contract to take 50 more slots to remove `ERC20SnapshotUpgradeable` from the parent
+/// contract list.
+/// We can simplify the code since we no longer need to maintain upgradability with Hekla.
+abstract contract EssentialContract_ is EssentialContract {
+    uint256[50] private __slots_previously_used_by_ERC20SnapshotUpgradeable;
+}
+
 /// @title TaikoToken
 /// @notice The TaikoToken (TKO), in the protocol is used for prover collateral
 /// in the form of bonds. It is an ERC20 token with 18 decimal places of
 /// precision.
 /// @dev Labeled in AddressResolver as "taiko_token"
 /// @custom:security-contact [email protected]
-contract TaikoToken is EssentialContract, ERC20SnapshotUpgradeable, ERC20VotesUpgradeable {
+contract TaikoToken is EssentialContract_, ERC20VotesUpgradeable {
     uint256[50] private __gap;
 
     error TKO_INVALID_ADDR();
@@ -37,7 +44,6 @@ contract TaikoToken is EssentialContract, ERC20SnapshotUpgradeable, ERC20VotesUp
         __Essential_init(_owner, _addressManager);
         __Context_init_unchained();
         __ERC20_init(_name, _symbol);
-        __ERC20Snapshot_init();
         __ERC20Votes_init();
         __ERC20Permit_init(_name);
 
@@ -78,46 +84,4 @@ contract TaikoToken is EssentialContract, ERC20SnapshotUpgradeable, ERC20VotesUp
         if (_to == address(this)) revert TKO_INVALID_ADDR();
         return super.transferFrom(_from, _to, _amount);
     }
-
-    function _beforeTokenTransfer(
-        address _from,
-        address _to,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20SnapshotUpgradeable)
-    {
-        return super._beforeTokenTransfer(_from, _to, _amount);
-    }
-
-    function _afterTokenTransfer(
-        address _from,
-        address _to,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable)
-    {
-        return super._afterTokenTransfer(_from, _to, _amount);
-    }
-
-    function _mint(
-        address _to,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable)
-    {
-        return super._mint(_to, _amount);
-    }
-
-    function _burn(
-        address _from,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable)
-    {
-        return super._burn(_from, _amount);
-    }
 }

packages/protocol/contracts/tokenvault/BridgedERC20.sol

@@ -1,16 +1,23 @@
 // SPDX-License-Identifier: MIT
 pragma solidity 0.8.24;
 
-import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20SnapshotUpgradeable.sol";
 import "@openzeppelin/contracts-upgradeable/token/ERC20/extensions/ERC20VotesUpgradeable.sol";
 import "./LibBridgedToken.sol";
 import "./BridgedERC20Base.sol";
 
+/// @notice BridgedERC20 was `BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesUpgradeable`.
+/// We use this contract to take 50 more slots to remove `ERC20SnapshotUpgradeable` from the parent
+/// contract list.
+/// We can simplify the code since we no longer need to maintain upgradability with Hekla.
+abstract contract BridgedERC20Base_ is BridgedERC20Base {
+    uint256[50] private __slots_previously_used_by_ERC20SnapshotUpgradeable;
+}
+
 /// @title BridgedERC20
 /// @notice An upgradeable ERC20 contract that represents tokens bridged from
 /// another chain.
 /// @custom:security-contact [email protected]
-contract BridgedERC20 is BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesUpgradeable {
+contract BridgedERC20 is BridgedERC20Base_, ERC20VotesUpgradeable {
     /// @dev Slot 1.
     address public srcToken;
 
@@ -20,7 +27,7 @@ contract BridgedERC20 is BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesU
     uint256 public srcChainId;
 
     /// @dev Slot 3.
-    address public snapshooter;
+    address private __deprecated1;
 
     uint256[47] private __gap;
 
@@ -50,7 +57,6 @@ contract BridgedERC20 is BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesU
         LibBridgedToken.validateInputs(_srcToken, _srcChainId, _symbol, _name);
         __Essential_init(_owner, _addressManager);
         __ERC20_init(_name, _symbol);
-        __ERC20Snapshot_init();
         __ERC20Votes_init();
         __ERC20Permit_init(_name);
 
@@ -85,38 +91,18 @@ contract BridgedERC20 is BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesU
         return (srcToken, srcChainId);
     }
 
-    /// @dev For ERC20SnapshotUpgradeable and ERC20VotesUpgradeable, need to implement the following
-    /// functions
-    function _beforeTokenTransfer(
-        address _from,
-        address _to,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20SnapshotUpgradeable)
-    {
+    function _beforeTokenTransfer(address _from, address _to, uint256 _amount) internal override {
         if (_to == address(this)) revert BTOKEN_CANNOT_RECEIVE();
         if (paused()) revert INVALID_PAUSE_STATUS();
         return super._beforeTokenTransfer(_from, _to, _amount);
     }
 
-    function _afterTokenTransfer(
-        address _from,
-        address _to,
-        uint256 _amount
-    )
-        internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable)
-    {
-        return super._afterTokenTransfer(_from, _to, _amount);
-    }
-
     function _mint(
         address _to,
         uint256 _amount
     )
         internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable, BridgedERC20Base)
+        override(BridgedERC20Base, ERC20VotesUpgradeable)
     {
         return super._mint(_to, _amount);
     }
@@ -126,7 +112,7 @@ contract BridgedERC20 is BridgedERC20Base, ERC20SnapshotUpgradeable, ERC20VotesU
         uint256 _amount
     )
         internal
-        override(ERC20Upgradeable, ERC20VotesUpgradeable, BridgedERC20Base)
+        override(BridgedERC20Base, ERC20VotesUpgradeable)
     {
         return super._burn(_from, _amount);
     }

packages/protocol/contracts/tokenvault/BridgedERC721.sol

@@ -84,13 +84,13 @@ contract BridgedERC721 is EssentialContract, ERC721Upgradeable {
 
     /// @notice Gets the name of the token.
     /// @return The name.
-    function name() public view override(ERC721Upgradeable) returns (string memory) {
+    function name() public view override returns (string memory) {
         return LibBridgedToken.buildName(super.name(), srcChainId);
     }
 
     /// @notice Gets the symbol of the bridged token.
     /// @return The symbol.
-    function symbol() public view override(ERC721Upgradeable) returns (string memory) {
+    function symbol() public view override returns (string memory) {
         return LibBridgedToken.buildSymbol(super.symbol());
     }