Feat: OptimismMintableUpgradableERC20

packages/contracts-bedrock/src/universal/OptimismMintableUpgradableERC20.sol

@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.8.15;
+
+import { ERC20Upgradeable } from "@openzeppelin/contracts-upgradeable/token/ERC20/ERC20Upgradeable.sol";
+import { IERC165 } from "@openzeppelin/contracts/utils/introspection/IERC165.sol";
+import { Initializable } from "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
+import { ILegacyMintableERC20, IOptimismMintableERC20 } from "src/universal/IOptimismMintableERC20.sol";
+import { ISemver } from "src/universal/ISemver.sol";
+
+/// @title OptimismMintableUpgradableERC20
+/// @notice OptimismMintableUpgradableERC20 is a standard extension of the base ERC20 token contract designed
+///         to allow the StandardBridge contracts to mint and burn tokens. This makes it possible to
+///         use an OptimismMintablERC20 as the L2 representation of an L1 token, or vice-versa.
+///         Designed to be backwards compatible with the older StandardL2ERC20 token which was only
+///         meant for use on L2.
+contract OptimismMintableUpgradableERC20 is Initializable, IOptimismMintableERC20, ILegacyMintableERC20, ERC20Upgradeable, ISemver {
+    /// @notice Address of the corresponding version of this token on the remote chain.
+    /// @notice Breaking the naming convention to remain as close as possible to the non-
+    ///         upgradable version (where this is immutable)
+    address public REMOTE_TOKEN;
+
+    /// @notice Address of the StandardBridge on this network.
+    /// @notice Breaking the naming convention to remain as close as possible to the non-
+    ///         upgradable version (where this is immutable)
+    address public BRIDGE;
+
+    /// @notice Decimals of the token
+    /// @notice Breaking the naming convention to remain as close as possible to the non-
+    ///         upgradable version (where this is immutable)
+    uint8 private DECIMALS;
+
+    /// @notice Emitted whenever tokens are minted for an account.
+    /// @param account Address of the account tokens are being minted for.
+    /// @param amount  Amount of tokens minted.
+    event Mint(address indexed account, uint256 amount);
+
+    /// @notice Emitted whenever tokens are burned from an account.
+    /// @param account Address of the account tokens are being burned from.
+    /// @param amount  Amount of tokens burned.
+    event Burn(address indexed account, uint256 amount);
+
+    /// @notice A modifier that only allows the bridge to call
+    modifier onlyBridge() {
+        require(msg.sender == BRIDGE, "OptimismMintableERC20: only bridge can mint and burn");
+        _;
+    }
+
+    /// @notice Semantic version.
+    /// @custom:semver 1.3.0
+    string public constant version = "1.3.0";
+
+    constructor() {
+        _disableInitializers();
+    }
+
+    /// @param _bridge      Address of the L2 standard bridge.
+    /// @param _remoteToken Address of the corresponding L1 token.
+    /// @param _name        ERC20 name.
+    /// @param _symbol      ERC20 symbol.
+    function initialize(
+        address _bridge,
+        address _remoteToken,
+        string memory _name,
+        string memory _symbol,
+        uint8 _decimals
+    ) initializer public
+    {
+        __ERC20_init(_name, _symbol);
+        REMOTE_TOKEN = _remoteToken;
+        BRIDGE = _bridge;
+        DECIMALS = _decimals;
+    }
+
+    /// @notice Allows the StandardBridge on this network to mint tokens.
+    /// @param _to     Address to mint tokens to.
+    /// @param _amount Amount of tokens to mint.
+    function mint(
+        address _to,
+        uint256 _amount
+    )
+        external
+        virtual
+        override(IOptimismMintableERC20, ILegacyMintableERC20)
+        onlyBridge
+    {
+        _mint(_to, _amount);
+        emit Mint(_to, _amount);
+    }
+
+    /// @notice Allows the StandardBridge on this network to burn tokens.
+    /// @param _from   Address to burn tokens from.
+    /// @param _amount Amount of tokens to burn.
+    function burn(
+        address _from,
+        uint256 _amount
+    )
+        external
+        virtual
+        override(IOptimismMintableERC20, ILegacyMintableERC20)
+        onlyBridge
+    {
+        _burn(_from, _amount);
+        emit Burn(_from, _amount);
+    }
+
+    /// @notice ERC165 interface check function.
+    /// @param _interfaceId Interface ID to check.
+    /// @return Whether or not the interface is supported by this contract.
+    function supportsInterface(bytes4 _interfaceId) external pure virtual returns (bool) {
+        bytes4 iface1 = type(IERC165).interfaceId;
+        // Interface corresponding to the legacy L2StandardERC20.
+        bytes4 iface2 = type(ILegacyMintableERC20).interfaceId;
+        // Interface corresponding to the updated OptimismMintableERC20 (this contract).
+        bytes4 iface3 = type(IOptimismMintableERC20).interfaceId;
+        return _interfaceId == iface1 || _interfaceId == iface2 || _interfaceId == iface3;
+    }
+
+    /// @custom:legacy
+    /// @notice Legacy getter for the remote token. Use REMOTE_TOKEN going forward.
+    function l1Token() public view returns (address) {
+        return REMOTE_TOKEN;
+    }
+
+    /// @custom:legacy
+    /// @notice Legacy getter for the bridge. Use BRIDGE going forward.
+    function l2Bridge() public view returns (address) {
+        return BRIDGE;
+    }
+
+    /// @custom:legacy
+    /// @notice Legacy getter for REMOTE_TOKEN.
+    function remoteToken() public view returns (address) {
+        return REMOTE_TOKEN;
+    }
+
+    /// @custom:legacy
+    /// @notice Legacy getter for BRIDGE.
+    function bridge() public view returns (address) {
+        return BRIDGE;
+    }
+
+    /// @dev Returns the number of decimals used to get its user representation.
+    /// For example, if `decimals` equals `2`, a balance of `505` tokens should
+    /// be displayed to a user as `5.05` (`505 / 10 ** 2`).
+    /// NOTE: This information is only used for _display_ purposes: it in
+    /// no way affects any of the arithmetic of the contract, including
+    /// {IERC20-balanceOf} and {IERC20-transfer}.
+    function decimals() public view override returns (uint8) {
+        return DECIMALS;
+    }
+}