feat: add OptimismMintableFiatTokenV2_2 for compatibility with IOptimismMintableERC20

.env.example

@@ -79,3 +79,6 @@ BLACKLIST_FILE_NAME=blacklist.remote.json
 
 # [OPTIONAL] The API key to an Etherscan flavor block explorer.
 # ETHERSCAN_KEY=
+
+# The address of the corresponding token contract on L1
+L1_REMOTE_TOKEN=

@types/AnyFiatTokenV2Instance.d.ts

@@ -19,6 +19,7 @@
 import { FiatTokenV2Instance } from "./generated/FiatTokenV2";
 import { FiatTokenV2_1Instance } from "./generated/FiatTokenV2_1";
 import { FiatTokenV2_2Instance } from "./generated/FiatTokenV2_2";
+import { OptimismMintableFiatTokenV2_2Instance } from "./generated/OptimismMintableFiatTokenV2_2";
 
 export interface FiatTokenV2_2InstanceExtended extends FiatTokenV2_2Instance {
   permit?: typeof FiatTokenV2Instance.permit;
@@ -27,7 +28,16 @@ export interface FiatTokenV2_2InstanceExtended extends FiatTokenV2_2Instance {
   cancelAuthorization?: typeof FiatTokenV2Instance.cancelAuthorization;
 }
 
+export interface OptimismMintableFiatTokenV2_2InstanceExtended
+  extends OptimismMintableFiatTokenV2_2Instance {
+  permit?: typeof FiatTokenV2Instance.permit;
+  transferWithAuthorization?: typeof FiatTokenV2Instance.transferWithAuthorization;
+  receiveWithAuthorization?: typeof FiatTokenV2Instance.receiveWithAuthorization;
+  cancelAuthorization?: typeof FiatTokenV2Instance.cancelAuthorization;
+}
+
 export type AnyFiatTokenV2Instance =
   | FiatTokenV2Instance
   | FiatTokenV2_1Instance
-  | FiatTokenV2_2InstanceExtended;
+  | FiatTokenV2_2InstanceExtended
+  | OptimismMintableFiatTokenV2_2InstanceExtended;

contracts/v2/IOptimismMintableFiatToken.sol

@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.6.12;
+
+import { IERC165 } from "@openzeppelin/contracts/introspection/IERC165.sol";
+
+/**
+ * @title IOptimismMintableERC20
+ * @notice This interface is available on the OptimismMintableERC20 contract.
+ *         We declare it as a separate interface so that it can be used in
+ *         custom implementations of OptimismMintableERC20.
+ * @notice From https://github.com/ethereum-optimism/optimism/blob/6b231760b3f352d5c4f6df8431b67d836f316f84/packages/contracts-bedrock/src/universal/IOptimismMintableERC20.sol#L10-L18
+ */
+interface IOptimismMintableERC20 is IERC165 {
+    function remoteToken() external view returns (address);
+
+    function bridge() external returns (address);
+
+    function mint(address _to, uint256 _amount) external;
+
+    function burn(address _from, uint256 _amount) external;
+}
+
+/**
+ * @title IOptimismMintableFiatToken
+ * @author Lattice (https://lattice.xyz)
+ * @notice This interface adds the functions from IOptimismMintableERC20 missing from FiatTokenV2_2.
+ *         It doesn't include `mint(address _to, uint256 _amount)`, as this function already exists
+ *         on FiatTokenV2_2 (from FiatTokenV1), and can't be overridden. The only difference is a
+ *         (bool) return type for the FiatTokenV1 version, which doesn't matter for consumers of
+ *         IOptimismMintableERC20 that don't expect a return type.
+ */
+interface IOptimismMintableFiatToken is IERC165 {
+    function remoteToken() external view returns (address);
+
+    function bridge() external returns (address);
+
+    function burn(address _from, uint256 _amount) external;
+}

contracts/v2/OptimismMintableFiatTokenV2_2.sol

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.6.12;
+
+import { FiatTokenV1 } from "../v1/FiatTokenV1.sol";
+import { FiatTokenV2_2 } from "./FiatTokenV2_2.sol";
+import {
+    IOptimismMintableERC20,
+    IOptimismMintableFiatToken
+} from "./IOptimismMintableFiatToken.sol";
+import { IERC165 } from "@openzeppelin/contracts/introspection/IERC165.sol";
+
+/**
+ * @title OptimismMintableFiatTokenV2_2
+ * @author Lattice (https://lattice.xyz)
+ * @notice Adds compatibility with IOptimismMintableERC20 to the Bridged USDC Standard,
+ *         so it can be used with Optimism's StandardBridge.
+ */
+contract OptimismMintableFiatTokenV2_2 is
+    FiatTokenV2_2,
+    IOptimismMintableFiatToken
+{
+    address private immutable l1RemoteToken;
+
+    constructor(address _l1RemoteToken) public FiatTokenV2_2() {
+        l1RemoteToken = _l1RemoteToken;
+    }
+
+    function remoteToken() external override view returns (address) {
+        return l1RemoteToken;
+    }
+
+    function bridge() external override returns (address) {
+        // OP Stack L2StandardBridge predeploy
+        // https://specs.optimism.io/protocol/predeploys.html
+        return address(0x4200000000000000000000000000000000000010);
+    }
+
+    function supportsInterface(bytes4 interfaceId)
+        external
+        override
+        view
+        returns (bool)
+    {
+        return
+            interfaceId == type(IOptimismMintableERC20).interfaceId ||
+            interfaceId == type(IERC165).interfaceId;
+    }
+
+    /**
+     * @notice Allows a minter to burn tokens for the given account.
+     * @dev The caller must be a minter, must not be blacklisted, and the amount to burn
+     *      should be less than or equal to the account's balance.
+     *      The function is a requirement for IOptimismMintableERC20.
+     *      It is mostly equivalent to FiatTokenV1.burn, with the only change being
+     *      the additional _from parameter to burn from instead of burning from msg.sender.
+     * @param _amount the amount of tokens to be burned.
+     */
+    function burn(address _from, uint256 _amount)
+        external
+        override
+        whenNotPaused
+        onlyMinters
+        notBlacklisted(msg.sender)
+    {
+        uint256 balance = _balanceOf(_from);
+        require(_amount > 0, "FiatToken: burn amount not greater than 0");
+        require(balance >= _amount, "FiatToken: burn amount exceeds balance");
+
+        totalSupply_ = totalSupply_.sub(_amount);
+        _setBalance(_from, balance.sub(_amount));
+        emit Burn(_from, _amount);
+        emit Transfer(_from, address(0), _amount);
+    }
+}

scripts/deploy/DeployImpl.sol

@@ -19,6 +19,9 @@
 pragma solidity 0.6.12;
 
 import { FiatTokenV2_2 } from "../../contracts/v2/FiatTokenV2_2.sol";
+import {
+    OptimismMintableFiatTokenV2_2
+} from "../../contracts/v2/OptimismMintableFiatTokenV2_2.sol";
 
 /**
  * @notice A utility contract that exposes a re-useable getOrDeployImpl function.
@@ -63,4 +66,49 @@ contract DeployImpl {
 
         return fiatTokenV2_2;
     }
+
+    /**
+     * @notice helper function that either
+     * 1) deploys the implementation contract if the input is the zero address, or
+     * 2) loads an instance of an existing contract when input is not the zero address.
+     *
+     * @param impl configured of the implementation contract, where address(0) represents a new instance should be deployed
+     * @param l1RemoteToken token on the L1 corresponding to this bridged version of the token
+     * @return OptimismMintableFiatTokenV2_2 newly deployed or loaded instance
+     */
+    function getOrDeployImpl(address impl, address l1RemoteToken)
+        internal
+        returns (FiatTokenV2_2)
+    {
+        OptimismMintableFiatTokenV2_2 fiatTokenV2_2;
+
+        if (impl == address(0)) {
+            fiatTokenV2_2 = new OptimismMintableFiatTokenV2_2(l1RemoteToken);
+
+            // Initializing the implementation contract with dummy values here prevents
+            // the contract from being reinitialized later on with different values.
+            // Dummy values can be used here as the proxy contract will store the actual values
+            // for the deployed token.
+            fiatTokenV2_2.initialize({
+                tokenName: "",
+                tokenSymbol: "",
+                tokenCurrency: "",
+                tokenDecimals: 0,
+                newMasterMinter: THROWAWAY_ADDRESS,
+                newPauser: THROWAWAY_ADDRESS,
+                newBlacklister: THROWAWAY_ADDRESS,
+                newOwner: THROWAWAY_ADDRESS
+            });
+            fiatTokenV2_2.initializeV2({ newName: "" });
+            fiatTokenV2_2.initializeV2_1({ lostAndFound: THROWAWAY_ADDRESS });
+            fiatTokenV2_2.initializeV2_2({
+                accountsToBlacklist: new address[](0),
+                newSymbol: ""
+            });
+        } else {
+            fiatTokenV2_2 = OptimismMintableFiatTokenV2_2(impl);
+        }
+
+        return fiatTokenV2_2;
+    }
 }

scripts/deploy/deploy-fiat-token.s.sol

@@ -23,6 +23,9 @@ import { Script } from "forge-std/Script.sol";
 import { DeployImpl } from "./DeployImpl.sol";
 import { FiatTokenProxy } from "../../contracts/v1/FiatTokenProxy.sol";
 import { FiatTokenV2_2 } from "../../contracts/v2/FiatTokenV2_2.sol";
+import {
+    OptimismMintableFiatTokenV2_2
+} from "../../contracts/v2/OptimismMintableFiatTokenV2_2.sol";
 import { MasterMinter } from "../../contracts/minting/MasterMinter.sol";
 
 /**
@@ -49,6 +52,8 @@ contract DeployFiatToken is Script, DeployImpl {
 
     uint256 private deployerPrivateKey;
 
+    address l1RemoteToken;
+
     /**
      * @notice initialize variables from environment
      */
@@ -70,6 +75,8 @@ contract DeployFiatToken is Script, DeployImpl {
 
         deployerPrivateKey = vm.envUint("DEPLOYER_PRIVATE_KEY");
 
+        l1RemoteToken = vm.envOr("L1_REMOTE_TOKEN", address(0));
+
         console.log("TOKEN_NAME: '%s'", tokenName);
         console.log("TOKEN_SYMBOL: '%s'", tokenSymbol);
         console.log("TOKEN_CURRENCY: '%s'", tokenCurrency);
@@ -81,6 +88,7 @@ contract DeployFiatToken is Script, DeployImpl {
         console.log("PAUSER_ADDRESS: '%s'", pauser);
         console.log("BLACKLISTER_ADDRESS: '%s'", blacklister);
         console.log("LOST_AND_FOUND_ADDRESS: '%s'", lostAndFound);
+        console.log("L1_REMOTE_TOKEN: '%s'", l1RemoteToken);
     }
 
     /**
@@ -99,7 +107,13 @@ contract DeployFiatToken is Script, DeployImpl {
         // If there is an existing implementation contract,
         // we can simply point the newly deployed proxy contract to it.
         // Otherwise, deploy the latest implementation contract code to the network.
-        FiatTokenV2_2 fiatTokenV2_2 = getOrDeployImpl(_impl);
+        // If l1RemoteToken is set, deploy an OptimimsFiatToken.
+        FiatTokenV2_2 fiatTokenV2_2;
+        if (l1RemoteToken != address(0)) {
+            fiatTokenV2_2 = getOrDeployImpl(_impl, l1RemoteToken);
+        } else {
+            fiatTokenV2_2 = getOrDeployImpl(_impl);
+        }
 
         FiatTokenProxy proxy = new FiatTokenProxy(address(fiatTokenV2_2));
 

scripts/deploy/set-l2-standard-bridge.s.sol

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+pragma solidity 0.6.12;
+
+import "forge-std/console.sol"; // solhint-disable no-global-import, no-console
+import { Script } from "forge-std/Script.sol";
+import {
+    OptimismMintableFiatTokenV2_2
+} from "../../contracts/v2/OptimismMintableFiatTokenV2_2.sol";
+import { MasterMinter } from "../../contracts/minting/MasterMinter.sol";
+
+/**
+ * A utility script to set the token's l2StandardBridge as the minter
+ */
+contract SetL2StandardBridge is Script {
+    /**
+     * @notice main function that will be run by forge
+     */
+    function run(
+        address masterMinterOwner,
+        OptimismMintableFiatTokenV2_2 optimismMintableFiatTokenV2_2
+    ) external {
+        address l2StandardBridge = optimismMintableFiatTokenV2_2.bridge();
+        if (l2StandardBridge == address(0)) {
+            revert("Expected no-zero bridge address");
+        }
+        MasterMinter masterMinter = MasterMinter(
+            optimismMintableFiatTokenV2_2.masterMinter()
+        );
+
+        vm.startBroadcast(masterMinterOwner);
+        masterMinter.configureController(masterMinterOwner, l2StandardBridge);
+        masterMinter.configureMinter(type(uint256).max);
+        masterMinter.removeController(masterMinterOwner);
+        vm.stopBroadcast();
+    }
+}

test/helpers/index.ts

@@ -26,6 +26,7 @@ import {
   FiatTokenV2_1Instance,
   FiatTokenV2_2Instance,
   FiatTokenV2Instance,
+  OptimismMintableFiatTokenV2_2Instance,
 } from "../../@types/generated";
 import _ from "lodash";
 
@@ -140,7 +141,8 @@ export async function initializeToVersion(
     | FiatTokenV1_1Instance
     | FiatTokenV2Instance
     | FiatTokenV2_1Instance
-    | FiatTokenV2_2Instance,
+    | FiatTokenV2_2Instance
+    | OptimismMintableFiatTokenV2_2Instance,
   version: "1" | "1.1" | "2" | "2.1" | "2.2",
   fiatTokenOwner: string,
   lostAndFound: string,

test/helpers/storageSlots.behavior.ts

@@ -26,6 +26,9 @@ const FiatTokenV1_1 = artifacts.require("FiatTokenV1_1");
 const FiatTokenV2 = artifacts.require("FiatTokenV2");
 const FiatTokenV2_1 = artifacts.require("FiatTokenV2_1");
 const FiatTokenV2_2 = artifacts.require("FiatTokenV2_2");
+const OptimismMintableFiatTokenV2_2 = artifacts.require(
+  "OptimismMintableFiatTokenV2_2"
+);
 
 export const STORAGE_SLOT_NUMBERS = {
   _deprecatedBlacklisted: 3,
@@ -37,9 +40,11 @@ export function usesOriginalStorageSlotPositions<
 >({
   Contract,
   version,
+  constructorArgs,
 }: {
   Contract: Truffle.Contract<T>;
   version: 1 | 1.1 | 2 | 2.1 | 2.2;
+  constructorArgs?: unknown[];
 }): void {
   describe("uses original storage slot positions", () => {
     const [name, symbol, currency, decimals] = ["USD Coin", "USDC", "USD", 6];
@@ -71,7 +76,7 @@ export function usesOriginalStorageSlotPositions<
     let domainSeparator: string;
 
     beforeEach(async () => {
-      fiatToken = await Contract.new();
+      fiatToken = await Contract.new(...(constructorArgs || []));
       proxy = await FiatTokenProxy.new(fiatToken.address);
       await proxy.changeAdmin(proxyAdmin);
 
@@ -113,7 +118,9 @@ export function usesOriginalStorageSlotPositions<
         await proxyAsFiatTokenV2_1.initializeV2_1(lostAndFound);
       }
       if (version >= 2.2) {
-        const proxyAsFiatTokenV2_2 = await FiatTokenV2_2.at(proxy.address);
+        const proxyAsFiatTokenV2_2 = constructorArgs
+          ? await OptimismMintableFiatTokenV2_2.at(proxy.address)
+          : await FiatTokenV2_2.at(proxy.address);
         await proxyAsFiatTokenV2_2.initializeV2_2([], symbol);
       }
     });

test/misc/gas.ts

@@ -119,13 +119,17 @@ describe(`gas costs for version ${TARGET_VERSION}`, () => {
   });
 
   it("burn() entire balance", async () => {
-    const tx = await fiatToken.burn(entireBalance, { from: fiatTokenOwner });
-    console.log(consoleMessage, tx.receipt.gasUsed);
+    if ("burn" in fiatToken) {
+      const tx = await fiatToken.burn(entireBalance, { from: fiatTokenOwner });
+      console.log(consoleMessage, tx.receipt.gasUsed);
+    }
   });
 
   it("burn() partial balance", async () => {
-    const tx = await fiatToken.burn(partialBalance, { from: fiatTokenOwner });
-    console.log(consoleMessage, tx.receipt.gasUsed);
+    if ("burn" in fiatToken) {
+      const tx = await fiatToken.burn(partialBalance, { from: fiatTokenOwner });
+      console.log(consoleMessage, tx.receipt.gasUsed);
+    }
   });
 
   it("transfer() where both parties have a balance before and after", async () => {