feat:POL token migration

contracts/common/tokens/POLTokenMock.sol

@@ -0,0 +1,56 @@
+pragma solidity ^0.5.2;
+
+import "openzeppelin-solidity/contracts/token/ERC20/ERC20Mintable.sol";
+import "openzeppelin-solidity/contracts/utils/Address.sol";
+
+
+contract POLTokenMock is ERC20Mintable {
+    using Address for address;
+
+    // detailed ERC20
+    string public name;
+    string public symbol;
+    uint8 public decimals = 18;
+
+    constructor(string memory _name, string memory _symbol) public {
+        name = _name;
+        symbol = _symbol;
+
+        uint256 value = 10**10 * (10**18);
+        mint(msg.sender, value);
+    }
+
+    function safeTransfer(IERC20 token, address to, uint256 value) public {
+        callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
+    }
+
+    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) public {
+        callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
+    }
+
+    /**
+     * @dev Imitates a Solidity high-level call (i.e. a regular function call to a contract), relaxing the requirement
+     * on the return value: the return value is optional (but if data is returned, it must equal true).
+     * @param token The token targeted by the call.
+     * @param data The call data (encoded using abi.encode or one of its variants).
+     */
+    function callOptionalReturn(IERC20 token, bytes memory data) private {
+        // We need to perform a low level call here, to bypass Solidity's return data size checking mechanism, since
+        // we're implementing it ourselves.
+
+        // A Solidity high level call has three parts:
+        //  1. The target address is checked to verify it contains contract code
+        //  2. The call itself is made, and success asserted
+        //  3. The return value is decoded, which in turn checks the size of the returned data.
+
+        require(address(token).isContract());
+
+        // solhint-disable-next-line avoid-low-level-calls
+        (bool success, bytes memory returndata) = address(token).call(data);
+        require(success);
+
+        if (returndata.length > 0) { // Return data is optional
+            require(abi.decode(returndata, (bool)));
+        }
+    }
+}

contracts/root/depositManager/DepositManager.sol

@@ -14,13 +14,20 @@ import {StateSender} from "../stateSyncer/StateSender.sol";
 import {GovernanceLockable} from "../../common/mixin/GovernanceLockable.sol";
 import {RootChain} from "../RootChain.sol";
 
+interface IPolygonMigration {
+    function migrate(uint256 amount) external;
+}
 
 contract DepositManager is DepositManagerStorage, IDepositManager, ERC721Holder {
     using SafeMath for uint256;
     using SafeERC20 for IERC20;
 
     modifier isTokenMapped(address _token) {
-        require(registry.isTokenMapped(_token), "TOKEN_NOT_SUPPORTED");
+        // new: exception for POL token
+        require(
+            registry.isTokenMapped(_token) || _token == registry.contractMap(keccak256("pol")),
+            "TOKEN_NOT_SUPPORTED"
+        );
         _;
     }
 
@@ -36,25 +43,48 @@ contract DepositManager is DepositManagerStorage, IDepositManager, ERC721Holder
         depositEther();
     }
 
+    // new: governance function to migrate MATIC to POL
+    function migrateMatic(uint256 _amount) external onlyGovernance {
+        _migrateMatic(_amount);
+    }
+
+    function _migrateMatic(uint256 _amount) private {
+        IERC20 matic = IERC20(registry.contractMap(keccak256("matic")));
+
+        // check that _amount is not too high
+        require(matic.balanceOf(address(this)) >= _amount, "amount exceeds this contract's MATIC balance");
+
+        // approve
+        matic.approve(registry.contractMap(keccak256("polygonMigration")), _amount);
+
+        // call migrate function
+        IPolygonMigration(registry.contractMap(keccak256("polygonMigration"))).migrate(_amount);
+    }
+
     function updateMaxErc20Deposit(uint256 maxDepositAmount) public onlyGovernance {
         require(maxDepositAmount != 0);
         emit MaxErc20DepositUpdate(maxErc20Deposit, maxDepositAmount);
         maxErc20Deposit = maxDepositAmount;
     }
 
-    function transferAssets(
-        address _token,
-        address _user,
-        uint256 _amountOrNFTId
-    ) external isPredicateAuthorized {
+    function transferAssets(address _token, address _user, uint256 _amountOrNFTId) external isPredicateAuthorized {
         address wethToken = registry.getWethTokenAddress();
+
         if (registry.isERC721(_token)) {
             IERC721(_token).transferFrom(address(this), _user, _amountOrNFTId);
         } else if (_token == wethToken) {
             WETH t = WETH(_token);
             t.withdraw(_amountOrNFTId, _user);
         } else {
-            require(IERC20(_token).transfer(_user, _amountOrNFTId), "TRANSFER_FAILED");
+            // new: pay out POL when MATIC is withdrawn
+            if (_token == registry.contractMap(keccak256("matic"))) {
+                require(
+                    IERC20(registry.contractMap(keccak256("pol"))).transfer(_user, _amountOrNFTId),
+                    "TRANSFER_FAILED"
+                );
+            } else {
+                require(IERC20(_token).transfer(_user, _amountOrNFTId), "TRANSFER_FAILED");
+            }
         }
     }
 
@@ -104,21 +134,14 @@ contract DepositManager is DepositManagerStorage, IDepositManager, ERC721Holder
         stateSender = StateSender(_stateSender);
     }
 
-    function depositERC20ForUser(
-        address _token,
-        address _user,
-        uint256 _amount
-    ) public {
+    function depositERC20ForUser(address _token, address _user, uint256 _amount) public {
         require(_amount <= maxErc20Deposit, "exceed maximum deposit amount");
         IERC20(_token).safeTransferFrom(msg.sender, address(this), _amount);
+
         _safeCreateDepositBlock(_user, _token, _amount);
     }
 
-    function depositERC721ForUser(
-        address _token,
-        address _user,
-        uint256 _tokenId
-    ) public {
+    function depositERC721ForUser(address _token, address _user, uint256 _tokenId) public {
         require(registry.isTokenMappedAndIsErc721(_token), "not erc721");
 
         _safeTransferERC721(msg.sender, _token, _tokenId);
@@ -138,20 +161,19 @@ contract DepositManager is DepositManagerStorage, IDepositManager, ERC721Holder
         address _token,
         uint256 _amountOrToken
     ) internal onlyWhenUnlocked isTokenMapped(_token) {
-        _createDepositBlock(
-            _user,
-            _token,
-            _amountOrToken,
-            rootChain.updateDepositId(1) /* returns _depositId */
-        );
+        _createDepositBlock(_user, _token, _amountOrToken, rootChain.updateDepositId(1) /* returns _depositId */);
     }
 
-    function _createDepositBlock(
-        address _user,
-        address _token,
-        uint256 _amountOrToken,
-        uint256 _depositId
-    ) internal {
+    function _createDepositBlock(address _user, address _token, uint256 _amountOrToken, uint256 _depositId) internal {
+        // new: auto-migrate MATIC to POL
+        if (_token == registry.contractMap(keccak256("matic"))) {
+            _migrateMatic(_amountOrToken);
+        }
+        // new: bridge POL as MATIC, child chain behaviour does not change
+        else if (_token == registry.contractMap(keccak256("pol"))) {
+            _token = registry.contractMap(keccak256("matic"));
+        }
+
         deposits[_depositId] = DepositBlock(keccak256(abi.encodePacked(_user, _token, _amountOrToken)), now);
         stateSender.syncState(childChain, abi.encode(_user, _token, _amountOrToken, _depositId));
         emit NewDepositBlock(_user, _token, _amountOrToken, _depositId);

contracts/test/PolygonMigrationTest.sol

@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.5.2;
+
+import {IERC20} from "openzeppelin-solidity/contracts/token/ERC20/IERC20.sol";
+import {SafeERC20} from "openzeppelin-solidity/contracts/token/ERC20/SafeERC20.sol";
+
+// this impl was shortened for testing purposes
+// full impl at https://github.com/0xPolygon/indicia/blob/main/src/PolygonMigration.sol
+contract PolygonMigrationTest {
+    using SafeERC20 for IERC20;
+
+    event Migrated(address indexed account, uint256 amount);
+
+    IERC20 public polygon;
+    IERC20 public matic;
+
+    function setTokenAddresses(address matic_, address polygon_) external {
+        if (matic_ == address(0)) revert();
+        matic = IERC20(matic_);
+
+        if (polygon_ == address(0)) revert();
+        polygon = IERC20(polygon_);
+    }
+
+    /// @notice This function allows for migrating MATIC tokens to POL tokens
+    /// @dev The function does not do any validation since the migration is a one-way process
+    /// @param amount Amount of MATIC to migrate
+    function migrate(uint256 amount) external {
+        emit Migrated(msg.sender, amount);
+
+        matic.safeTransferFrom(msg.sender, address(this), amount);
+        polygon.safeTransfer(msg.sender, amount);
+    }
+}

migrations/4_initialize_state.js

@@ -1,6 +1,7 @@
 const ethUtils = require('ethereumjs-util')
 const bluebird = require('bluebird')
 const utils = require('./utils')
+
 const Registry = artifacts.require('Registry')
 const ValidatorShare = artifacts.require('ValidatorShare')
 const DepositManagerProxy = artifacts.require('DepositManagerProxy')
@@ -16,13 +17,6 @@ const MaticWeth = artifacts.require('MaticWETH')
 const Governance = artifacts.require('Governance')
 const EventsHubProxy = artifacts.require('EventsHubProxy')
 
-async function updateContractMap(governance, registry, nameHash, value) {
-  return governance.update(
-    registry.address,
-    registry.contract.methods.updateContractMap(nameHash, value).encodeABI()
-  )
-}
-
 module.exports = async function(deployer) {
   deployer.then(async() => {
     const contractAddresses = utils.getContractAddresses()
@@ -57,52 +51,52 @@ module.exports = async function(deployer) {
         TransferWithSigPredicate,
         EventsHubProxy
       ) {
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('validatorShare'),
+          'validatorShare',
           validatorShare.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('depositManager'),
+          'depositManager',
           depositManagerProxy.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('withdrawManager'),
+          'withdrawManager',
           withdrawManagerProxy.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('stakeManager'),
+          'stakeManager',
           stakeManagerProxy.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('slashingManager'),
+          'slashingManager',
           slashingManager.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('stateSender'),
+          'stateSender',
           stateSender.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('wethToken'),
+          'wethToken',
           MaticWeth.address
         )
-        await updateContractMap(
+        await utils.updateContractMap(
           governance,
           registry,
-          ethUtils.keccak256('eventsHub'),
+          'eventsHub',
           EventsHubProxy.address
         )