Merge pull request #4 from bttcprotocol/fix_usdt_withdraw

fix usdt withdraw

contracts/lib/SafeERC20.sol

@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity >=0.6.0 <0.8.0;
+
+import "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+import "@openzeppelin/contracts/math/SafeMath.sol";
+import "@openzeppelin/contracts/utils/Address.sol";
+
+/**
+ * @title SafeERC20
+ * @dev Wrappers around ERC20 operations that throw on failure (when the token
+ * contract returns false). Tokens that return no value (and instead revert or
+ * throw on failure) are also supported, non-reverting calls are assumed to be
+ * successful.
+ * To use this library you can add a `using SafeERC20 for IERC20;` statement to your contract,
+ * which allows you to call the safe operations as `token.safeTransfer(...)`, etc.
+ */
+library SafeERC20 {
+    using SafeMath for uint256;
+    using Address for address;
+
+    address constant USDTAddr = 0xa614f803B6FD780986A42c78Ec9c7f77e6DeD13C;
+
+    function safeTransfer(IERC20 token, address to, uint256 value) internal {
+        if (address(token) == USDTAddr) {
+            (bool success, bytes memory data) = address(token).call(abi.encodeWithSelector(0xa9059cbb, to, value));
+            require(success, "SafeTRC20: low-level call failed");
+        } else {
+            _callOptionalReturn(token, abi.encodeWithSelector(token.transfer.selector, to, value));
+        }
+    }
+
+    function safeTransferFrom(IERC20 token, address from, address to, uint256 value) internal {
+        _callOptionalReturn(token, abi.encodeWithSelector(token.transferFrom.selector, from, to, value));
+    }
+
+    /**
+     * @dev Deprecated. This function has issues similar to the ones found in
+     * {IERC20-approve}, and its usage is discouraged.
+     *
+     * Whenever possible, use {safeIncreaseAllowance} and
+     * {safeDecreaseAllowance} instead.
+     */
+    function safeApprove(IERC20 token, address spender, uint256 value) internal {
+        // safeApprove should only be called when setting an initial allowance,
+        // or when resetting it to zero. To increase and decrease it, use
+        // 'safeIncreaseAllowance' and 'safeDecreaseAllowance'
+        // solhint-disable-next-line max-line-length
+        require((value == 0) || (token.allowance(address(this), spender) == 0),
+            "SafeERC20: approve from non-zero to non-zero allowance"
+        );
+        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, value));
+    }
+
+    function safeIncreaseAllowance(IERC20 token, address spender, uint256 value) internal {
+        uint256 newAllowance = token.allowance(address(this), spender).add(value);
+        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
+    }
+
+    function safeDecreaseAllowance(IERC20 token, address spender, uint256 value) internal {
+        uint256 newAllowance = token.allowance(address(this), spender).sub(value, "SafeERC20: decreased allowance below zero");
+        _callOptionalReturn(token, abi.encodeWithSelector(token.approve.selector, spender, newAllowance));
+    }
+
+    /**
+     * @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 not be false).
+     * @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. We use {Address.functionCall} to perform this call, which verifies that
+        // the target address contains contract code and also asserts for success in the low-level call.
+
+        bytes memory returndata = address(token).functionCall(data, "SafeERC20: low-level call failed");
+        if (returndata.length > 0) { // Return data is optional
+            // solhint-disable-next-line max-line-length
+            require(abi.decode(returndata, (bool)), "SafeERC20: ERC20 operation did not succeed");
+        }
+    }
+}

contracts/root/TokenPredicates/ERC20Predicate.sol

@@ -1,7 +1,7 @@
 pragma solidity 0.6.6;
 
 import {IERC20} from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
-import {SafeERC20} from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
+import {SafeERC20} from "../../lib/SafeERC20.sol";
 import {AccessControlMixin} from "../../common/AccessControlMixin.sol";
 import {RLPReader} from "../../lib/RLPReader.sol";
 import {ITokenPredicate} from "./ITokenPredicate.sol";