Update solidity

contracts/connectors/refinance.sol

@@ -1,8 +1,153 @@
-pragma solidity ^0.7.0;
+pragma solidity ^0.7.6;
 pragma experimental ABIEncoderV2;
 
-import { SafeERC20 } from "@openzeppelin/contracts/token/ERC20/SafeERC20.sol";
-import { IERC20 } from "@openzeppelin/contracts/token/ERC20/IERC20.sol";
+/**
+ * @dev Interface of the ERC20 standard as defined in the EIP.
+ */
+interface IERC20 {
+    /**
+     * @dev Returns the amount of tokens in existence.
+     */
+    function totalSupply() external view returns (uint256);
+
+    /**
+     * @dev Returns the amount of tokens owned by `account`.
+     */
+    function balanceOf(address account) external view returns (uint256);
+
+    /**
+     * @dev Moves `amount` tokens from the caller's account to `recipient`.
+     *
+     * Returns a boolean value indicating whether the operation succeeded.
+     *
+     * Emits a {Transfer} event.
+     */
+    function transfer(address recipient, uint256 amount) external returns (bool);
+
+    /**
+     * @dev Returns the remaining number of tokens that `spender` will be
+     * allowed to spend on behalf of `owner` through {transferFrom}. This is
+     * zero by default.
+     *
+     * This value changes when {approve} or {transferFrom} are called.
+     */
+    function allowance(address owner, address spender) external view returns (uint256);
+
+    /**
+     * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
+     *
+     * Returns a boolean value indicating whether the operation succeeded.
+     *
+     * IMPORTANT: Beware that changing an allowance with this method brings the risk
+     * that someone may use both the old and the new allowance by unfortunate
+     * transaction ordering. One possible solution to mitigate this race
+     * condition is to first reduce the spender's allowance to 0 and set the
+     * desired value afterwards:
+     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
+     *
+     * Emits an {Approval} event.
+     */
+    function approve(address spender, uint256 amount) external returns (bool);
+
+    /**
+     * @dev Moves `amount` tokens from `sender` to `recipient` using the
+     * allowance mechanism. `amount` is then deducted from the caller's
+     * allowance.
+     *
+     * Returns a boolean value indicating whether the operation succeeded.
+     *
+     * Emits a {Transfer} event.
+     */
+    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
+
+    /**
+     * @dev Emitted when `value` tokens are moved from one account (`from`) to
+     * another (`to`).
+     *
+     * Note that `value` may be zero.
+     */
+    event Transfer(address indexed from, address indexed to, uint256 value);
+
+    /**
+     * @dev Emitted when the allowance of a `spender` for an `owner` is set by
+     * a call to {approve}. `value` is the new allowance.
+     */
+    event Approval(address indexed owner, address indexed spender, uint256 value);
+}
+
+/**
+ * @dev Collection of functions related to the address type
+ */
+library Address {
+    function isContract(address account) internal view returns (bool) {
+        // According to EIP-1052, 0x0 is the value returned for not-yet created accounts
+        // and 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470 is returned
+        // for accounts without code, i.e. `keccak256('')`
+        bytes32 codehash;
+        bytes32 accountHash = 0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470;
+        // solhint-disable-next-line no-inline-assembly
+        assembly { codehash := extcodehash(account) }
+        return (codehash != accountHash && codehash != 0x0);
+    }
+
+
+    /**
+     * @dev Same as {xref-Address-functionCall-address-bytes-}[`functionCall`], but with
+     * `errorMessage` as a fallback revert reason when `target` reverts.
+     *
+     * _Available since v3.1._
+     */
+    function functionCall(address target, bytes memory data, string memory errorMessage) internal returns (bytes memory) {
+        return _functionCallWithValue(target, data, 0, errorMessage);
+    }
+
+    function _functionCallWithValue(address target, bytes memory data, uint256 weiValue, string memory errorMessage) private returns (bytes memory) {
+        require(isContract(target), "Address: call to non-contract");
+
+        // solhint-disable-next-line avoid-low-level-calls
+        (bool success, bytes memory returndata) = target.call{ value: weiValue }(data);
+        if (success) {
+            return returndata;
+        } else {
+            // Look for revert reason and bubble it up if present
+            if (returndata.length > 0) {
+                // The easiest way to bubble the revert reason is using memory via assembly
+
+                // solhint-disable-next-line no-inline-assembly
+                assembly {
+                    let returndata_size := mload(returndata)
+                    revert(add(32, returndata), returndata_size)
+                }
+            } else {
+                revert(errorMessage);
+            }
+        }
+    }
+}
+
+library SafeERC20 {
+    using Address for address;
+
+    function safeTransfer(IERC20 token, address to, uint256 value) internal {
+        _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));
+    }
+
+    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");
+        }
+    }
+}
 
 interface TokenInterface {
     function approve(address, uint256) external;
@@ -805,9 +950,10 @@ contract AaveV2Helpers is AaveV1Helpers {
 contract RefinanceResolver is AaveV2Helpers {
 
     function refinance(RefinanceData calldata data) external payable {
-
         require(data.source != data.target, "source-and-target-unequal");
 
+        CommonData memory commonData;
+
         commonData.length = data.tokens.length;
 
         require(data.borrowAmts.length == commonData.length, "length-mismatch");
@@ -864,5 +1010,5 @@ contract RefinanceResolver is AaveV2Helpers {
 }
 
 contract ConnectRefinance is RefinanceResolver {
-    string public name = "Refinance-v1";
+    string public name = "Refinance-v1.2";
 }