Initial commit

contracts/fees/TokenDistributor.sol

@@ -8,7 +8,7 @@ import '@openzeppelin/contracts/utils/ReentrancyGuard.sol';
 
 import '../libraries/openzeppelin-upgradeability/VersionedInitializable.sol';
 import '../interfaces/IExchangeAdapter.sol';
-import '../libraries/UniversalERC20.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {PercentageMath} from '../libraries/PercentageMath.sol';
 
 /// @title TokenDistributor
@@ -24,7 +24,7 @@ import {PercentageMath} from '../libraries/PercentageMath.sol';
 contract TokenDistributor is ReentrancyGuard, VersionedInitializable {
   using SafeMath for uint256;
   using PercentageMath for uint256;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
 
   struct Distribution {
     address[] receivers;
@@ -102,7 +102,7 @@ contract TokenDistributor is ReentrancyGuard, VersionedInitializable {
   /// @param _tokens list of ERC20 tokens to distribute
   function distribute(IERC20[] memory _tokens) public {
     for (uint256 i = 0; i < _tokens.length; i++) {
-      uint256 _balanceToDistribute = _tokens[i].universalBalanceOf(address(this));
+      uint256 _balanceToDistribute = _tokens[i].balanceOf(address(this));
 
       if (_balanceToDistribute <= 0) {
         continue;
@@ -128,7 +128,7 @@ contract TokenDistributor is ReentrancyGuard, VersionedInitializable {
     public
   {
     for (uint256 i = 0; i < _tokens.length; i++) {
-      uint256 _amountToDistribute = _tokens[i].universalBalanceOf(address(this)).percentMul(
+      uint256 _amountToDistribute = _tokens[i].balanceOf(address(this)).percentMul(
         _percentages[i]
       );
 
@@ -170,7 +170,7 @@ contract TokenDistributor is ReentrancyGuard, VersionedInitializable {
       }
 
       if (_distribution.receivers[j] != address(0)) {
-        _token.universalTransfer(_distribution.receivers[j], _amount);
+        _token.safeTransfer(_distribution.receivers[j], _amount);
         emit Distributed(_distribution.receivers[j], _distribution.percentages[j], _amount);
       } else {
         uint256 _amountToBurn = _amount;

contracts/flashloan/base/FlashLoanReceiverBase.sol

@@ -5,11 +5,11 @@ import '@openzeppelin/contracts/math/SafeMath.sol';
 import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 import '../interfaces/IFlashLoanReceiver.sol';
 import '../../interfaces/ILendingPoolAddressesProvider.sol';
-import '../../libraries/UniversalERC20.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import '@nomiclabs/buidler/console.sol';
 
 abstract contract FlashLoanReceiverBase is IFlashLoanReceiver {
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
   using SafeMath for uint256;
 
   ILendingPoolAddressesProvider public addressesProvider;
@@ -33,14 +33,7 @@ abstract contract FlashLoanReceiverBase is IFlashLoanReceiver {
     address _reserve,
     uint256 _amount
   ) internal {
-    IERC20(_reserve).universalTransfer(_destination, _amount);
+    IERC20(_reserve).safeTransfer(_destination, _amount);
   }
 
-  function getBalanceInternal(address _target, address _reserve) internal view returns (uint256) {
-    if (IERC20(_reserve).isETH()) {
-      return _target.balance;
-    }
-
-    return IERC20(_reserve).balanceOf(_target);
-  }
 }

contracts/lendingpool/LendingPool.sol

@@ -17,7 +17,6 @@ import '../libraries/GenericLogic.sol';
 import '../libraries/ValidationLogic.sol';
 import '../libraries/ReserveConfiguration.sol';
 import '../libraries/UserConfiguration.sol';
-import '../libraries/UniversalERC20.sol';
 import '../tokenization/interfaces/IStableDebtToken.sol';
 import '../tokenization/interfaces/IVariableDebtToken.sol';
 
@@ -25,6 +24,7 @@ import '../interfaces/IFeeProvider.sol';
 import '../flashloan/interfaces/IFlashLoanReceiver.sol';
 import './LendingPoolLiquidationManager.sol';
 import '../interfaces/IPriceOracleGetter.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import '@nomiclabs/buidler/console.sol';
 
 /**
@@ -49,7 +49,7 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
 
   LendingPoolAddressesProvider public addressesProvider;
   IFeeProvider feeProvider;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
 
   mapping(address => ReserveLogic.ReserveData) internal reserves;
   mapping(address => UserConfiguration.Map) internal usersConfig;
@@ -280,7 +280,7 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
     aToken.mintOnDeposit(msg.sender, _amount);
 
     //transfer to the aToken contract
-    IERC20(_reserve).universalTransferFrom(msg.sender, address(aToken), _amount, true);
+    IERC20(_reserve).safeTransferFrom(msg.sender, address(aToken), _amount);
 
     //solium-disable-next-line
     emit Deposit(_reserve, msg.sender, _amount, _referralCode, block.timestamp);
@@ -457,22 +457,12 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
       usersConfig[_onBehalfOf].setBorrowing(reserve.index, false);
     }
 
-    IERC20(_reserve).universalTransferFrom(
+    IERC20(_reserve).safeTransferFrom(
       msg.sender,
       reserve.aTokenAddress,
-      vars.paybackAmount,
+      vars.paybackAmount
-      false
     );
 
-    if (IERC20(_reserve).isETH()) {
-      //send excess ETH back to the caller if needed
-      uint256 exceedAmount = msg.value.sub(vars.paybackAmount);
-
-      if (exceedAmount > 0) {
-        IERC20(_reserve).universalTransfer(msg.sender, exceedAmount);
-      }
-    }
-
     emit Repay(
       _reserve,
       _onBehalfOf,
@@ -673,7 +663,7 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
     vars.aTokenAddress = payable(reserve.aTokenAddress);
 
     //check that the reserve has enough available liquidity
-    vars.availableLiquidityBefore = IERC20(_reserve).universalBalanceOf(vars.aTokenAddress);
+    vars.availableLiquidityBefore = IERC20(_reserve).balanceOf(vars.aTokenAddress);
 
     //calculate amount fee
     vars.amountFee = _amount.mul(FLASHLOAN_FEE_TOTAL).div(10000);
@@ -702,7 +692,7 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
     receiver.executeOperation(_reserve, vars.aTokenAddress, _amount, vars.amountFee, _params);
 
     //check that the actual balance of the core contract includes the returned amount
-    uint256 availableLiquidityAfter = IERC20(_reserve).universalBalanceOf(vars.aTokenAddress);
+    uint256 availableLiquidityAfter = IERC20(_reserve).balanceOf(vars.aTokenAddress);
 
     require(
       availableLiquidityAfter == vars.availableLiquidityBefore.add(vars.amountFee),
@@ -798,7 +788,7 @@ contract LendingPool is ReentrancyGuard, VersionedInitializable {
   {
     ReserveLogic.ReserveData memory reserve = reserves[_reserve];
     return (
-      IERC20(_reserve).universalBalanceOf(reserve.aTokenAddress),
+      IERC20(_reserve).balanceOf(reserve.aTokenAddress),
       IERC20(reserve.stableDebtTokenAddress).totalSupply(),
       IERC20(reserve.variableDebtTokenAddress).totalSupply(),
       reserve.currentLiquidityRate,

contracts/lendingpool/LendingPoolLiquidationManager.sol

@@ -18,10 +18,10 @@ import '../interfaces/IPriceOracleGetter.sol';
 import '../libraries/GenericLogic.sol';
 import '../libraries/Helpers.sol';
 import '../libraries/ReserveLogic.sol';
-import '../libraries/UniversalERC20.sol';
 import '../libraries/ReserveConfiguration.sol';
 import '../libraries/UserConfiguration.sol';
 import {PercentageMath} from '../libraries/PercentageMath.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 
 /**
  * @title LendingPoolLiquidationManager contract
@@ -29,7 +29,7 @@ import {PercentageMath} from '../libraries/PercentageMath.sol';
  * @notice Implements the liquidation function.
  **/
 contract LendingPoolLiquidationManager is ReentrancyGuard, VersionedInitializable {
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
   using SafeMath for uint256;
   using WadRayMath for uint256;
   using PercentageMath for uint256;
@@ -205,7 +205,7 @@ contract LendingPoolLiquidationManager is ReentrancyGuard, VersionedInitializabl
 
     //if liquidator reclaims the underlying asset, we make sure there is enough available collateral in the reserve
     if (!_receiveAToken) {
-      uint256 currentAvailableCollateral = IERC20(_collateral).universalBalanceOf(
+      uint256 currentAvailableCollateral = IERC20(_collateral).balanceOf(
         address(vars.collateralAtoken)
       );
       if (currentAvailableCollateral < vars.maxCollateralToLiquidate) {
@@ -252,11 +252,10 @@ contract LendingPoolLiquidationManager is ReentrancyGuard, VersionedInitializabl
     }
 
     //transfers the principal currency to the aToken
-    IERC20(_reserve).universalTransferFrom(
+    IERC20(_reserve).safeTransferFrom(
       msg.sender,
       principalReserve.aTokenAddress,
-      vars.actualAmountToLiquidate,
+      vars.actualAmountToLiquidate
-      true
     );
 
     emit LiquidationCall(

contracts/libraries/ReserveLogic.sol

@@ -5,7 +5,7 @@ import {SafeMath} from '@openzeppelin/contracts/math/SafeMath.sol';
 import {IERC20} from '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 import {MathUtils} from './MathUtils.sol';
 import {IPriceOracleGetter} from '../interfaces/IPriceOracleGetter.sol';
-import {UniversalERC20} from './UniversalERC20.sol';
+import {SafeERC20}  from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {IStableDebtToken} from '../tokenization/interfaces/IStableDebtToken.sol';
 import {ReserveConfiguration} from './ReserveConfiguration.sol';
 
@@ -24,7 +24,7 @@ import '@nomiclabs/buidler/console.sol';
 library ReserveLogic {
   using SafeMath for uint256;
   using WadRayMath for uint256;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
   using Address for address;
   using ReserveLogic for ReserveLogic.ReserveData;
   using ReserveConfiguration for ReserveConfiguration.Map;
@@ -253,7 +253,7 @@ library ReserveLogic {
     returns (uint256)
   {
     return
-      IERC20(_reserveAddress).universalBalanceOf(address(this)).add(_reserve.getTotalBorrows());
+      IERC20(_reserveAddress).balanceOf(address(this)).add(_reserve.getTotalBorrows());
   }
 
   /**
@@ -272,7 +272,7 @@ library ReserveLogic {
     uint256 currentAvgStableRate = IStableDebtToken(_reserve.stableDebtTokenAddress)
       .getAverageStableRate();
 
-    uint256 balance = IERC20(_reserveAddress).universalBalanceOf(_reserve.aTokenAddress);
+    uint256 balance = IERC20(_reserveAddress).balanceOf(_reserve.aTokenAddress);
 
     (
       uint256 newLiquidityRate,
@@ -348,7 +348,7 @@ library ReserveLogic {
       return 0;
     }
 
-    uint256 availableLiquidity = IERC20(_reserveAddress).universalBalanceOf(address(this));
+    uint256 availableLiquidity = IERC20(_reserveAddress).balanceOf(address(this));
 
     return totalBorrows.rayDiv(availableLiquidity.add(totalBorrows));
   }

contracts/libraries/UniversalERC20.sol

@@ -1,174 +0,0 @@
-// SPDX-License-Identifier: agpl-3.0
-pragma solidity ^0.6.8;
-
-import '@openzeppelin/contracts/math/SafeMath.sol';
-import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
-import '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
-import '@nomiclabs/buidler/console.sol';
-
-/**
- * @title UniversalERC20 library
- * @author Aave inspired by @k06a (Anton Bukov)
- * original version: https://github.com/CryptoManiacsZone/1inchProtocol/blob/master/contracts/UniversalERC20.sol
- * @dev Provides unified interface for ERC20 and native ETH operations
- **/
-library UniversalERC20 {
-  using SafeMath for uint256;
-  using SafeERC20 for IERC20;
-
-  IERC20 private constant ZERO_ADDRESS = IERC20(0x0000000000000000000000000000000000000000);
-  // @notice mock address of ETH
-  IERC20 private constant ETH_ADDRESS = IERC20(0xEeeeeEeeeEeEeeEeEeEeeEEEeeeeEeeeeeeeEEeE);
-
-  uint256 private constant DEFAULT_TRANSFER_GAS = 50000;
-
-  /**
-   * @dev Moves amount of asset from caller to recipient
-   * @param token underlying asset address
-   * @param to asset recipient
-   * @param amount to move
-   **/
-  function universalTransfer(
-    IERC20 token,
-    address to,
-    uint256 amount
-  ) internal {
-    if (amount == 0) {
-      return;
-    }
-
-    if (isETH(token)) {
-      (bool result, ) = payable(to).call{value: amount, gas: DEFAULT_TRANSFER_GAS}('');
-      require(result, 'ETH_TRANSFER_FAILED');
-    } else {
-      token.safeTransfer(to, amount);
-    }
-  }
-
-  /**
-   * @dev Moves amount of asset from sender to recipient
-   * in terms of ETH it redirects amount in transaction to recipient
-   * @param token underlying asset address
-   * @param from asset sender
-   * @param to asset recipient
-   * @param amount to move
-   * @param returnExcess if true returns exceeded amount to sender
-   **/
-  function universalTransferFrom(
-    IERC20 token,
-    address from,
-    address to,
-    uint256 amount,
-    bool returnExcess
-  ) internal {
-    if (amount == 0) {
-      return;
-    }
-
-    if (isETH(token)) {
-      require(msg.value >= amount, 'Wrong usage of ETH.universalTransferFrom()'); // TODO: think one more time from == msg.sender
-      if (to != address(this)) {
-        (bool result, ) = payable(to).call{value: amount, gas: DEFAULT_TRANSFER_GAS}('');
-        require(result, 'ETH_TRANSFER_FAILED');
-      }
-      if (returnExcess && msg.value > amount) {
-        (bool result, ) = address(uint160(from)).call.value(msg.value.sub(amount)).gas(
-          DEFAULT_TRANSFER_GAS
-        )('');
-        require(result, 'ETH_TRANSFER_FAILED');
-      }
-    } else {
-      token.safeTransferFrom(from, to, amount);
-    }
-  }
-
-  /**
-   * @dev Moves amount of asset from caller to this contract
-   * @param token underlying asset address
-   * @param amount to move
-   **/
-  function universalTransferFromSenderToThis(
-    IERC20 token,
-    uint256 amount,
-    bool returnExcess
-  ) internal {
-    if (amount == 0) {
-      return;
-    }
-
-    if (isETH(token)) {
-      require(msg.value >= amount, 'The amount and the value sent to deposit do not match');
-      if (returnExcess) {
-        // Return remainder if exist
-        (bool result, ) = msg.sender.call{value: msg.value.sub(amount), gas: DEFAULT_TRANSFER_GAS}(
-          ''
-        );
-        require(result, 'ETH_TRANSFER_FAILED');
-      }
-    } else {
-      token.safeTransferFrom(msg.sender, address(this), amount);
-    }
-  }
-
-  /**
-   * @dev Sets the allowance over the caller's tokens to recipient address.
-   * @param token underlying asset address
-   * @param to allowance recipient
-   * @param amount of the allowance
-   **/
-  function universalApprove(
-    IERC20 token,
-    address to,
-    uint256 amount
-  ) internal {
-    if (!isETH(token)) {
-      if (amount > 0 && token.allowance(address(this), to) > 0) {
-        token.safeApprove(to, 0);
-      }
-      token.safeApprove(to, amount);
-    }
-  }
-
-  /**
-   * @dev Returns the amount of underlying asset owned by address
-   * @param token underlying asset address
-   * @param who address to check
-   * @return balance of the who address
-   **/
-  function universalBalanceOf(IERC20 token, address who) internal view returns (uint256) {
-    if (isETH(token)) {
-      return who.balance;
-    } else {
-      return token.balanceOf(who);
-    }
-  }
-
-  /**
-   * @dev Returns decimals of underlying asset
-   * @param token underlying asset address
-   * @return decimals
-   **/
-  function universalDecimals(IERC20 token) internal view returns (uint256) {
-    if (isETH(token)) {
-      return 18;
-    }
-
-    (bool success, bytes memory data) = address(token).staticcall.gas(10000)(
-      abi.encodeWithSignature('decimals()')
-    );
-    if (!success || data.length == 0) {
-      (success, data) = address(token).staticcall.gas(10000)(abi.encodeWithSignature('DECIMALS()'));
-    }
-
-    return (success && data.length > 0) ? abi.decode(data, (uint256)) : 18;
-  }
-
-  /**
-   * @dev Checks is underlying asset ETH or not
-   * @param token underlying asset address
-   * @return boolean
-   **/
-  function isETH(IERC20 token) internal pure returns (bool) {
-    return (address(token) == address(ETH_ADDRESS));
-  }
-}

contracts/libraries/ValidationLogic.sol

@@ -9,7 +9,7 @@ import {ReserveLogic} from './ReserveLogic.sol';
 import {GenericLogic} from './GenericLogic.sol';
 import {WadRayMath} from './WadRayMath.sol';
 import {PercentageMath} from './PercentageMath.sol';
-import {UniversalERC20} from './UniversalERC20.sol';
+import {SafeERC20}  from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {ReserveConfiguration} from './ReserveConfiguration.sol';
 import {UserConfiguration} from './UserConfiguration.sol';
 import {IPriceOracleGetter} from '../interfaces/IPriceOracleGetter.sol';
@@ -26,7 +26,7 @@ library ValidationLogic {
   using SafeMath for uint256;
   using WadRayMath for uint256;
   using PercentageMath for uint256;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
   using ReserveConfiguration for ReserveConfiguration.Map;
   using UserConfiguration for UserConfiguration.Map;
 
@@ -59,7 +59,7 @@ library ValidationLogic {
 
     require(msg.sender == _reserve.aTokenAddress, '31');
 
-    uint256 currentAvailableLiquidity = IERC20(_reserveAddress).universalBalanceOf(
+    uint256 currentAvailableLiquidity = IERC20(_reserveAddress).balanceOf(
       address(_reserve.aTokenAddress)
     );
 
@@ -135,7 +135,7 @@ library ValidationLogic {
     );
 
     //check that the amount is available in the reserve
-    vars.availableLiquidity = IERC20(_reserveAddress).universalBalanceOf(
+    vars.availableLiquidity = IERC20(_reserveAddress).balanceOf(
       address(_reserve.aTokenAddress)
     );
 
@@ -238,11 +238,6 @@ library ValidationLogic {
       _amountSent != uint256(-1) || msg.sender == _onBehalfOf,
       'To repay on behalf of an user an explicit amount to repay is needed'
     );
-
-    require(
-      !IERC20(_reserveAddress).isETH() || _msgValue >= _actualPaybackAmount,
-      'Invalid msg.value sent for the repayment'
-    );
   }
 
   /**

contracts/misc/ChainlinkProxyPriceProvider.sol

@@ -6,7 +6,7 @@ import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 
 import '../interfaces/IPriceOracleGetter.sol';
 import '../interfaces/IChainlinkAggregator.sol';
-import '../libraries/UniversalERC20.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 
 /// @title ChainlinkProxyPriceProvider
 /// @author Aave
@@ -16,7 +16,7 @@ import '../libraries/UniversalERC20.sol';
 /// - Owned by the Aave governance system, allowed to add sources for assets, replace them
 ///   and change the fallbackOracle
 contract ChainlinkProxyPriceProvider is IPriceOracleGetter, Ownable {
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
 
   event AssetSourceUpdated(address indexed asset, address indexed source);
   event FallbackOracleUpdated(address indexed fallbackOracle);
@@ -77,9 +77,6 @@ contract ChainlinkProxyPriceProvider is IPriceOracleGetter, Ownable {
   /// @param _asset The asset address
   function getAssetPrice(address _asset) public override view returns (uint256) {
     IChainlinkAggregator source = assetsSources[_asset];
-    if (IERC20(_asset).isETH()) {
-      return 1 ether;
-    } else {
       // If there is no registered source for the asset, call the fallbackOracle
       if (address(source) == address(0)) {
         return IPriceOracleGetter(fallbackOracle).getAssetPrice(_asset);
@@ -91,7 +88,6 @@ contract ChainlinkProxyPriceProvider is IPriceOracleGetter, Ownable {
           return IPriceOracleGetter(fallbackOracle).getAssetPrice(_asset);
         }
       }
-    }
   }
 
   /// @notice Gets a list of prices from a list of assets addresses

contracts/misc/WalletBalanceProvider.sol

@@ -6,7 +6,7 @@ import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 
 import '../configuration/LendingPoolAddressesProvider.sol';
 import '../lendingpool/LendingPool.sol';
-import '../libraries/UniversalERC20.sol';
+import {SafeERC20} from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 
 /**
  * @title WalletBalanceProvider contract
@@ -18,7 +18,7 @@ import '../libraries/UniversalERC20.sol';
 contract WalletBalanceProvider {
   using Address for address payable;
   using Address for address;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
 
   LendingPoolAddressesProvider provider;
 
@@ -65,14 +65,10 @@ contract WalletBalanceProvider {
     for (uint256 i = 0; i < _users.length; i++) {
       for (uint256 j = 0; j < _tokens.length; j++) {
         uint256 _offset = i * _tokens.length;
-        if (IERC20(_tokens[j]).isETH()) {
+        if (!_tokens[j].isContract()) {
-          balances[_offset + j] = _users[i].balance; // ETH balance
+          revert('INVALID_TOKEN');
         } else {
-          if (!_tokens[j].isContract()) {
+          balances[_offset + j] = balanceOf(_users[i], _tokens[j]);
-            revert('INVALID_TOKEN');
-          } else {
-            balances[_offset + j] = balanceOf(_users[i], _tokens[j]);
-          }
         }
       }
     }
@@ -101,11 +97,7 @@ contract WalletBalanceProvider {
         balances[j] = 0;
         continue;
       }
-      if (IERC20(reserves[j]).isETH()) {
         balances[j] = balanceOf(_user, reserves[j]);
-      } else {
-        balances[j] = _user.balance; // ETH balance
-      }
     }
 
     return (reserves, balances);

contracts/mocks/flashloan/MockFlashLoanReceiver.sol

@@ -6,11 +6,11 @@ import '@openzeppelin/contracts/token/ERC20/IERC20.sol';
 
 import '../../flashloan/base/FlashLoanReceiverBase.sol';
 import '../tokens/MintableERC20.sol';
-import '../../libraries/UniversalERC20.sol';
+import {SafeERC20}  from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 
 contract MockFlashLoanReceiver is FlashLoanReceiverBase {
   using SafeMath for uint256;
-  using UniversalERC20 for IERC20;
+  using SafeERC20 for IERC20;
 
   event ExecutedWithFail(address _reserve, uint256 _amount, uint256 _fee);
   event ExecutedWithSuccess(address _reserve, uint256 _amount, uint256 _fee);
@@ -35,7 +35,7 @@ contract MockFlashLoanReceiver is FlashLoanReceiverBase {
 
     //check the contract has the specified balance
     require(
-      _amount <= getBalanceInternal(address(this), _reserve),
+      _amount <= IERC20(_reserve).balanceOf(address(this)),
       'Invalid balance for the contract'
     );
 
@@ -47,9 +47,7 @@ contract MockFlashLoanReceiver is FlashLoanReceiverBase {
     //execution does not fail - mint tokens and return them to the _destination
     //note: if the reserve is eth, the mock contract must receive at least _fee ETH before calling executeOperation
 
-    if (!IERC20(_reserve).isETH()) {
+    token.mint(_fee);
-      token.mint(_fee);
-    }
 
     //returning amount + fee to the destination
     transferFundsBackInternal(_reserve, _destination, _amount.add(_fee));

contracts/tokenization/AToken.sol

@@ -4,7 +4,7 @@ pragma solidity ^0.6.8;
 import {ERC20} from './ERC20.sol';
 import {LendingPool} from '../lendingpool/LendingPool.sol';
 import {WadRayMath} from '../libraries/WadRayMath.sol';
-import {UniversalERC20} from '../libraries/UniversalERC20.sol';
+import {SafeERC20}  from '@openzeppelin/contracts/token/ERC20/SafeERC20.sol';
 import {
   VersionedInitializable
 } from '../libraries/openzeppelin-upgradeability/VersionedInitializable.sol';
@@ -19,7 +19,7 @@ import '@nomiclabs/buidler/console.sol';
  */
 contract AToken is VersionedInitializable, ERC20 {
   using WadRayMath for uint256;
-  using UniversalERC20 for ERC20;
+  using SafeERC20 for ERC20;
 
   uint256 public constant UINT_MAX_VALUE = uint256(-1);
 
@@ -702,17 +702,14 @@ contract AToken is VersionedInitializable, ERC20 {
     onlyLendingPool
     returns (uint256)
   {
-    ERC20(underlyingAssetAddress).universalTransfer(_target, _amount);
+    ERC20(underlyingAssetAddress).safeTransfer(_target, _amount);
     return _amount;
   }
 
   /**
-   * @dev receive() function for aTokens who hold ETH as the underlying asset
+   * @dev aTokens should not receive ETH
    **/
   receive() external payable {
-    require(
+    revert();
-      ERC20(underlyingAssetAddress).isETH(),
-      'Transfers are only allowed if the underlying asset is ETH'
-    );
   }
 }

contracts/tokenization/StableDebtToken.sol

@@ -188,7 +188,7 @@ contract StableDebtToken is IStableDebtToken, DebtTokenBase {
       uint256 previousBalance,
       uint256 currentBalance,
       uint256 balanceIncrease
-    ) = _calculateCumulatedBalance(_user);
+    ) = _calculateBalanceIncrease(_user);
 
     uint256 supplyBeforeBurn = totalSupply.add(balanceIncrease);
     uint256 supplyAfterBurn = supplyBeforeBurn.sub(_amount);

contracts/tokenization/VariableDebtToken.sol

@@ -99,7 +99,7 @@ contract VariableDebtToken is DebtTokenBase, IVariableDebtToken {
       uint256 previousBalance,
       uint256 currentBalance,
       uint256 balanceIncrease
-    ) = _calculateCumulatedBalance(_user);
+    ) = _calculateBalanceIncrease(_user);
 
     _mint(_user, _amount.add(balanceIncrease));