i have this basic contract that should work, but it keeps reverting because of the approve call in the constructor, i also notice transferFrom calls from my contract also fails after manually approving, what could be wrong.

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.4.22 <0.7.0;

interface IaToken {
    function balanceOf(address _user) external view returns (uint256);
    function redeem(uint256 _amount) external;

interface IERC20 {
    function totalSupply() external view returns(uint256);
    function balanceOf(address account) external view returns (uint256);
    function allowance(address owner, address spender) external view returns(uint256);
    function transfer(address recipient, uint256 amount) external view returns(bool);
    function approve(address spender, uint256 amount) external view returns(bool);
    function transferFrom(address sender, address recipient, uint256 amount) external view returns(bool);

interface IAaveLendingPool {
    function deposit(address _reserve, uint256 _amount, uint16 _referralCode) external;

contract AaveExample {
    IERC20 public dai = IERC20(0xFf795577d9AC8bD7D90Ee22b6C1703490b6512FD);
    IaToken public aToken = IaToken(0x58AD4cB396411B691A9AAb6F74545b2C5217FE6a);
    IAaveLendingPool public aaveLendingPool = IAaveLendingPool(0x580D4Fdc4BF8f9b5ae2fb9225D584fED4AD5375c);
    mapping(address => uint256) public userDepositedDai;
    constructor() public {
        dai.approve(address(0xB4bE310666D2f909789Fb1a2FD09a9bEB0Edd99D), type(uint256).max);
    function userDepositDai(uint256 _amountInDai) external {
        userDepositedDai[msg.sender] = _amountInDai;
        require(dai.transferFrom(msg.sender, address(this), _amountInDai), "DAI Transfer failed!");
        aaveLendingPool.deposit(address(dai), _amountInDai, 0);
    function userWithdrawDai(uint256 _amountInDai) external {
        require(userDepositedDai[msg.sender] >= _amountInDai, "You cannot withdraw more than deposited!");

        require(dai.transferFrom(address(this), msg.sender, _amountInDai), "DAI Transfer failed!");
        userDepositedDai[msg.sender] = userDepositedDai[msg.sender] - _amountInDai;

1 Answer 1


As I mentioned in Discord :), the problem is in the IERC20 interface - it mentions approve (and others) as a view function.

  • 1
    Thanks man, posted it here before i got your answer...
    – Prometheus
    Commented Jan 10, 2022 at 11:32

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