flash mint full code

[t4sk]

// SPDX-License-Identifier: MIT
pragma solidity ^0.8;

interface WETH10 {
  function flashLoan(
    address receiver,
    address token,
    uint value,
    bytes calldata data
  ) external returns (bool);
}

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);
}

contract TestWethFlashMint {
  // WETH 10
  address private WETH = 0xf4BB2e28688e89fCcE3c0580D37d36A7672E8A9F;
  bytes32 public immutable CALLBACK_SUCCESS =
    keccak256("ERC3156FlashBorrower.onFlashLoan");

  address public sender;
  address public token;

  event Log(string name, uint val);

  function flash() external {
    uint total = IERC20(WETH).totalSupply();
    // borrow more than available
    uint amount = total + 1;

    emit Log("total supply", total);

    IERC20(WETH).approve(WETH, amount);

    bytes memory data = "";
    WETH10(WETH).flashLoan(address(this), WETH, amount, data);
  }

  // called by WETH10
  function onFlashLoan(
    address _sender,
    address _token,
    uint amount,
    uint fee,
    bytes calldata data
  ) external returns (bytes32) {
    uint bal = IERC20(WETH).balanceOf(address(this));

    sender = _sender;
    token = _token;

    emit Log("amount", amount);
    emit Log("fee", fee);
    emit Log("balance", bal);

    return CALLBACK_SUCCESS;
  }
}