// SPDX-License-Identifier: MIT // OpenZeppelin Contracts (last updated v4.9.0) (token/ERC20/extensions/ERC20Wrapper.sol) pragma solidity ^0.8.20; import {IERC20, IERC20Metadata, ERC20} from "../ERC20.sol"; import {SafeERC20} from "../utils/SafeERC20.sol"; /** * @dev Extension of the ERC20 token contract to support token wrapping. * * Users can deposit and withdraw "underlying tokens" and receive a matching number of "wrapped tokens". This is useful * in conjunction with other modules. For example, combining this wrapping mechanism with {ERC20Votes} will allow the * wrapping of an existing "basic" ERC20 into a governance token. */ abstract contract ERC20Wrapper is ERC20 { IERC20 private immutable _underlying; /** * @dev The underlying token couldn't be wrapped. */ error ERC20InvalidUnderlying(address token); constructor(IERC20 underlyingToken) { if (underlyingToken == this) { revert ERC20InvalidUnderlying(address(this)); } _underlying = underlyingToken; } /** * @dev See {ERC20-decimals}. */ function decimals() public view virtual override returns (uint8) { try IERC20Metadata(address(_underlying)).decimals() returns (uint8 value) { return value; } catch { return super.decimals(); } } /** * @dev Returns the address of the underlying ERC-20 token that is being wrapped. */ function underlying() public view returns (IERC20) { return _underlying; } /** * @dev Allow a user to deposit underlying tokens and mint the corresponding number of wrapped tokens. */ function depositFor(address account, uint256 value) public virtual returns (bool) { address sender = _msgSender(); if (sender == address(this)) { revert ERC20InvalidSender(address(this)); } if (account == address(this)) { revert ERC20InvalidReceiver(account); } SafeERC20.safeTransferFrom(_underlying, sender, address(this), value); _mint(account, value); return true; } /** * @dev Allow a user to burn a number of wrapped tokens and withdraw the corresponding number of underlying tokens. */ function withdrawTo(address account, uint256 value) public virtual returns (bool) { if (account == address(this)) { revert ERC20InvalidReceiver(account); } _burn(_msgSender(), value); SafeERC20.safeTransfer(_underlying, account, value); return true; } /** * @dev Mint wrapped token to cover any underlyingTokens that would have been transferred by mistake. Internal * function that can be exposed with access control if desired. */ function _recover(address account) internal virtual returns (uint256) { uint256 value = _underlying.balanceOf(address(this)) - totalSupply(); _mint(account, value); return value; } }