我有一份使用 Open-Zeppelin SafeMath 的合同,但派生合同不承认该声明。
Base.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.7.4;
import "@openzeppelin/contracts-ethereum-package/contracts/math/SafeMath.sol";
contract Base {
using SafeMath for uint256;
}
测试.sol
// SPDX-License-Identifier: MIT
pragma solidity ^0.7.4;
import "Base.sol";
contract Test is Base {
function getnum(uint256 _number) external view returns (uint256) {
return _number.add(_number);
}
}
但我不断收到此错误:
Member "add" not found or not visible after argument-dependent lookup in uint256.